1	/*
2	* Copyright (c) Yann Collet, Facebook, Inc.
3	* All rights reserved.
4	*
5	* This source code is licensed under both the BSD-style license (found in the
6	* LICENSE file in the root directory of this source tree) and the GPLv2 (found
7	* in the COPYING file in the root directory of this source tree).
8	* You may select, at your option, one of the above-listed licenses.
9	*/
10
11	#ifndef ZSTD_H_235446
12	#define ZSTD_H_235446
13
14	/* ====== Dependency ======*/
15	#include <linux/limits.h> /* INT_MAX */
16	#include <linux/types.h> /* size_t */
17
18
19	/* ===== ZSTDLIB_API : control library symbols visibility ===== */
20	#ifndef ZSTDLIB_VISIBLE
21	# if (__GNUC__ >= 4) && !defined(__MINGW32__)
22	# define ZSTDLIB_VISIBLE __attribute__ ((visibility ("default")))
23	# define ZSTDLIB_HIDDEN __attribute__ ((visibility ("hidden")))
24	# else
25	# define ZSTDLIB_VISIBLE
26	# define ZSTDLIB_HIDDEN
27	# endif
28	#endif
29	#define ZSTDLIB_API ZSTDLIB_VISIBLE
30
31
32	/* *****************************************************************************
33	Introduction
34
35	zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
36	real-time compression scenarios at zlib-level and better compression ratios.
37	The zstd compression library provides in-memory compression and decompression
38	functions.
39
40	The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
41	which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
42	caution, as they require more memory. The library also offers negative
43	compression levels, which extend the range of speed vs. ratio preferences.
44	The lower the level, the faster the speed (at the cost of compression).
45
46	Compression can be done in:
47	- a single step (described as Simple API)
48	- a single step, reusing a context (described as Explicit context)
49	- unbounded multiple steps (described as Streaming compression)
50
51	The compression ratio achievable on small data can be highly improved using
52	a dictionary. Dictionary compression can be performed in:
53	- a single step (described as Simple dictionary API)
54	- a single step, reusing a dictionary (described as Bulk-processing
55	dictionary API)
56
57	Advanced experimental functions can be accessed using
58	`#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
59
60	Advanced experimental APIs should never be used with a dynamically-linked
61	library. They are not "stable"; their definitions or signatures may change in
62	the future. Only static linking is allowed.
63	*******************************************************************************/
64
65	/*------ Version ------*/
66	#define ZSTD_VERSION_MAJOR 1
67	#define ZSTD_VERSION_MINOR 5
68	#define ZSTD_VERSION_RELEASE 2
69	#define ZSTD_VERSION_NUMBER (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
70
71	/*! ZSTD_versionNumber() :
72	* Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE). */
73	ZSTDLIB_API unsigned ZSTD_versionNumber(void);
74
75	#define ZSTD_LIB_VERSION ZSTD_VERSION_MAJOR.ZSTD_VERSION_MINOR.ZSTD_VERSION_RELEASE
76	#define ZSTD_QUOTE(str) #str
77	#define ZSTD_EXPAND_AND_QUOTE(str) ZSTD_QUOTE(str)
78	#define ZSTD_VERSION_STRING ZSTD_EXPAND_AND_QUOTE(ZSTD_LIB_VERSION)
79
80	/*! ZSTD_versionString() :
81	* Return runtime library version, like "1.4.5". Requires v1.3.0+. */
82	ZSTDLIB_API const char* ZSTD_versionString(void);
83
84	/* *************************************
85	* Default constant
86	***************************************/
87	#ifndef ZSTD_CLEVEL_DEFAULT
88	# define ZSTD_CLEVEL_DEFAULT 3
89	#endif
90
91	/* *************************************
92	* Constants
93	***************************************/
94
95	/* All magic numbers are supposed read/written to/from files/memory using little-endian convention */
96	#define ZSTD_MAGICNUMBER 0xFD2FB528 /* valid since v0.8.0 */
97	#define ZSTD_MAGIC_DICTIONARY 0xEC30A437 /* valid since v0.7.0 */
98	#define ZSTD_MAGIC_SKIPPABLE_START 0x184D2A50 /* all 16 values, from 0x184D2A50 to 0x184D2A5F, signal the beginning of a skippable frame */
99	#define ZSTD_MAGIC_SKIPPABLE_MASK 0xFFFFFFF0
100
101	#define ZSTD_BLOCKSIZELOG_MAX 17
102	#define ZSTD_BLOCKSIZE_MAX (1<<ZSTD_BLOCKSIZELOG_MAX)
103
104
105	/* *************************************
106	* Simple API
107	***************************************/
108	/*! ZSTD_compress() :
109	* Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
110	* Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
111	* @return : compressed size written into `dst` (<= `dstCapacity),
112	* or an error code if it fails (which can be tested using ZSTD_isError()). */
113	ZSTDLIB_API size_t ZSTD_compress( void* dst, size_t dstCapacity,
114	const void* src, size_t srcSize,
115	int compressionLevel);
116
117	/*! ZSTD_decompress() :
118	* `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
119	* `dstCapacity` is an upper bound of originalSize to regenerate.
120	* If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
121	* @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
122	* or an errorCode if it fails (which can be tested using ZSTD_isError()). */
123	ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
124	const void* src, size_t compressedSize);
125
126	/*! ZSTD_getFrameContentSize() : requires v1.3.0+
127	* `src` should point to the start of a ZSTD encoded frame.
128	* `srcSize` must be at least as large as the frame header.
129	* hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
130	* @return : - decompressed size of `src` frame content, if known
131	* - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
132	* - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
133	* note 1 : a 0 return value means the frame is valid but "empty".
134	* note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
135	* When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
136	* In which case, it's necessary to use streaming mode to decompress data.
137	* Optionally, application can rely on some implicit limit,
138	* as ZSTD_decompress() only needs an upper bound of decompressed size.
139	* (For example, data could be necessarily cut into blocks <= 16 KB).
140	* note 3 : decompressed size is always present when compression is completed using single-pass functions,
141	* such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
142	* note 4 : decompressed size can be very large (64-bits value),
143	* potentially larger than what local system can handle as a single memory segment.
144	* In which case, it's necessary to use streaming mode to decompress data.
145	* note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
146	* Always ensure return value fits within application's authorized limits.
147	* Each application can set its own limits.
148	* note 6 : This function replaces ZSTD_getDecompressedSize() */
149	#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
150	#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
151	ZSTDLIB_API unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
152
153	/*! ZSTD_getDecompressedSize() :
154	* NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
155	* Both functions work the same way, but ZSTD_getDecompressedSize() blends
156	* "empty", "unknown" and "error" results to the same return value (0),
157	* while ZSTD_getFrameContentSize() gives them separate return values.
158	* @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. */
159	ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
160
161	/*! ZSTD_findFrameCompressedSize() : Requires v1.4.0+
162	* `src` should point to the start of a ZSTD frame or skippable frame.
163	* `srcSize` must be >= first frame size
164	* @return : the compressed size of the first frame starting at `src`,
165	* suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
166	* or an error code if input is invalid */
167	ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
168
169
170	/*====== Helper functions ======*/
171	#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) /* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */
172	ZSTDLIB_API size_t ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case single-pass scenario */
173	ZSTDLIB_API unsigned ZSTD_isError(size_t code); /*!< tells if a `size_t` function result is an error code */
174	ZSTDLIB_API const char* ZSTD_getErrorName(size_t code); /*!< provides readable string from an error code */
175	ZSTDLIB_API int ZSTD_minCLevel(void); /*!< minimum negative compression level allowed, requires v1.4.0+ */
176	ZSTDLIB_API int ZSTD_maxCLevel(void); /*!< maximum compression level available */
177	ZSTDLIB_API int ZSTD_defaultCLevel(void); /*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */
178
179
180	/* *************************************
181	* Explicit context
182	***************************************/
183	/*= Compression context
184	* When compressing many times,
185	* it is recommended to allocate a context just once,
186	* and re-use it for each successive compression operation.
187	* This will make workload friendlier for system's memory.
188	* Note : re-using context is just a speed / resource optimization.
189	* It doesn't change the compression ratio, which remains identical.
190	* Note 2 : In multi-threaded environments,
191	* use one different context per thread for parallel execution.
192	*/
193	typedef struct ZSTD_CCtx_s ZSTD_CCtx;
194	ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx(void);
195	ZSTDLIB_API size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); /* accept NULL pointer */
196
197	/*! ZSTD_compressCCtx() :
198	* Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
199	* Important : in order to behave similarly to `ZSTD_compress()`,
200	* this function compresses at requested compression level,
201	* __ignoring any other parameter__ .
202	* If any advanced parameter was set using the advanced API,
203	* they will all be reset. Only `compressionLevel` remains.
204	*/
205	ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
206	void* dst, size_t dstCapacity,
207	const void* src, size_t srcSize,
208	int compressionLevel);
209
210	/*= Decompression context
211	* When decompressing many times,
212	* it is recommended to allocate a context only once,
213	* and re-use it for each successive compression operation.
214	* This will make workload friendlier for system's memory.
215	* Use one context per thread for parallel execution. */
216	typedef struct ZSTD_DCtx_s ZSTD_DCtx;
217	ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void);
218	ZSTDLIB_API size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); /* accept NULL pointer */
219
220	/*! ZSTD_decompressDCtx() :
221	* Same as ZSTD_decompress(),
222	* requires an allocated ZSTD_DCtx.
223	* Compatible with sticky parameters.
224	*/
225	ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
226	void* dst, size_t dstCapacity,
227	const void* src, size_t srcSize);
228
229
230	/* *******************************************
231	* Advanced compression API (Requires v1.4.0+)
232	**********************************************/
233
234	/* API design :
235	* Parameters are pushed one by one into an existing context,
236	* using ZSTD_CCtx_set*() functions.
237	* Pushed parameters are sticky : they are valid for next compressed frame, and any subsequent frame.
238	* "sticky" parameters are applicable to `ZSTD_compress2()` and `ZSTD_compressStream*()` !
239	* __They do not apply to "simple" one-shot variants such as ZSTD_compressCCtx()__ .
240	*
241	* It's possible to reset all parameters to "default" using ZSTD_CCtx_reset().
242	*
243	* This API supersedes all other "advanced" API entry points in the experimental section.
244	* In the future, we expect to remove from experimental API entry points which are redundant with this API.
245	*/
246
247
248	/* Compression strategies, listed from fastest to strongest */
249	typedef enum { ZSTD_fast=1,
250	ZSTD_dfast=2,
251	ZSTD_greedy=3,
252	ZSTD_lazy=4,
253	ZSTD_lazy2=5,
254	ZSTD_btlazy2=6,
255	ZSTD_btopt=7,
256	ZSTD_btultra=8,
257	ZSTD_btultra2=9
258	/* note : new strategies _might_ be added in the future.
259	Only the order (from fast to strong) is guaranteed */
260	} ZSTD_strategy;
261
262	typedef enum {
263
264	/* compression parameters
265	* Note: When compressing with a ZSTD_CDict these parameters are superseded
266	* by the parameters used to construct the ZSTD_CDict.
267	* See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
268	ZSTD_c_compressionLevel=100, /* Set compression parameters according to pre-defined cLevel table.
269	* Note that exact compression parameters are dynamically determined,
270	* depending on both compression level and srcSize (when known).
271	* Default level is ZSTD_CLEVEL_DEFAULT==3.
272	* Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
273	* Note 1 : it's possible to pass a negative compression level.
274	* Note 2 : setting a level does not automatically set all other compression parameters
275	* to default. Setting this will however eventually dynamically impact the compression
276	* parameters which have not been manually set. The manually set
277	* ones will 'stick'. */
278	/* Advanced compression parameters :
279	* It's possible to pin down compression parameters to some specific values.
280	* In which case, these values are no longer dynamically selected by the compressor */
281	ZSTD_c_windowLog=101, /* Maximum allowed back-reference distance, expressed as power of 2.
282	* This will set a memory budget for streaming decompression,
283	* with larger values requiring more memory
284	* and typically compressing more.
285	* Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
286	* Special: value 0 means "use default windowLog".
287	* Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
288	* requires explicitly allowing such size at streaming decompression stage. */
289	ZSTD_c_hashLog=102, /* Size of the initial probe table, as a power of 2.
290	* Resulting memory usage is (1 << (hashLog+2)).
291	* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
292	* Larger tables improve compression ratio of strategies <= dFast,
293	* and improve speed of strategies > dFast.
294	* Special: value 0 means "use default hashLog". */
295	ZSTD_c_chainLog=103, /* Size of the multi-probe search table, as a power of 2.
296	* Resulting memory usage is (1 << (chainLog+2)).
297	* Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
298	* Larger tables result in better and slower compression.
299	* This parameter is useless for "fast" strategy.
300	* It's still useful when using "dfast" strategy,
301	* in which case it defines a secondary probe table.
302	* Special: value 0 means "use default chainLog". */
303	ZSTD_c_searchLog=104, /* Number of search attempts, as a power of 2.
304	* More attempts result in better and slower compression.
305	* This parameter is useless for "fast" and "dFast" strategies.
306	* Special: value 0 means "use default searchLog". */
307	ZSTD_c_minMatch=105, /* Minimum size of searched matches.
308	* Note that Zstandard can still find matches of smaller size,
309	* it just tweaks its search algorithm to look for this size and larger.
310	* Larger values increase compression and decompression speed, but decrease ratio.
311	* Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
312	* Note that currently, for all strategies < btopt, effective minimum is 4.
313	* , for all strategies > fast, effective maximum is 6.
314	* Special: value 0 means "use default minMatchLength". */
315	ZSTD_c_targetLength=106, /* Impact of this field depends on strategy.
316	* For strategies btopt, btultra & btultra2:
317	* Length of Match considered "good enough" to stop search.
318	* Larger values make compression stronger, and slower.
319	* For strategy fast:
320	* Distance between match sampling.
321	* Larger values make compression faster, and weaker.
322	* Special: value 0 means "use default targetLength". */
323	ZSTD_c_strategy=107, /* See ZSTD_strategy enum definition.
324	* The higher the value of selected strategy, the more complex it is,
325	* resulting in stronger and slower compression.
326	* Special: value 0 means "use default strategy". */
327	/* LDM mode parameters */
328	ZSTD_c_enableLongDistanceMatching=160, /* Enable long distance matching.
329	* This parameter is designed to improve compression ratio
330	* for large inputs, by finding large matches at long distance.
331	* It increases memory usage and window size.
332	* Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
333	* except when expressly set to a different value.
334	* Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
335	* compression strategy >= ZSTD_btopt (== compression level 16+) */
336	ZSTD_c_ldmHashLog=161, /* Size of the table for long distance matching, as a power of 2.
337	* Larger values increase memory usage and compression ratio,
338	* but decrease compression speed.
339	* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
340	* default: windowlog - 7.
341	* Special: value 0 means "automatically determine hashlog". */
342	ZSTD_c_ldmMinMatch=162, /* Minimum match size for long distance matcher.
343	* Larger/too small values usually decrease compression ratio.
344	* Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
345	* Special: value 0 means "use default value" (default: 64). */
346	ZSTD_c_ldmBucketSizeLog=163, /* Log size of each bucket in the LDM hash table for collision resolution.
347	* Larger values improve collision resolution but decrease compression speed.
348	* The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
349	* Special: value 0 means "use default value" (default: 3). */
350	ZSTD_c_ldmHashRateLog=164, /* Frequency of inserting/looking up entries into the LDM hash table.
351	* Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
352	* Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
353	* Larger values improve compression speed.
354	* Deviating far from default value will likely result in a compression ratio decrease.
355	* Special: value 0 means "automatically determine hashRateLog". */
356
357	/* frame parameters */
358	ZSTD_c_contentSizeFlag=200, /* Content size will be written into frame header _whenever known_ (default:1)
359	* Content size must be known at the beginning of compression.
360	* This is automatically the case when using ZSTD_compress2(),
361	* For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
362	ZSTD_c_checksumFlag=201, /* A 32-bits checksum of content is written at end of frame (default:0) */
363	ZSTD_c_dictIDFlag=202, /* When applicable, dictionary's ID is written into frame header (default:1) */
364
365	/* multi-threading parameters */
366	/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).
367	* Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
368	* In a situation where it's unknown if the linked library supports multi-threading or not,
369	* setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
370	*/
371	ZSTD_c_nbWorkers=400, /* Select how many threads will be spawned to compress in parallel.
372	* When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
373	* ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
374	* while compression is performed in parallel, within worker thread(s).
375	* (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
376	* in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
377	* More workers improve speed, but also increase memory usage.
378	* Default value is `0`, aka "single-threaded mode" : no worker is spawned,
379	* compression is performed inside Caller's thread, and all invocations are blocking */
380	ZSTD_c_jobSize=401, /* Size of a compression job. This value is enforced only when nbWorkers >= 1.
381	* Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
382	* 0 means default, which is dynamically determined based on compression parameters.
383	* Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest.
384	* The minimum size is automatically and transparently enforced. */
385	ZSTD_c_overlapLog=402, /* Control the overlap size, as a fraction of window size.
386	* The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
387	* It helps preserve compression ratio, while each job is compressed in parallel.
388	* This value is enforced only when nbWorkers >= 1.
389	* Larger values increase compression ratio, but decrease speed.
390	* Possible values range from 0 to 9 :
391	* - 0 means "default" : value will be determined by the library, depending on strategy
392	* - 1 means "no overlap"
393	* - 9 means "full overlap", using a full window size.
394	* Each intermediate rank increases/decreases load size by a factor 2 :
395	* 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default
396	* default value varies between 6 and 9, depending on strategy */
397
398	/* note : additional experimental parameters are also available
399	* within the experimental section of the API.
400	* At the time of this writing, they include :
401	* ZSTD_c_rsyncable
402	* ZSTD_c_format
403	* ZSTD_c_forceMaxWindow
404	* ZSTD_c_forceAttachDict
405	* ZSTD_c_literalCompressionMode
406	* ZSTD_c_targetCBlockSize
407	* ZSTD_c_srcSizeHint
408	* ZSTD_c_enableDedicatedDictSearch
409	* ZSTD_c_stableInBuffer
410	* ZSTD_c_stableOutBuffer
411	* ZSTD_c_blockDelimiters
412	* ZSTD_c_validateSequences
413	* ZSTD_c_useBlockSplitter
414	* ZSTD_c_useRowMatchFinder
415	* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
416	* note : never ever use experimentalParam? names directly;
417	* also, the enums values themselves are unstable and can still change.
418	*/
419	ZSTD_c_experimentalParam1=500,
420	ZSTD_c_experimentalParam2=10,
421	ZSTD_c_experimentalParam3=1000,
422	ZSTD_c_experimentalParam4=1001,
423	ZSTD_c_experimentalParam5=1002,
424	ZSTD_c_experimentalParam6=1003,
425	ZSTD_c_experimentalParam7=1004,
426	ZSTD_c_experimentalParam8=1005,
427	ZSTD_c_experimentalParam9=1006,
428	ZSTD_c_experimentalParam10=1007,
429	ZSTD_c_experimentalParam11=1008,
430	ZSTD_c_experimentalParam12=1009,
431	ZSTD_c_experimentalParam13=1010,
432	ZSTD_c_experimentalParam14=1011,
433	ZSTD_c_experimentalParam15=1012
434	} ZSTD_cParameter;
435
436	typedef struct {
437	size_t error;
438	int lowerBound;
439	int upperBound;
440	} ZSTD_bounds;
441
442	/*! ZSTD_cParam_getBounds() :
443	* All parameters must belong to an interval with lower and upper bounds,
444	* otherwise they will either trigger an error or be automatically clamped.
445	* @return : a structure, ZSTD_bounds, which contains
446	* - an error status field, which must be tested using ZSTD_isError()
447	* - lower and upper bounds, both inclusive
448	*/
449	ZSTDLIB_API ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
450
451	/*! ZSTD_CCtx_setParameter() :
452	* Set one compression parameter, selected by enum ZSTD_cParameter.
453	* All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
454	* Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
455	* Setting a parameter is generally only possible during frame initialization (before starting compression).
456	* Exception : when using multi-threading mode (nbWorkers >= 1),
457	* the following parameters can be updated _during_ compression (within same frame):
458	* => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
459	* new parameters will be active for next job only (after a flush()).
460	* @return : an error code (which can be tested using ZSTD_isError()).
461	*/
462	ZSTDLIB_API size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
463
464	/*! ZSTD_CCtx_setPledgedSrcSize() :
465	* Total input data size to be compressed as a single frame.
466	* Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
467	* This value will also be controlled at end of frame, and trigger an error if not respected.
468	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
469	* Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
470	* In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
471	* ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
472	* Note 2 : pledgedSrcSize is only valid once, for the next frame.
473	* It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
474	* Note 3 : Whenever all input data is provided and consumed in a single round,
475	* for example with ZSTD_compress2(),
476	* or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
477	* this value is automatically overridden by srcSize instead.
478	*/
479	ZSTDLIB_API size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
480
481	typedef enum {
482	ZSTD_reset_session_only = 1,
483	ZSTD_reset_parameters = 2,
484	ZSTD_reset_session_and_parameters = 3
485	} ZSTD_ResetDirective;
486
487	/*! ZSTD_CCtx_reset() :
488	* There are 2 different things that can be reset, independently or jointly :
489	* - The session : will stop compressing current frame, and make CCtx ready to start a new one.
490	* Useful after an error, or to interrupt any ongoing compression.
491	* Any internal data not yet flushed is cancelled.
492	* Compression parameters and dictionary remain unchanged.
493	* They will be used to compress next frame.
494	* Resetting session never fails.
495	* - The parameters : changes all parameters back to "default".
496	* This removes any reference to any dictionary too.
497	* Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
498	* otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
499	* - Both : similar to resetting the session, followed by resetting parameters.
500	*/
501	ZSTDLIB_API size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
502
503	/*! ZSTD_compress2() :
504	* Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
505	* ZSTD_compress2() always starts a new frame.
506	* Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
507	* - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
508	* - The function is always blocking, returns when compression is completed.
509	* Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
510	* @return : compressed size written into `dst` (<= `dstCapacity),
511	* or an error code if it fails (which can be tested using ZSTD_isError()).
512	*/
513	ZSTDLIB_API size_t ZSTD_compress2( ZSTD_CCtx* cctx,
514	void* dst, size_t dstCapacity,
515	const void* src, size_t srcSize);
516
517
518	/* *********************************************
519	* Advanced decompression API (Requires v1.4.0+)
520	************************************************/
521
522	/* The advanced API pushes parameters one by one into an existing DCtx context.
523	* Parameters are sticky, and remain valid for all following frames
524	* using the same DCtx context.
525	* It's possible to reset parameters to default values using ZSTD_DCtx_reset().
526	* Note : This API is compatible with existing ZSTD_decompressDCtx() and ZSTD_decompressStream().
527	* Therefore, no new decompression function is necessary.
528	*/
529
530	typedef enum {
531
532	ZSTD_d_windowLogMax=100, /* Select a size limit (in power of 2) beyond which
533	* the streaming API will refuse to allocate memory buffer
534	* in order to protect the host from unreasonable memory requirements.
535	* This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
536	* By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
537	* Special: value 0 means "use default maximum windowLog". */
538
539	/* note : additional experimental parameters are also available
540	* within the experimental section of the API.
541	* At the time of this writing, they include :
542	* ZSTD_d_format
543	* ZSTD_d_stableOutBuffer
544	* ZSTD_d_forceIgnoreChecksum
545	* ZSTD_d_refMultipleDDicts
546	* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
547	* note : never ever use experimentalParam? names directly
548	*/
549	ZSTD_d_experimentalParam1=1000,
550	ZSTD_d_experimentalParam2=1001,
551	ZSTD_d_experimentalParam3=1002,
552	ZSTD_d_experimentalParam4=1003
553
554	} ZSTD_dParameter;
555
556	/*! ZSTD_dParam_getBounds() :
557	* All parameters must belong to an interval with lower and upper bounds,
558	* otherwise they will either trigger an error or be automatically clamped.
559	* @return : a structure, ZSTD_bounds, which contains
560	* - an error status field, which must be tested using ZSTD_isError()
561	* - both lower and upper bounds, inclusive
562	*/
563	ZSTDLIB_API ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
564
565	/*! ZSTD_DCtx_setParameter() :
566	* Set one compression parameter, selected by enum ZSTD_dParameter.
567	* All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
568	* Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
569	* Setting a parameter is only possible during frame initialization (before starting decompression).
570	* @return : 0, or an error code (which can be tested using ZSTD_isError()).
571	*/
572	ZSTDLIB_API size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
573
574	/*! ZSTD_DCtx_reset() :
575	* Return a DCtx to clean state.
576	* Session and parameters can be reset jointly or separately.
577	* Parameters can only be reset when no active frame is being decompressed.
578	* @return : 0, or an error code, which can be tested with ZSTD_isError()
579	*/
580	ZSTDLIB_API size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
581
582
583	/* **************************
584	* Streaming
585	****************************/
586
587	typedef struct ZSTD_inBuffer_s {
588	const void* src; /*< start of input buffer */
589	size_t size; /*< size of input buffer */
590	size_t pos; /*< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */
591	} ZSTD_inBuffer;
592
593	typedef struct ZSTD_outBuffer_s {
594	void* dst; /*< start of output buffer */
595	size_t size; /*< size of output buffer */
596	size_t pos; /*< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */
597	} ZSTD_outBuffer;
598
599
600
601	/*-***********************************************************************
602	* Streaming compression - HowTo
603	*
604	* A ZSTD_CStream object is required to track streaming operation.
605	* Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
606	* ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
607	* It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
608	*
609	* For parallel execution, use one separate ZSTD_CStream per thread.
610	*
611	* note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
612	*
613	* Parameters are sticky : when starting a new compression on the same context,
614	* it will re-use the same sticky parameters as previous compression session.
615	* When in doubt, it's recommended to fully initialize the context before usage.
616	* Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
617	* ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
618	* set more specific parameters, the pledged source size, or load a dictionary.
619	*
620	* Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
621	* consume input stream. The function will automatically update both `pos`
622	* fields within `input` and `output`.
623	* Note that the function may not consume the entire input, for example, because
624	* the output buffer is already full, in which case `input.pos < input.size`.
625	* The caller must check if input has been entirely consumed.
626	* If not, the caller must make some room to receive more compressed data,
627	* and then present again remaining input data.
628	* note: ZSTD_e_continue is guaranteed to make some forward progress when called,
629	* but doesn't guarantee maximal forward progress. This is especially relevant
630	* when compressing with multiple threads. The call won't block if it can
631	* consume some input, but if it can't it will wait for some, but not all,
632	* output to be flushed.
633	* @return : provides a minimum amount of data remaining to be flushed from internal buffers
634	* or an error code, which can be tested using ZSTD_isError().
635	*
636	* At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
637	* using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
638	* Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
639	* In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
640	* You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
641	* operation.
642	* note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
643	* block until the flush is complete or the output buffer is full.
644	* @return : 0 if internal buffers are entirely flushed,
645	* >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
646	* or an error code, which can be tested using ZSTD_isError().
647	*
648	* Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
649	* It will perform a flush and write frame epilogue.
650	* The epilogue is required for decoders to consider a frame completed.
651	* flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
652	* You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
653	* start a new frame.
654	* note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
655	* block until the flush is complete or the output buffer is full.
656	* @return : 0 if frame fully completed and fully flushed,
657	* >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
658	* or an error code, which can be tested using ZSTD_isError().
659	*
660	* *******************************************************************/
661
662	typedef ZSTD_CCtx ZSTD_CStream; /*< CCtx and CStream are now effectively same object (>= v1.3.0) */
663	/* Continue to distinguish them for compatibility with older versions <= v1.2.0 */
664	/*===== ZSTD_CStream management functions =====*/
665	ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(void);
666	ZSTDLIB_API size_t ZSTD_freeCStream(ZSTD_CStream* zcs); /* accept NULL pointer */
667
668	/*===== Streaming compression functions =====*/
669	typedef enum {
670	ZSTD_e_continue=0, /* collect more data, encoder decides when to output compressed result, for optimal compression ratio */
671	ZSTD_e_flush=1, /* flush any data provided so far,
672	* it creates (at least) one new block, that can be decoded immediately on reception;
673	* frame will continue: any future data can still reference previously compressed data, improving compression.
674	* note : multithreaded compression will block to flush as much output as possible. */
675	ZSTD_e_end=2 /* flush any remaining data _and_ close current frame.
676	* note that frame is only closed after compressed data is fully flushed (return value == 0).
677	* After that point, any additional data starts a new frame.
678	* note : each frame is independent (does not reference any content from previous frame).
679	: note : multithreaded compression will block to flush as much output as possible. */
680	} ZSTD_EndDirective;
681
682	/*! ZSTD_compressStream2() : Requires v1.4.0+
683	* Behaves about the same as ZSTD_compressStream, with additional control on end directive.
684	* - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
685	* - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
686	* - output->pos must be <= dstCapacity, input->pos must be <= srcSize
687	* - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
688	* - endOp must be a valid directive
689	* - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
690	* - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available,
691	* and then immediately returns, just indicating that there is some data remaining to be flushed.
692	* The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
693	* - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking.
694	* - @return provides a minimum amount of data remaining to be flushed from internal buffers
695	* or an error code, which can be tested using ZSTD_isError().
696	* if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
697	* This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
698	* For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
699	* - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
700	* only ZSTD_e_end or ZSTD_e_flush operations are allowed.
701	* Before starting a new compression job, or changing compression parameters,
702	* it is required to fully flush internal buffers.
703	*/
704	ZSTDLIB_API size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
705	ZSTD_outBuffer* output,
706	ZSTD_inBuffer* input,
707	ZSTD_EndDirective endOp);
708
709
710	/* These buffer sizes are softly recommended.
711	* They are not required : ZSTD_compressStream*() happily accepts any buffer size, for both input and output.
712	* Respecting the recommended size just makes it a bit easier for ZSTD_compressStream*(),
713	* reducing the amount of memory shuffling and buffering, resulting in minor performance savings.
714	*
715	* However, note that these recommendations are from the perspective of a C caller program.
716	* If the streaming interface is invoked from some other language,
717	* especially managed ones such as Java or Go, through a foreign function interface such as jni or cgo,
718	* a major performance rule is to reduce crossing such interface to an absolute minimum.
719	* It's not rare that performance ends being spent more into the interface, rather than compression itself.
720	* In which cases, prefer using large buffers, as large as practical,
721	* for both input and output, to reduce the nb of roundtrips.
722	*/
723	ZSTDLIB_API size_t ZSTD_CStreamInSize(void); /*< recommended size for input buffer */
724	ZSTDLIB_API size_t ZSTD_CStreamOutSize(void); /*< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */
725
726
727	/* *****************************************************************************
728	* This following is a legacy streaming API, available since v1.0+ .
729	* It can be replaced by ZSTD_CCtx_reset() and ZSTD_compressStream2().
730	* It is redundant, but remains fully supported.
731	* Streaming in combination with advanced parameters and dictionary compression
732	* can only be used through the new API.
733	******************************************************************************/
734
735	/*!
736	* Equivalent to:
737	*
738	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
739	* ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
740	* ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
741	*/
742	ZSTDLIB_API size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
743	/*!
744	* Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
745	* NOTE: The return value is different. ZSTD_compressStream() returns a hint for
746	* the next read size (if non-zero and not an error). ZSTD_compressStream2()
747	* returns the minimum nb of bytes left to flush (if non-zero and not an error).
748	*/
749	ZSTDLIB_API size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
750	/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */
751	ZSTDLIB_API size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
752	/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */
753	ZSTDLIB_API size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
754
755
756	/*-***************************************************************************
757	* Streaming decompression - HowTo
758	*
759	* A ZSTD_DStream object is required to track streaming operations.
760	* Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
761	* ZSTD_DStream objects can be re-used multiple times.
762	*
763	* Use ZSTD_initDStream() to start a new decompression operation.
764	* @return : recommended first input size
765	* Alternatively, use advanced API to set specific properties.
766	*
767	* Use ZSTD_decompressStream() repetitively to consume your input.
768	* The function will update both `pos` fields.
769	* If `input.pos < input.size`, some input has not been consumed.
770	* It's up to the caller to present again remaining data.
771	* The function tries to flush all data decoded immediately, respecting output buffer size.
772	* If `output.pos < output.size`, decoder has flushed everything it could.
773	* But if `output.pos == output.size`, there might be some data left within internal buffers.,
774	* In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
775	* Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
776	* @return : 0 when a frame is completely decoded and fully flushed,
777	* or an error code, which can be tested using ZSTD_isError(),
778	* or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
779	* the return value is a suggested next input size (just a hint for better latency)
780	* that will never request more than the remaining frame size.
781	* *******************************************************************************/
782
783	typedef ZSTD_DCtx ZSTD_DStream; /*< DCtx and DStream are now effectively same object (>= v1.3.0) */
784	/* For compatibility with versions <= v1.2.0, prefer differentiating them. */
785	/*===== ZSTD_DStream management functions =====*/
786	ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(void);
787	ZSTDLIB_API size_t ZSTD_freeDStream(ZSTD_DStream* zds); /* accept NULL pointer */
788
789	/*===== Streaming decompression functions =====*/
790
791	/* This function is redundant with the advanced API and equivalent to:
792	*
793	* ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
794	* ZSTD_DCtx_refDDict(zds, NULL);
795	*/
796	ZSTDLIB_API size_t ZSTD_initDStream(ZSTD_DStream* zds);
797
798	ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
799
800	ZSTDLIB_API size_t ZSTD_DStreamInSize(void); /*!< recommended size for input buffer */
801	ZSTDLIB_API size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */
802
803
804	/* ************************
805	* Simple dictionary API
806	***************************/
807	/*! ZSTD_compress_usingDict() :
808	* Compression at an explicit compression level using a Dictionary.
809	* A dictionary can be any arbitrary data segment (also called a prefix),
810	* or a buffer with specified information (see zdict.h).
811	* Note : This function loads the dictionary, resulting in significant startup delay.
812	* It's intended for a dictionary used only once.
813	* Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. */
814	ZSTDLIB_API size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
815	void* dst, size_t dstCapacity,
816	const void* src, size_t srcSize,
817	const void* dict,size_t dictSize,
818	int compressionLevel);
819
820	/*! ZSTD_decompress_usingDict() :
821	* Decompression using a known Dictionary.
822	* Dictionary must be identical to the one used during compression.
823	* Note : This function loads the dictionary, resulting in significant startup delay.
824	* It's intended for a dictionary used only once.
825	* Note : When `dict == NULL || dictSize < 8` no dictionary is used. */
826	ZSTDLIB_API size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
827	void* dst, size_t dstCapacity,
828	const void* src, size_t srcSize,
829	const void* dict,size_t dictSize);
830
831
832	/* *********************************
833	* Bulk processing dictionary API
834	**********************************/
835	typedef struct ZSTD_CDict_s ZSTD_CDict;
836
837	/*! ZSTD_createCDict() :
838	* When compressing multiple messages or blocks using the same dictionary,
839	* it's recommended to digest the dictionary only once, since it's a costly operation.
840	* ZSTD_createCDict() will create a state from digesting a dictionary.
841	* The resulting state can be used for future compression operations with very limited startup cost.
842	* ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
843	* @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
844	* Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
845	* Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
846	* in which case the only thing that it transports is the @compressionLevel.
847	* This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
848	* expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. */
849	ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
850	int compressionLevel);
851
852	/*! ZSTD_freeCDict() :
853	* Function frees memory allocated by ZSTD_createCDict().
854	* If a NULL pointer is passed, no operation is performed. */
855	ZSTDLIB_API size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
856
857	/*! ZSTD_compress_usingCDict() :
858	* Compression using a digested Dictionary.
859	* Recommended when same dictionary is used multiple times.
860	* Note : compression level is _decided at dictionary creation time_,
861	* and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) */
862	ZSTDLIB_API size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
863	void* dst, size_t dstCapacity,
864	const void* src, size_t srcSize,
865	const ZSTD_CDict* cdict);
866
867
868	typedef struct ZSTD_DDict_s ZSTD_DDict;
869
870	/*! ZSTD_createDDict() :
871	* Create a digested dictionary, ready to start decompression operation without startup delay.
872	* dictBuffer can be released after DDict creation, as its content is copied inside DDict. */
873	ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
874
875	/*! ZSTD_freeDDict() :
876	* Function frees memory allocated with ZSTD_createDDict()
877	* If a NULL pointer is passed, no operation is performed. */
878	ZSTDLIB_API size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
879
880	/*! ZSTD_decompress_usingDDict() :
881	* Decompression using a digested Dictionary.
882	* Recommended when same dictionary is used multiple times. */
883	ZSTDLIB_API size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
884	void* dst, size_t dstCapacity,
885	const void* src, size_t srcSize,
886	const ZSTD_DDict* ddict);
887
888
889	/* ******************************
890	* Dictionary helper functions
891	*******************************/
892
893	/*! ZSTD_getDictID_fromDict() : Requires v1.4.0+
894	* Provides the dictID stored within dictionary.
895	* if @return == 0, the dictionary is not conformant with Zstandard specification.
896	* It can still be loaded, but as a content-only dictionary. */
897	ZSTDLIB_API unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
898
899	/*! ZSTD_getDictID_fromCDict() : Requires v1.5.0+
900	* Provides the dictID of the dictionary loaded into `cdict`.
901	* If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
902	* Non-conformant dictionaries can still be loaded, but as content-only dictionaries. */
903	ZSTDLIB_API unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
904
905	/*! ZSTD_getDictID_fromDDict() : Requires v1.4.0+
906	* Provides the dictID of the dictionary loaded into `ddict`.
907	* If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
908	* Non-conformant dictionaries can still be loaded, but as content-only dictionaries. */
909	ZSTDLIB_API unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
910
911	/*! ZSTD_getDictID_fromFrame() : Requires v1.4.0+
912	* Provides the dictID required to decompressed the frame stored within `src`.
913	* If @return == 0, the dictID could not be decoded.
914	* This could for one of the following reasons :
915	* - The frame does not require a dictionary to be decoded (most common case).
916	* - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
917	* Note : this use case also happens when using a non-conformant dictionary.
918	* - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
919	* - This is not a Zstandard frame.
920	* When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. */
921	ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
922
923
924	/* *****************************************************************************
925	* Advanced dictionary and prefix API (Requires v1.4.0+)
926	*
927	* This API allows dictionaries to be used with ZSTD_compress2(),
928	* ZSTD_compressStream2(), and ZSTD_decompressDCtx(). Dictionaries are sticky, and
929	* only reset with the context is reset with ZSTD_reset_parameters or
930	* ZSTD_reset_session_and_parameters. Prefixes are single-use.
931	******************************************************************************/
932
933
934	/*! ZSTD_CCtx_loadDictionary() : Requires v1.4.0+
935	* Create an internal CDict from `dict` buffer.
936	* Decompression will have to use same dictionary.
937	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
938	* Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
939	* meaning "return to no-dictionary mode".
940	* Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
941	* To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters).
942	* Note 2 : Loading a dictionary involves building tables.
943	* It's also a CPU consuming operation, with non-negligible impact on latency.
944	* Tables are dependent on compression parameters, and for this reason,
945	* compression parameters can no longer be changed after loading a dictionary.
946	* Note 3 :`dict` content will be copied internally.
947	* Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
948	* In such a case, dictionary buffer must outlive its users.
949	* Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
950	* to precisely select how dictionary content must be interpreted. */
951	ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
952
953	/*! ZSTD_CCtx_refCDict() : Requires v1.4.0+
954	* Reference a prepared dictionary, to be used for all next compressed frames.
955	* Note that compression parameters are enforced from within CDict,
956	* and supersede any compression parameter previously set within CCtx.
957	* The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
958	* The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
959	* The dictionary will remain valid for future compressed frames using same CCtx.
960	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
961	* Special : Referencing a NULL CDict means "return to no-dictionary mode".
962	* Note 1 : Currently, only one dictionary can be managed.
963	* Referencing a new dictionary effectively "discards" any previous one.
964	* Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. */
965	ZSTDLIB_API size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
966
967	/*! ZSTD_CCtx_refPrefix() : Requires v1.4.0+
968	* Reference a prefix (single-usage dictionary) for next compressed frame.
969	* A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
970	* Decompression will need same prefix to properly regenerate data.
971	* Compressing with a prefix is similar in outcome as performing a diff and compressing it,
972	* but performs much faster, especially during decompression (compression speed is tunable with compression level).
973	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
974	* Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
975	* Note 1 : Prefix buffer is referenced. It **must** outlive compression.
976	* Its content must remain unmodified during compression.
977	* Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
978	* ensure that the window size is large enough to contain the entire source.
979	* See ZSTD_c_windowLog.
980	* Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
981	* It's a CPU consuming operation, with non-negligible impact on latency.
982	* If there is a need to use the same prefix multiple times, consider loadDictionary instead.
983	* Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
984	* Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. */
985	ZSTDLIB_API size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
986	const void* prefix, size_t prefixSize);
987
988	/*! ZSTD_DCtx_loadDictionary() : Requires v1.4.0+
989	* Create an internal DDict from dict buffer,
990	* to be used to decompress next frames.
991	* The dictionary remains valid for all future frames, until explicitly invalidated.
992	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
993	* Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
994	* meaning "return to no-dictionary mode".
995	* Note 1 : Loading a dictionary involves building tables,
996	* which has a non-negligible impact on CPU usage and latency.
997	* It's recommended to "load once, use many times", to amortize the cost
998	* Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
999	* Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
1000	* Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
1001	* how dictionary content is loaded and interpreted.
1002	*/
1003	ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1004
1005	/*! ZSTD_DCtx_refDDict() : Requires v1.4.0+
1006	* Reference a prepared dictionary, to be used to decompress next frames.
1007	* The dictionary remains active for decompression of future frames using same DCtx.
1008	*
1009	* If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
1010	* will store the DDict references in a table, and the DDict used for decompression
1011	* will be determined at decompression time, as per the dict ID in the frame.
1012	* The memory for the table is allocated on the first call to refDDict, and can be
1013	* freed with ZSTD_freeDCtx().
1014	*
1015	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
1016	* Note 1 : Currently, only one dictionary can be managed.
1017	* Referencing a new dictionary effectively "discards" any previous one.
1018	* Special: referencing a NULL DDict means "return to no-dictionary mode".
1019	* Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
1020	*/
1021	ZSTDLIB_API size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
1022
1023	/*! ZSTD_DCtx_refPrefix() : Requires v1.4.0+
1024	* Reference a prefix (single-usage dictionary) to decompress next frame.
1025	* This is the reverse operation of ZSTD_CCtx_refPrefix(),
1026	* and must use the same prefix as the one used during compression.
1027	* Prefix is **only used once**. Reference is discarded at end of frame.
1028	* End of frame is reached when ZSTD_decompressStream() returns 0.
1029	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
1030	* Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
1031	* Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
1032	* Prefix buffer must remain unmodified up to the end of frame,
1033	* reached when ZSTD_decompressStream() returns 0.
1034	* Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
1035	* Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
1036	* Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
1037	* A full dictionary is more costly, as it requires building tables.
1038	*/
1039	ZSTDLIB_API size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
1040	const void* prefix, size_t prefixSize);
1041
1042	/* === Memory management === */
1043
1044	/*! ZSTD_sizeof_*() : Requires v1.4.0+
1045	* These functions give the _current_ memory usage of selected object.
1046	* Note that object memory usage can evolve (increase or decrease) over time. */
1047	ZSTDLIB_API size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
1048	ZSTDLIB_API size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
1049	ZSTDLIB_API size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
1050	ZSTDLIB_API size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
1051	ZSTDLIB_API size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
1052	ZSTDLIB_API size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
1053
1054	#endif /* ZSTD_H_235446 */
1055
1056
1057	/* **************************************************************************************
1058	* ADVANCED AND EXPERIMENTAL FUNCTIONS
1059	****************************************************************************************
1060	* The definitions in the following section are considered experimental.
1061	* They are provided for advanced scenarios.
1062	* They should never be used with a dynamic library, as prototypes may change in the future.
1063	* Use them only in association with static linking.
1064	* ***************************************************************************************/
1065
1066	#if !defined(ZSTD_H_ZSTD_STATIC_LINKING_ONLY)
1067	#define ZSTD_H_ZSTD_STATIC_LINKING_ONLY
1068
1069	/* This can be overridden externally to hide static symbols. */
1070	#ifndef ZSTDLIB_STATIC_API
1071	#define ZSTDLIB_STATIC_API ZSTDLIB_VISIBLE
1072	#endif
1073
1074	/* Deprecation warnings :
1075	* Should these warnings be a problem, it is generally possible to disable them,
1076	* typically with -Wno-deprecated-declarations for gcc or _CRT_SECURE_NO_WARNINGS in Visual.
1077	* Otherwise, it's also possible to define ZSTD_DISABLE_DEPRECATE_WARNINGS.
1078	*/
1079	#ifdef ZSTD_DISABLE_DEPRECATE_WARNINGS
1080	# define ZSTD_DEPRECATED(message) ZSTDLIB_STATIC_API /* disable deprecation warnings */
1081	#else
1082	# if (defined(GNUC) && (GNUC > 4 || (GNUC == 4 && GNUC_MINOR >= 5))) || defined(__clang__)
1083	# define ZSTD_DEPRECATED(message) ZSTDLIB_STATIC_API __attribute__((deprecated(message)))
1084	# elif (__GNUC__ >= 3)
1085	# define ZSTD_DEPRECATED(message) ZSTDLIB_STATIC_API __attribute__((deprecated))
1086	# else
1087	# pragma message("WARNING: You need to implement ZSTD_DEPRECATED for this compiler")
1088	# define ZSTD_DEPRECATED(message) ZSTDLIB_STATIC_API
1089	# endif
1090	#endif /* ZSTD_DISABLE_DEPRECATE_WARNINGS */
1091
1092	/* **************************************************************************************
1093	* experimental API (static linking only)
1094	****************************************************************************************
1095	* The following symbols and constants
1096	* are not planned to join "stable API" status in the near future.
1097	* They can still change in future versions.
1098	* Some of them are planned to remain in the static_only section indefinitely.
1099	* Some of them might be removed in the future (especially when redundant with existing stable functions)
1100	* ***************************************************************************************/
1101
1102	#define ZSTD_FRAMEHEADERSIZE_PREFIX(format) ((format) == ZSTD_f_zstd1 ? 5 : 1) /* minimum input size required to query frame header size */
1103	#define ZSTD_FRAMEHEADERSIZE_MIN(format) ((format) == ZSTD_f_zstd1 ? 6 : 2)
1104	#define ZSTD_FRAMEHEADERSIZE_MAX 18 /* can be useful for static allocation */
1105	#define ZSTD_SKIPPABLEHEADERSIZE 8
1106
1107	/* compression parameter bounds */
1108	#define ZSTD_WINDOWLOG_MAX_32 30
1109	#define ZSTD_WINDOWLOG_MAX_64 31
1110	#define ZSTD_WINDOWLOG_MAX ((int)(sizeof(size_t) == 4 ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
1111	#define ZSTD_WINDOWLOG_MIN 10
1112	#define ZSTD_HASHLOG_MAX ((ZSTD_WINDOWLOG_MAX < 30) ? ZSTD_WINDOWLOG_MAX : 30)
1113	#define ZSTD_HASHLOG_MIN 6
1114	#define ZSTD_CHAINLOG_MAX_32 29
1115	#define ZSTD_CHAINLOG_MAX_64 30
1116	#define ZSTD_CHAINLOG_MAX ((int)(sizeof(size_t) == 4 ? ZSTD_CHAINLOG_MAX_32 : ZSTD_CHAINLOG_MAX_64))
1117	#define ZSTD_CHAINLOG_MIN ZSTD_HASHLOG_MIN
1118	#define ZSTD_SEARCHLOG_MAX (ZSTD_WINDOWLOG_MAX-1)
1119	#define ZSTD_SEARCHLOG_MIN 1
1120	#define ZSTD_MINMATCH_MAX 7 /* only for ZSTD_fast, other strategies are limited to 6 */
1121	#define ZSTD_MINMATCH_MIN 3 /* only for ZSTD_btopt+, faster strategies are limited to 4 */
1122	#define ZSTD_TARGETLENGTH_MAX ZSTD_BLOCKSIZE_MAX
1123	#define ZSTD_TARGETLENGTH_MIN 0 /* note : comparing this constant to an unsigned results in a tautological test */
1124	#define ZSTD_STRATEGY_MIN ZSTD_fast
1125	#define ZSTD_STRATEGY_MAX ZSTD_btultra2
1126
1127
1128	#define ZSTD_OVERLAPLOG_MIN 0
1129	#define ZSTD_OVERLAPLOG_MAX 9
1130
1131	#define ZSTD_WINDOWLOG_LIMIT_DEFAULT 27 /* by default, the streaming decoder will refuse any frame
1132	* requiring larger than (1<<ZSTD_WINDOWLOG_LIMIT_DEFAULT) window size,
1133	* to preserve host's memory from unreasonable requirements.
1134	* This limit can be overridden using ZSTD_DCtx_setParameter(,ZSTD_d_windowLogMax,).
1135	* The limit does not apply for one-pass decoders (such as ZSTD_decompress()), since no additional memory is allocated */
1136
1137
1138	/* LDM parameter bounds */
1139	#define ZSTD_LDM_HASHLOG_MIN ZSTD_HASHLOG_MIN
1140	#define ZSTD_LDM_HASHLOG_MAX ZSTD_HASHLOG_MAX
1141	#define ZSTD_LDM_MINMATCH_MIN 4
1142	#define ZSTD_LDM_MINMATCH_MAX 4096
1143	#define ZSTD_LDM_BUCKETSIZELOG_MIN 1
1144	#define ZSTD_LDM_BUCKETSIZELOG_MAX 8
1145	#define ZSTD_LDM_HASHRATELOG_MIN 0
1146	#define ZSTD_LDM_HASHRATELOG_MAX (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN)
1147
1148	/* Advanced parameter bounds */
1149	#define ZSTD_TARGETCBLOCKSIZE_MIN 64
1150	#define ZSTD_TARGETCBLOCKSIZE_MAX ZSTD_BLOCKSIZE_MAX
1151	#define ZSTD_SRCSIZEHINT_MIN 0
1152	#define ZSTD_SRCSIZEHINT_MAX INT_MAX
1153
1154
1155	/* --- Advanced types --- */
1156
1157	typedef struct ZSTD_CCtx_params_s ZSTD_CCtx_params;
1158
1159	typedef struct {
1160	unsigned int offset; /* The offset of the match. (NOT the same as the offset code)
1161	* If offset == 0 and matchLength == 0, this sequence represents the last
1162	* literals in the block of litLength size.
1163	*/
1164
1165	unsigned int litLength; /* Literal length of the sequence. */
1166	unsigned int matchLength; /* Match length of the sequence. */
1167
1168	/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.
1169	* In this case, we will treat the sequence as a marker for a block boundary.
1170	*/
1171
1172	unsigned int rep; /* Represents which repeat offset is represented by the field 'offset'.
1173	* Ranges from [0, 3].
1174	*
1175	* Repeat offsets are essentially previous offsets from previous sequences sorted in
1176	* recency order. For more detail, see doc/zstd_compression_format.md
1177	*
1178	* If rep == 0, then 'offset' does not contain a repeat offset.
1179	* If rep > 0:
1180	* If litLength != 0:
1181	* rep == 1 --> offset == repeat_offset_1
1182	* rep == 2 --> offset == repeat_offset_2
1183	* rep == 3 --> offset == repeat_offset_3
1184	* If litLength == 0:
1185	* rep == 1 --> offset == repeat_offset_2
1186	* rep == 2 --> offset == repeat_offset_3
1187	* rep == 3 --> offset == repeat_offset_1 - 1
1188	*
1189	* Note: This field is optional. ZSTD_generateSequences() will calculate the value of
1190	* 'rep', but repeat offsets do not necessarily need to be calculated from an external
1191	* sequence provider's perspective. For example, ZSTD_compressSequences() does not
1192	* use this 'rep' field at all (as of now).
1193	*/
1194	} ZSTD_Sequence;
1195
1196	typedef struct {
1197	unsigned windowLog; /*< largest match distance : larger == more compression, more memory needed during decompression */
1198	unsigned chainLog; /*< fully searched segment : larger == more compression, slower, more memory (useless for fast) */
1199	unsigned hashLog; /*< dispatch table : larger == faster, more memory */
1200	unsigned searchLog; /*< nb of searches : larger == more compression, slower */
1201	unsigned minMatch; /*< match length searched : larger == faster decompression, sometimes less compression */
1202	unsigned targetLength; /*< acceptable match size for optimal parser (only) : larger == more compression, slower */
1203	ZSTD_strategy strategy; /*< see ZSTD_strategy definition above */
1204	} ZSTD_compressionParameters;
1205
1206	typedef struct {
1207	int contentSizeFlag; /*< 1: content size will be in frame header (when known) */
1208	int checksumFlag; /*< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */
1209	int noDictIDFlag; /*< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */
1210	} ZSTD_frameParameters;
1211
1212	typedef struct {
1213	ZSTD_compressionParameters cParams;
1214	ZSTD_frameParameters fParams;
1215	} ZSTD_parameters;
1216
1217	typedef enum {
1218	ZSTD_dct_auto = 0, /* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */
1219	ZSTD_dct_rawContent = 1, /* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */
1220	ZSTD_dct_fullDict = 2 /* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */
1221	} ZSTD_dictContentType_e;
1222
1223	typedef enum {
1224	ZSTD_dlm_byCopy = 0, /*< Copy dictionary content internally */
1225	ZSTD_dlm_byRef = 1 /*< Reference dictionary content -- the dictionary buffer must outlive its users. */
1226	} ZSTD_dictLoadMethod_e;
1227
1228	typedef enum {
1229	ZSTD_f_zstd1 = 0, /* zstd frame format, specified in zstd_compression_format.md (default) */
1230	ZSTD_f_zstd1_magicless = 1 /* Variant of zstd frame format, without initial 4-bytes magic number.
1231	* Useful to save 4 bytes per generated frame.
1232	* Decoder cannot recognise automatically this format, requiring this instruction. */
1233	} ZSTD_format_e;
1234
1235	typedef enum {
1236	/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */
1237	ZSTD_d_validateChecksum = 0,
1238	ZSTD_d_ignoreChecksum = 1
1239	} ZSTD_forceIgnoreChecksum_e;
1240
1241	typedef enum {
1242	/* Note: this enum controls ZSTD_d_refMultipleDDicts */
1243	ZSTD_rmd_refSingleDDict = 0,
1244	ZSTD_rmd_refMultipleDDicts = 1
1245	} ZSTD_refMultipleDDicts_e;
1246
1247	typedef enum {
1248	/* Note: this enum and the behavior it controls are effectively internal
1249	* implementation details of the compressor. They are expected to continue
1250	* to evolve and should be considered only in the context of extremely
1251	* advanced performance tuning.
1252	*
1253	* Zstd currently supports the use of a CDict in three ways:
1254	*
1255	* - The contents of the CDict can be copied into the working context. This
1256	* means that the compression can search both the dictionary and input
1257	* while operating on a single set of internal tables. This makes
1258	* the compression faster per-byte of input. However, the initial copy of
1259	* the CDict's tables incurs a fixed cost at the beginning of the
1260	* compression. For small compressions (< 8 KB), that copy can dominate
1261	* the cost of the compression.
1262	*
1263	* - The CDict's tables can be used in-place. In this model, compression is
1264	* slower per input byte, because the compressor has to search two sets of
1265	* tables. However, this model incurs no start-up cost (as long as the
1266	* working context's tables can be reused). For small inputs, this can be
1267	* faster than copying the CDict's tables.
1268	*
1269	* - The CDict's tables are not used at all, and instead we use the working
1270	* context alone to reload the dictionary and use params based on the source
1271	* size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
1272	* This method is effective when the dictionary sizes are very small relative
1273	* to the input size, and the input size is fairly large to begin with.
1274	*
1275	* Zstd has a simple internal heuristic that selects which strategy to use
1276	* at the beginning of a compression. However, if experimentation shows that
1277	* Zstd is making poor choices, it is possible to override that choice with
1278	* this enum.
1279	*/
1280	ZSTD_dictDefaultAttach = 0, /* Use the default heuristic. */
1281	ZSTD_dictForceAttach = 1, /* Never copy the dictionary. */
1282	ZSTD_dictForceCopy = 2, /* Always copy the dictionary. */
1283	ZSTD_dictForceLoad = 3 /* Always reload the dictionary */
1284	} ZSTD_dictAttachPref_e;
1285
1286	typedef enum {
1287	ZSTD_lcm_auto = 0, /*< Automatically determine the compression mode based on the compression level.
1288	* Negative compression levels will be uncompressed, and positive compression
1289	* levels will be compressed. */
1290	ZSTD_lcm_huffman = 1, /*< Always attempt Huffman compression. Uncompressed literals will still be
1291	* emitted if Huffman compression is not profitable. */
1292	ZSTD_lcm_uncompressed = 2 /*< Always emit uncompressed literals. */
1293	} ZSTD_literalCompressionMode_e;
1294
1295	typedef enum {
1296	/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final
1297	* decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable
1298	* or ZSTD_ps_disable allow for a force enable/disable the feature.
1299	*/
1300	ZSTD_ps_auto = 0, /* Let the library automatically determine whether the feature shall be enabled */
1301	ZSTD_ps_enable = 1, /* Force-enable the feature */
1302	ZSTD_ps_disable = 2 /* Do not use the feature */
1303	} ZSTD_paramSwitch_e;
1304
1305	/* *************************************
1306	* Frame size functions
1307	***************************************/
1308
1309	/*! ZSTD_findDecompressedSize() :
1310	* `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1311	* `srcSize` must be the _exact_ size of this series
1312	* (i.e. there should be a frame boundary at `src + srcSize`)
1313	* @return : - decompressed size of all data in all successive frames
1314	* - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1315	* - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1316	*
1317	* note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1318	* When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1319	* In which case, it's necessary to use streaming mode to decompress data.
1320	* note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1321	* note 3 : decompressed size can be very large (64-bits value),
1322	* potentially larger than what local system can handle as a single memory segment.
1323	* In which case, it's necessary to use streaming mode to decompress data.
1324	* note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1325	* Always ensure result fits within application's authorized limits.
1326	* Each application can set its own limits.
1327	* note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1328	* read each contained frame header. This is fast as most of the data is skipped,
1329	* however it does mean that all frame data must be present and valid. */
1330	ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1331
1332	/*! ZSTD_decompressBound() :
1333	* `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1334	* `srcSize` must be the _exact_ size of this series
1335	* (i.e. there should be a frame boundary at `src + srcSize`)
1336	* @return : - upper-bound for the decompressed size of all data in all successive frames
1337	* - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1338	*
1339	* note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame.
1340	* note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
1341	* in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
1342	* note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
1343	* upper-bound = # blocks * min(128 KB, Window_Size)
1344	*/
1345	ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
1346
1347	/*! ZSTD_frameHeaderSize() :
1348	* srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1349	* @return : size of the Frame Header,
1350	* or an error code (if srcSize is too small) */
1351	ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1352
1353	typedef enum {
1354	ZSTD_sf_noBlockDelimiters = 0, /* Representation of ZSTD_Sequence has no block delimiters, sequences only */
1355	ZSTD_sf_explicitBlockDelimiters = 1 /* Representation of ZSTD_Sequence contains explicit block delimiters */
1356	} ZSTD_sequenceFormat_e;
1357
1358	/*! ZSTD_generateSequences() :
1359	* Generate sequences using ZSTD_compress2, given a source buffer.
1360	*
1361	* Each block will end with a dummy sequence
1362	* with offset == 0, matchLength == 0, and litLength == length of last literals.
1363	* litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
1364	* simply acts as a block delimiter.
1365	*
1366	* zc can be used to insert custom compression params.
1367	* This function invokes ZSTD_compress2
1368	*
1369	* The output of this function can be fed into ZSTD_compressSequences() with CCtx
1370	* setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
1371	* @return : number of sequences generated
1372	*/
1373
1374	ZSTDLIB_STATIC_API size_t ZSTD_generateSequences(ZSTD_CCtx* zc, ZSTD_Sequence* outSeqs,
1375	size_t outSeqsSize, const void* src, size_t srcSize);
1376
1377	/*! ZSTD_mergeBlockDelimiters() :
1378	* Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
1379	* by merging them into the literals of the next sequence.
1380	*
1381	* As such, the final generated result has no explicit representation of block boundaries,
1382	* and the final last literals segment is not represented in the sequences.
1383	*
1384	* The output of this function can be fed into ZSTD_compressSequences() with CCtx
1385	* setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
1386	* @return : number of sequences left after merging
1387	*/
1388	ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
1389
1390	/*! ZSTD_compressSequences() :
1391	* Compress an array of ZSTD_Sequence, generated from the original source buffer, into dst.
1392	* If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
1393	* The entire source is compressed into a single frame.
1394	*
1395	* The compression behavior changes based on cctx params. In particular:
1396	* If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1397	* no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
1398	* the block size derived from the cctx, and sequences may be split. This is the default setting.
1399	*
1400	* If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1401	* block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
1402	*
1403	* If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
1404	* behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
1405	* specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
1406	*
1407	* In addition to the two adjustable experimental params, there are other important cctx params.
1408	* - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN.
1409	* - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
1410	* - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
1411	* is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
1412	*
1413	* Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
1414	* Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
1415	* and cannot emit an RLE block that disagrees with the repcode history
1416	* @return : final compressed size or a ZSTD error.
1417	*/
1418	ZSTDLIB_STATIC_API size_t ZSTD_compressSequences(ZSTD_CCtx* const cctx, void* dst, size_t dstSize,
1419	const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
1420	const void* src, size_t srcSize);
1421
1422
1423	/*! ZSTD_writeSkippableFrame() :
1424	* Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
1425	*
1426	* Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number,
1427	* ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
1428	* As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
1429	* the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
1430	*
1431	* Returns an error if destination buffer is not large enough, if the source size is not representable
1432	* with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
1433	*
1434	* @return : number of bytes written or a ZSTD error.
1435	*/
1436	ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
1437	const void* src, size_t srcSize, unsigned magicVariant);
1438
1439	/*! ZSTD_readSkippableFrame() :
1440	* Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer.
1441	*
1442	* The parameter magicVariant will receive the magicVariant that was supplied when the frame was written,
1443	* i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested
1444	* in the magicVariant.
1445	*
1446	* Returns an error if destination buffer is not large enough, or if the frame is not skippable.
1447	*
1448	* @return : number of bytes written or a ZSTD error.
1449	*/
1450	ZSTDLIB_API size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant,
1451	const void* src, size_t srcSize);
1452
1453	/*! ZSTD_isSkippableFrame() :
1454	* Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame.
1455	*/
1456	ZSTDLIB_API unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size);
1457
1458
1459
1460	/* *************************************
1461	* Memory management
1462	***************************************/
1463
1464	/*! ZSTD_estimate*() :
1465	* These functions make it possible to estimate memory usage
1466	* of a future {D,C}Ctx, before its creation.
1467	*
1468	* ZSTD_estimateCCtxSize() will provide a memory budget large enough
1469	* for any compression level up to selected one.
1470	* Note : Unlike ZSTD_estimateCStreamSize*(), this estimate
1471	* does not include space for a window buffer.
1472	* Therefore, the estimation is only guaranteed for single-shot compressions, not streaming.
1473	* The estimate will assume the input may be arbitrarily large,
1474	* which is the worst case.
1475	*
1476	* When srcSize can be bound by a known and rather "small" value,
1477	* this fact can be used to provide a tighter estimation
1478	* because the CCtx compression context will need less memory.
1479	* This tighter estimation can be provided by more advanced functions
1480	* ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
1481	* and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
1482	* Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
1483	*
1484	* Note 2 : only single-threaded compression is supported.
1485	* ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1486	*/
1487	ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
1488	ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1489	ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1490	ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void);
1491
1492	/*! ZSTD_estimateCStreamSize() :
1493	* ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
1494	* It will also consider src size to be arbitrarily "large", which is worst case.
1495	* If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1496	* ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1497	* ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
1498	* Note : CStream size estimation is only correct for single-threaded compression.
1499	* ZSTD_DStream memory budget depends on window Size.
1500	* This information can be passed manually, using ZSTD_estimateDStreamSize,
1501	* or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
1502	* Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1503	* an internal ?Dict will be created, which additional size is not estimated here.
1504	* In this case, get total size by adding ZSTD_estimate?DictSize */
1505	ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
1506	ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1507	ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1508	ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t windowSize);
1509	ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
1510
1511	/*! ZSTD_estimate?DictSize() :
1512	* ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1513	* ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1514	* Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1515	*/
1516	ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1517	ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1518	ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1519
1520	/*! ZSTD_initStatic*() :
1521	* Initialize an object using a pre-allocated fixed-size buffer.
1522	* workspace: The memory area to emplace the object into.
1523	* Provided pointer *must be 8-bytes aligned*.
1524	* Buffer must outlive object.
1525	* workspaceSize: Use ZSTD_estimate*Size() to determine
1526	* how large workspace must be to support target scenario.
1527	* @return : pointer to object (same address as workspace, just different type),
1528	* or NULL if error (size too small, incorrect alignment, etc.)
1529	* Note : zstd will never resize nor malloc() when using a static buffer.
1530	* If the object requires more memory than available,
1531	* zstd will just error out (typically ZSTD_error_memory_allocation).
1532	* Note 2 : there is no corresponding "free" function.
1533	* Since workspace is allocated externally, it must be freed externally too.
1534	* Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1535	* into its associated cParams.
1536	* Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1537	* ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1538	* Limitation 2 : static cctx currently not compatible with multi-threading.
1539	* Limitation 3 : static dctx is incompatible with legacy support.
1540	*/
1541	ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1542	ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); /*< same as ZSTD_initStaticCCtx() */
1543
1544	ZSTDLIB_STATIC_API ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize);
1545	ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); /*< same as ZSTD_initStaticDCtx() */
1546
1547	ZSTDLIB_STATIC_API const ZSTD_CDict* ZSTD_initStaticCDict(
1548	void* workspace, size_t workspaceSize,
1549	const void* dict, size_t dictSize,
1550	ZSTD_dictLoadMethod_e dictLoadMethod,
1551	ZSTD_dictContentType_e dictContentType,
1552	ZSTD_compressionParameters cParams);
1553
1554	ZSTDLIB_STATIC_API const ZSTD_DDict* ZSTD_initStaticDDict(
1555	void* workspace, size_t workspaceSize,
1556	const void* dict, size_t dictSize,
1557	ZSTD_dictLoadMethod_e dictLoadMethod,
1558	ZSTD_dictContentType_e dictContentType);
1559
1560
1561	/*! Custom memory allocation :
1562	* These prototypes make it possible to pass your own allocation/free functions.
1563	* ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1564	* All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1565	*/
1566	typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1567	typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
1568	typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1569	static
1570	__attribute__((__unused__))
1571	ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; /*< this constant defers to stdlib's functions */
1572
1573	ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
1574	ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
1575	ZSTDLIB_STATIC_API ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
1576	ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
1577
1578	ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
1579	ZSTD_dictLoadMethod_e dictLoadMethod,
1580	ZSTD_dictContentType_e dictContentType,
1581	ZSTD_compressionParameters cParams,
1582	ZSTD_customMem customMem);
1583
1584	/*! Thread pool :
1585	* These prototypes make it possible to share a thread pool among multiple compression contexts.
1586	* This can limit resources for applications with multiple threads where each one uses
1587	* a threaded compression mode (via ZSTD_c_nbWorkers parameter).
1588	* ZSTD_createThreadPool creates a new thread pool with a given number of threads.
1589	* Note that the lifetime of such pool must exist while being used.
1590	* ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value
1591	* to use an internal thread pool).
1592	* ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer.
1593	*/
1594	typedef struct POOL_ctx_s ZSTD_threadPool;
1595	ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads);
1596	ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); /* accept NULL pointer */
1597	ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool);
1598
1599
1600	/*
1601	* This API is temporary and is expected to change or disappear in the future!
1602	*/
1603	ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_advanced2(
1604	const void* dict, size_t dictSize,
1605	ZSTD_dictLoadMethod_e dictLoadMethod,
1606	ZSTD_dictContentType_e dictContentType,
1607	const ZSTD_CCtx_params* cctxParams,
1608	ZSTD_customMem customMem);
1609
1610	ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_advanced(
1611	const void* dict, size_t dictSize,
1612	ZSTD_dictLoadMethod_e dictLoadMethod,
1613	ZSTD_dictContentType_e dictContentType,
1614	ZSTD_customMem customMem);
1615
1616
1617	/* *************************************
1618	* Advanced compression functions
1619	***************************************/
1620
1621	/*! ZSTD_createCDict_byReference() :
1622	* Create a digested dictionary for compression
1623	* Dictionary content is just referenced, not duplicated.
1624	* As a consequence, `dictBuffer` **must** outlive CDict,
1625	* and its content must remain unmodified throughout the lifetime of CDict.
1626	* note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef */
1627	ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1628
1629	/*! ZSTD_getCParams() :
1630	* @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1631	* `estimatedSrcSize` value is optional, select 0 if not known */
1632	ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1633
1634	/*! ZSTD_getParams() :
1635	* same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1636	* All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 */
1637	ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1638
1639	/*! ZSTD_checkCParams() :
1640	* Ensure param values remain within authorized range.
1641	* @return 0 on success, or an error code (can be checked with ZSTD_isError()) */
1642	ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1643
1644	/*! ZSTD_adjustCParams() :
1645	* optimize params for a given `srcSize` and `dictSize`.
1646	* `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
1647	* `dictSize` must be `0` when there is no dictionary.
1648	* cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
1649	* This function never fails (wide contract) */
1650	ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1651
1652	/*! ZSTD_compress_advanced() :
1653	* Note : this function is now DEPRECATED.
1654	* It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
1655	* This prototype will generate compilation warnings. */
1656	ZSTD_DEPRECATED("use ZSTD_compress2")
1657	size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1658	void* dst, size_t dstCapacity,
1659	const void* src, size_t srcSize,
1660	const void* dict,size_t dictSize,
1661	ZSTD_parameters params);
1662
1663	/*! ZSTD_compress_usingCDict_advanced() :
1664	* Note : this function is now DEPRECATED.
1665	* It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
1666	* This prototype will generate compilation warnings. */
1667	ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
1668	size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1669	void* dst, size_t dstCapacity,
1670	const void* src, size_t srcSize,
1671	const ZSTD_CDict* cdict,
1672	ZSTD_frameParameters fParams);
1673
1674
1675	/*! ZSTD_CCtx_loadDictionary_byReference() :
1676	* Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1677	* It saves some memory, but also requires that `dict` outlives its usage within `cctx` */
1678	ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1679
1680	/*! ZSTD_CCtx_loadDictionary_advanced() :
1681	* Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1682	* how to load the dictionary (by copy ? by reference ?)
1683	* and how to interpret it (automatic ? force raw mode ? full mode only ?) */
1684	ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1685
1686	/*! ZSTD_CCtx_refPrefix_advanced() :
1687	* Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1688	* how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) */
1689	ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1690
1691	/* === experimental parameters === */
1692	/* these parameters can be used with ZSTD_setParameter()
1693	* they are not guaranteed to remain supported in the future */
1694
1695	/* Enables rsyncable mode,
1696	* which makes compressed files more rsync friendly
1697	* by adding periodic synchronization points to the compressed data.
1698	* The target average block size is ZSTD_c_jobSize / 2.
1699	* It's possible to modify the job size to increase or decrease
1700	* the granularity of the synchronization point.
1701	* Once the jobSize is smaller than the window size,
1702	* it will result in compression ratio degradation.
1703	* NOTE 1: rsyncable mode only works when multithreading is enabled.
1704	* NOTE 2: rsyncable performs poorly in combination with long range mode,
1705	* since it will decrease the effectiveness of synchronization points,
1706	* though mileage may vary.
1707	* NOTE 3: Rsyncable mode limits maximum compression speed to ~400 MB/s.
1708	* If the selected compression level is already running significantly slower,
1709	* the overall speed won't be significantly impacted.
1710	*/
1711	#define ZSTD_c_rsyncable ZSTD_c_experimentalParam1
1712
1713	/* Select a compression format.
1714	* The value must be of type ZSTD_format_e.
1715	* See ZSTD_format_e enum definition for details */
1716	#define ZSTD_c_format ZSTD_c_experimentalParam2
1717
1718	/* Force back-reference distances to remain < windowSize,
1719	* even when referencing into Dictionary content (default:0) */
1720	#define ZSTD_c_forceMaxWindow ZSTD_c_experimentalParam3
1721
1722	/* Controls whether the contents of a CDict
1723	* are used in place, or copied into the working context.
1724	* Accepts values from the ZSTD_dictAttachPref_e enum.
1725	* See the comments on that enum for an explanation of the feature. */
1726	#define ZSTD_c_forceAttachDict ZSTD_c_experimentalParam4
1727
1728	/* Controlled with ZSTD_paramSwitch_e enum.
1729	* Default is ZSTD_ps_auto.
1730	* Set to ZSTD_ps_disable to never compress literals.
1731	* Set to ZSTD_ps_enable to always compress literals. (Note: uncompressed literals
1732	* may still be emitted if huffman is not beneficial to use.)
1733	*
1734	* By default, in ZSTD_ps_auto, the library will decide at runtime whether to use
1735	* literals compression based on the compression parameters - specifically,
1736	* negative compression levels do not use literal compression.
1737	*/
1738	#define ZSTD_c_literalCompressionMode ZSTD_c_experimentalParam5
1739
1740	/* Tries to fit compressed block size to be around targetCBlockSize.
1741	* No target when targetCBlockSize == 0.
1742	* There is no guarantee on compressed block size (default:0) */
1743	#define ZSTD_c_targetCBlockSize ZSTD_c_experimentalParam6
1744
1745	/* User's best guess of source size.
1746	* Hint is not valid when srcSizeHint == 0.
1747	* There is no guarantee that hint is close to actual source size,
1748	* but compression ratio may regress significantly if guess considerably underestimates */
1749	#define ZSTD_c_srcSizeHint ZSTD_c_experimentalParam7
1750
1751	/* Controls whether the new and experimental "dedicated dictionary search
1752	* structure" can be used. This feature is still rough around the edges, be
1753	* prepared for surprising behavior!
1754	*
1755	* How to use it:
1756	*
1757	* When using a CDict, whether to use this feature or not is controlled at
1758	* CDict creation, and it must be set in a CCtxParams set passed into that
1759	* construction (via ZSTD_createCDict_advanced2()). A compression will then
1760	* use the feature or not based on how the CDict was constructed; the value of
1761	* this param, set in the CCtx, will have no effect.
1762	*
1763	* However, when a dictionary buffer is passed into a CCtx, such as via
1764	* ZSTD_CCtx_loadDictionary(), this param can be set on the CCtx to control
1765	* whether the CDict that is created internally can use the feature or not.
1766	*
1767	* What it does:
1768	*
1769	* Normally, the internal data structures of the CDict are analogous to what
1770	* would be stored in a CCtx after compressing the contents of a dictionary.
1771	* To an approximation, a compression using a dictionary can then use those
1772	* data structures to simply continue what is effectively a streaming
1773	* compression where the simulated compression of the dictionary left off.
1774	* Which is to say, the search structures in the CDict are normally the same
1775	* format as in the CCtx.
1776	*
1777	* It is possible to do better, since the CDict is not like a CCtx: the search
1778	* structures are written once during CDict creation, and then are only read
1779	* after that, while the search structures in the CCtx are both read and
1780	* written as the compression goes along. This means we can choose a search
1781	* structure for the dictionary that is read-optimized.
1782	*
1783	* This feature enables the use of that different structure.
1784	*
1785	* Note that some of the members of the ZSTD_compressionParameters struct have
1786	* different semantics and constraints in the dedicated search structure. It is
1787	* highly recommended that you simply set a compression level in the CCtxParams
1788	* you pass into the CDict creation call, and avoid messing with the cParams
1789	* directly.
1790	*
1791	* Effects:
1792	*
1793	* This will only have any effect when the selected ZSTD_strategy
1794	* implementation supports this feature. Currently, that's limited to
1795	* ZSTD_greedy, ZSTD_lazy, and ZSTD_lazy2.
1796	*
1797	* Note that this means that the CDict tables can no longer be copied into the
1798	* CCtx, so the dict attachment mode ZSTD_dictForceCopy will no longer be
1799	* usable. The dictionary can only be attached or reloaded.
1800	*
1801	* In general, you should expect compression to be faster--sometimes very much
1802	* so--and CDict creation to be slightly slower. Eventually, we will probably
1803	* make this mode the default.
1804	*/
1805	#define ZSTD_c_enableDedicatedDictSearch ZSTD_c_experimentalParam8
1806
1807	/* ZSTD_c_stableInBuffer
1808	* Experimental parameter.
1809	* Default is 0 == disabled. Set to 1 to enable.
1810	*
1811	* Tells the compressor that the ZSTD_inBuffer will ALWAYS be the same
1812	* between calls, except for the modifications that zstd makes to pos (the
1813	* caller must not modify pos). This is checked by the compressor, and
1814	* compression will fail if it ever changes. This means the only flush
1815	* mode that makes sense is ZSTD_e_end, so zstd will error if ZSTD_e_end
1816	* is not used. The data in the ZSTD_inBuffer in the range [src, src + pos)
1817	* MUST not be modified during compression or you will get data corruption.
1818	*
1819	* When this flag is enabled zstd won't allocate an input window buffer,
1820	* because the user guarantees it can reference the ZSTD_inBuffer until
1821	* the frame is complete. But, it will still allocate an output buffer
1822	* large enough to fit a block (see ZSTD_c_stableOutBuffer). This will also
1823	* avoid the memcpy() from the input buffer to the input window buffer.
1824	*
1825	* NOTE: ZSTD_compressStream2() will error if ZSTD_e_end is not used.
1826	* That means this flag cannot be used with ZSTD_compressStream().
1827	*
1828	* NOTE: So long as the ZSTD_inBuffer always points to valid memory, using
1829	* this flag is ALWAYS memory safe, and will never access out-of-bounds
1830	* memory. However, compression WILL fail if you violate the preconditions.
1831	*
1832	* WARNING: The data in the ZSTD_inBuffer in the range [dst, dst + pos) MUST
1833	* not be modified during compression or you will get data corruption. This
1834	* is because zstd needs to reference data in the ZSTD_inBuffer to find
1835	* matches. Normally zstd maintains its own window buffer for this purpose,
1836	* but passing this flag tells zstd to use the user provided buffer.
1837	*/
1838	#define ZSTD_c_stableInBuffer ZSTD_c_experimentalParam9
1839
1840	/* ZSTD_c_stableOutBuffer
1841	* Experimental parameter.
1842	* Default is 0 == disabled. Set to 1 to enable.
1843	*
1844	* Tells he compressor that the ZSTD_outBuffer will not be resized between
1845	* calls. Specifically: (out.size - out.pos) will never grow. This gives the
1846	* compressor the freedom to say: If the compressed data doesn't fit in the
1847	* output buffer then return ZSTD_error_dstSizeTooSmall. This allows us to
1848	* always decompress directly into the output buffer, instead of decompressing
1849	* into an internal buffer and copying to the output buffer.
1850	*
1851	* When this flag is enabled zstd won't allocate an output buffer, because
1852	* it can write directly to the ZSTD_outBuffer. It will still allocate the
1853	* input window buffer (see ZSTD_c_stableInBuffer).
1854	*
1855	* Zstd will check that (out.size - out.pos) never grows and return an error
1856	* if it does. While not strictly necessary, this should prevent surprises.
1857	*/
1858	#define ZSTD_c_stableOutBuffer ZSTD_c_experimentalParam10
1859
1860	/* ZSTD_c_blockDelimiters
1861	* Default is 0 == ZSTD_sf_noBlockDelimiters.
1862	*
1863	* For use with sequence compression API: ZSTD_compressSequences().
1864	*
1865	* Designates whether or not the given array of ZSTD_Sequence contains block delimiters
1866	* and last literals, which are defined as sequences with offset == 0 and matchLength == 0.
1867	* See the definition of ZSTD_Sequence for more specifics.
1868	*/
1869	#define ZSTD_c_blockDelimiters ZSTD_c_experimentalParam11
1870
1871	/* ZSTD_c_validateSequences
1872	* Default is 0 == disabled. Set to 1 to enable sequence validation.
1873	*
1874	* For use with sequence compression API: ZSTD_compressSequences().
1875	* Designates whether or not we validate sequences provided to ZSTD_compressSequences()
1876	* during function execution.
1877	*
1878	* Without validation, providing a sequence that does not conform to the zstd spec will cause
1879	* undefined behavior, and may produce a corrupted block.
1880	*
1881	* With validation enabled, a if sequence is invalid (see doc/zstd_compression_format.md for
1882	* specifics regarding offset/matchlength requirements) then the function will bail out and
1883	* return an error.
1884	*
1885	*/
1886	#define ZSTD_c_validateSequences ZSTD_c_experimentalParam12
1887
1888	/* ZSTD_c_useBlockSplitter
1889	* Controlled with ZSTD_paramSwitch_e enum.
1890	* Default is ZSTD_ps_auto.
1891	* Set to ZSTD_ps_disable to never use block splitter.
1892	* Set to ZSTD_ps_enable to always use block splitter.
1893	*
1894	* By default, in ZSTD_ps_auto, the library will decide at runtime whether to use
1895	* block splitting based on the compression parameters.
1896	*/
1897	#define ZSTD_c_useBlockSplitter ZSTD_c_experimentalParam13
1898
1899	/* ZSTD_c_useRowMatchFinder
1900	* Controlled with ZSTD_paramSwitch_e enum.
1901	* Default is ZSTD_ps_auto.
1902	* Set to ZSTD_ps_disable to never use row-based matchfinder.
1903	* Set to ZSTD_ps_enable to force usage of row-based matchfinder.
1904	*
1905	* By default, in ZSTD_ps_auto, the library will decide at runtime whether to use
1906	* the row-based matchfinder based on support for SIMD instructions and the window log.
1907	* Note that this only pertains to compression strategies: greedy, lazy, and lazy2
1908	*/
1909	#define ZSTD_c_useRowMatchFinder ZSTD_c_experimentalParam14
1910
1911	/* ZSTD_c_deterministicRefPrefix
1912	* Default is 0 == disabled. Set to 1 to enable.
1913	*
1914	* Zstd produces different results for prefix compression when the prefix is
1915	* directly adjacent to the data about to be compressed vs. when it isn't.
1916	* This is because zstd detects that the two buffers are contiguous and it can
1917	* use a more efficient match finding algorithm. However, this produces different
1918	* results than when the two buffers are non-contiguous. This flag forces zstd
1919	* to always load the prefix in non-contiguous mode, even if it happens to be
1920	* adjacent to the data, to guarantee determinism.
1921	*
1922	* If you really care about determinism when using a dictionary or prefix,
1923	* like when doing delta compression, you should select this option. It comes
1924	* at a speed penalty of about ~2.5% if the dictionary and data happened to be
1925	* contiguous, and is free if they weren't contiguous. We don't expect that
1926	* intentionally making the dictionary and data contiguous will be worth the
1927	* cost to memcpy() the data.
1928	*/
1929	#define ZSTD_c_deterministicRefPrefix ZSTD_c_experimentalParam15
1930
1931	/*! ZSTD_CCtx_getParameter() :
1932	* Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1933	* and store it into int* value.
1934	* @return : 0, or an error code (which can be tested with ZSTD_isError()).
1935	*/
1936	ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1937
1938
1939	/*! ZSTD_CCtx_params :
1940	* Quick howto :
1941	* - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1942	* - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
1943	* an existing ZSTD_CCtx_params structure.
1944	* This is similar to
1945	* ZSTD_CCtx_setParameter().
1946	* - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1947	* an existing CCtx.
1948	* These parameters will be applied to
1949	* all subsequent frames.
1950	* - ZSTD_compressStream2() : Do compression using the CCtx.
1951	* - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer.
1952	*
1953	* This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1954	* for static allocation of CCtx for single-threaded compression.
1955	*/
1956	ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1957	ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); /* accept NULL pointer */
1958
1959	/*! ZSTD_CCtxParams_reset() :
1960	* Reset params to default values.
1961	*/
1962	ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1963
1964	/*! ZSTD_CCtxParams_init() :
1965	* Initializes the compression parameters of cctxParams according to
1966	* compression level. All other parameters are reset to their default values.
1967	*/
1968	ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1969
1970	/*! ZSTD_CCtxParams_init_advanced() :
1971	* Initializes the compression and frame parameters of cctxParams according to
1972	* params. All other parameters are reset to their default values.
1973	*/
1974	ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1975
1976	/*! ZSTD_CCtxParams_setParameter() : Requires v1.4.0+
1977	* Similar to ZSTD_CCtx_setParameter.
1978	* Set one compression parameter, selected by enum ZSTD_cParameter.
1979	* Parameters must be applied to a ZSTD_CCtx using
1980	* ZSTD_CCtx_setParametersUsingCCtxParams().
1981	* @result : a code representing success or failure (which can be tested with
1982	* ZSTD_isError()).
1983	*/
1984	ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1985
1986	/*! ZSTD_CCtxParams_getParameter() :
1987	* Similar to ZSTD_CCtx_getParameter.
1988	* Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1989	* @result : 0, or an error code (which can be tested with ZSTD_isError()).
1990	*/
1991	ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1992
1993	/*! ZSTD_CCtx_setParametersUsingCCtxParams() :
1994	* Apply a set of ZSTD_CCtx_params to the compression context.
1995	* This can be done even after compression is started,
1996	* if nbWorkers==0, this will have no impact until a new compression is started.
1997	* if nbWorkers>=1, new parameters will be picked up at next job,
1998	* with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1999	*/
2000	ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
2001	ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
2002
2003	/*! ZSTD_compressStream2_simpleArgs() :
2004	* Same as ZSTD_compressStream2(),
2005	* but using only integral types as arguments.
2006	* This variant might be helpful for binders from dynamic languages
2007	* which have troubles handling structures containing memory pointers.
2008	*/
2009	ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs (
2010	ZSTD_CCtx* cctx,
2011	void* dst, size_t dstCapacity, size_t* dstPos,
2012	const void* src, size_t srcSize, size_t* srcPos,
2013	ZSTD_EndDirective endOp);
2014
2015
2016	/* *************************************
2017	* Advanced decompression functions
2018	***************************************/
2019
2020	/*! ZSTD_isFrame() :
2021	* Tells if the content of `buffer` starts with a valid Frame Identifier.
2022	* Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
2023	* Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
2024	* Note 3 : Skippable Frame Identifiers are considered valid. */
2025	ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size);
2026
2027	/*! ZSTD_createDDict_byReference() :
2028	* Create a digested dictionary, ready to start decompression operation without startup delay.
2029	* Dictionary content is referenced, and therefore stays in dictBuffer.
2030	* It is important that dictBuffer outlives DDict,
2031	* it must remain read accessible throughout the lifetime of DDict */
2032	ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
2033
2034	/*! ZSTD_DCtx_loadDictionary_byReference() :
2035	* Same as ZSTD_DCtx_loadDictionary(),
2036	* but references `dict` content instead of copying it into `dctx`.
2037	* This saves memory if `dict` remains around.,
2038	* However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. */
2039	ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
2040
2041	/*! ZSTD_DCtx_loadDictionary_advanced() :
2042	* Same as ZSTD_DCtx_loadDictionary(),
2043	* but gives direct control over
2044	* how to load the dictionary (by copy ? by reference ?)
2045	* and how to interpret it (automatic ? force raw mode ? full mode only ?). */
2046	ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
2047
2048	/*! ZSTD_DCtx_refPrefix_advanced() :
2049	* Same as ZSTD_DCtx_refPrefix(), but gives finer control over
2050	* how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) */
2051	ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
2052
2053	/*! ZSTD_DCtx_setMaxWindowSize() :
2054	* Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
2055	* This protects a decoder context from reserving too much memory for itself (potential attack scenario).
2056	* This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
2057	* By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
2058	* @return : 0, or an error code (which can be tested using ZSTD_isError()).
2059	*/
2060	ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
2061
2062	/*! ZSTD_DCtx_getParameter() :
2063	* Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
2064	* and store it into int* value.
2065	* @return : 0, or an error code (which can be tested with ZSTD_isError()).
2066	*/
2067	ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
2068
2069	/* ZSTD_d_format
2070	* experimental parameter,
2071	* allowing selection between ZSTD_format_e input compression formats
2072	*/
2073	#define ZSTD_d_format ZSTD_d_experimentalParam1
2074	/* ZSTD_d_stableOutBuffer
2075	* Experimental parameter.
2076	* Default is 0 == disabled. Set to 1 to enable.
2077	*
2078	* Tells the decompressor that the ZSTD_outBuffer will ALWAYS be the same
2079	* between calls, except for the modifications that zstd makes to pos (the
2080	* caller must not modify pos). This is checked by the decompressor, and
2081	* decompression will fail if it ever changes. Therefore the ZSTD_outBuffer
2082	* MUST be large enough to fit the entire decompressed frame. This will be
2083	* checked when the frame content size is known. The data in the ZSTD_outBuffer
2084	* in the range [dst, dst + pos) MUST not be modified during decompression
2085	* or you will get data corruption.
2086	*
2087	* When this flags is enabled zstd won't allocate an output buffer, because
2088	* it can write directly to the ZSTD_outBuffer, but it will still allocate
2089	* an input buffer large enough to fit any compressed block. This will also
2090	* avoid the memcpy() from the internal output buffer to the ZSTD_outBuffer.
2091	* If you need to avoid the input buffer allocation use the buffer-less
2092	* streaming API.
2093	*
2094	* NOTE: So long as the ZSTD_outBuffer always points to valid memory, using
2095	* this flag is ALWAYS memory safe, and will never access out-of-bounds
2096	* memory. However, decompression WILL fail if you violate the preconditions.
2097	*
2098	* WARNING: The data in the ZSTD_outBuffer in the range [dst, dst + pos) MUST
2099	* not be modified during decompression or you will get data corruption. This
2100	* is because zstd needs to reference data in the ZSTD_outBuffer to regenerate
2101	* matches. Normally zstd maintains its own buffer for this purpose, but passing
2102	* this flag tells zstd to use the user provided buffer.
2103	*/
2104	#define ZSTD_d_stableOutBuffer ZSTD_d_experimentalParam2
2105
2106	/* ZSTD_d_forceIgnoreChecksum
2107	* Experimental parameter.
2108	* Default is 0 == disabled. Set to 1 to enable
2109	*
2110	* Tells the decompressor to skip checksum validation during decompression, regardless
2111	* of whether checksumming was specified during compression. This offers some
2112	* slight performance benefits, and may be useful for debugging.
2113	* Param has values of type ZSTD_forceIgnoreChecksum_e
2114	*/
2115	#define ZSTD_d_forceIgnoreChecksum ZSTD_d_experimentalParam3
2116
2117	/* ZSTD_d_refMultipleDDicts
2118	* Experimental parameter.
2119	* Default is 0 == disabled. Set to 1 to enable
2120	*
2121	* If enabled and dctx is allocated on the heap, then additional memory will be allocated
2122	* to store references to multiple ZSTD_DDict. That is, multiple calls of ZSTD_refDDict()
2123	* using a given ZSTD_DCtx, rather than overwriting the previous DDict reference, will instead
2124	* store all references. At decompression time, the appropriate dictID is selected
2125	* from the set of DDicts based on the dictID in the frame.
2126	*
2127	* Usage is simply calling ZSTD_refDDict() on multiple dict buffers.
2128	*
2129	* Param has values of byte ZSTD_refMultipleDDicts_e
2130	*
2131	* WARNING: Enabling this parameter and calling ZSTD_DCtx_refDDict(), will trigger memory
2132	* allocation for the hash table. ZSTD_freeDCtx() also frees this memory.
2133	* Memory is allocated as per ZSTD_DCtx::customMem.
2134	*
2135	* Although this function allocates memory for the table, the user is still responsible for
2136	* memory management of the underlying ZSTD_DDict* themselves.
2137	*/
2138	#define ZSTD_d_refMultipleDDicts ZSTD_d_experimentalParam4
2139
2140
2141	/*! ZSTD_DCtx_setFormat() :
2142	* This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
2143	* Instruct the decoder context about what kind of data to decode next.
2144	* This instruction is mandatory to decode data without a fully-formed header,
2145	* such ZSTD_f_zstd1_magicless for example.
2146	* @return : 0, or an error code (which can be tested using ZSTD_isError()). */
2147	ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
2148	size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
2149
2150	/*! ZSTD_decompressStream_simpleArgs() :
2151	* Same as ZSTD_decompressStream(),
2152	* but using only integral types as arguments.
2153	* This can be helpful for binders from dynamic languages
2154	* which have troubles handling structures containing memory pointers.
2155	*/
2156	ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs (
2157	ZSTD_DCtx* dctx,
2158	void* dst, size_t dstCapacity, size_t* dstPos,
2159	const void* src, size_t srcSize, size_t* srcPos);
2160
2161
2162	/* ******************************************************************
2163	* Advanced streaming functions
2164	* Warning : most of these functions are now redundant with the Advanced API.
2165	* Once Advanced API reaches "stable" status,
2166	* redundant functions will be deprecated, and then at some point removed.
2167	********************************************************************/
2168
2169	/*===== Advanced Streaming compression functions =====*/
2170
2171	/*! ZSTD_initCStream_srcSize() :
2172	* This function is DEPRECATED, and equivalent to:
2173	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
2174	* ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
2175	* ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
2176	* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
2177	*
2178	* pledgedSrcSize must be correct. If it is not known at init time, use
2179	* ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
2180	* "0" also disables frame content size field. It may be enabled in the future.
2181	* This prototype will generate compilation warnings.
2182	*/
2183	ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
2184	size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
2185	int compressionLevel,
2186	unsigned long long pledgedSrcSize);
2187
2188	/*! ZSTD_initCStream_usingDict() :
2189	* This function is DEPRECATED, and is equivalent to:
2190	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
2191	* ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
2192	* ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
2193	*
2194	* Creates of an internal CDict (incompatible with static CCtx), except if
2195	* dict == NULL or dictSize < 8, in which case no dict is used.
2196	* Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
2197	* it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
2198	* This prototype will generate compilation warnings.
2199	*/
2200	ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
2201	size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
2202	const void* dict, size_t dictSize,
2203	int compressionLevel);
2204
2205	/*! ZSTD_initCStream_advanced() :
2206	* This function is DEPRECATED, and is approximately equivalent to:
2207	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
2208	* // Pseudocode: Set each zstd parameter and leave the rest as-is.
2209	* for ((param, value) : params) {
2210	* ZSTD_CCtx_setParameter(zcs, param, value);
2211	* }
2212	* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
2213	* ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
2214	*
2215	* dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
2216	* pledgedSrcSize must be correct.
2217	* If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
2218	* This prototype will generate compilation warnings.
2219	*/
2220	ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
2221	size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
2222	const void* dict, size_t dictSize,
2223	ZSTD_parameters params,
2224	unsigned long long pledgedSrcSize);
2225
2226	/*! ZSTD_initCStream_usingCDict() :
2227	* This function is DEPRECATED, and equivalent to:
2228	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
2229	* ZSTD_CCtx_refCDict(zcs, cdict);
2230	*
2231	* note : cdict will just be referenced, and must outlive compression session
2232	* This prototype will generate compilation warnings.
2233	*/
2234	ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
2235	size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
2236
2237	/*! ZSTD_initCStream_usingCDict_advanced() :
2238	* This function is DEPRECATED, and is approximately equivalent to:
2239	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
2240	* // Pseudocode: Set each zstd frame parameter and leave the rest as-is.
2241	* for ((fParam, value) : fParams) {
2242	* ZSTD_CCtx_setParameter(zcs, fParam, value);
2243	* }
2244	* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
2245	* ZSTD_CCtx_refCDict(zcs, cdict);
2246	*
2247	* same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
2248	* pledgedSrcSize must be correct. If srcSize is not known at init time, use
2249	* value ZSTD_CONTENTSIZE_UNKNOWN.
2250	* This prototype will generate compilation warnings.
2251	*/
2252	ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
2253	size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
2254	const ZSTD_CDict* cdict,
2255	ZSTD_frameParameters fParams,
2256	unsigned long long pledgedSrcSize);
2257
2258	/*! ZSTD_resetCStream() :
2259	* This function is DEPRECATED, and is equivalent to:
2260	* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
2261	* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
2262	* Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
2263	* ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
2264	* explicitly specified.
2265	*
2266	* start a new frame, using same parameters from previous frame.
2267	* This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
2268	* Note that zcs must be init at least once before using ZSTD_resetCStream().
2269	* If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
2270	* If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
2271	* For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
2272	* but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
2273	* @return : 0, or an error code (which can be tested using ZSTD_isError())
2274	* This prototype will generate compilation warnings.
2275	*/
2276	ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
2277	size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
2278
2279
2280	typedef struct {
2281	unsigned long long ingested; /* nb input bytes read and buffered */
2282	unsigned long long consumed; /* nb input bytes actually compressed */
2283	unsigned long long produced; /* nb of compressed bytes generated and buffered */
2284	unsigned long long flushed; /* nb of compressed bytes flushed : not provided; can be tracked from caller side */
2285	unsigned currentJobID; /* MT only : latest started job nb */
2286	unsigned nbActiveWorkers; /* MT only : nb of workers actively compressing at probe time */
2287	} ZSTD_frameProgression;
2288
2289	/* ZSTD_getFrameProgression() :
2290	* tells how much data has been ingested (read from input)
2291	* consumed (input actually compressed) and produced (output) for current frame.
2292	* Note : (ingested - consumed) is amount of input data buffered internally, not yet compressed.
2293	* Aggregates progression inside active worker threads.
2294	*/
2295	ZSTDLIB_STATIC_API ZSTD_frameProgression ZSTD_getFrameProgression(const ZSTD_CCtx* cctx);
2296
2297	/*! ZSTD_toFlushNow() :
2298	* Tell how many bytes are ready to be flushed immediately.
2299	* Useful for multithreading scenarios (nbWorkers >= 1).
2300	* Probe the oldest active job, defined as oldest job not yet entirely flushed,
2301	* and check its output buffer.
2302	* @return : amount of data stored in oldest job and ready to be flushed immediately.
2303	* if @return == 0, it means either :
2304	* + there is no active job (could be checked with ZSTD_frameProgression()), or
2305	* + oldest job is still actively compressing data,
2306	* but everything it has produced has also been flushed so far,
2307	* therefore flush speed is limited by production speed of oldest job
2308	* irrespective of the speed of concurrent (and newer) jobs.
2309	*/
2310	ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
2311
2312
2313	/*===== Advanced Streaming decompression functions =====*/
2314
2315	/*!
2316	* This function is deprecated, and is equivalent to:
2317	*
2318	* ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
2319	* ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
2320	*
2321	* note: no dictionary will be used if dict == NULL or dictSize < 8
2322	* Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
2323	*/
2324	ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
2325
2326	/*!
2327	* This function is deprecated, and is equivalent to:
2328	*
2329	* ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
2330	* ZSTD_DCtx_refDDict(zds, ddict);
2331	*
2332	* note : ddict is referenced, it must outlive decompression session
2333	* Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
2334	*/
2335	ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
2336
2337	/*!
2338	* This function is deprecated, and is equivalent to:
2339	*
2340	* ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
2341	*
2342	* re-use decompression parameters from previous init; saves dictionary loading
2343	* Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
2344	*/
2345	ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
2346
2347
2348	/* *******************************************************************
2349	* Buffer-less and synchronous inner streaming functions
2350	*
2351	* This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
2352	* But it's also a complex one, with several restrictions, documented below.
2353	* Prefer normal streaming API for an easier experience.
2354	********************************************************************* */
2355
2356	/*
2357	Buffer-less streaming compression (synchronous mode)
2358
2359	A ZSTD_CCtx object is required to track streaming operations.
2360	Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
2361	ZSTD_CCtx object can be re-used multiple times within successive compression operations.
2362
2363	Start by initializing a context.
2364	Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression.
2365	It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
2366
2367	Then, consume your input using ZSTD_compressContinue().
2368	There are some important considerations to keep in mind when using this advanced function :
2369	- ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
2370	- Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
2371	- Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
2372	Worst case evaluation is provided by ZSTD_compressBound().
2373	ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
2374	- ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
2375	It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
2376	- ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
2377	In which case, it will "discard" the relevant memory section from its history.
2378
2379	Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
2380	It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
2381	Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
2382
2383	`ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
2384	*/
2385
2386	/*===== Buffer-less streaming compression functions =====*/
2387	ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
2388	ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
2389	ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); /*< note: fails if cdict==NULL */
2390	ZSTDLIB_STATIC_API size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); /*< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */
2391
2392	ZSTDLIB_STATIC_API size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2393	ZSTDLIB_STATIC_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2394
2395	/* The ZSTD_compressBegin_advanced() and ZSTD_compressBegin_usingCDict_advanced() are now DEPRECATED and will generate a compiler warning */
2396	ZSTD_DEPRECATED("use advanced API to access custom parameters")
2397	size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); /*< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */
2398	ZSTD_DEPRECATED("use advanced API to access custom parameters")
2399	size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); /* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */
2400	/*
2401	Buffer-less streaming decompression (synchronous mode)
2402
2403	A ZSTD_DCtx object is required to track streaming operations.
2404	Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
2405	A ZSTD_DCtx object can be re-used multiple times.
2406
2407	First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
2408	Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
2409	Data fragment must be large enough to ensure successful decoding.
2410	`ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
2411	@result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
2412	>0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
2413	errorCode, which can be tested using ZSTD_isError().
2414
2415	It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
2416	such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
2417	Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
2418	As a consequence, check that values remain within valid application range.
2419	For example, do not allocate memory blindly, check that `windowSize` is within expectation.
2420	Each application can set its own limits, depending on local restrictions.
2421	For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
2422
2423	ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
2424	ZSTD_decompressContinue() is very sensitive to contiguity,
2425	if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
2426	or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
2427	There are multiple ways to guarantee this condition.
2428
2429	The most memory efficient way is to use a round buffer of sufficient size.
2430	Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
2431	which can @return an error code if required value is too large for current system (in 32-bits mode).
2432	In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
2433	up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
2434	which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
2435	At which point, decoding can resume from the beginning of the buffer.
2436	Note that already decoded data stored in the buffer should be flushed before being overwritten.
2437
2438	There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
2439
2440	Finally, if you control the compression process, you can also ignore all buffer size rules,
2441	as long as the encoder and decoder progress in "lock-step",
2442	aka use exactly the same buffer sizes, break contiguity at the same place, etc.
2443
2444	Once buffers are setup, start decompression, with ZSTD_decompressBegin().
2445	If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
2446
2447	Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
2448	ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
2449	ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
2450
2451	@result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
2452	It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
2453	It can also be an error code, which can be tested with ZSTD_isError().
2454
2455	A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
2456	Context can then be reset to start a new decompression.
2457
2458	Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
2459	This information is not required to properly decode a frame.
2460
2461	== Special case : skippable frames ==
2462
2463	Skippable frames allow integration of user-defined data into a flow of concatenated frames.
2464	Skippable frames will be ignored (skipped) by decompressor.
2465	The format of skippable frames is as follows :
2466	a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
2467	b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
2468	c) Frame Content - any content (User Data) of length equal to Frame Size
2469	For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
2470	For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
2471	*/
2472
2473	/*===== Buffer-less streaming decompression functions =====*/
2474	typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
2475	typedef struct {
2476	unsigned long long frameContentSize; /* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */
2477	unsigned long long windowSize; /* can be very large, up to <= frameContentSize */
2478	unsigned blockSizeMax;
2479	ZSTD_frameType_e frameType; /* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */
2480	unsigned headerSize;
2481	unsigned dictID;
2482	unsigned checksumFlag;
2483	} ZSTD_frameHeader;
2484
2485	/*! ZSTD_getFrameHeader() :
2486	* decode Frame Header, or requires larger `srcSize`.
2487	* @return : 0, `zfhPtr` is correctly filled,
2488	* >0, `srcSize` is too small, value is wanted `srcSize` amount,
2489	* or an error code, which can be tested using ZSTD_isError() */
2490	ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); /*< doesn't consume input */
2491	/*! ZSTD_getFrameHeader_advanced() :
2492	* same as ZSTD_getFrameHeader(),
2493	* with added capability to select a format (like ZSTD_f_zstd1_magicless) */
2494	ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
2495	ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); /*< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */
2496
2497	ZSTDLIB_STATIC_API size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
2498	ZSTDLIB_STATIC_API size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
2499	ZSTDLIB_STATIC_API size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
2500
2501	ZSTDLIB_STATIC_API size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
2502	ZSTDLIB_STATIC_API size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2503
2504	/* misc */
2505	ZSTDLIB_STATIC_API void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
2506	typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
2507	ZSTDLIB_STATIC_API ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
2508
2509
2510
2511
2512	/* ============================ */
2513	/* Block level API */
2514	/* ============================ */
2515
2516	/*!
2517	Block functions produce and decode raw zstd blocks, without frame metadata.
2518	Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
2519	But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
2520
2521	A few rules to respect :
2522	- Compressing and decompressing require a context structure
2523	+ Use ZSTD_createCCtx() and ZSTD_createDCtx()
2524	- It is necessary to init context before starting
2525	+ compression : any ZSTD_compressBegin*() variant, including with dictionary
2526	+ decompression : any ZSTD_decompressBegin*() variant, including with dictionary
2527	+ copyCCtx() and copyDCtx() can be used too
2528	- Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
2529	+ If input is larger than a block size, it's necessary to split input data into multiple blocks
2530	+ For inputs larger than a single block, consider using regular ZSTD_compress() instead.
2531	Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
2532	- When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
2533	===> In which case, nothing is produced into `dst` !
2534	+ User __must__ test for such outcome and deal directly with uncompressed data
2535	+ A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
2536	Doing so would mess up with statistics history, leading to potential data corruption.
2537	+ ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
2538	+ In case of multiple successive blocks, should some of them be uncompressed,
2539	decoder must be informed of their existence in order to follow proper history.
2540	Use ZSTD_insertBlock() for such a case.
2541	*/
2542
2543	/*===== Raw zstd block functions =====*/
2544	ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
2545	ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2546	ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2547	ZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); /*< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */
2548
2549
2550	#endif /* ZSTD_H_ZSTD_STATIC_LINKING_ONLY */
2551
2552