1//===- Endian.h - Utilities for IO with endian specific data ----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file declares generic functions to read and write endian specific data.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_SUPPORT_ENDIAN_H
14#define LLVM_SUPPORT_ENDIAN_H
15
16#include "llvm/ADT/bit.h"
17#include "llvm/Support/Compiler.h"
18#include "llvm/Support/SwapByteOrder.h"
19#include <cassert>
20#include <cstddef>
21#include <cstdint>
22#include <cstring>
23#include <type_traits>
24
25namespace llvm {
26namespace support {
27
28// These are named values for common alignments.
29enum {aligned = 0, unaligned = 1};
30
31namespace detail {
32
33/// ::value is either alignment, or alignof(T) if alignment is 0.
34template<class T, int alignment>
35struct PickAlignment {
36 enum { value = alignment == 0 ? alignof(T) : alignment };
37};
38
39} // end namespace detail
40
41namespace endian {
42
43template <typename value_type>
44[[nodiscard]] inline value_type byte_swap(value_type value, endianness endian) {
45 if (endian != llvm::endianness::native)
46 sys::swapByteOrder(value);
47 return value;
48}
49
50/// Swap the bytes of value to match the given endianness.
51template <typename value_type, endianness endian>
52[[nodiscard]] inline value_type byte_swap(value_type value) {
53 return byte_swap(value, endian);
54}
55
56/// Read a value of a particular endianness from memory.
57template <typename value_type, std::size_t alignment = unaligned>
58[[nodiscard]] inline value_type read(const void *memory, endianness endian) {
59 value_type ret;
60
61 memcpy(static_cast<void *>(&ret),
62 LLVM_ASSUME_ALIGNED(
63 memory, (detail::PickAlignment<value_type, alignment>::value)),
64 sizeof(value_type));
65 return byte_swap<value_type>(ret, endian);
66}
67
68template <typename value_type, endianness endian, std::size_t alignment>
69[[nodiscard]] inline value_type read(const void *memory) {
70 return read<value_type, alignment>(memory, endian);
71}
72
73/// Read a value of a particular endianness from a buffer, and increment the
74/// buffer past that value.
75template <typename value_type, std::size_t alignment = unaligned,
76 typename CharT>
77[[nodiscard]] inline value_type readNext(const CharT *&memory,
78 endianness endian) {
79 value_type ret = read<value_type, alignment>(memory, endian);
80 memory += sizeof(value_type);
81 return ret;
82}
83
84template <typename value_type, endianness endian,
85 std::size_t alignment = unaligned, typename CharT>
86[[nodiscard]] inline value_type readNext(const CharT *&memory) {
87 return readNext<value_type, alignment, CharT>(memory, endian);
88}
89
90/// Write a value to memory with a particular endianness.
91template <typename value_type, std::size_t alignment = unaligned>
92inline void write(void *memory, value_type value, endianness endian) {
93 value = byte_swap<value_type>(value, endian);
94 memcpy(LLVM_ASSUME_ALIGNED(
95 memory, (detail::PickAlignment<value_type, alignment>::value)),
96 &value, sizeof(value_type));
97}
98
99template<typename value_type,
100 endianness endian,
101 std::size_t alignment>
102inline void write(void *memory, value_type value) {
103 write<value_type, alignment>(memory, value, endian);
104}
105
106/// Write a value of a particular endianness, and increment the buffer past that
107/// value.
108template <typename value_type, std::size_t alignment = unaligned,
109 typename CharT>
110inline void writeNext(CharT *&memory, value_type value, endianness endian) {
111 write(memory, value, endian);
112 memory += sizeof(value_type);
113}
114
115template <typename value_type, endianness endian,
116 std::size_t alignment = unaligned, typename CharT>
117inline void writeNext(CharT *&memory, value_type value) {
118 writeNext<value_type, alignment, CharT>(memory, value, endian);
119}
120
121template <typename value_type>
122using make_unsigned_t = std::make_unsigned_t<value_type>;
123
124/// Read a value of a particular endianness from memory, for a location
125/// that starts at the given bit offset within the first byte.
126template <typename value_type, endianness endian, std::size_t alignment>
127[[nodiscard]] inline value_type readAtBitAlignment(const void *memory,
128 uint64_t startBit) {
129 assert(startBit < 8);
130 if (startBit == 0)
131 return read<value_type, endian, alignment>(memory);
132 else {
133 // Read two values and compose the result from them.
134 value_type val[2];
135 memcpy(&val[0],
136 LLVM_ASSUME_ALIGNED(
137 memory, (detail::PickAlignment<value_type, alignment>::value)),
138 sizeof(value_type) * 2);
139 val[0] = byte_swap<value_type, endian>(val[0]);
140 val[1] = byte_swap<value_type, endian>(val[1]);
141
142 // Shift bits from the lower value into place.
143 make_unsigned_t<value_type> lowerVal = val[0] >> startBit;
144 // Mask off upper bits after right shift in case of signed type.
145 make_unsigned_t<value_type> numBitsFirstVal =
146 (sizeof(value_type) * 8) - startBit;
147 lowerVal &= ((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1;
148
149 // Get the bits from the upper value.
150 make_unsigned_t<value_type> upperVal =
151 val[1] & (((make_unsigned_t<value_type>)1 << startBit) - 1);
152 // Shift them in to place.
153 upperVal <<= numBitsFirstVal;
154
155 return lowerVal | upperVal;
156 }
157}
158
159/// Write a value to memory with a particular endianness, for a location
160/// that starts at the given bit offset within the first byte.
161template <typename value_type, endianness endian, std::size_t alignment>
162inline void writeAtBitAlignment(void *memory, value_type value,
163 uint64_t startBit) {
164 assert(startBit < 8);
165 if (startBit == 0)
166 write<value_type, endian, alignment>(memory, value);
167 else {
168 // Read two values and shift the result into them.
169 value_type val[2];
170 memcpy(&val[0],
171 LLVM_ASSUME_ALIGNED(
172 memory, (detail::PickAlignment<value_type, alignment>::value)),
173 sizeof(value_type) * 2);
174 val[0] = byte_swap<value_type, endian>(val[0]);
175 val[1] = byte_swap<value_type, endian>(val[1]);
176
177 // Mask off any existing bits in the upper part of the lower value that
178 // we want to replace.
179 val[0] &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
180 make_unsigned_t<value_type> numBitsFirstVal =
181 (sizeof(value_type) * 8) - startBit;
182 make_unsigned_t<value_type> lowerVal = value;
183 if (startBit > 0) {
184 // Mask off the upper bits in the new value that are not going to go into
185 // the lower value. This avoids a left shift of a negative value, which
186 // is undefined behavior.
187 lowerVal &= (((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1);
188 // Now shift the new bits into place
189 lowerVal <<= startBit;
190 }
191 val[0] |= lowerVal;
192
193 // Mask off any existing bits in the lower part of the upper value that
194 // we want to replace.
195 val[1] &= ~(((make_unsigned_t<value_type>)1 << startBit) - 1);
196 // Next shift the bits that go into the upper value into position.
197 make_unsigned_t<value_type> upperVal = value >> numBitsFirstVal;
198 // Mask off upper bits after right shift in case of signed type.
199 upperVal &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
200 val[1] |= upperVal;
201
202 // Finally, rewrite values.
203 val[0] = byte_swap<value_type, endian>(val[0]);
204 val[1] = byte_swap<value_type, endian>(val[1]);
205 memcpy(LLVM_ASSUME_ALIGNED(
206 memory, (detail::PickAlignment<value_type, alignment>::value)),
207 &val[0], sizeof(value_type) * 2);
208 }
209}
210
211} // end namespace endian
212
213namespace detail {
214
215template <typename ValueType, endianness Endian, std::size_t Alignment,
216 std::size_t ALIGN = PickAlignment<ValueType, Alignment>::value>
217struct packed_endian_specific_integral {
218 using value_type = ValueType;
219 static constexpr endianness endian = Endian;
220 static constexpr std::size_t alignment = Alignment;
221
222 packed_endian_specific_integral() = default;
223
224 explicit packed_endian_specific_integral(value_type val) { *this = val; }
225
226 operator value_type() const {
227 return endian::read<value_type, endian, alignment>(
228 (const void*)Value.buffer);
229 }
230
231 void operator=(value_type newValue) {
232 endian::write<value_type, endian, alignment>(
233 (void*)Value.buffer, newValue);
234 }
235
236 packed_endian_specific_integral &operator+=(value_type newValue) {
237 *this = *this + newValue;
238 return *this;
239 }
240
241 packed_endian_specific_integral &operator-=(value_type newValue) {
242 *this = *this - newValue;
243 return *this;
244 }
245
246 packed_endian_specific_integral &operator|=(value_type newValue) {
247 *this = *this | newValue;
248 return *this;
249 }
250
251 packed_endian_specific_integral &operator&=(value_type newValue) {
252 *this = *this & newValue;
253 return *this;
254 }
255
256private:
257 struct {
258 alignas(ALIGN) char buffer[sizeof(value_type)];
259 } Value;
260
261public:
262 struct ref {
263 explicit ref(void *Ptr) : Ptr(Ptr) {}
264
265 operator value_type() const {
266 return endian::read<value_type, endian, alignment>(Ptr);
267 }
268
269 void operator=(value_type NewValue) {
270 endian::write<value_type, endian, alignment>(Ptr, NewValue);
271 }
272
273 private:
274 void *Ptr;
275 };
276};
277
278} // end namespace detail
279
280using ulittle16_t =
281 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
282 unaligned>;
283using ulittle32_t =
284 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
285 unaligned>;
286using ulittle64_t =
287 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
288 unaligned>;
289
290using little16_t =
291 detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
292 unaligned>;
293using little32_t =
294 detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
295 unaligned>;
296using little64_t =
297 detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
298 unaligned>;
299
300using aligned_ulittle16_t =
301 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
302 aligned>;
303using aligned_ulittle32_t =
304 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
305 aligned>;
306using aligned_ulittle64_t =
307 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
308 aligned>;
309
310using aligned_little16_t =
311 detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
312 aligned>;
313using aligned_little32_t =
314 detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
315 aligned>;
316using aligned_little64_t =
317 detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
318 aligned>;
319
320using ubig16_t =
321 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
322 unaligned>;
323using ubig32_t =
324 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
325 unaligned>;
326using ubig64_t =
327 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
328 unaligned>;
329
330using big16_t =
331 detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
332 unaligned>;
333using big32_t =
334 detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
335 unaligned>;
336using big64_t =
337 detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
338 unaligned>;
339
340using aligned_ubig16_t =
341 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
342 aligned>;
343using aligned_ubig32_t =
344 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
345 aligned>;
346using aligned_ubig64_t =
347 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
348 aligned>;
349
350using aligned_big16_t =
351 detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
352 aligned>;
353using aligned_big32_t =
354 detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
355 aligned>;
356using aligned_big64_t =
357 detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
358 aligned>;
359
360using unaligned_uint16_t =
361 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::native,
362 unaligned>;
363using unaligned_uint32_t =
364 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::native,
365 unaligned>;
366using unaligned_uint64_t =
367 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::native,
368 unaligned>;
369
370using unaligned_int16_t =
371 detail::packed_endian_specific_integral<int16_t, llvm::endianness::native,
372 unaligned>;
373using unaligned_int32_t =
374 detail::packed_endian_specific_integral<int32_t, llvm::endianness::native,
375 unaligned>;
376using unaligned_int64_t =
377 detail::packed_endian_specific_integral<int64_t, llvm::endianness::native,
378 unaligned>;
379
380template <typename T>
381using little_t =
382 detail::packed_endian_specific_integral<T, llvm::endianness::little,
383 unaligned>;
384template <typename T>
385using big_t = detail::packed_endian_specific_integral<T, llvm::endianness::big,
386 unaligned>;
387
388template <typename T>
389using aligned_little_t =
390 detail::packed_endian_specific_integral<T, llvm::endianness::little,
391 aligned>;
392template <typename T>
393using aligned_big_t =
394 detail::packed_endian_specific_integral<T, llvm::endianness::big, aligned>;
395
396namespace endian {
397
398template <typename T, endianness E> [[nodiscard]] inline T read(const void *P) {
399 return *(const detail::packed_endian_specific_integral<T, E, unaligned> *)P;
400}
401
402[[nodiscard]] inline uint16_t read16(const void *P, endianness E) {
403 return read<uint16_t>(memory: P, endian: E);
404}
405[[nodiscard]] inline uint32_t read32(const void *P, endianness E) {
406 return read<uint32_t>(memory: P, endian: E);
407}
408[[nodiscard]] inline uint64_t read64(const void *P, endianness E) {
409 return read<uint64_t>(memory: P, endian: E);
410}
411
412template <endianness E> [[nodiscard]] inline uint16_t read16(const void *P) {
413 return read<uint16_t, E>(P);
414}
415template <endianness E> [[nodiscard]] inline uint32_t read32(const void *P) {
416 return read<uint32_t, E>(P);
417}
418template <endianness E> [[nodiscard]] inline uint64_t read64(const void *P) {
419 return read<uint64_t, E>(P);
420}
421
422[[nodiscard]] inline uint16_t read16le(const void *P) {
423 return read16<llvm::endianness::little>(P);
424}
425[[nodiscard]] inline uint32_t read32le(const void *P) {
426 return read32<llvm::endianness::little>(P);
427}
428[[nodiscard]] inline uint64_t read64le(const void *P) {
429 return read64<llvm::endianness::little>(P);
430}
431[[nodiscard]] inline uint16_t read16be(const void *P) {
432 return read16<llvm::endianness::big>(P);
433}
434[[nodiscard]] inline uint32_t read32be(const void *P) {
435 return read32<llvm::endianness::big>(P);
436}
437[[nodiscard]] inline uint64_t read64be(const void *P) {
438 return read64<llvm::endianness::big>(P);
439}
440
441template <typename T, endianness E> inline void write(void *P, T V) {
442 *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
443}
444
445inline void write16(void *P, uint16_t V, endianness E) {
446 write<uint16_t>(memory: P, value: V, endian: E);
447}
448inline void write32(void *P, uint32_t V, endianness E) {
449 write<uint32_t>(memory: P, value: V, endian: E);
450}
451inline void write64(void *P, uint64_t V, endianness E) {
452 write<uint64_t>(memory: P, value: V, endian: E);
453}
454
455template <endianness E> inline void write16(void *P, uint16_t V) {
456 write<uint16_t, E>(P, V);
457}
458template <endianness E> inline void write32(void *P, uint32_t V) {
459 write<uint32_t, E>(P, V);
460}
461template <endianness E> inline void write64(void *P, uint64_t V) {
462 write<uint64_t, E>(P, V);
463}
464
465inline void write16le(void *P, uint16_t V) {
466 write16<llvm::endianness::little>(P, V);
467}
468inline void write32le(void *P, uint32_t V) {
469 write32<llvm::endianness::little>(P, V);
470}
471inline void write64le(void *P, uint64_t V) {
472 write64<llvm::endianness::little>(P, V);
473}
474inline void write16be(void *P, uint16_t V) {
475 write16<llvm::endianness::big>(P, V);
476}
477inline void write32be(void *P, uint32_t V) {
478 write32<llvm::endianness::big>(P, V);
479}
480inline void write64be(void *P, uint64_t V) {
481 write64<llvm::endianness::big>(P, V);
482}
483
484} // end namespace endian
485
486} // end namespace support
487} // end namespace llvm
488
489#endif // LLVM_SUPPORT_ENDIAN_H
490

source code of include/llvm-20/llvm/Support/Endian.h