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

source code of include/llvm-17/llvm/Support/Endian.h