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]]
53LLVM_DEPRECATED("Pass endian as a function argument instead",
54 "byte_swap") inline value_type byte_swap(value_type value) {
55 return byte_swap(value, endian);
56}
57
58/// Read a value of a particular endianness from memory.
59template <typename value_type, std::size_t alignment = unaligned>
60[[nodiscard]] inline value_type read(const void *memory, endianness endian) {
61 value_type ret;
62
63 memcpy(static_cast<void *>(&ret),
64 LLVM_ASSUME_ALIGNED(
65 memory, (detail::PickAlignment<value_type, alignment>::value)),
66 sizeof(value_type));
67 return byte_swap<value_type>(ret, endian);
68}
69
70template <typename value_type, endianness endian, std::size_t alignment>
71[[nodiscard]] LLVM_DEPRECATED("Pass endian as a function argument instead",
72 "read") inline value_type
73 read(const void *memory) {
74 return read<value_type, alignment>(memory, endian);
75}
76
77/// Read a value of a particular endianness from a buffer, and increment the
78/// buffer past that value.
79template <typename value_type, std::size_t alignment = unaligned,
80 typename CharT>
81[[nodiscard]] inline value_type readNext(const CharT *&memory,
82 endianness endian) {
83 value_type ret = read<value_type, alignment>(memory, endian);
84 memory += sizeof(value_type);
85 return ret;
86}
87
88template <typename value_type, endianness endian,
89 std::size_t alignment = unaligned, typename CharT>
90[[nodiscard]] inline value_type readNext(const CharT *&memory) {
91 return readNext<value_type, alignment, CharT>(memory, endian);
92}
93
94/// Write a value to memory with a particular endianness.
95template <typename value_type, std::size_t alignment = unaligned>
96inline void write(void *memory, value_type value, endianness endian) {
97 value = byte_swap<value_type>(value, endian);
98 memcpy(LLVM_ASSUME_ALIGNED(
99 memory, (detail::PickAlignment<value_type, alignment>::value)),
100 &value, sizeof(value_type));
101}
102
103template <typename value_type, endianness endian, std::size_t alignment>
104LLVM_DEPRECATED("Pass endian as a function argument instead", "write")
105inline void write(void *memory, value_type value) {
106 write<value_type, alignment>(memory, value, endian);
107}
108
109/// Write a value of a particular endianness, and increment the buffer past that
110/// value.
111template <typename value_type, std::size_t alignment = unaligned,
112 typename CharT>
113inline void writeNext(CharT *&memory, value_type value, endianness endian) {
114 write(memory, value, endian);
115 memory += sizeof(value_type);
116}
117
118template <typename value_type, endianness endian,
119 std::size_t alignment = unaligned, typename CharT>
120inline void writeNext(CharT *&memory, value_type value) {
121 writeNext<value_type, alignment, CharT>(memory, value, endian);
122}
123
124template <typename value_type>
125using make_unsigned_t = std::make_unsigned_t<value_type>;
126
127/// Read a value of a particular endianness from memory, for a location
128/// that starts at the given bit offset within the first byte.
129template <typename value_type, endianness endian, std::size_t alignment>
130[[nodiscard]] inline value_type readAtBitAlignment(const void *memory,
131 uint64_t startBit) {
132 assert(startBit < 8);
133 if (startBit == 0)
134 return read<value_type, alignment>(memory, endian);
135 else {
136 // Read two values and compose the result from them.
137 value_type val[2];
138 memcpy(&val[0],
139 LLVM_ASSUME_ALIGNED(
140 memory, (detail::PickAlignment<value_type, alignment>::value)),
141 sizeof(value_type) * 2);
142 val[0] = byte_swap<value_type>(val[0], endian);
143 val[1] = byte_swap<value_type>(val[1], endian);
144
145 // Shift bits from the lower value into place.
146 make_unsigned_t<value_type> lowerVal = val[0] >> startBit;
147 // Mask off upper bits after right shift in case of signed type.
148 make_unsigned_t<value_type> numBitsFirstVal =
149 (sizeof(value_type) * 8) - startBit;
150 lowerVal &= ((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1;
151
152 // Get the bits from the upper value.
153 make_unsigned_t<value_type> upperVal =
154 val[1] & (((make_unsigned_t<value_type>)1 << startBit) - 1);
155 // Shift them in to place.
156 upperVal <<= numBitsFirstVal;
157
158 return lowerVal | upperVal;
159 }
160}
161
162/// Write a value to memory with a particular endianness, for a location
163/// that starts at the given bit offset within the first byte.
164template <typename value_type, endianness endian, std::size_t alignment>
165inline void writeAtBitAlignment(void *memory, value_type value,
166 uint64_t startBit) {
167 assert(startBit < 8);
168 if (startBit == 0)
169 write<value_type, alignment>(memory, value, endian);
170 else {
171 // Read two values and shift the result into them.
172 value_type val[2];
173 memcpy(&val[0],
174 LLVM_ASSUME_ALIGNED(
175 memory, (detail::PickAlignment<value_type, alignment>::value)),
176 sizeof(value_type) * 2);
177 val[0] = byte_swap<value_type>(val[0], endian);
178 val[1] = byte_swap<value_type>(val[1], endian);
179
180 // Mask off any existing bits in the upper part of the lower value that
181 // we want to replace.
182 val[0] &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
183 make_unsigned_t<value_type> numBitsFirstVal =
184 (sizeof(value_type) * 8) - startBit;
185 make_unsigned_t<value_type> lowerVal = value;
186 if (startBit > 0) {
187 // Mask off the upper bits in the new value that are not going to go into
188 // the lower value. This avoids a left shift of a negative value, which
189 // is undefined behavior.
190 lowerVal &= (((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1);
191 // Now shift the new bits into place
192 lowerVal <<= startBit;
193 }
194 val[0] |= lowerVal;
195
196 // Mask off any existing bits in the lower part of the upper value that
197 // we want to replace.
198 val[1] &= ~(((make_unsigned_t<value_type>)1 << startBit) - 1);
199 // Next shift the bits that go into the upper value into position.
200 make_unsigned_t<value_type> upperVal = value >> numBitsFirstVal;
201 // Mask off upper bits after right shift in case of signed type.
202 upperVal &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
203 val[1] |= upperVal;
204
205 // Finally, rewrite values.
206 val[0] = byte_swap<value_type>(val[0], endian);
207 val[1] = byte_swap<value_type>(val[1], endian);
208 memcpy(LLVM_ASSUME_ALIGNED(
209 memory, (detail::PickAlignment<value_type, alignment>::value)),
210 &val[0], sizeof(value_type) * 2);
211 }
212}
213
214} // end namespace endian
215
216namespace detail {
217
218template <typename ValueType, endianness Endian, std::size_t Alignment,
219 std::size_t ALIGN = PickAlignment<ValueType, Alignment>::value>
220struct packed_endian_specific_integral {
221 using value_type = ValueType;
222 static constexpr endianness endian = Endian;
223 static constexpr std::size_t alignment = Alignment;
224
225 packed_endian_specific_integral() = default;
226
227 explicit packed_endian_specific_integral(value_type val) { *this = val; }
228
229 value_type value() const {
230 return endian::read<value_type, alignment>((const void *)Value.buffer,
231 endian);
232 }
233 operator value_type() const { return value(); }
234
235 void operator=(value_type newValue) {
236 endian::write<value_type, alignment>((void *)Value.buffer, newValue,
237 endian);
238 }
239
240 packed_endian_specific_integral &operator+=(value_type newValue) {
241 *this = *this + newValue;
242 return *this;
243 }
244
245 packed_endian_specific_integral &operator-=(value_type newValue) {
246 *this = *this - newValue;
247 return *this;
248 }
249
250 packed_endian_specific_integral &operator|=(value_type newValue) {
251 *this = *this | newValue;
252 return *this;
253 }
254
255 packed_endian_specific_integral &operator&=(value_type newValue) {
256 *this = *this & newValue;
257 return *this;
258 }
259
260private:
261 struct {
262 alignas(ALIGN) char buffer[sizeof(value_type)];
263 } Value;
264
265public:
266 struct ref {
267 explicit ref(void *Ptr) : Ptr(Ptr) {}
268
269 operator value_type() const {
270 return endian::read<value_type, alignment>(Ptr, endian);
271 }
272
273 void operator=(value_type NewValue) {
274 endian::write<value_type, alignment>(Ptr, NewValue, endian);
275 }
276
277 private:
278 void *Ptr;
279 };
280};
281
282} // end namespace detail
283
284using ulittle8_t =
285 detail::packed_endian_specific_integral<uint8_t, llvm::endianness::little,
286 unaligned>;
287using ulittle16_t =
288 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
289 unaligned>;
290using ulittle32_t =
291 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
292 unaligned>;
293using ulittle64_t =
294 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
295 unaligned>;
296
297using little16_t =
298 detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
299 unaligned>;
300using little32_t =
301 detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
302 unaligned>;
303using little64_t =
304 detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
305 unaligned>;
306
307using aligned_ulittle16_t =
308 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
309 aligned>;
310using aligned_ulittle32_t =
311 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
312 aligned>;
313using aligned_ulittle64_t =
314 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
315 aligned>;
316
317using aligned_little16_t =
318 detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
319 aligned>;
320using aligned_little32_t =
321 detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
322 aligned>;
323using aligned_little64_t =
324 detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
325 aligned>;
326
327using ubig16_t =
328 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
329 unaligned>;
330using ubig32_t =
331 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
332 unaligned>;
333using ubig64_t =
334 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
335 unaligned>;
336
337using big16_t =
338 detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
339 unaligned>;
340using big32_t =
341 detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
342 unaligned>;
343using big64_t =
344 detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
345 unaligned>;
346
347using aligned_ubig16_t =
348 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
349 aligned>;
350using aligned_ubig32_t =
351 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
352 aligned>;
353using aligned_ubig64_t =
354 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
355 aligned>;
356
357using aligned_big16_t =
358 detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
359 aligned>;
360using aligned_big32_t =
361 detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
362 aligned>;
363using aligned_big64_t =
364 detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
365 aligned>;
366
367using unaligned_uint16_t =
368 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::native,
369 unaligned>;
370using unaligned_uint32_t =
371 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::native,
372 unaligned>;
373using unaligned_uint64_t =
374 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::native,
375 unaligned>;
376
377using unaligned_int16_t =
378 detail::packed_endian_specific_integral<int16_t, llvm::endianness::native,
379 unaligned>;
380using unaligned_int32_t =
381 detail::packed_endian_specific_integral<int32_t, llvm::endianness::native,
382 unaligned>;
383using unaligned_int64_t =
384 detail::packed_endian_specific_integral<int64_t, llvm::endianness::native,
385 unaligned>;
386
387template <typename T>
388using little_t =
389 detail::packed_endian_specific_integral<T, llvm::endianness::little,
390 unaligned>;
391template <typename T>
392using big_t = detail::packed_endian_specific_integral<T, llvm::endianness::big,
393 unaligned>;
394
395template <typename T>
396using aligned_little_t =
397 detail::packed_endian_specific_integral<T, llvm::endianness::little,
398 aligned>;
399template <typename T>
400using aligned_big_t =
401 detail::packed_endian_specific_integral<T, llvm::endianness::big, aligned>;
402
403namespace endian {
404
405template <typename T, endianness E> [[nodiscard]] inline T read(const void *P) {
406 return *(const detail::packed_endian_specific_integral<T, E, unaligned> *)P;
407}
408
409[[nodiscard]] inline uint16_t read16(const void *P, endianness E) {
410 return read<uint16_t>(memory: P, endian: E);
411}
412[[nodiscard]] inline uint32_t read32(const void *P, endianness E) {
413 return read<uint32_t>(memory: P, endian: E);
414}
415[[nodiscard]] inline uint64_t read64(const void *P, endianness E) {
416 return read<uint64_t>(memory: P, endian: E);
417}
418
419template <endianness E> [[nodiscard]] inline uint16_t read16(const void *P) {
420 return read<uint16_t, E>(P);
421}
422template <endianness E> [[nodiscard]] inline uint32_t read32(const void *P) {
423 return read<uint32_t, E>(P);
424}
425template <endianness E> [[nodiscard]] inline uint64_t read64(const void *P) {
426 return read<uint64_t, E>(P);
427}
428
429[[nodiscard]] inline uint16_t read16le(const void *P) {
430 return read16<llvm::endianness::little>(P);
431}
432[[nodiscard]] inline uint32_t read32le(const void *P) {
433 return read32<llvm::endianness::little>(P);
434}
435[[nodiscard]] inline uint64_t read64le(const void *P) {
436 return read64<llvm::endianness::little>(P);
437}
438[[nodiscard]] inline uint16_t read16be(const void *P) {
439 return read16<llvm::endianness::big>(P);
440}
441[[nodiscard]] inline uint32_t read32be(const void *P) {
442 return read32<llvm::endianness::big>(P);
443}
444[[nodiscard]] inline uint64_t read64be(const void *P) {
445 return read64<llvm::endianness::big>(P);
446}
447
448template <typename T, endianness E> inline void write(void *P, T V) {
449 *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
450}
451
452inline void write16(void *P, uint16_t V, endianness E) {
453 write<uint16_t>(memory: P, value: V, endian: E);
454}
455inline void write32(void *P, uint32_t V, endianness E) {
456 write<uint32_t>(memory: P, value: V, endian: E);
457}
458inline void write64(void *P, uint64_t V, endianness E) {
459 write<uint64_t>(memory: P, value: V, endian: E);
460}
461
462template <endianness E> inline void write16(void *P, uint16_t V) {
463 write<uint16_t, E>(P, V);
464}
465template <endianness E> inline void write32(void *P, uint32_t V) {
466 write<uint32_t, E>(P, V);
467}
468template <endianness E> inline void write64(void *P, uint64_t V) {
469 write<uint64_t, E>(P, V);
470}
471
472inline void write16le(void *P, uint16_t V) {
473 write16<llvm::endianness::little>(P, V);
474}
475inline void write32le(void *P, uint32_t V) {
476 write32<llvm::endianness::little>(P, V);
477}
478inline void write64le(void *P, uint64_t V) {
479 write64<llvm::endianness::little>(P, V);
480}
481inline void write16be(void *P, uint16_t V) {
482 write16<llvm::endianness::big>(P, V);
483}
484inline void write32be(void *P, uint32_t V) {
485 write32<llvm::endianness::big>(P, V);
486}
487inline void write64be(void *P, uint64_t V) {
488 write64<llvm::endianness::big>(P, V);
489}
490
491} // end namespace endian
492
493} // end namespace support
494} // end namespace llvm
495
496#endif // LLVM_SUPPORT_ENDIAN_H
497