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
25 namespace llvm {
26 namespace support {
27
28 // These are named values for common alignments.
29 enum {aligned = 0, unaligned = 1};
30
31 namespace detail {
32
33 /// ::value is either alignment, or alignof(T) if alignment is 0.
34 template<class T, int alignment>
35 struct PickAlignment {
36 enum { value = alignment == 0 ? alignof(T) : alignment };
37 };
38
39 } // end namespace detail
40
41 namespace endian {
42
43 template <typename value_type>
byte_swap(value_type value,endianness endian)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.
51 template <typename value_type, endianness endian>
byte_swap(value_type value)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.
57 template <typename value_type, std::size_t alignment = unaligned>
read(const void * memory,endianness endian)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
68 template <typename value_type, endianness endian, std::size_t alignment>
read(const void * memory)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.
75 template <typename value_type, std::size_t alignment = unaligned,
76 typename CharT>
readNext(const CharT * & memory,endianness endian)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
84 template <typename value_type, endianness endian,
85 std::size_t alignment = unaligned, typename CharT>
readNext(const CharT * & memory)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.
91 template <typename value_type, std::size_t alignment = unaligned>
write(void * memory,value_type value,endianness endian)92 inline 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
99 template<typename value_type,
100 endianness endian,
101 std::size_t alignment>
write(void * memory,value_type value)102 inline 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.
108 template <typename value_type, std::size_t alignment = unaligned,
109 typename CharT>
writeNext(CharT * & memory,value_type value,endianness endian)110 inline void writeNext(CharT *&memory, value_type value, endianness endian) {
111 write(memory, value, endian);
112 memory += sizeof(value_type);
113 }
114
115 template <typename value_type, endianness endian,
116 std::size_t alignment = unaligned, typename CharT>
writeNext(CharT * & memory,value_type value)117 inline void writeNext(CharT *&memory, value_type value) {
118 writeNext<value_type, alignment, CharT>(memory, value, endian);
119 }
120
121 template <typename value_type>
122 using 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.
126 template <typename value_type, endianness endian, std::size_t alignment>
readAtBitAlignment(const void * memory,uint64_t startBit)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.
161 template <typename value_type, endianness endian, std::size_t alignment>
writeAtBitAlignment(void * memory,value_type value,uint64_t startBit)162 inline 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
213 namespace detail {
214
215 template <typename ValueType, endianness Endian, std::size_t Alignment,
216 std::size_t ALIGN = PickAlignment<ValueType, Alignment>::value>
217 struct 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
packed_endian_specific_integralpacked_endian_specific_integral224 explicit packed_endian_specific_integral(value_type val) { *this = val; }
225
valuepacked_endian_specific_integral226 value_type value() const {
227 return endian::read<value_type, endian, alignment>(
228 (const void*)Value.buffer);
229 }
value_typepacked_endian_specific_integral230 operator value_type() const { return value(); }
231
232 void operator=(value_type newValue) {
233 endian::write<value_type, endian, alignment>(
234 (void*)Value.buffer, newValue);
235 }
236
237 packed_endian_specific_integral &operator+=(value_type newValue) {
238 *this = *this + newValue;
239 return *this;
240 }
241
242 packed_endian_specific_integral &operator-=(value_type newValue) {
243 *this = *this - newValue;
244 return *this;
245 }
246
247 packed_endian_specific_integral &operator|=(value_type newValue) {
248 *this = *this | newValue;
249 return *this;
250 }
251
252 packed_endian_specific_integral &operator&=(value_type newValue) {
253 *this = *this & newValue;
254 return *this;
255 }
256
257 private:
258 struct {
259 alignas(ALIGN) char buffer[sizeof(value_type)];
260 } Value;
261
262 public:
263 struct ref {
refpacked_endian_specific_integral::ref264 explicit ref(void *Ptr) : Ptr(Ptr) {}
265
value_typepacked_endian_specific_integral::ref266 operator value_type() const {
267 return endian::read<value_type, endian, alignment>(Ptr);
268 }
269
270 void operator=(value_type NewValue) {
271 endian::write<value_type, endian, alignment>(Ptr, NewValue);
272 }
273
274 private:
275 void *Ptr;
276 };
277 };
278
279 } // end namespace detail
280
281 using ulittle8_t =
282 detail::packed_endian_specific_integral<uint8_t, llvm::endianness::little,
283 unaligned>;
284 using ulittle16_t =
285 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
286 unaligned>;
287 using ulittle32_t =
288 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
289 unaligned>;
290 using ulittle64_t =
291 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
292 unaligned>;
293
294 using little16_t =
295 detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
296 unaligned>;
297 using little32_t =
298 detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
299 unaligned>;
300 using little64_t =
301 detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
302 unaligned>;
303
304 using aligned_ulittle16_t =
305 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
306 aligned>;
307 using aligned_ulittle32_t =
308 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
309 aligned>;
310 using aligned_ulittle64_t =
311 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
312 aligned>;
313
314 using aligned_little16_t =
315 detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
316 aligned>;
317 using aligned_little32_t =
318 detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
319 aligned>;
320 using aligned_little64_t =
321 detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
322 aligned>;
323
324 using ubig16_t =
325 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
326 unaligned>;
327 using ubig32_t =
328 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
329 unaligned>;
330 using ubig64_t =
331 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
332 unaligned>;
333
334 using big16_t =
335 detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
336 unaligned>;
337 using big32_t =
338 detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
339 unaligned>;
340 using big64_t =
341 detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
342 unaligned>;
343
344 using aligned_ubig16_t =
345 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
346 aligned>;
347 using aligned_ubig32_t =
348 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
349 aligned>;
350 using aligned_ubig64_t =
351 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
352 aligned>;
353
354 using aligned_big16_t =
355 detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
356 aligned>;
357 using aligned_big32_t =
358 detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
359 aligned>;
360 using aligned_big64_t =
361 detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
362 aligned>;
363
364 using unaligned_uint16_t =
365 detail::packed_endian_specific_integral<uint16_t, llvm::endianness::native,
366 unaligned>;
367 using unaligned_uint32_t =
368 detail::packed_endian_specific_integral<uint32_t, llvm::endianness::native,
369 unaligned>;
370 using unaligned_uint64_t =
371 detail::packed_endian_specific_integral<uint64_t, llvm::endianness::native,
372 unaligned>;
373
374 using unaligned_int16_t =
375 detail::packed_endian_specific_integral<int16_t, llvm::endianness::native,
376 unaligned>;
377 using unaligned_int32_t =
378 detail::packed_endian_specific_integral<int32_t, llvm::endianness::native,
379 unaligned>;
380 using unaligned_int64_t =
381 detail::packed_endian_specific_integral<int64_t, llvm::endianness::native,
382 unaligned>;
383
384 template <typename T>
385 using little_t =
386 detail::packed_endian_specific_integral<T, llvm::endianness::little,
387 unaligned>;
388 template <typename T>
389 using big_t = detail::packed_endian_specific_integral<T, llvm::endianness::big,
390 unaligned>;
391
392 template <typename T>
393 using aligned_little_t =
394 detail::packed_endian_specific_integral<T, llvm::endianness::little,
395 aligned>;
396 template <typename T>
397 using aligned_big_t =
398 detail::packed_endian_specific_integral<T, llvm::endianness::big, aligned>;
399
400 namespace endian {
401
read(const void * P)402 template <typename T, endianness E> [[nodiscard]] inline T read(const void *P) {
403 return *(const detail::packed_endian_specific_integral<T, E, unaligned> *)P;
404 }
405
read16(const void * P,endianness E)406 [[nodiscard]] inline uint16_t read16(const void *P, endianness E) {
407 return read<uint16_t>(P, E);
408 }
read32(const void * P,endianness E)409 [[nodiscard]] inline uint32_t read32(const void *P, endianness E) {
410 return read<uint32_t>(P, E);
411 }
read64(const void * P,endianness E)412 [[nodiscard]] inline uint64_t read64(const void *P, endianness E) {
413 return read<uint64_t>(P, E);
414 }
415
read16(const void * P)416 template <endianness E> [[nodiscard]] inline uint16_t read16(const void *P) {
417 return read<uint16_t, E>(P);
418 }
read32(const void * P)419 template <endianness E> [[nodiscard]] inline uint32_t read32(const void *P) {
420 return read<uint32_t, E>(P);
421 }
read64(const void * P)422 template <endianness E> [[nodiscard]] inline uint64_t read64(const void *P) {
423 return read<uint64_t, E>(P);
424 }
425
read16le(const void * P)426 [[nodiscard]] inline uint16_t read16le(const void *P) {
427 return read16<llvm::endianness::little>(P);
428 }
read32le(const void * P)429 [[nodiscard]] inline uint32_t read32le(const void *P) {
430 return read32<llvm::endianness::little>(P);
431 }
read64le(const void * P)432 [[nodiscard]] inline uint64_t read64le(const void *P) {
433 return read64<llvm::endianness::little>(P);
434 }
read16be(const void * P)435 [[nodiscard]] inline uint16_t read16be(const void *P) {
436 return read16<llvm::endianness::big>(P);
437 }
read32be(const void * P)438 [[nodiscard]] inline uint32_t read32be(const void *P) {
439 return read32<llvm::endianness::big>(P);
440 }
read64be(const void * P)441 [[nodiscard]] inline uint64_t read64be(const void *P) {
442 return read64<llvm::endianness::big>(P);
443 }
444
write(void * P,T V)445 template <typename T, endianness E> inline void write(void *P, T V) {
446 *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
447 }
448
write16(void * P,uint16_t V,endianness E)449 inline void write16(void *P, uint16_t V, endianness E) {
450 write<uint16_t>(P, V, E);
451 }
write32(void * P,uint32_t V,endianness E)452 inline void write32(void *P, uint32_t V, endianness E) {
453 write<uint32_t>(P, V, E);
454 }
write64(void * P,uint64_t V,endianness E)455 inline void write64(void *P, uint64_t V, endianness E) {
456 write<uint64_t>(P, V, E);
457 }
458
write16(void * P,uint16_t V)459 template <endianness E> inline void write16(void *P, uint16_t V) {
460 write<uint16_t, E>(P, V);
461 }
write32(void * P,uint32_t V)462 template <endianness E> inline void write32(void *P, uint32_t V) {
463 write<uint32_t, E>(P, V);
464 }
write64(void * P,uint64_t V)465 template <endianness E> inline void write64(void *P, uint64_t V) {
466 write<uint64_t, E>(P, V);
467 }
468
write16le(void * P,uint16_t V)469 inline void write16le(void *P, uint16_t V) {
470 write16<llvm::endianness::little>(P, V);
471 }
write32le(void * P,uint32_t V)472 inline void write32le(void *P, uint32_t V) {
473 write32<llvm::endianness::little>(P, V);
474 }
write64le(void * P,uint64_t V)475 inline void write64le(void *P, uint64_t V) {
476 write64<llvm::endianness::little>(P, V);
477 }
write16be(void * P,uint16_t V)478 inline void write16be(void *P, uint16_t V) {
479 write16<llvm::endianness::big>(P, V);
480 }
write32be(void * P,uint32_t V)481 inline void write32be(void *P, uint32_t V) {
482 write32<llvm::endianness::big>(P, V);
483 }
write64be(void * P,uint64_t V)484 inline void write64be(void *P, uint64_t V) {
485 write64<llvm::endianness::big>(P, V);
486 }
487
488 } // end namespace endian
489
490 } // end namespace support
491 } // end namespace llvm
492
493 #endif // LLVM_SUPPORT_ENDIAN_H
494