xref: /freebsd-src/contrib/llvm-project/llvm/include/llvm/Support/Endian.h (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583) 
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>
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>
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>
58 [[nodiscard]] inline value_type read(const void *memory, endianness endian) {
59   value_type ret;
60 
61   memcpy(&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>
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>
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>
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>
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>
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>
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>
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>
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>
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 
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 
256 private:
257   struct {
258     alignas(ALIGN) char buffer[sizeof(value_type)];
259   } Value;
260 
261 public:
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 
280 using ulittle16_t =
281     detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
282                                             unaligned>;
283 using ulittle32_t =
284     detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
285                                             unaligned>;
286 using ulittle64_t =
287     detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
288                                             unaligned>;
289 
290 using little16_t =
291     detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
292                                             unaligned>;
293 using little32_t =
294     detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
295                                             unaligned>;
296 using little64_t =
297     detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
298                                             unaligned>;
299 
300 using aligned_ulittle16_t =
301     detail::packed_endian_specific_integral<uint16_t, llvm::endianness::little,
302                                             aligned>;
303 using aligned_ulittle32_t =
304     detail::packed_endian_specific_integral<uint32_t, llvm::endianness::little,
305                                             aligned>;
306 using aligned_ulittle64_t =
307     detail::packed_endian_specific_integral<uint64_t, llvm::endianness::little,
308                                             aligned>;
309 
310 using aligned_little16_t =
311     detail::packed_endian_specific_integral<int16_t, llvm::endianness::little,
312                                             aligned>;
313 using aligned_little32_t =
314     detail::packed_endian_specific_integral<int32_t, llvm::endianness::little,
315                                             aligned>;
316 using aligned_little64_t =
317     detail::packed_endian_specific_integral<int64_t, llvm::endianness::little,
318                                             aligned>;
319 
320 using ubig16_t =
321     detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
322                                             unaligned>;
323 using ubig32_t =
324     detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
325                                             unaligned>;
326 using ubig64_t =
327     detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
328                                             unaligned>;
329 
330 using big16_t =
331     detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
332                                             unaligned>;
333 using big32_t =
334     detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
335                                             unaligned>;
336 using big64_t =
337     detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
338                                             unaligned>;
339 
340 using aligned_ubig16_t =
341     detail::packed_endian_specific_integral<uint16_t, llvm::endianness::big,
342                                             aligned>;
343 using aligned_ubig32_t =
344     detail::packed_endian_specific_integral<uint32_t, llvm::endianness::big,
345                                             aligned>;
346 using aligned_ubig64_t =
347     detail::packed_endian_specific_integral<uint64_t, llvm::endianness::big,
348                                             aligned>;
349 
350 using aligned_big16_t =
351     detail::packed_endian_specific_integral<int16_t, llvm::endianness::big,
352                                             aligned>;
353 using aligned_big32_t =
354     detail::packed_endian_specific_integral<int32_t, llvm::endianness::big,
355                                             aligned>;
356 using aligned_big64_t =
357     detail::packed_endian_specific_integral<int64_t, llvm::endianness::big,
358                                             aligned>;
359 
360 using unaligned_uint16_t =
361     detail::packed_endian_specific_integral<uint16_t, llvm::endianness::native,
362                                             unaligned>;
363 using unaligned_uint32_t =
364     detail::packed_endian_specific_integral<uint32_t, llvm::endianness::native,
365                                             unaligned>;
366 using unaligned_uint64_t =
367     detail::packed_endian_specific_integral<uint64_t, llvm::endianness::native,
368                                             unaligned>;
369 
370 using unaligned_int16_t =
371     detail::packed_endian_specific_integral<int16_t, llvm::endianness::native,
372                                             unaligned>;
373 using unaligned_int32_t =
374     detail::packed_endian_specific_integral<int32_t, llvm::endianness::native,
375                                             unaligned>;
376 using unaligned_int64_t =
377     detail::packed_endian_specific_integral<int64_t, llvm::endianness::native,
378                                             unaligned>;
379 
380 template <typename T>
381 using little_t =
382     detail::packed_endian_specific_integral<T, llvm::endianness::little,
383                                             unaligned>;
384 template <typename T>
385 using big_t = detail::packed_endian_specific_integral<T, llvm::endianness::big,
386                                                       unaligned>;
387 
388 template <typename T>
389 using aligned_little_t =
390     detail::packed_endian_specific_integral<T, llvm::endianness::little,
391                                             aligned>;
392 template <typename T>
393 using aligned_big_t =
394     detail::packed_endian_specific_integral<T, llvm::endianness::big, aligned>;
395 
396 namespace endian {
397 
398 template <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>(P, E);
404 }
405 [[nodiscard]] inline uint32_t read32(const void *P, endianness E) {
406   return read<uint32_t>(P, E);
407 }
408 [[nodiscard]] inline uint64_t read64(const void *P, endianness E) {
409   return read<uint64_t>(P, E);
410 }
411 
412 template <endianness E> [[nodiscard]] inline uint16_t read16(const void *P) {
413   return read<uint16_t, E>(P);
414 }
415 template <endianness E> [[nodiscard]] inline uint32_t read32(const void *P) {
416   return read<uint32_t, E>(P);
417 }
418 template <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 
441 template <typename T, endianness E> inline void write(void *P, T V) {
442   *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
443 }
444 
445 inline void write16(void *P, uint16_t V, endianness E) {
446   write<uint16_t>(P, V, E);
447 }
448 inline void write32(void *P, uint32_t V, endianness E) {
449   write<uint32_t>(P, V, E);
450 }
451 inline void write64(void *P, uint64_t V, endianness E) {
452   write<uint64_t>(P, V, E);
453 }
454 
455 template <endianness E> inline void write16(void *P, uint16_t V) {
456   write<uint16_t, E>(P, V);
457 }
458 template <endianness E> inline void write32(void *P, uint32_t V) {
459   write<uint32_t, E>(P, V);
460 }
461 template <endianness E> inline void write64(void *P, uint64_t V) {
462   write<uint64_t, E>(P, V);
463 }
464 
465 inline void write16le(void *P, uint16_t V) {
466   write16<llvm::endianness::little>(P, V);
467 }
468 inline void write32le(void *P, uint32_t V) {
469   write32<llvm::endianness::little>(P, V);
470 }
471 inline void write64le(void *P, uint64_t V) {
472   write64<llvm::endianness::little>(P, V);
473 }
474 inline void write16be(void *P, uint16_t V) {
475   write16<llvm::endianness::big>(P, V);
476 }
477 inline void write32be(void *P, uint32_t V) {
478   write32<llvm::endianness::big>(P, V);
479 }
480 inline 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