1 //===- Endian.h - Utilities for IO with endian specific data ----*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file declares generic functions to read and write endian specific data.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #ifndef LLVM_SUPPORT_ENDIAN_H
15 #define LLVM_SUPPORT_ENDIAN_H
16
17 #include "llvm/Support/AlignOf.h"
18 #include "llvm/Support/Compiler.h"
19 #include "llvm/Support/Host.h"
20 #include "llvm/Support/SwapByteOrder.h"
21 #include <cassert>
22 #include <cstddef>
23 #include <cstdint>
24 #include <cstring>
25 #include <type_traits>
26
27 namespace llvm {
28 namespace support {
29
30 enum endianness {big, little, native};
31
32 // These are named values for common alignments.
33 enum {aligned = 0, unaligned = 1};
34
35 namespace detail {
36
37 /// ::value is either alignment, or alignof(T) if alignment is 0.
38 template<class T, int alignment>
39 struct PickAlignment {
40 enum { value = alignment == 0 ? alignof(T) : alignment };
41 };
42
43 } // end namespace detail
44
45 namespace endian {
46
system_endianness()47 constexpr endianness system_endianness() {
48 return sys::IsBigEndianHost ? big : little;
49 }
50
51 template <typename value_type>
byte_swap(value_type value,endianness endian)52 inline value_type byte_swap(value_type value, endianness endian) {
53 if ((endian != native) && (endian != system_endianness()))
54 sys::swapByteOrder(value);
55 return value;
56 }
57
58 /// Swap the bytes of value to match the given endianness.
59 template<typename value_type, endianness endian>
byte_swap(value_type value)60 inline value_type byte_swap(value_type value) {
61 return byte_swap(value, endian);
62 }
63
64 /// Read a value of a particular endianness from memory.
65 template <typename value_type, std::size_t alignment>
read(const void * memory,endianness endian)66 inline value_type read(const void *memory, endianness endian) {
67 value_type ret;
68
69 memcpy(&ret,
70 LLVM_ASSUME_ALIGNED(
71 memory, (detail::PickAlignment<value_type, alignment>::value)),
72 sizeof(value_type));
73 return byte_swap<value_type>(ret, endian);
74 }
75
76 template<typename value_type,
77 endianness endian,
78 std::size_t alignment>
read(const void * memory)79 inline value_type read(const void *memory) {
80 return read<value_type, alignment>(memory, endian);
81 }
82
83 /// Read a value of a particular endianness from a buffer, and increment the
84 /// buffer past that value.
85 template <typename value_type, std::size_t alignment, typename CharT>
readNext(const CharT * & memory,endianness endian)86 inline value_type readNext(const CharT *&memory, endianness endian) {
87 value_type ret = read<value_type, alignment>(memory, endian);
88 memory += sizeof(value_type);
89 return ret;
90 }
91
92 template<typename value_type, endianness endian, std::size_t alignment,
93 typename CharT>
readNext(const CharT * & memory)94 inline value_type readNext(const CharT *&memory) {
95 return readNext<value_type, alignment, CharT>(memory, endian);
96 }
97
98 /// Write a value to memory with a particular endianness.
99 template <typename value_type, std::size_t alignment>
write(void * memory,value_type value,endianness endian)100 inline void write(void *memory, value_type value, endianness endian) {
101 value = byte_swap<value_type>(value, endian);
102 memcpy(LLVM_ASSUME_ALIGNED(
103 memory, (detail::PickAlignment<value_type, alignment>::value)),
104 &value, sizeof(value_type));
105 }
106
107 template<typename value_type,
108 endianness endian,
109 std::size_t alignment>
write(void * memory,value_type value)110 inline void write(void *memory, value_type value) {
111 write<value_type, alignment>(memory, value, endian);
112 }
113
114 template <typename value_type>
115 using make_unsigned_t = typename std::make_unsigned<value_type>::type;
116
117 /// Read a value of a particular endianness from memory, for a location
118 /// that starts at the given bit offset within the first byte.
119 template <typename value_type, endianness endian, std::size_t alignment>
readAtBitAlignment(const void * memory,uint64_t startBit)120 inline value_type readAtBitAlignment(const void *memory, uint64_t startBit) {
121 assert(startBit < 8);
122 if (startBit == 0)
123 return read<value_type, endian, alignment>(memory);
124 else {
125 // Read two values and compose the result from them.
126 value_type val[2];
127 memcpy(&val[0],
128 LLVM_ASSUME_ALIGNED(
129 memory, (detail::PickAlignment<value_type, alignment>::value)),
130 sizeof(value_type) * 2);
131 val[0] = byte_swap<value_type, endian>(val[0]);
132 val[1] = byte_swap<value_type, endian>(val[1]);
133
134 // Shift bits from the lower value into place.
135 make_unsigned_t<value_type> lowerVal = val[0] >> startBit;
136 // Mask off upper bits after right shift in case of signed type.
137 make_unsigned_t<value_type> numBitsFirstVal =
138 (sizeof(value_type) * 8) - startBit;
139 lowerVal &= ((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1;
140
141 // Get the bits from the upper value.
142 make_unsigned_t<value_type> upperVal =
143 val[1] & (((make_unsigned_t<value_type>)1 << startBit) - 1);
144 // Shift them in to place.
145 upperVal <<= numBitsFirstVal;
146
147 return lowerVal | upperVal;
148 }
149 }
150
151 /// Write a value to memory with a particular endianness, for a location
152 /// that starts at the given bit offset within the first byte.
153 template <typename value_type, endianness endian, std::size_t alignment>
writeAtBitAlignment(void * memory,value_type value,uint64_t startBit)154 inline void writeAtBitAlignment(void *memory, value_type value,
155 uint64_t startBit) {
156 assert(startBit < 8);
157 if (startBit == 0)
158 write<value_type, endian, alignment>(memory, value);
159 else {
160 // Read two values and shift the result into them.
161 value_type val[2];
162 memcpy(&val[0],
163 LLVM_ASSUME_ALIGNED(
164 memory, (detail::PickAlignment<value_type, alignment>::value)),
165 sizeof(value_type) * 2);
166 val[0] = byte_swap<value_type, endian>(val[0]);
167 val[1] = byte_swap<value_type, endian>(val[1]);
168
169 // Mask off any existing bits in the upper part of the lower value that
170 // we want to replace.
171 val[0] &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
172 make_unsigned_t<value_type> numBitsFirstVal =
173 (sizeof(value_type) * 8) - startBit;
174 make_unsigned_t<value_type> lowerVal = value;
175 if (startBit > 0) {
176 // Mask off the upper bits in the new value that are not going to go into
177 // the lower value. This avoids a left shift of a negative value, which
178 // is undefined behavior.
179 lowerVal &= (((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1);
180 // Now shift the new bits into place
181 lowerVal <<= startBit;
182 }
183 val[0] |= lowerVal;
184
185 // Mask off any existing bits in the lower part of the upper value that
186 // we want to replace.
187 val[1] &= ~(((make_unsigned_t<value_type>)1 << startBit) - 1);
188 // Next shift the bits that go into the upper value into position.
189 make_unsigned_t<value_type> upperVal = value >> numBitsFirstVal;
190 // Mask off upper bits after right shift in case of signed type.
191 upperVal &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
192 val[1] |= upperVal;
193
194 // Finally, rewrite values.
195 val[0] = byte_swap<value_type, endian>(val[0]);
196 val[1] = byte_swap<value_type, endian>(val[1]);
197 memcpy(LLVM_ASSUME_ALIGNED(
198 memory, (detail::PickAlignment<value_type, alignment>::value)),
199 &val[0], sizeof(value_type) * 2);
200 }
201 }
202
203 } // end namespace endian
204
205 namespace detail {
206
207 template<typename value_type,
208 endianness endian,
209 std::size_t alignment>
210 struct packed_endian_specific_integral {
211 packed_endian_specific_integral() = default;
212
packed_endian_specific_integralpacked_endian_specific_integral213 explicit packed_endian_specific_integral(value_type val) { *this = val; }
214
value_typepacked_endian_specific_integral215 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
245 private:
246 AlignedCharArray<PickAlignment<value_type, alignment>::value,
247 sizeof(value_type)> Value;
248
249 public:
250 struct ref {
refpacked_endian_specific_integral::ref251 explicit ref(void *Ptr) : Ptr(Ptr) {}
252
value_typepacked_endian_specific_integral::ref253 operator value_type() const {
254 return endian::read<value_type, endian, alignment>(Ptr);
255 }
256
257 void operator=(value_type NewValue) {
258 endian::write<value_type, endian, alignment>(Ptr, NewValue);
259 }
260
261 private:
262 void *Ptr;
263 };
264 };
265
266 } // end namespace detail
267
268 using ulittle16_t =
269 detail::packed_endian_specific_integral<uint16_t, little, unaligned>;
270 using ulittle32_t =
271 detail::packed_endian_specific_integral<uint32_t, little, unaligned>;
272 using ulittle64_t =
273 detail::packed_endian_specific_integral<uint64_t, little, unaligned>;
274
275 using little16_t =
276 detail::packed_endian_specific_integral<int16_t, little, unaligned>;
277 using little32_t =
278 detail::packed_endian_specific_integral<int32_t, little, unaligned>;
279 using little64_t =
280 detail::packed_endian_specific_integral<int64_t, little, unaligned>;
281
282 using aligned_ulittle16_t =
283 detail::packed_endian_specific_integral<uint16_t, little, aligned>;
284 using aligned_ulittle32_t =
285 detail::packed_endian_specific_integral<uint32_t, little, aligned>;
286 using aligned_ulittle64_t =
287 detail::packed_endian_specific_integral<uint64_t, little, aligned>;
288
289 using aligned_little16_t =
290 detail::packed_endian_specific_integral<int16_t, little, aligned>;
291 using aligned_little32_t =
292 detail::packed_endian_specific_integral<int32_t, little, aligned>;
293 using aligned_little64_t =
294 detail::packed_endian_specific_integral<int64_t, little, aligned>;
295
296 using ubig16_t =
297 detail::packed_endian_specific_integral<uint16_t, big, unaligned>;
298 using ubig32_t =
299 detail::packed_endian_specific_integral<uint32_t, big, unaligned>;
300 using ubig64_t =
301 detail::packed_endian_specific_integral<uint64_t, big, unaligned>;
302
303 using big16_t =
304 detail::packed_endian_specific_integral<int16_t, big, unaligned>;
305 using big32_t =
306 detail::packed_endian_specific_integral<int32_t, big, unaligned>;
307 using big64_t =
308 detail::packed_endian_specific_integral<int64_t, big, unaligned>;
309
310 using aligned_ubig16_t =
311 detail::packed_endian_specific_integral<uint16_t, big, aligned>;
312 using aligned_ubig32_t =
313 detail::packed_endian_specific_integral<uint32_t, big, aligned>;
314 using aligned_ubig64_t =
315 detail::packed_endian_specific_integral<uint64_t, big, aligned>;
316
317 using aligned_big16_t =
318 detail::packed_endian_specific_integral<int16_t, big, aligned>;
319 using aligned_big32_t =
320 detail::packed_endian_specific_integral<int32_t, big, aligned>;
321 using aligned_big64_t =
322 detail::packed_endian_specific_integral<int64_t, big, aligned>;
323
324 using unaligned_uint16_t =
325 detail::packed_endian_specific_integral<uint16_t, native, unaligned>;
326 using unaligned_uint32_t =
327 detail::packed_endian_specific_integral<uint32_t, native, unaligned>;
328 using unaligned_uint64_t =
329 detail::packed_endian_specific_integral<uint64_t, native, unaligned>;
330
331 using unaligned_int16_t =
332 detail::packed_endian_specific_integral<int16_t, native, unaligned>;
333 using unaligned_int32_t =
334 detail::packed_endian_specific_integral<int32_t, native, unaligned>;
335 using unaligned_int64_t =
336 detail::packed_endian_specific_integral<int64_t, native, unaligned>;
337
338 namespace endian {
339
read(const void * P,endianness E)340 template <typename T> inline T read(const void *P, endianness E) {
341 return read<T, unaligned>(P, E);
342 }
343
read(const void * P)344 template <typename T, endianness E> inline T read(const void *P) {
345 return *(const detail::packed_endian_specific_integral<T, E, unaligned> *)P;
346 }
347
read16(const void * P,endianness E)348 inline uint16_t read16(const void *P, endianness E) {
349 return read<uint16_t>(P, E);
350 }
read32(const void * P,endianness E)351 inline uint32_t read32(const void *P, endianness E) {
352 return read<uint32_t>(P, E);
353 }
read64(const void * P,endianness E)354 inline uint64_t read64(const void *P, endianness E) {
355 return read<uint64_t>(P, E);
356 }
357
read16(const void * P)358 template <endianness E> inline uint16_t read16(const void *P) {
359 return read<uint16_t, E>(P);
360 }
read32(const void * P)361 template <endianness E> inline uint32_t read32(const void *P) {
362 return read<uint32_t, E>(P);
363 }
read64(const void * P)364 template <endianness E> inline uint64_t read64(const void *P) {
365 return read<uint64_t, E>(P);
366 }
367
read16le(const void * P)368 inline uint16_t read16le(const void *P) { return read16<little>(P); }
read32le(const void * P)369 inline uint32_t read32le(const void *P) { return read32<little>(P); }
read64le(const void * P)370 inline uint64_t read64le(const void *P) { return read64<little>(P); }
read16be(const void * P)371 inline uint16_t read16be(const void *P) { return read16<big>(P); }
read32be(const void * P)372 inline uint32_t read32be(const void *P) { return read32<big>(P); }
read64be(const void * P)373 inline uint64_t read64be(const void *P) { return read64<big>(P); }
374
write(void * P,T V,endianness E)375 template <typename T> inline void write(void *P, T V, endianness E) {
376 write<T, unaligned>(P, V, E);
377 }
378
write(void * P,T V)379 template <typename T, endianness E> inline void write(void *P, T V) {
380 *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
381 }
382
write16(void * P,uint16_t V,endianness E)383 inline void write16(void *P, uint16_t V, endianness E) {
384 write<uint16_t>(P, V, E);
385 }
write32(void * P,uint32_t V,endianness E)386 inline void write32(void *P, uint32_t V, endianness E) {
387 write<uint32_t>(P, V, E);
388 }
write64(void * P,uint64_t V,endianness E)389 inline void write64(void *P, uint64_t V, endianness E) {
390 write<uint64_t>(P, V, E);
391 }
392
write16(void * P,uint16_t V)393 template <endianness E> inline void write16(void *P, uint16_t V) {
394 write<uint16_t, E>(P, V);
395 }
write32(void * P,uint32_t V)396 template <endianness E> inline void write32(void *P, uint32_t V) {
397 write<uint32_t, E>(P, V);
398 }
write64(void * P,uint64_t V)399 template <endianness E> inline void write64(void *P, uint64_t V) {
400 write<uint64_t, E>(P, V);
401 }
402
write16le(void * P,uint16_t V)403 inline void write16le(void *P, uint16_t V) { write16<little>(P, V); }
write32le(void * P,uint32_t V)404 inline void write32le(void *P, uint32_t V) { write32<little>(P, V); }
write64le(void * P,uint64_t V)405 inline void write64le(void *P, uint64_t V) { write64<little>(P, V); }
write16be(void * P,uint16_t V)406 inline void write16be(void *P, uint16_t V) { write16<big>(P, V); }
write32be(void * P,uint32_t V)407 inline void write32be(void *P, uint32_t V) { write32<big>(P, V); }
write64be(void * P,uint64_t V)408 inline void write64be(void *P, uint64_t V) { write64<big>(P, V); }
409
410 } // end namespace endian
411
412 } // end namespace support
413 } // end namespace llvm
414
415 #endif // LLVM_SUPPORT_ENDIAN_H
416