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
27namespace llvm {
28namespace support {
29
30enum endianness {big, little, native};
31
32// These are named values for common alignments.
33enum {aligned = 0, unaligned = 1};
34
35namespace detail {
36
37/// ::value is either alignment, or alignof(T) if alignment is 0.
38template<class T, int alignment>
39struct PickAlignment {
40 enum { value = alignment == 0 ? alignof(T) : alignment };
41};
42
43} // end namespace detail
44
45namespace endian {
46
47constexpr endianness system_endianness() {
48 return sys::IsBigEndianHost ? big : little;
49}
50
51template <typename value_type>
52inline 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.
59template<typename value_type, endianness endian>
60inline 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.
65template <typename value_type, std::size_t alignment>
66inline 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
76template<typename value_type,
77 endianness endian,
78 std::size_t alignment>
79inline 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.
85template <typename value_type, std::size_t alignment, typename CharT>
86inline 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
92template<typename value_type, endianness endian, std::size_t alignment,
93 typename CharT>
94inline 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.
99template <typename value_type, std::size_t alignment>
100inline 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
107template<typename value_type,
108 endianness endian,
109 std::size_t alignment>
110inline void write(void *memory, value_type value) {
111 write<value_type, alignment>(memory, value, endian);
112}
113
114template <typename value_type>
115using 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.
119template <typename value_type, endianness endian, std::size_t alignment>
120inline 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.
153template <typename value_type, endianness endian, std::size_t alignment>
154inline 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
205namespace detail {
206
207template<typename value_type,
208 endianness endian,
209 std::size_t alignment>
210struct packed_endian_specific_integral {
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 AlignedCharArray<PickAlignment<value_type, alignment>::value,
247 sizeof(value_type)> Value;
248
249public:
250 struct ref {
251 explicit ref(void *Ptr) : Ptr(Ptr) {}
252
253 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
268using ulittle16_t =
269 detail::packed_endian_specific_integral<uint16_t, little, unaligned>;
270using ulittle32_t =
271 detail::packed_endian_specific_integral<uint32_t, little, unaligned>;
272using ulittle64_t =
273 detail::packed_endian_specific_integral<uint64_t, little, unaligned>;
274
275using little16_t =
276 detail::packed_endian_specific_integral<int16_t, little, unaligned>;
277using little32_t =
278 detail::packed_endian_specific_integral<int32_t, little, unaligned>;
279using little64_t =
280 detail::packed_endian_specific_integral<int64_t, little, unaligned>;
281
282using aligned_ulittle16_t =
283 detail::packed_endian_specific_integral<uint16_t, little, aligned>;
284using aligned_ulittle32_t =
285 detail::packed_endian_specific_integral<uint32_t, little, aligned>;
286using aligned_ulittle64_t =
287 detail::packed_endian_specific_integral<uint64_t, little, aligned>;
288
289using aligned_little16_t =
290 detail::packed_endian_specific_integral<int16_t, little, aligned>;
291using aligned_little32_t =
292 detail::packed_endian_specific_integral<int32_t, little, aligned>;
293using aligned_little64_t =
294 detail::packed_endian_specific_integral<int64_t, little, aligned>;
295
296using ubig16_t =
297 detail::packed_endian_specific_integral<uint16_t, big, unaligned>;
298using ubig32_t =
299 detail::packed_endian_specific_integral<uint32_t, big, unaligned>;
300using ubig64_t =
301 detail::packed_endian_specific_integral<uint64_t, big, unaligned>;
302
303using big16_t =
304 detail::packed_endian_specific_integral<int16_t, big, unaligned>;
305using big32_t =
306 detail::packed_endian_specific_integral<int32_t, big, unaligned>;
307using big64_t =
308 detail::packed_endian_specific_integral<int64_t, big, unaligned>;
309
310using aligned_ubig16_t =
311 detail::packed_endian_specific_integral<uint16_t, big, aligned>;
312using aligned_ubig32_t =
313 detail::packed_endian_specific_integral<uint32_t, big, aligned>;
314using aligned_ubig64_t =
315 detail::packed_endian_specific_integral<uint64_t, big, aligned>;
316
317using aligned_big16_t =
318 detail::packed_endian_specific_integral<int16_t, big, aligned>;
319using aligned_big32_t =
320 detail::packed_endian_specific_integral<int32_t, big, aligned>;
321using aligned_big64_t =
322 detail::packed_endian_specific_integral<int64_t, big, aligned>;
323
324using unaligned_uint16_t =
325 detail::packed_endian_specific_integral<uint16_t, native, unaligned>;
326using unaligned_uint32_t =
327 detail::packed_endian_specific_integral<uint32_t, native, unaligned>;
328using unaligned_uint64_t =
329 detail::packed_endian_specific_integral<uint64_t, native, unaligned>;
330
331using unaligned_int16_t =
332 detail::packed_endian_specific_integral<int16_t, native, unaligned>;
333using unaligned_int32_t =
334 detail::packed_endian_specific_integral<int32_t, native, unaligned>;
335using unaligned_int64_t =
336 detail::packed_endian_specific_integral<int64_t, native, unaligned>;
337
338namespace endian {
339
340template <typename T> inline T read(const void *P, endianness E) {
341 return read<T, unaligned>(P, E);
342}
343
344template <typename T, endianness E> inline T read(const void *P) {
345 return *(const detail::packed_endian_specific_integral<T, E, unaligned> *)P;
346}
347
348inline uint16_t read16(const void *P, endianness E) {
349 return read<uint16_t>(P, E);
350}
351inline uint32_t read32(const void *P, endianness E) {
352 return read<uint32_t>(P, E);
353}
354inline uint64_t read64(const void *P, endianness E) {
355 return read<uint64_t>(P, E);
356}
357
358template <endianness E> inline uint16_t read16(const void *P) {
359 return read<uint16_t, E>(P);
360}
361template <endianness E> inline uint32_t read32(const void *P) {
362 return read<uint32_t, E>(P);
363}
364template <endianness E> inline uint64_t read64(const void *P) {
365 return read<uint64_t, E>(P);
366}
367
368inline uint16_t read16le(const void *P) { return read16<little>(P); }
369inline uint32_t read32le(const void *P) { return read32<little>(P); }
370inline uint64_t read64le(const void *P) { return read64<little>(P); }
371inline uint16_t read16be(const void *P) { return read16<big>(P); }
372inline uint32_t read32be(const void *P) { return read32<big>(P); }
373inline uint64_t read64be(const void *P) { return read64<big>(P); }
374
375template <typename T> inline void write(void *P, T V, endianness E) {
376 write<T, unaligned>(P, V, E);
377}
378
379template <typename T, endianness E> inline void write(void *P, T V) {
380 *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
381}
382
383inline void write16(void *P, uint16_t V, endianness E) {
384 write<uint16_t>(P, V, E);
385}
386inline void write32(void *P, uint32_t V, endianness E) {
387 write<uint32_t>(P, V, E);
388}
389inline void write64(void *P, uint64_t V, endianness E) {
390 write<uint64_t>(P, V, E);
391}
392
393template <endianness E> inline void write16(void *P, uint16_t V) {
394 write<uint16_t, E>(P, V);
395}
396template <endianness E> inline void write32(void *P, uint32_t V) {
397 write<uint32_t, E>(P, V);
398}
399template <endianness E> inline void write64(void *P, uint64_t V) {
400 write<uint64_t, E>(P, V);
401}
402
403inline void write16le(void *P, uint16_t V) { write16<little>(P, V); }
404inline void write32le(void *P, uint32_t V) { write32<little>(P, V); }
405inline void write64le(void *P, uint64_t V) { write64<little>(P, V); }
406inline void write16be(void *P, uint16_t V) { write16<big>(P, V); }
407inline void write32be(void *P, uint32_t V) { write32<big>(P, V); }
408inline 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