summaryrefslogtreecommitdiff
path: root/absl/base/internal/endian.h
blob: 9677530e8de320bf3f8d00e9bd0e1567996a2377 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#ifndef ABSL_BASE_INTERNAL_ENDIAN_H_
#define ABSL_BASE_INTERNAL_ENDIAN_H_

// The following guarantees declaration of the byte swap functions
#ifdef _MSC_VER
#include <stdlib.h>  // NOLINT(build/include)
#elif defined(__FreeBSD__)
#include <sys/endian.h>
#elif defined(__GLIBC__)
#include <byteswap.h>  // IWYU pragma: export
#endif

#include <cstdint>
#include "absl/base/config.h"
#include "absl/base/internal/unaligned_access.h"
#include "absl/base/port.h"

namespace absl {
ABSL_NAMESPACE_BEGIN

// Use compiler byte-swapping intrinsics if they are available.  32-bit
// and 64-bit versions are available in Clang and GCC as of GCC 4.3.0.
// The 16-bit version is available in Clang and GCC only as of GCC 4.8.0.
// For simplicity, we enable them all only for GCC 4.8.0 or later.
#if defined(__clang__) || \
    (defined(__GNUC__) && \
     ((__GNUC__ == 4 && __GNUC_MINOR__ >= 8) || __GNUC__ >= 5))
inline uint64_t gbswap_64(uint64_t host_int) {
  return __builtin_bswap64(host_int);
}
inline uint32_t gbswap_32(uint32_t host_int) {
  return __builtin_bswap32(host_int);
}
inline uint16_t gbswap_16(uint16_t host_int) {
  return __builtin_bswap16(host_int);
}

#elif defined(_MSC_VER)
inline uint64_t gbswap_64(uint64_t host_int) {
  return _byteswap_uint64(host_int);
}
inline uint32_t gbswap_32(uint32_t host_int) {
  return _byteswap_ulong(host_int);
}
inline uint16_t gbswap_16(uint16_t host_int) {
  return _byteswap_ushort(host_int);
}

#else
inline uint64_t gbswap_64(uint64_t host_int) {
#if defined(__GNUC__) && defined(__x86_64__) && !defined(__APPLE__)
  // Adapted from /usr/include/byteswap.h.  Not available on Mac.
  if (__builtin_constant_p(host_int)) {
    return __bswap_constant_64(host_int);
  } else {
    uint64_t result;
    __asm__("bswap %0" : "=r"(result) : "0"(host_int));
    return result;
  }
#elif defined(__GLIBC__)
  return bswap_64(host_int);
#else
  return (((host_int & uint64_t{0xFF}) << 56) |
          ((host_int & uint64_t{0xFF00}) << 40) |
          ((host_int & uint64_t{0xFF0000}) << 24) |
          ((host_int & uint64_t{0xFF000000}) << 8) |
          ((host_int & uint64_t{0xFF00000000}) >> 8) |
          ((host_int & uint64_t{0xFF0000000000}) >> 24) |
          ((host_int & uint64_t{0xFF000000000000}) >> 40) |
          ((host_int & uint64_t{0xFF00000000000000}) >> 56));
#endif  // bswap_64
}

inline uint32_t gbswap_32(uint32_t host_int) {
#if defined(__GLIBC__)
  return bswap_32(host_int);
#else
  return (((host_int & uint32_t{0xFF}) << 24) |
          ((host_int & uint32_t{0xFF00}) << 8) |
          ((host_int & uint32_t{0xFF0000}) >> 8) |
          ((host_int & uint32_t{0xFF000000}) >> 24));
#endif
}

inline uint16_t gbswap_16(uint16_t host_int) {
#if defined(__GLIBC__)
  return bswap_16(host_int);
#else
  return (((host_int & uint16_t{0xFF}) << 8) |
          ((host_int & uint16_t{0xFF00}) >> 8));
#endif
}

#endif  // intrinsics available

#ifdef ABSL_IS_LITTLE_ENDIAN

// Definitions for ntohl etc. that don't require us to include
// netinet/in.h. We wrap gbswap_32 and gbswap_16 in functions rather
// than just #defining them because in debug mode, gcc doesn't
// correctly handle the (rather involved) definitions of bswap_32.
// gcc guarantees that inline functions are as fast as macros, so
// this isn't a performance hit.
inline uint16_t ghtons(uint16_t x) { return gbswap_16(x); }
inline uint32_t ghtonl(uint32_t x) { return gbswap_32(x); }
inline uint64_t ghtonll(uint64_t x) { return gbswap_64(x); }

#elif defined ABSL_IS_BIG_ENDIAN

// These definitions are simpler on big-endian machines
// These are functions instead of macros to avoid self-assignment warnings
// on calls such as "i = ghtnol(i);".  This also provides type checking.
inline uint16_t ghtons(uint16_t x) { return x; }
inline uint32_t ghtonl(uint32_t x) { return x; }
inline uint64_t ghtonll(uint64_t x) { return x; }

#else
#error \
    "Unsupported byte order: Either ABSL_IS_BIG_ENDIAN or " \
       "ABSL_IS_LITTLE_ENDIAN must be defined"
#endif  // byte order

inline uint16_t gntohs(uint16_t x) { return ghtons(x); }
inline uint32_t gntohl(uint32_t x) { return ghtonl(x); }
inline uint64_t gntohll(uint64_t x) { return ghtonll(x); }

// Utilities to convert numbers between the current hosts's native byte
// order and little-endian byte order
//
// Load/Store methods are alignment safe
namespace little_endian {
// Conversion functions.
#ifdef ABSL_IS_LITTLE_ENDIAN

inline uint16_t FromHost16(uint16_t x) { return x; }
inline uint16_t ToHost16(uint16_t x) { return x; }

inline uint32_t FromHost32(uint32_t x) { return x; }
inline uint32_t ToHost32(uint32_t x) { return x; }

inline uint64_t FromHost64(uint64_t x) { return x; }
inline uint64_t ToHost64(uint64_t x) { return x; }

inline constexpr bool IsLittleEndian() { return true; }

#elif defined ABSL_IS_BIG_ENDIAN

inline uint16_t FromHost16(uint16_t x) { return gbswap_16(x); }
inline uint16_t ToHost16(uint16_t x) { return gbswap_16(x); }

inline uint32_t FromHost32(uint32_t x) { return gbswap_32(x); }
inline uint32_t ToHost32(uint32_t x) { return gbswap_32(x); }

inline uint64_t FromHost64(uint64_t x) { return gbswap_64(x); }
inline uint64_t ToHost64(uint64_t x) { return gbswap_64(x); }

inline constexpr bool IsLittleEndian() { return false; }

#endif /* ENDIAN */

// Functions to do unaligned loads and stores in little-endian order.
inline uint16_t Load16(const void *p) {
  return ToHost16(ABSL_INTERNAL_UNALIGNED_LOAD16(p));
}

inline void Store16(void *p, uint16_t v) {
  ABSL_INTERNAL_UNALIGNED_STORE16(p, FromHost16(v));
}

inline uint32_t Load32(const void *p) {
  return ToHost32(ABSL_INTERNAL_UNALIGNED_LOAD32(p));
}

inline void Store32(void *p, uint32_t v) {
  ABSL_INTERNAL_UNALIGNED_STORE32(p, FromHost32(v));
}

inline uint64_t Load64(const void *p) {
  return ToHost64(ABSL_INTERNAL_UNALIGNED_LOAD64(p));
}

inline void Store64(void *p, uint64_t v) {
  ABSL_INTERNAL_UNALIGNED_STORE64(p, FromHost64(v));
}

}  // namespace little_endian

// Utilities to convert numbers between the current hosts's native byte
// order and big-endian byte order (same as network byte order)
//
// Load/Store methods are alignment safe
namespace big_endian {
#ifdef ABSL_IS_LITTLE_ENDIAN

inline uint16_t FromHost16(uint16_t x) { return gbswap_16(x); }
inline uint16_t ToHost16(uint16_t x) { return gbswap_16(x); }

inline uint32_t FromHost32(uint32_t x) { return gbswap_32(x); }
inline uint32_t ToHost32(uint32_t x) { return gbswap_32(x); }

inline uint64_t FromHost64(uint64_t x) { return gbswap_64(x); }
inline uint64_t ToHost64(uint64_t x) { return gbswap_64(x); }

inline constexpr bool IsLittleEndian() { return true; }

#elif defined ABSL_IS_BIG_ENDIAN

inline uint16_t FromHost16(uint16_t x) { return x; }
inline uint16_t ToHost16(uint16_t x) { return x; }

inline uint32_t FromHost32(uint32_t x) { return x; }
inline uint32_t ToHost32(uint32_t x) { return x; }

inline uint64_t FromHost64(uint64_t x) { return x; }
inline uint64_t ToHost64(uint64_t x) { return x; }

inline constexpr bool IsLittleEndian() { return false; }

#endif /* ENDIAN */

// Functions to do unaligned loads and stores in big-endian order.
inline uint16_t Load16(const void *p) {
  return ToHost16(ABSL_INTERNAL_UNALIGNED_LOAD16(p));
}

inline void Store16(void *p, uint16_t v) {
  ABSL_INTERNAL_UNALIGNED_STORE16(p, FromHost16(v));
}

inline uint32_t Load32(const void *p) {
  return ToHost32(ABSL_INTERNAL_UNALIGNED_LOAD32(p));
}

inline void Store32(void *p, uint32_t v) {
  ABSL_INTERNAL_UNALIGNED_STORE32(p, FromHost32(v));
}

inline uint64_t Load64(const void *p) {
  return ToHost64(ABSL_INTERNAL_UNALIGNED_LOAD64(p));
}

inline void Store64(void *p, uint64_t v) {
  ABSL_INTERNAL_UNALIGNED_STORE64(p, FromHost64(v));
}

}  // namespace big_endian

ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_BASE_INTERNAL_ENDIAN_H_