1// Copyright 2013 Google Inc. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//
15// Macros for endianness, branch prediction and unaligned loads and stores.
16
17#ifndef BROTLI_ENC_PORT_H_
18#define BROTLI_ENC_PORT_H_
19
20#if defined OS_LINUX || defined OS_CYGWIN
21#include <endian.h>
22#elif defined OS_FREEBSD
23#include <machine/endian.h>
24#elif defined OS_MACOSX
25#include <machine/endian.h>
26/* Let's try and follow the Linux convention */
27#define __BYTE_ORDER  BYTE_ORDER
28#define __LITTLE_ENDIAN LITTLE_ENDIAN
29#define __BIG_ENDIAN BIG_ENDIAN
30#endif
31
32// define the macros IS_LITTLE_ENDIAN or IS_BIG_ENDIAN
33// using the above endian definitions from endian.h if
34// endian.h was included
35#ifdef __BYTE_ORDER
36#if __BYTE_ORDER == __LITTLE_ENDIAN
37#define IS_LITTLE_ENDIAN
38#endif
39
40#if __BYTE_ORDER == __BIG_ENDIAN
41#define IS_BIG_ENDIAN
42#endif
43
44#else
45
46#if defined(__LITTLE_ENDIAN__)
47#define IS_LITTLE_ENDIAN
48#elif defined(__BIG_ENDIAN__)
49#define IS_BIG_ENDIAN
50#endif
51#endif  // __BYTE_ORDER
52
53#if defined(COMPILER_GCC3)
54#define PREDICT_FALSE(x) (__builtin_expect(x, 0))
55#define PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
56#else
57#define PREDICT_FALSE(x) x
58#define PREDICT_TRUE(x) x
59#endif
60
61// Portable handling of unaligned loads, stores, and copies.
62// On some platforms, like ARM, the copy functions can be more efficient
63// then a load and a store.
64
65#if defined(ARCH_PIII) || defined(ARCH_ATHLON) || \
66  defined(ARCH_K8) || defined(_ARCH_PPC)
67
68// x86 and x86-64 can perform unaligned loads/stores directly;
69// modern PowerPC hardware can also do unaligned integer loads and stores;
70// but note: the FPU still sends unaligned loads and stores to a trap handler!
71
72#define BROTLI_UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32_t *>(_p))
73#define BROTLI_UNALIGNED_LOAD64(_p) (*reinterpret_cast<const uint64_t *>(_p))
74
75#define BROTLI_UNALIGNED_STORE32(_p, _val) \
76  (*reinterpret_cast<uint32_t *>(_p) = (_val))
77#define BROTLI_UNALIGNED_STORE64(_p, _val) \
78  (*reinterpret_cast<uint64_t *>(_p) = (_val))
79
80#elif defined(__arm__) && \
81  !defined(__ARM_ARCH_5__) && \
82  !defined(__ARM_ARCH_5T__) && \
83  !defined(__ARM_ARCH_5TE__) && \
84  !defined(__ARM_ARCH_5TEJ__) && \
85  !defined(__ARM_ARCH_6__) && \
86  !defined(__ARM_ARCH_6J__) && \
87  !defined(__ARM_ARCH_6K__) && \
88  !defined(__ARM_ARCH_6Z__) && \
89  !defined(__ARM_ARCH_6ZK__) && \
90  !defined(__ARM_ARCH_6T2__)
91
92// ARMv7 and newer support native unaligned accesses, but only of 16-bit
93// and 32-bit values (not 64-bit); older versions either raise a fatal signal,
94// do an unaligned read and rotate the words around a bit, or do the reads very
95// slowly (trip through kernel mode).
96
97#define BROTLI_UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32_t *>(_p))
98#define BROTLI_UNALIGNED_STORE32(_p, _val) \
99  (*reinterpret_cast<uint32_t *>(_p) = (_val))
100
101inline uint64_t BROTLI_UNALIGNED_LOAD64(const void *p) {
102  uint64_t t;
103  memcpy(&t, p, sizeof t);
104  return t;
105}
106
107inline void BROTLI_UNALIGNED_STORE64(void *p, uint64_t v) {
108  memcpy(p, &v, sizeof v);
109}
110
111#else
112
113// These functions are provided for architectures that don't support
114// unaligned loads and stores.
115
116inline uint32_t BROTLI_UNALIGNED_LOAD32(const void *p) {
117  uint32_t t;
118  memcpy(&t, p, sizeof t);
119  return t;
120}
121
122inline uint64_t BROTLI_UNALIGNED_LOAD64(const void *p) {
123  uint64_t t;
124  memcpy(&t, p, sizeof t);
125  return t;
126}
127
128inline void BROTLI_UNALIGNED_STORE32(void *p, uint32_t v) {
129  memcpy(p, &v, sizeof v);
130}
131
132inline void BROTLI_UNALIGNED_STORE64(void *p, uint64_t v) {
133  memcpy(p, &v, sizeof v);
134}
135
136#endif
137
138#endif  // BROTLI_ENC_PORT_H_
139