unaligned_access.h
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1 //
2 // Copyright 2017 The Abseil Authors.
3 //
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
7 //
8 // https://www.apache.org/licenses/LICENSE-2.0
9 //
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
15 //
16 
17 #ifndef ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
18 #define ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
19 
20 #include <string.h>
21 #include <cstdint>
22 
23 #include "absl/base/attributes.h"
24 
25 // unaligned APIs
26 
27 // Portable handling of unaligned loads, stores, and copies.
28 
29 // The unaligned API is C++ only. The declarations use C++ features
30 // (namespaces, inline) which are absent or incompatible in C.
31 #if defined(__cplusplus)
32 
33 #if defined(ADDRESS_SANITIZER) || defined(THREAD_SANITIZER) ||\
34  defined(MEMORY_SANITIZER)
35 // Consider we have an unaligned load/store of 4 bytes from address 0x...05.
36 // AddressSanitizer will treat it as a 3-byte access to the range 05:07 and
37 // will miss a bug if 08 is the first unaddressable byte.
38 // ThreadSanitizer will also treat this as a 3-byte access to 05:07 and will
39 // miss a race between this access and some other accesses to 08.
40 // MemorySanitizer will correctly propagate the shadow on unaligned stores
41 // and correctly report bugs on unaligned loads, but it may not properly
42 // update and report the origin of the uninitialized memory.
43 // For all three tools, replacing an unaligned access with a tool-specific
44 // callback solves the problem.
45 
46 // Make sure uint16_t/uint32_t/uint64_t are defined.
47 #include <stdint.h>
48 
49 extern "C" {
50 uint16_t __sanitizer_unaligned_load16(const void *p);
51 uint32_t __sanitizer_unaligned_load32(const void *p);
52 uint64_t __sanitizer_unaligned_load64(const void *p);
53 void __sanitizer_unaligned_store16(void *p, uint16_t v);
54 void __sanitizer_unaligned_store32(void *p, uint32_t v);
55 void __sanitizer_unaligned_store64(void *p, uint64_t v);
56 } // extern "C"
57 
58 namespace absl {
59 namespace base_internal {
60 
61 inline uint16_t UnalignedLoad16(const void *p) {
62  return __sanitizer_unaligned_load16(p);
63 }
64 
65 inline uint32_t UnalignedLoad32(const void *p) {
66  return __sanitizer_unaligned_load32(p);
67 }
68 
69 inline uint64_t UnalignedLoad64(const void *p) {
70  return __sanitizer_unaligned_load64(p);
71 }
72 
73 inline void UnalignedStore16(void *p, uint16_t v) {
74  __sanitizer_unaligned_store16(p, v);
75 }
76 
77 inline void UnalignedStore32(void *p, uint32_t v) {
78  __sanitizer_unaligned_store32(p, v);
79 }
80 
81 inline void UnalignedStore64(void *p, uint64_t v) {
82  __sanitizer_unaligned_store64(p, v);
83 }
84 
85 } // namespace base_internal
86 } // namespace absl
87 
88 #define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \
89  (absl::base_internal::UnalignedLoad16(_p))
90 #define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \
91  (absl::base_internal::UnalignedLoad32(_p))
92 #define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \
93  (absl::base_internal::UnalignedLoad64(_p))
94 
95 #define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \
96  (absl::base_internal::UnalignedStore16(_p, _val))
97 #define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \
98  (absl::base_internal::UnalignedStore32(_p, _val))
99 #define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \
100  (absl::base_internal::UnalignedStore64(_p, _val))
101 
102 #else
103 
104 namespace absl {
105 namespace base_internal {
106 
107 inline uint16_t UnalignedLoad16(const void *p) {
108  uint16_t t;
109  memcpy(&t, p, sizeof t);
110  return t;
111 }
112 
113 inline uint32_t UnalignedLoad32(const void *p) {
114  uint32_t t;
115  memcpy(&t, p, sizeof t);
116  return t;
117 }
118 
119 inline uint64_t UnalignedLoad64(const void *p) {
120  uint64_t t;
121  memcpy(&t, p, sizeof t);
122  return t;
123 }
124 
125 inline void UnalignedStore16(void *p, uint16_t v) { memcpy(p, &v, sizeof v); }
126 
127 inline void UnalignedStore32(void *p, uint32_t v) { memcpy(p, &v, sizeof v); }
128 
129 inline void UnalignedStore64(void *p, uint64_t v) { memcpy(p, &v, sizeof v); }
130 
131 } // namespace base_internal
132 } // namespace absl
133 
134 #define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \
135  (absl::base_internal::UnalignedLoad16(_p))
136 #define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \
137  (absl::base_internal::UnalignedLoad32(_p))
138 #define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \
139  (absl::base_internal::UnalignedLoad64(_p))
140 
141 #define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \
142  (absl::base_internal::UnalignedStore16(_p, _val))
143 #define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \
144  (absl::base_internal::UnalignedStore32(_p, _val))
145 #define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \
146  (absl::base_internal::UnalignedStore64(_p, _val))
147 
148 #endif
149 
150 #endif // defined(__cplusplus), end of unaligned API
151 
152 #endif // ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
int v
Definition: variant_test.cc:81
Definition: algorithm.h:29


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autogenerated on Mon Feb 28 2022 21:31:21