tvl-depot/absl/base/internal/unaligned_access.h
Abseil Team 1e39f8626a Export of internal Abseil changes
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b842b7fd9b1289be31f0b7ee8e62e48e550747cf by Greg Falcon <gfalcon@google.com>:

Change the Cord str_format formatter to use iteration instead of CordReader.

When Cord is publicly released, CordReader is not going with it.

PiperOrigin-RevId: 284780736

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28e76c08ea7185a7ff9f4e0e02ae565fbbf7980f by Greg Falcon <gfalcon@google.com>:

Implementation detail change.

Introduce ABSL_NAMESPACE_BEGIN and _END annotation macros which indicate the beginning and end of a `namespace absl` scope.  Currently these do nothing, but they will be used to inject an inline namespace for LTS builds (to avoid symbol collisions against other Abseil versions).

These macros should not be used by end users, because end users should never write `namespace absl {` in their own code.

This CL applies these annotations to all code under //absl/base/.  The rest of Abseil will be annotated in this way in follow-up CLs.

PiperOrigin-RevId: 284776410

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e1711dc6d696dcca50d4e7d4b4d8f3076575b7ec by Abseil Team <absl-team@google.com>:

--help changed to report long flags.

PiperOrigin-RevId: 284757720

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78f66a68f428bbbd19d8d60e1125f43ba765fd35 by Tom Manshreck <shreck@google.com>:

Update comment on + or - in SimpleAToi()

PiperOrigin-RevId: 284231843
GitOrigin-RevId: b842b7fd9b1289be31f0b7ee8e62e48e550747cf
Change-Id: I3046b31391bd11c8bc4abab7785a863c377cd757
2019-12-10 15:07:05 -05:00

158 lines
4.8 KiB
C++

//
// 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_UNALIGNED_ACCESS_H_
#define ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_
#include <string.h>
#include <cstdint>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
// unaligned APIs
// Portable handling of unaligned loads, stores, and copies.
// The unaligned API is C++ only. The declarations use C++ features
// (namespaces, inline) which are absent or incompatible in C.
#if defined(__cplusplus)
#if defined(ADDRESS_SANITIZER) || defined(THREAD_SANITIZER) ||\
defined(MEMORY_SANITIZER)
// Consider we have an unaligned load/store of 4 bytes from address 0x...05.
// AddressSanitizer will treat it as a 3-byte access to the range 05:07 and
// will miss a bug if 08 is the first unaddressable byte.
// ThreadSanitizer will also treat this as a 3-byte access to 05:07 and will
// miss a race between this access and some other accesses to 08.
// MemorySanitizer will correctly propagate the shadow on unaligned stores
// and correctly report bugs on unaligned loads, but it may not properly
// update and report the origin of the uninitialized memory.
// For all three tools, replacing an unaligned access with a tool-specific
// callback solves the problem.
// Make sure uint16_t/uint32_t/uint64_t are defined.
#include <stdint.h>
extern "C" {
uint16_t __sanitizer_unaligned_load16(const void *p);
uint32_t __sanitizer_unaligned_load32(const void *p);
uint64_t __sanitizer_unaligned_load64(const void *p);
void __sanitizer_unaligned_store16(void *p, uint16_t v);
void __sanitizer_unaligned_store32(void *p, uint32_t v);
void __sanitizer_unaligned_store64(void *p, uint64_t v);
} // extern "C"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace base_internal {
inline uint16_t UnalignedLoad16(const void *p) {
return __sanitizer_unaligned_load16(p);
}
inline uint32_t UnalignedLoad32(const void *p) {
return __sanitizer_unaligned_load32(p);
}
inline uint64_t UnalignedLoad64(const void *p) {
return __sanitizer_unaligned_load64(p);
}
inline void UnalignedStore16(void *p, uint16_t v) {
__sanitizer_unaligned_store16(p, v);
}
inline void UnalignedStore32(void *p, uint32_t v) {
__sanitizer_unaligned_store32(p, v);
}
inline void UnalignedStore64(void *p, uint64_t v) {
__sanitizer_unaligned_store64(p, v);
}
} // namespace base_internal
ABSL_NAMESPACE_END
} // namespace absl
#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \
(absl::base_internal::UnalignedLoad16(_p))
#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \
(absl::base_internal::UnalignedLoad32(_p))
#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \
(absl::base_internal::UnalignedLoad64(_p))
#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \
(absl::base_internal::UnalignedStore16(_p, _val))
#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \
(absl::base_internal::UnalignedStore32(_p, _val))
#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \
(absl::base_internal::UnalignedStore64(_p, _val))
#else
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace base_internal {
inline uint16_t UnalignedLoad16(const void *p) {
uint16_t t;
memcpy(&t, p, sizeof t);
return t;
}
inline uint32_t UnalignedLoad32(const void *p) {
uint32_t t;
memcpy(&t, p, sizeof t);
return t;
}
inline uint64_t UnalignedLoad64(const void *p) {
uint64_t t;
memcpy(&t, p, sizeof t);
return t;
}
inline void UnalignedStore16(void *p, uint16_t v) { memcpy(p, &v, sizeof v); }
inline void UnalignedStore32(void *p, uint32_t v) { memcpy(p, &v, sizeof v); }
inline void UnalignedStore64(void *p, uint64_t v) { memcpy(p, &v, sizeof v); }
} // namespace base_internal
ABSL_NAMESPACE_END
} // namespace absl
#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \
(absl::base_internal::UnalignedLoad16(_p))
#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \
(absl::base_internal::UnalignedLoad32(_p))
#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \
(absl::base_internal::UnalignedLoad64(_p))
#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \
(absl::base_internal::UnalignedStore16(_p, _val))
#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \
(absl::base_internal::UnalignedStore32(_p, _val))
#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \
(absl::base_internal::UnalignedStore64(_p, _val))
#endif
#endif // defined(__cplusplus), end of unaligned API
#endif // ABSL_BASE_INTERNAL_UNALIGNED_ACCESS_H_