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absl/base/internal/endian.h
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267
absl/base/internal/endian.h
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// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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#ifndef ABSL_BASE_INTERNAL_ENDIAN_H_
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#define ABSL_BASE_INTERNAL_ENDIAN_H_
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// The following guarantees declaration of the byte swap functions
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#ifdef _MSC_VER
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#include <stdlib.h> // NOLINT(build/include)
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#elif defined(__APPLE__)
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// Mac OS X / Darwin features
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#include <libkern/OSByteOrder.h>
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#elif defined(__GLIBC__)
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#include <byteswap.h> // IWYU pragma: export
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#endif
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#include <cstdint>
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#include "absl/base/config.h"
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#include "absl/base/internal/unaligned_access.h"
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#include "absl/base/port.h"
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namespace absl {
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// Use compiler byte-swapping intrinsics if they are available. 32-bit
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// and 64-bit versions are available in Clang and GCC as of GCC 4.3.0.
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// The 16-bit version is available in Clang and GCC only as of GCC 4.8.0.
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// For simplicity, we enable them all only for GCC 4.8.0 or later.
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#if defined(__clang__) || \
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(defined(__GNUC__) && \
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((__GNUC__ == 4 && __GNUC_MINOR__ >= 8) || __GNUC__ >= 5))
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inline uint64_t gbswap_64(uint64_t host_int) {
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return __builtin_bswap64(host_int);
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}
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inline uint32_t gbswap_32(uint32_t host_int) {
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return __builtin_bswap32(host_int);
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}
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inline uint16_t gbswap_16(uint16_t host_int) {
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return __builtin_bswap16(host_int);
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}
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#elif defined(_MSC_VER)
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inline uint64_t gbswap_64(uint64_t host_int) {
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return _byteswap_uint64(host_int);
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}
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inline uint32_t gbswap_32(uint32_t host_int) {
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return _byteswap_ulong(host_int);
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}
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inline uint16_t gbswap_16(uint16_t host_int) {
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return _byteswap_ushort(host_int);
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}
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#elif defined(__APPLE__)
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inline uint64_t gbswap_64(uint64_t host_int) { return OSSwapInt16(host_int); }
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inline uint32_t gbswap_32(uint32_t host_int) { return OSSwapInt32(host_int); }
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inline uint16_t gbswap_16(uint16_t host_int) { return OSSwapInt64(host_int); }
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#else
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inline uint64_t gbswap_64(uint64_t host_int) {
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#if defined(__GNUC__) && defined(__x86_64__) && !defined(__APPLE__)
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// Adapted from /usr/include/byteswap.h. Not available on Mac.
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if (__builtin_constant_p(host_int)) {
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return __bswap_constant_64(host_int);
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} else {
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register uint64_t result;
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__asm__("bswap %0" : "=r"(result) : "0"(host_int));
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return result;
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}
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#elif defined(__GLIBC__)
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return bswap_64(host_int);
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#else
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return (((x & uint64_t{(0xFF}) << 56) |
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((x & uint64_t{(0xFF00}) << 40) |
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((x & uint64_t{(0xFF0000}) << 24) |
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((x & uint64_t{(0xFF000000}) << 8) |
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((x & uint64_t{(0xFF00000000}) >> 8) |
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((x & uint64_t{(0xFF0000000000}) >> 24) |
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((x & uint64_t{(0xFF000000000000}) >> 40) |
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((x & uint64_t{(0xFF00000000000000}) >> 56));
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#endif // bswap_64
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}
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inline uint32_t gbswap_32(uint32_t host_int) {
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#if defined(__GLIBC__)
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return bswap_32(host_int);
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#else
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return (((x & 0xFF) << 24) | ((x & 0xFF00) << 8) | ((x & 0xFF0000) >> 8) |
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((x & 0xFF000000) >> 24));
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#endif
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}
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inline uint16_t gbswap_16(uint16_t host_int) {
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#if defined(__GLIBC__)
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return bswap_16(host_int);
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#else
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return uint16_t{((x & 0xFF) << 8) | ((x & 0xFF00) >> 8)};
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#endif
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}
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#endif // intrinics available
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#ifdef ABSL_IS_LITTLE_ENDIAN
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// Definitions for ntohl etc. that don't require us to include
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// netinet/in.h. We wrap gbswap_32 and gbswap_16 in functions rather
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// than just #defining them because in debug mode, gcc doesn't
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// correctly handle the (rather involved) definitions of bswap_32.
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// gcc guarantees that inline functions are as fast as macros, so
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// this isn't a performance hit.
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inline uint16_t ghtons(uint16_t x) { return gbswap_16(x); }
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inline uint32_t ghtonl(uint32_t x) { return gbswap_32(x); }
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inline uint64_t ghtonll(uint64_t x) { return gbswap_64(x); }
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#elif defined ABSL_IS_BIG_ENDIAN
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// These definitions are simpler on big-endian machines
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// These are functions instead of macros to avoid self-assignment warnings
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// on calls such as "i = ghtnol(i);". This also provides type checking.
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inline uint16_t ghtons(uint16_t x) { return x; }
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inline uint32_t ghtonl(uint32_t x) { return x; }
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inline uint64_t ghtonll(uint64_t x) { return x; }
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#else
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#error \
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"Unsupported byte order: Either ABSL_IS_BIG_ENDIAN or " \
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"ABSL_IS_LITTLE_ENDIAN must be defined"
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#endif // byte order
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inline uint16_t gntohs(uint16_t x) { return ghtons(x); }
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inline uint32_t gntohl(uint32_t x) { return ghtonl(x); }
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inline uint64_t gntohll(uint64_t x) { return ghtonll(x); }
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// Utilities to convert numbers between the current hosts's native byte
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// order and little-endian byte order
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//
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// Load/Store methods are alignment safe
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namespace little_endian {
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// Conversion functions.
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#ifdef ABSL_IS_LITTLE_ENDIAN
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inline uint16_t FromHost16(uint16_t x) { return x; }
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inline uint16_t ToHost16(uint16_t x) { return x; }
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inline uint32_t FromHost32(uint32_t x) { return x; }
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inline uint32_t ToHost32(uint32_t x) { return x; }
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inline uint64_t FromHost64(uint64_t x) { return x; }
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inline uint64_t ToHost64(uint64_t x) { return x; }
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inline constexpr bool IsLittleEndian() { return true; }
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#elif defined ABSL_IS_BIG_ENDIAN
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inline uint16_t FromHost16(uint16_t x) { return gbswap_16(x); }
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inline uint16_t ToHost16(uint16_t x) { return gbswap_16(x); }
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inline uint32_t FromHost32(uint32_t x) { return gbswap_32(x); }
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inline uint32_t ToHost32(uint32_t x) { return gbswap_32(x); }
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inline uint64_t FromHost64(uint64_t x) { return gbswap_64(x); }
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inline uint64_t ToHost64(uint64_t x) { return gbswap_64(x); }
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inline constexpr bool IsLittleEndian() { return false; }
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#endif /* ENDIAN */
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// Functions to do unaligned loads and stores in little-endian order.
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inline uint16_t Load16(const void *p) {
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return ToHost16(ABSL_INTERNAL_UNALIGNED_LOAD16(p));
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}
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inline void Store16(void *p, uint16_t v) {
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ABSL_INTERNAL_UNALIGNED_STORE16(p, FromHost16(v));
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}
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inline uint32_t Load32(const void *p) {
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return ToHost32(ABSL_INTERNAL_UNALIGNED_LOAD32(p));
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}
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inline void Store32(void *p, uint32_t v) {
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ABSL_INTERNAL_UNALIGNED_STORE32(p, FromHost32(v));
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}
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inline uint64_t Load64(const void *p) {
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return ToHost64(ABSL_INTERNAL_UNALIGNED_LOAD64(p));
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}
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inline void Store64(void *p, uint64_t v) {
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ABSL_INTERNAL_UNALIGNED_STORE64(p, FromHost64(v));
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}
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} // namespace little_endian
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// Utilities to convert numbers between the current hosts's native byte
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// order and big-endian byte order (same as network byte order)
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//
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// Load/Store methods are alignment safe
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namespace big_endian {
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#ifdef ABSL_IS_LITTLE_ENDIAN
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inline uint16_t FromHost16(uint16_t x) { return gbswap_16(x); }
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inline uint16_t ToHost16(uint16_t x) { return gbswap_16(x); }
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inline uint32_t FromHost32(uint32_t x) { return gbswap_32(x); }
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inline uint32_t ToHost32(uint32_t x) { return gbswap_32(x); }
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inline uint64_t FromHost64(uint64_t x) { return gbswap_64(x); }
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inline uint64_t ToHost64(uint64_t x) { return gbswap_64(x); }
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inline constexpr bool IsLittleEndian() { return true; }
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#elif defined ABSL_IS_BIG_ENDIAN
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inline uint16_t FromHost16(uint16_t x) { return x; }
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inline uint16_t ToHost16(uint16_t x) { return x; }
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inline uint32_t FromHost32(uint32_t x) { return x; }
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inline uint32_t ToHost32(uint32_t x) { return x; }
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inline uint64_t FromHost64(uint64_t x) { return x; }
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inline uint64_t ToHost64(uint64_t x) { return x; }
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inline constexpr bool IsLittleEndian() { return false; }
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#endif /* ENDIAN */
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// Functions to do unaligned loads and stores in big-endian order.
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inline uint16_t Load16(const void *p) {
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return ToHost16(ABSL_INTERNAL_UNALIGNED_LOAD16(p));
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}
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inline void Store16(void *p, uint16_t v) {
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ABSL_INTERNAL_UNALIGNED_STORE16(p, FromHost16(v));
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}
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inline uint32_t Load32(const void *p) {
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return ToHost32(ABSL_INTERNAL_UNALIGNED_LOAD32(p));
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}
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inline void Store32(void *p, uint32_t v) {
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ABSL_INTERNAL_UNALIGNED_STORE32(p, FromHost32(v));
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}
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inline uint64_t Load64(const void *p) {
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return ToHost64(ABSL_INTERNAL_UNALIGNED_LOAD64(p));
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}
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inline void Store64(void *p, uint64_t v) {
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ABSL_INTERNAL_UNALIGNED_STORE64(p, FromHost64(v));
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}
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} // namespace big_endian
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} // namespace absl
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#endif // ABSL_BASE_INTERNAL_ENDIAN_H_
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