mirror of
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492 lines
16 KiB
C++
492 lines
16 KiB
C++
// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// Various stubs for the open-source version of Snappy.
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#ifndef THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
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#define THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <stdint.h>
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#include <cassert>
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#include <cstdlib>
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#include <cstring>
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#include <limits>
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#include <string>
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#ifdef HAVE_SYS_MMAN_H
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#include <sys/mman.h>
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#endif
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#if defined(_MSC_VER)
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#include <intrin.h>
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#endif // defined(_MSC_VER)
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#ifndef __has_feature
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#define __has_feature(x) 0
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#endif
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#if __has_feature(memory_sanitizer)
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#include <sanitizer/msan_interface.h>
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#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) \
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__msan_unpoison((address), (size))
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#else
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#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) /* empty */
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#endif // __has_feature(memory_sanitizer)
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#include "snappy-stubs-public.h"
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// Used to enable 64-bit optimized versions of some routines.
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#if defined(__PPC64__) || defined(__powerpc64__)
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#define ARCH_PPC 1
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#elif defined(__aarch64__) || defined(_M_ARM64)
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#define ARCH_ARM 1
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#endif
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// Needed by OS X, among others.
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#ifndef MAP_ANONYMOUS
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#define MAP_ANONYMOUS MAP_ANON
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#endif
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// The size of an array, if known at compile-time.
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// Will give unexpected results if used on a pointer.
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// We undefine it first, since some compilers already have a definition.
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#ifdef ARRAYSIZE
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#undef ARRAYSIZE
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#endif
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#define ARRAYSIZE(a) int{sizeof(a) / sizeof(*(a))}
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// Static prediction hints.
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#ifdef HAVE_BUILTIN_EXPECT
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#define SNAPPY_PREDICT_FALSE(x) (__builtin_expect(x, 0))
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#define SNAPPY_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
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#else
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#define SNAPPY_PREDICT_FALSE(x) x
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#define SNAPPY_PREDICT_TRUE(x) x
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#endif
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// Inlining hints.
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#ifdef HAVE_ATTRIBUTE_ALWAYS_INLINE
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#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
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#else
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#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE
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#endif
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// This is only used for recomputing the tag byte table used during
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// decompression; for simplicity we just remove it from the open-source
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// version (anyone who wants to regenerate it can just do the call
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// themselves within main()).
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#define DEFINE_bool(flag_name, default_value, description) \
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bool FLAGS_ ## flag_name = default_value
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#define DECLARE_bool(flag_name) \
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extern bool FLAGS_ ## flag_name
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namespace snappy {
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static const uint32_t kuint32max = std::numeric_limits<uint32_t>::max();
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static const int64_t kint64max = std::numeric_limits<int64_t>::max();
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// Potentially unaligned loads and stores.
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inline uint16_t UNALIGNED_LOAD16(const void *p) {
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// Compiles to a single movzx/ldrh on clang/gcc/msvc.
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uint16_t v;
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std::memcpy(&v, p, sizeof(v));
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return v;
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}
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inline uint32_t UNALIGNED_LOAD32(const void *p) {
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// Compiles to a single mov/ldr on clang/gcc/msvc.
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uint32_t v;
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std::memcpy(&v, p, sizeof(v));
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return v;
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}
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inline uint64_t UNALIGNED_LOAD64(const void *p) {
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// Compiles to a single mov/ldr on clang/gcc/msvc.
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uint64_t v;
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std::memcpy(&v, p, sizeof(v));
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return v;
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}
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inline void UNALIGNED_STORE16(void *p, uint16_t v) {
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// Compiles to a single mov/strh on clang/gcc/msvc.
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std::memcpy(p, &v, sizeof(v));
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}
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inline void UNALIGNED_STORE32(void *p, uint32_t v) {
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// Compiles to a single mov/str on clang/gcc/msvc.
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std::memcpy(p, &v, sizeof(v));
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}
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inline void UNALIGNED_STORE64(void *p, uint64_t v) {
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// Compiles to a single mov/str on clang/gcc/msvc.
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std::memcpy(p, &v, sizeof(v));
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}
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// Convert to little-endian storage, opposite of network format.
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// Convert x from host to little endian: x = LittleEndian.FromHost(x);
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// convert x from little endian to host: x = LittleEndian.ToHost(x);
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//
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// Store values into unaligned memory converting to little endian order:
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// LittleEndian.Store16(p, x);
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//
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// Load unaligned values stored in little endian converting to host order:
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// x = LittleEndian.Load16(p);
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class LittleEndian {
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public:
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// Functions to do unaligned loads and stores in little-endian order.
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static inline uint16_t Load16(const void *ptr) {
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const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
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// Compiles to a single mov/str on recent clang and gcc.
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return (static_cast<uint16_t>(buffer[0])) |
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(static_cast<uint16_t>(buffer[1]) << 8);
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}
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static inline uint32_t Load32(const void *ptr) {
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const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
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// Compiles to a single mov/str on recent clang and gcc.
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return (static_cast<uint32_t>(buffer[0])) |
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(static_cast<uint32_t>(buffer[1]) << 8) |
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(static_cast<uint32_t>(buffer[2]) << 16) |
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(static_cast<uint32_t>(buffer[3]) << 24);
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}
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static inline uint64_t Load64(const void *ptr) {
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const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
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// Compiles to a single mov/str on recent clang and gcc.
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return (static_cast<uint64_t>(buffer[0])) |
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(static_cast<uint64_t>(buffer[1]) << 8) |
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(static_cast<uint64_t>(buffer[2]) << 16) |
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(static_cast<uint64_t>(buffer[3]) << 24) |
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(static_cast<uint64_t>(buffer[4]) << 32) |
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(static_cast<uint64_t>(buffer[5]) << 40) |
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(static_cast<uint64_t>(buffer[6]) << 48) |
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(static_cast<uint64_t>(buffer[7]) << 56);
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}
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static inline void Store16(void *dst, uint16_t value) {
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uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
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// Compiles to a single mov/str on recent clang and gcc.
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buffer[0] = static_cast<uint8_t>(value);
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buffer[1] = static_cast<uint8_t>(value >> 8);
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}
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static void Store32(void *dst, uint32_t value) {
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uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
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// Compiles to a single mov/str on recent clang and gcc.
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buffer[0] = static_cast<uint8_t>(value);
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buffer[1] = static_cast<uint8_t>(value >> 8);
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buffer[2] = static_cast<uint8_t>(value >> 16);
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buffer[3] = static_cast<uint8_t>(value >> 24);
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}
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static void Store64(void* dst, uint64_t value) {
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uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
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// Compiles to a single mov/str on recent clang and gcc.
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buffer[0] = static_cast<uint8_t>(value);
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buffer[1] = static_cast<uint8_t>(value >> 8);
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buffer[2] = static_cast<uint8_t>(value >> 16);
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buffer[3] = static_cast<uint8_t>(value >> 24);
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buffer[4] = static_cast<uint8_t>(value >> 32);
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buffer[5] = static_cast<uint8_t>(value >> 40);
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buffer[6] = static_cast<uint8_t>(value >> 48);
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buffer[7] = static_cast<uint8_t>(value >> 56);
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}
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static inline constexpr bool IsLittleEndian() {
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#if defined(SNAPPY_IS_BIG_ENDIAN)
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return false;
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#else
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return true;
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#endif // defined(SNAPPY_IS_BIG_ENDIAN)
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}
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};
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// Some bit-manipulation functions.
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class Bits {
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public:
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// Return floor(log2(n)) for positive integer n.
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static int Log2FloorNonZero(uint32_t n);
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// Return floor(log2(n)) for positive integer n. Returns -1 iff n == 0.
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static int Log2Floor(uint32_t n);
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// Return the first set least / most significant bit, 0-indexed. Returns an
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// undefined value if n == 0. FindLSBSetNonZero() is similar to ffs() except
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// that it's 0-indexed.
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static int FindLSBSetNonZero(uint32_t n);
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static int FindLSBSetNonZero64(uint64_t n);
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private:
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// No copying
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Bits(const Bits&);
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void operator=(const Bits&);
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};
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#if defined(HAVE_BUILTIN_CTZ)
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inline int Bits::Log2FloorNonZero(uint32_t n) {
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assert(n != 0);
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// (31 ^ x) is equivalent to (31 - x) for x in [0, 31]. An easy proof
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// represents subtraction in base 2 and observes that there's no carry.
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//
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// GCC and Clang represent __builtin_clz on x86 as 31 ^ _bit_scan_reverse(x).
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// Using "31 ^" here instead of "31 -" allows the optimizer to strip the
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// function body down to _bit_scan_reverse(x).
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return 31 ^ __builtin_clz(n);
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}
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inline int Bits::Log2Floor(uint32_t n) {
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return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
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}
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inline int Bits::FindLSBSetNonZero(uint32_t n) {
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assert(n != 0);
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return __builtin_ctz(n);
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}
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#elif defined(_MSC_VER)
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inline int Bits::Log2FloorNonZero(uint32_t n) {
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assert(n != 0);
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// NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
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unsigned long where;
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_BitScanReverse(&where, n);
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return static_cast<int>(where);
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}
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inline int Bits::Log2Floor(uint32_t n) {
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// NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
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unsigned long where;
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if (_BitScanReverse(&where, n))
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return static_cast<int>(where);
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return -1;
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}
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inline int Bits::FindLSBSetNonZero(uint32_t n) {
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assert(n != 0);
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// NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
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unsigned long where;
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if (_BitScanForward(&where, n))
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return static_cast<int>(where);
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return 32;
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}
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#else // Portable versions.
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inline int Bits::Log2FloorNonZero(uint32_t n) {
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assert(n != 0);
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int log = 0;
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uint32_t value = n;
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for (int i = 4; i >= 0; --i) {
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int shift = (1 << i);
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uint32_t x = value >> shift;
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if (x != 0) {
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value = x;
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log += shift;
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}
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}
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assert(value == 1);
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return log;
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}
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inline int Bits::Log2Floor(uint32_t n) {
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return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
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}
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inline int Bits::FindLSBSetNonZero(uint32_t n) {
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assert(n != 0);
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int rc = 31;
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for (int i = 4, shift = 1 << 4; i >= 0; --i) {
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const uint32_t x = n << shift;
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if (x != 0) {
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n = x;
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rc -= shift;
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}
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shift >>= 1;
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}
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return rc;
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}
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#endif // End portable versions.
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#if defined(HAVE_BUILTIN_CTZ)
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inline int Bits::FindLSBSetNonZero64(uint64_t n) {
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assert(n != 0);
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return __builtin_ctzll(n);
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}
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#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
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// _BitScanForward64() is only available on x64 and ARM64.
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inline int Bits::FindLSBSetNonZero64(uint64_t n) {
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assert(n != 0);
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// NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
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unsigned long where;
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if (_BitScanForward64(&where, n))
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return static_cast<int>(where);
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return 64;
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}
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#else // Portable version.
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// FindLSBSetNonZero64() is defined in terms of FindLSBSetNonZero().
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inline int Bits::FindLSBSetNonZero64(uint64_t n) {
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assert(n != 0);
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const uint32_t bottombits = static_cast<uint32_t>(n);
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if (bottombits == 0) {
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// Bottom bits are zero, so scan the top bits.
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return 32 + FindLSBSetNonZero(static_cast<uint32_t>(n >> 32));
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} else {
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return FindLSBSetNonZero(bottombits);
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}
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}
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#endif // End portable version.
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// Variable-length integer encoding.
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class Varint {
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public:
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// Maximum lengths of varint encoding of uint32_t.
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static const int kMax32 = 5;
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// Attempts to parse a varint32 from a prefix of the bytes in [ptr,limit-1].
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// Never reads a character at or beyond limit. If a valid/terminated varint32
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// was found in the range, stores it in *OUTPUT and returns a pointer just
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// past the last byte of the varint32. Else returns NULL. On success,
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// "result <= limit".
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static const char* Parse32WithLimit(const char* ptr, const char* limit,
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uint32_t* OUTPUT);
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// REQUIRES "ptr" points to a buffer of length sufficient to hold "v".
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// EFFECTS Encodes "v" into "ptr" and returns a pointer to the
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// byte just past the last encoded byte.
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static char* Encode32(char* ptr, uint32_t v);
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// EFFECTS Appends the varint representation of "value" to "*s".
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static void Append32(std::string* s, uint32_t value);
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};
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inline const char* Varint::Parse32WithLimit(const char* p,
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const char* l,
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uint32_t* OUTPUT) {
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const unsigned char* ptr = reinterpret_cast<const unsigned char*>(p);
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const unsigned char* limit = reinterpret_cast<const unsigned char*>(l);
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uint32_t b, result;
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if (ptr >= limit) return NULL;
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b = *(ptr++); result = b & 127; if (b < 128) goto done;
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if (ptr >= limit) return NULL;
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b = *(ptr++); result |= (b & 127) << 7; if (b < 128) goto done;
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if (ptr >= limit) return NULL;
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b = *(ptr++); result |= (b & 127) << 14; if (b < 128) goto done;
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if (ptr >= limit) return NULL;
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b = *(ptr++); result |= (b & 127) << 21; if (b < 128) goto done;
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if (ptr >= limit) return NULL;
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b = *(ptr++); result |= (b & 127) << 28; if (b < 16) goto done;
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return NULL; // Value is too long to be a varint32
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done:
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*OUTPUT = result;
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return reinterpret_cast<const char*>(ptr);
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}
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inline char* Varint::Encode32(char* sptr, uint32_t v) {
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// Operate on characters as unsigneds
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uint8_t* ptr = reinterpret_cast<uint8_t*>(sptr);
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static const uint8_t B = 128;
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if (v < (1 << 7)) {
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*(ptr++) = static_cast<uint8_t>(v);
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} else if (v < (1 << 14)) {
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*(ptr++) = static_cast<uint8_t>(v | B);
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*(ptr++) = static_cast<uint8_t>(v >> 7);
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} else if (v < (1 << 21)) {
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*(ptr++) = static_cast<uint8_t>(v | B);
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*(ptr++) = static_cast<uint8_t>((v >> 7) | B);
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*(ptr++) = static_cast<uint8_t>(v >> 14);
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} else if (v < (1 << 28)) {
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*(ptr++) = static_cast<uint8_t>(v | B);
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*(ptr++) = static_cast<uint8_t>((v >> 7) | B);
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*(ptr++) = static_cast<uint8_t>((v >> 14) | B);
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*(ptr++) = static_cast<uint8_t>(v >> 21);
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} else {
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*(ptr++) = static_cast<uint8_t>(v | B);
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*(ptr++) = static_cast<uint8_t>((v>>7) | B);
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*(ptr++) = static_cast<uint8_t>((v>>14) | B);
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*(ptr++) = static_cast<uint8_t>((v>>21) | B);
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*(ptr++) = static_cast<uint8_t>(v >> 28);
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}
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return reinterpret_cast<char*>(ptr);
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}
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// If you know the internal layout of the std::string in use, you can
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// replace this function with one that resizes the string without
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// filling the new space with zeros (if applicable) --
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// it will be non-portable but faster.
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inline void STLStringResizeUninitialized(std::string* s, size_t new_size) {
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s->resize(new_size);
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}
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// Return a mutable char* pointing to a string's internal buffer,
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// which may not be null-terminated. Writing through this pointer will
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// modify the string.
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//
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// string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
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// next call to a string method that invalidates iterators.
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|
//
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|
// As of 2006-04, there is no standard-blessed way of getting a
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|
// mutable reference to a string's internal buffer. However, issue 530
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// (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-defects.html#530)
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// proposes this as the method. It will officially be part of the standard
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// for C++0x. This should already work on all current implementations.
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inline char* string_as_array(std::string* str) {
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return str->empty() ? NULL : &*str->begin();
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}
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} // namespace snappy
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#endif // THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
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