snappy-stubs-internal.h | Explore in Territory

// Copyright 2011 Google Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Various stubs for the open-source version of Snappy.

#ifndef THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
#define THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdint.h>

#include <cassert>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <string>

#if HAVE_SYS_MMAN_H
#include <sys/mman.h>
#endif

#if HAVE_UNISTD_H
#include <unistd.h>
#endif

#if defined(_MSC_VER)
#include <intrin.h>
#endif  // defined(_MSC_VER)

#ifndef __has_feature
#define __has_feature …
#endif

#if __has_feature(memory_sanitizer)
#include <sanitizer/msan_interface.h>
#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED …
#else
#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) …
#endif  // __has_feature(memory_sanitizer)

#include "snappy-stubs-public.h"

// Used to enable 64-bit optimized versions of some routines.
#if defined(__PPC64__) || defined(__powerpc64__)
#define ARCH_PPC …
#elif defined(__aarch64__) || defined(_M_ARM64)
#define ARCH_ARM …
#endif

// Needed by OS X, among others.
#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS …
#endif

// The size of an array, if known at compile-time.
// Will give unexpected results if used on a pointer.
// We undefine it first, since some compilers already have a definition.
#ifdef ARRAYSIZE
#undef ARRAYSIZE
#endif
#define ARRAYSIZE(a) …

// Static prediction hints.
#if HAVE_BUILTIN_EXPECT
#define SNAPPY_PREDICT_FALSE(x) …
#define SNAPPY_PREDICT_TRUE(x) …
#else
#define SNAPPY_PREDICT_FALSE …
#define SNAPPY_PREDICT_TRUE …
#endif  // HAVE_BUILTIN_EXPECT

// Inlining hints.
#if HAVE_ATTRIBUTE_ALWAYS_INLINE
#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE …
#else
#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE
#endif  // HAVE_ATTRIBUTE_ALWAYS_INLINE

#if HAVE_BUILTIN_PREFETCH
#define SNAPPY_PREFETCH …
#else
#define SNAPPY_PREFETCH(ptr) …
#endif

// Stubbed version of ABSL_FLAG.
//
// In the open source version, flags can only be changed at compile time.
#define SNAPPY_FLAG(flag_type, flag_name, default_value, help) …

namespace snappy {

// Stubbed version of absl::GetFlag().
template <typename T>
inline T GetFlag(T flag) { … }

static const uint32_t kuint32max = …;
static const int64_t kint64max = …;

// Potentially unaligned loads and stores.

inline uint16_t UNALIGNED_LOAD16(const void *p) { … }

inline uint32_t UNALIGNED_LOAD32(const void *p) { … }

inline uint64_t UNALIGNED_LOAD64(const void *p) { … }

inline void UNALIGNED_STORE16(void *p, uint16_t v) { … }

inline void UNALIGNED_STORE32(void *p, uint32_t v) { … }

inline void UNALIGNED_STORE64(void *p, uint64_t v) { … }

// Convert to little-endian storage, opposite of network format.
// Convert x from host to little endian: x = LittleEndian.FromHost(x);
// convert x from little endian to host: x = LittleEndian.ToHost(x);
//
//  Store values into unaligned memory converting to little endian order:
//    LittleEndian.Store16(p, x);
//
//  Load unaligned values stored in little endian converting to host order:
//    x = LittleEndian.Load16(p);
class LittleEndian { … };

// Some bit-manipulation functions.
class Bits { … };

#if HAVE_BUILTIN_CTZ

inline int Bits::Log2FloorNonZero(uint32_t n) { … }

inline int Bits::Log2Floor(uint32_t n) { … }

inline int Bits::FindLSBSetNonZero(uint32_t n) { … }

#elif defined(_MSC_VER)

inline int Bits::Log2FloorNonZero(uint32_t n) {
  assert(n != 0);
  // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
  unsigned long where;
  _BitScanReverse(&where, n);
  return static_cast<int>(where);
}

inline int Bits::Log2Floor(uint32_t n) {
  // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
  unsigned long where;
  if (_BitScanReverse(&where, n))
    return static_cast<int>(where);
  return -1;
}

inline int Bits::FindLSBSetNonZero(uint32_t n) {
  assert(n != 0);
  // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
  unsigned long where;
  if (_BitScanForward(&where, n))
    return static_cast<int>(where);
  return 32;
}

#else  // Portable versions.

inline int Bits::Log2FloorNonZero(uint32_t n) {
  assert(n != 0);

  int log = 0;
  uint32_t value = n;
  for (int i = 4; i >= 0; --i) {
    int shift = (1 << i);
    uint32_t x = value >> shift;
    if (x != 0) {
      value = x;
      log += shift;
    }
  }
  assert(value == 1);
  return log;
}

inline int Bits::Log2Floor(uint32_t n) {
  return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
}

inline int Bits::FindLSBSetNonZero(uint32_t n) {
  assert(n != 0);

  int rc = 31;
  for (int i = 4, shift = 1 << 4; i >= 0; --i) {
    const uint32_t x = n << shift;
    if (x != 0) {
      n = x;
      rc -= shift;
    }
    shift >>= 1;
  }
  return rc;
}

#endif  // End portable versions.

#if HAVE_BUILTIN_CTZ

inline int Bits::FindLSBSetNonZero64(uint64_t n) { … }

#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
// _BitScanForward64() is only available on x64 and ARM64.

inline int Bits::FindLSBSetNonZero64(uint64_t n) {
  assert(n != 0);
  // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
  unsigned long where;
  if (_BitScanForward64(&where, n))
    return static_cast<int>(where);
  return 64;
}

#else  // Portable version.

// FindLSBSetNonZero64() is defined in terms of FindLSBSetNonZero().
inline int Bits::FindLSBSetNonZero64(uint64_t n) {
  assert(n != 0);

  const uint32_t bottombits = static_cast<uint32_t>(n);
  if (bottombits == 0) {
    // Bottom bits are zero, so scan the top bits.
    return 32 + FindLSBSetNonZero(static_cast<uint32_t>(n >> 32));
  } else {
    return FindLSBSetNonZero(bottombits);
  }
}

#endif  // HAVE_BUILTIN_CTZ

// Variable-length integer encoding.
class Varint { … };

inline const char* Varint::Parse32WithLimit(const char* p,
                                            const char* l,
                                            uint32_t* OUTPUT) { … }

inline char* Varint::Encode32(char* sptr, uint32_t v) { … }

// If you know the internal layout of the std::string in use, you can
// replace this function with one that resizes the string without
// filling the new space with zeros (if applicable) --
// it will be non-portable but faster.
inline void STLStringResizeUninitialized(std::string* s, size_t new_size) { … }

// Return a mutable char* pointing to a string's internal buffer,
// which may not be null-terminated. Writing through this pointer will
// modify the string.
//
// string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
// next call to a string method that invalidates iterators.
//
// As of 2006-04, there is no standard-blessed way of getting a
// mutable reference to a string's internal buffer. However, issue 530
// (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-defects.html#530)
// proposes this as the method. It will officially be part of the standard
// for C++0x. This should already work on all current implementations.
inline char* string_as_array(std::string* str) { … }

}  // namespace snappy

#endif  // THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
chromium/third_party/snappy/src/snappy-stubs-internal.h
