// 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(x) 0

#endif

#if __has_feature(memory_sanitizer)

#include <sanitizer/msan_interface.h>

#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) \

    __msan_unpoison((address), (size))

#else

#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) /* empty */

#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 1

#elif defined(__aarch64__) || defined(_M_ARM64)

#define ARCH_ARM 1

#endif

// Needed by OS X, among others.

#ifndef MAP_ANONYMOUS

#define MAP_ANONYMOUS MAP_ANON

#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) int{sizeof(a) / sizeof(*(a))}

// Static prediction hints.

#if HAVE_BUILTIN_EXPECT

#define SNAPPY_PREDICT_FALSE(x) (__builtin_expect(x, 0))

#define SNAPPY_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))

#else

#define SNAPPY_PREDICT_FALSE(x) x

#define SNAPPY_PREDICT_TRUE(x) x

#endif  // HAVE_BUILTIN_EXPECT

// Inlining hints.

#if HAVE_ATTRIBUTE_ALWAYS_INLINE

#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))

#else

#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE

#endif  // HAVE_ATTRIBUTE_ALWAYS_INLINE

#if HAVE_BUILTIN_PREFETCH

#define SNAPPY_PREFETCH(ptr) __builtin_prefetch(ptr, 0, 3)

#else

#define SNAPPY_PREFETCH(ptr) (void)(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) \

  flag_type FLAGS_ ## flag_name = default_value

namespace snappy {

// Stubbed version of absl::GetFlag().

template <typename T>

inline T GetFlag(T flag) { return flag; }

static const uint32_t kuint32max = std::numeric_limits<uint32_t>::max();

static const int64_t kint64max = std::numeric_limits<int64_t>::max();

// Potentially unaligned loads and stores.

inline uint16_t UNALIGNED_LOAD16(const void *p) {

  // Compiles to a single movzx/ldrh on clang/gcc/msvc.

  uint16_t v;

  std::memcpy(&v, p, sizeof(v));

  return v;

}

inline uint32_t UNALIGNED_LOAD32(const void *p) {

  // Compiles to a single mov/ldr on clang/gcc/msvc.

  uint32_t v;

  std::memcpy(&v, p, sizeof(v));

  return v;

}

inline uint64_t UNALIGNED_LOAD64(const void *p) {

  // Compiles to a single mov/ldr on clang/gcc/msvc.

  uint64_t v;

  std::memcpy(&v, p, sizeof(v));

  return v;

}

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

  // Compiles to a single mov/strh on clang/gcc/msvc.

  std::memcpy(p, &v, sizeof(v));

}

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

  // Compiles to a single mov/str on clang/gcc/msvc.

  std::memcpy(p, &v, sizeof(v));

}

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

  // Compiles to a single mov/str on clang/gcc/msvc.

  std::memcpy(p, &v, sizeof(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 {

 public:

  // Functions to do unaligned loads and stores in little-endian order.

  static inline uint16_t Load16(const void *ptr) {

    // Compiles to a single mov/str on recent clang and gcc.

#if SNAPPY_IS_BIG_ENDIAN

    const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);

    return (static_cast<uint16_t>(buffer[0])) |

            (static_cast<uint16_t>(buffer[1]) << 8);

#else

    // memcpy() turns into a single instruction early in the optimization

    // pipeline (relatively to a series of byte accesses). So, using memcpy

    // instead of byte accesses may lead to better decisions in more stages of

    // the optimization pipeline.

    uint16_t value;

    std::memcpy(&value, ptr, 2);

    return value;

#endif

  }

  static inline uint32_t Load32(const void *ptr) {

    // Compiles to a single mov/str on recent clang and gcc.

#if SNAPPY_IS_BIG_ENDIAN

    const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);

    return (static_cast<uint32_t>(buffer[0])) |

            (static_cast<uint32_t>(buffer[1]) << 8) |

            (static_cast<uint32_t>(buffer[2]) << 16) |

            (static_cast<uint32_t>(buffer[3]) << 24);

#else

    // See Load16() for the rationale of using memcpy().

    uint32_t value;

    std::memcpy(&value, ptr, 4);

    return value;

#endif

  }

  static inline uint64_t Load64(const void *ptr) {

    // Compiles to a single mov/str on recent clang and gcc.

#if SNAPPY_IS_BIG_ENDIAN

    const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);

    return (static_cast<uint64_t>(buffer[0])) |

            (static_cast<uint64_t>(buffer[1]) << 8) |

            (static_cast<uint64_t>(buffer[2]) << 16) |

            (static_cast<uint64_t>(buffer[3]) << 24) |

            (static_cast<uint64_t>(buffer[4]) << 32) |

            (static_cast<uint64_t>(buffer[5]) << 40) |

            (static_cast<uint64_t>(buffer[6]) << 48) |

            (static_cast<uint64_t>(buffer[7]) << 56);

#else

    // See Load16() for the rationale of using memcpy().

    uint64_t value;

    std::memcpy(&value, ptr, 8);

    return value;

#endif

  }

  static inline void Store16(void *dst, uint16_t value) {

    // Compiles to a single mov/str on recent clang and gcc.

#if SNAPPY_IS_BIG_ENDIAN

    uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);

    buffer[0] = static_cast<uint8_t>(value);

    buffer[1] = static_cast<uint8_t>(value >> 8);

#else

    // See Load16() for the rationale of using memcpy().

    std::memcpy(dst, &value, 2);

#endif

  }

  static void Store32(void *dst, uint32_t value) {

    // Compiles to a single mov/str on recent clang and gcc.

#if SNAPPY_IS_BIG_ENDIAN

    uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);

    buffer[0] = static_cast<uint8_t>(value);

    buffer[1] = static_cast<uint8_t>(value >> 8);

    buffer[2] = static_cast<uint8_t>(value >> 16);

    buffer[3] = static_cast<uint8_t>(value >> 24);

#else

    // See Load16() for the rationale of using memcpy().

    std::memcpy(dst, &value, 4);

#endif

  }

  static void Store64(void* dst, uint64_t value) {

    // Compiles to a single mov/str on recent clang and gcc.

#if SNAPPY_IS_BIG_ENDIAN

    uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);

    buffer[0] = static_cast<uint8_t>(value);

    buffer[1] = static_cast<uint8_t>(value >> 8);

    buffer[2] = static_cast<uint8_t>(value >> 16);

    buffer[3] = static_cast<uint8_t>(value >> 24);

    buffer[4] = static_cast<uint8_t>(value >> 32);

    buffer[5] = static_cast<uint8_t>(value >> 40);

    buffer[6] = static_cast<uint8_t>(value >> 48);

    buffer[7] = static_cast<uint8_t>(value >> 56);

#else

    // See Load16() for the rationale of using memcpy().

    std::memcpy(dst, &value, 8);

#endif

  }

  static inline constexpr bool IsLittleEndian() {

#if SNAPPY_IS_BIG_ENDIAN

    return false;

#else

    return true;

#endif  // SNAPPY_IS_BIG_ENDIAN

  }

};

// Some bit-manipulation functions.

class Bits {

 public:

  // Return floor(log2(n)) for positive integer n.

  static int Log2FloorNonZero(uint32_t n);

  // Return floor(log2(n)) for positive integer n.  Returns -1 iff n == 0.

  static int Log2Floor(uint32_t n);

  // Return the first set least / most significant bit, 0-indexed.  Returns an

  // undefined value if n == 0.  FindLSBSetNonZero() is similar to ffs() except

  // that it's 0-indexed.

  static int FindLSBSetNonZero(uint32_t n);

  static int FindLSBSetNonZero64(uint64_t n);

 private:

  // No copying

  Bits(const Bits&);

  void operator=(const Bits&);

};

#if HAVE_BUILTIN_CTZ

inline int Bits::Log2FloorNonZero(uint32_t n) {

  assert(n != 0);

  // (31 ^ x) is equivalent to (31 - x) for x in [0, 31]. An easy proof

  // represents subtraction in base 2 and observes that there's no carry.

  //

  // GCC and Clang represent __builtin_clz on x86 as 31 ^ _bit_scan_reverse(x).

  // Using "31 ^" here instead of "31 -" allows the optimizer to strip the

  // function body down to _bit_scan_reverse(x).

  return 31 ^ __builtin_clz(n);

}

inline int Bits::Log2Floor(uint32_t n) {

  return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);

}

inline int Bits::FindLSBSetNonZero(uint32_t n) {

  assert(n != 0);

  return __builtin_ctz(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) {

  assert(n != 0);

  return __builtin_ctzll(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 {

 public:

  // Maximum lengths of varint encoding of uint32_t.

  static const int kMax32 = 5;

  // Attempts to parse a varint32 from a prefix of the bytes in [ptr,limit-1].

  // Never reads a character at or beyond limit.  If a valid/terminated varint32

  // was found in the range, stores it in *OUTPUT and returns a pointer just

  // past the last byte of the varint32. Else returns NULL.  On success,

  // "result <= limit".

  static const char* Parse32WithLimit(const char* ptr, const char* limit,

                                      uint32_t* OUTPUT);

  // REQUIRES   "ptr" points to a buffer of length sufficient to hold "v".

  // EFFECTS    Encodes "v" into "ptr" and returns a pointer to the

  //            byte just past the last encoded byte.

  static char* Encode32(char* ptr, uint32_t v);

  // EFFECTS    Appends the varint representation of "value" to "*s".

  static void Append32(std::string* s, uint32_t value);

};

inline const char* Varint::Parse32WithLimit(const char* p,

                                            const char* l,

                                            uint32_t* OUTPUT) {

  const unsigned char* ptr = reinterpret_cast<const unsigned char*>(p);

  const unsigned char* limit = reinterpret_cast<const unsigned char*>(l);

  uint32_t b, result;

  if (ptr >= limit) return NULL;

  b = *(ptr++); result = b & 127;          if (b < 128) goto done;

  if (ptr >= limit) return NULL;

  b = *(ptr++); result |= (b & 127) <<  7; if (b < 128) goto done;

  if (ptr >= limit) return NULL;

  b = *(ptr++); result |= (b & 127) << 14; if (b < 128) goto done;

  if (ptr >= limit) return NULL;

  b = *(ptr++); result |= (b & 127) << 21; if (b < 128) goto done;

  if (ptr >= limit) return NULL;

  b = *(ptr++); result |= (b & 127) << 28; if (b < 16) goto done;

  return NULL;       // Value is too long to be a varint32

 done:

  *OUTPUT = result;

  return reinterpret_cast<const char*>(ptr);

}

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

  // Operate on characters as unsigneds

  uint8_t* ptr = reinterpret_cast<uint8_t*>(sptr);

  static const uint8_t B = 128;

  if (v < (1 << 7)) {

    *(ptr++) = static_cast<uint8_t>(v);

  } else if (v < (1 << 14)) {

    *(ptr++) = static_cast<uint8_t>(v | B);

    *(ptr++) = static_cast<uint8_t>(v >> 7);

  } else if (v < (1 << 21)) {

    *(ptr++) = static_cast<uint8_t>(v | B);

    *(ptr++) = static_cast<uint8_t>((v >> 7) | B);

    *(ptr++) = static_cast<uint8_t>(v >> 14);

  } else if (v < (1 << 28)) {

    *(ptr++) = static_cast<uint8_t>(v | B);

    *(ptr++) = static_cast<uint8_t>((v >> 7) | B);

    *(ptr++) = static_cast<uint8_t>((v >> 14) | B);

    *(ptr++) = static_cast<uint8_t>(v >> 21);

  } else {

    *(ptr++) = static_cast<uint8_t>(v | B);

    *(ptr++) = static_cast<uint8_t>((v>>7) | B);

    *(ptr++) = static_cast<uint8_t>((v>>14) | B);

    *(ptr++) = static_cast<uint8_t>((v>>21) | B);

    *(ptr++) = static_cast<uint8_t>(v >> 28);

  }

  return reinterpret_cast<char*>(ptr);

}

// 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) {

  s->resize(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) {

  return str->empty() ? NULL : &*str->begin();

}

}  // namespace snappy

#endif  // THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_