text: /*
  xxHash - Fast Hash algorithm
  Copyright (C) 2012-2014, Yann Collet.
  BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
  
  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.
  
  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.
  
  You can contact the author at :
  - xxHash source repository : http://code.google.com/p/xxhash/
  */
  
  
  //**************************************
  // Tuning parameters
  //**************************************
  // Unaligned memory access is automatically enabled for "common" CPU, such as x86.
  // For others CPU, the compiler will be more cautious, and insert extra code to ensure aligned access is respected.
  // If you know your target CPU supports unaligned memory access, you want to force this option manually to improve performance.
  // You can also enable this parameter if you know your input data will always be aligned (boundaries of 4, for U32).
  #if defined(__ARM_FEATURE_UNALIGNED) || defined(__i386) || defined(_M_IX86) || defined(__x86_64__) || defined(_M_X64)
  #  define XXH_USE_UNALIGNED_ACCESS 1
  #endif
  
  // XXH_ACCEPT_NULL_INPUT_POINTER :
  // If the input pointer is a null pointer, xxHash default behavior is to trigger a memory access error, since it is a bad pointer.
  // When this option is enabled, xxHash output for null input pointers will be the same as a null-length input.
  // This option has a very small performance cost (only measurable on small inputs).
  // By default, this option is disabled. To enable it, uncomment below define :
  //#define XXH_ACCEPT_NULL_INPUT_POINTER 1
  
  // XXH_FORCE_NATIVE_FORMAT :
  // By default, xxHash library provides endian-independent Hash values, based on little-endian convention.
  // Results are therefore identical for little-endian and big-endian CPU.
  // This comes at a performance cost for big-endian CPU, since some swapping is required to emulate little-endian format.
  // Should endian-independance be of no importance for your application, you may set the #define below to 1.
  // It will improve speed for Big-endian CPU.
  // This option has no impact on Little_Endian CPU.
  #define XXH_FORCE_NATIVE_FORMAT 0
  
  
  //**************************************
  // Compiler Specific Options
  //**************************************
  // Disable some Visual warning messages
  #ifdef _MSC_VER  // Visual Studio
  #  pragma warning(disable : 4127)      // disable: C4127: conditional expression is constant
  #  pragma warning(disable : 4804)      // disable: C4804: 'operation' : unsafe use of type 'bool' in operation (static assert line 313)
  #endif
  
  #ifdef _MSC_VER    // Visual Studio
  #  define FORCE_INLINE static __forceinline
  #else
  #  ifdef __GNUC__
  #    define FORCE_INLINE static inline __attribute__((always_inline))
  #  else
  #    define FORCE_INLINE static inline
  #  endif
  #endif
  
  
  //**************************************
  // Includes & Memory related functions
  //**************************************
  #include "xxhash.h"
  // Modify the local functions below should you wish to use some other memory related routines
  // for malloc(), free()
  #include <stdlib.h>
  FORCE_INLINE void* XXH_malloc(size_t s) { return malloc(s); }
  FORCE_INLINE void  XXH_free  (void* p)  { free(p); }
  // for memcpy()
  #include <string.h>
  FORCE_INLINE void* XXH_memcpy(void* dest, const void* src, size_t size) { return memcpy(dest,src,size); }
  
  
  namespace rocksdb {
  //**************************************
  // Basic Types
  //**************************************
  #if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   // C99
  # include <stdint.h>
    typedef uint8_t  BYTE;
    typedef uint16_t U16;
    typedef uint32_t U32;
    typedef  int32_t S32;
    typedef uint64_t U64;
  #else
    typedef unsigned char      BYTE;
    typedef unsigned short     U16;
    typedef unsigned int       U32;
    typedef   signed int       S32;
    typedef unsigned long long U64;
  #endif
  
  #if defined(__GNUC__)  && !defined(XXH_USE_UNALIGNED_ACCESS)
  #  define _PACKED __attribute__ ((packed))
  #else
  #  define _PACKED
  #endif
  
  #if !defined(XXH_USE_UNALIGNED_ACCESS) && !defined(__GNUC__)
  #  ifdef __IBMC__
  #    pragma pack(1)
  #  else
  #    pragma pack(push, 1)
  #  endif
  #endif
  
  typedef struct _U32_S { U32 v; } _PACKED U32_S;
  
  #if !defined(XXH_USE_UNALIGNED_ACCESS) && !defined(__GNUC__)
  #  pragma pack(pop)
  #endif
  
  #define A32(x) (((U32_S *)(x))->v)
  
  
  //***************************************
  // Compiler-specific Functions and Macros
  //***************************************
  #define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
  
  // Note : although _rotl exists for minGW (GCC under windows), performance seems poor
  #if defined(_MSC_VER)
  #  define XXH_rotl32(x,r) _rotl(x,r)
  #else
  #  define XXH_rotl32(x,r) ((x << r) | (x >> (32 - r)))
  #endif
  
  #if defined(_MSC_VER)     // Visual Studio
  #  define XXH_swap32 _byteswap_ulong
  #elif GCC_VERSION >= 403
  #  define XXH_swap32 __builtin_bswap32
  #else
  static inline U32 XXH_swap32 (U32 x) {
      return  ((x << 24) & 0xff000000 ) |
          ((x <<  8) & 0x00ff0000 ) |
          ((x >>  8) & 0x0000ff00 ) |
          ((x >> 24) & 0x000000ff );}
  #endif
  
  
  //**************************************
  // Constants
  //**************************************
  #define PRIME32_1   2654435761U
  #define PRIME32_2   2246822519U
  #define PRIME32_3   3266489917U
  #define PRIME32_4    668265263U
  #define PRIME32_5    374761393U
  
  
  //**************************************
  // Architecture Macros
  //**************************************
  typedef enum { XXH_bigEndian=0, XXH_littleEndian=1 } XXH_endianess;
  #ifndef XXH_CPU_LITTLE_ENDIAN   // It is possible to define XXH_CPU_LITTLE_ENDIAN externally, for example using a compiler switch
      static const int one = 1;
  #   define XXH_CPU_LITTLE_ENDIAN   (*(char*)(&one))
  #endif
  
  
  //**************************************
  // Macros
  //**************************************
  #define XXH_STATIC_ASSERT(c)   { enum { XXH_static_assert = 1/(!!(c)) }; }    // use only *after* variable declarations
  
  
  //****************************
  // Memory reads
  //****************************
  typedef enum { XXH_aligned, XXH_unaligned } XXH_alignment;
  
  FORCE_INLINE U32 XXH_readLE32_align(const U32* ptr, XXH_endianess endian, XXH_alignment align)
  {
      if (align==XXH_unaligned)
          return endian==XXH_littleEndian ? A32(ptr) : XXH_swap32(A32(ptr));
      else
          return endian==XXH_littleEndian ? *ptr : XXH_swap32(*ptr);
  }
  
  FORCE_INLINE U32 XXH_readLE32(const U32* ptr, XXH_endianess endian) { return XXH_readLE32_align(ptr, endian, XXH_unaligned); }
  
  
  //****************************
  // Simple Hash Functions
  //****************************
  FORCE_INLINE U32 XXH32_endian_align(const void* input, int len, U32 seed, XXH_endianess endian, XXH_alignment align)
  {
      const BYTE* p = (const BYTE*)input;
      const BYTE* const bEnd = p + len;
      U32 h32;
  
  #ifdef XXH_ACCEPT_NULL_INPUT_POINTER
      if (p==NULL) { len=0; p=(const BYTE*)(size_t)16; }
  #endif
  
      if (len>=16)
      {
          const BYTE* const limit = bEnd - 16;
          U32 v1 = seed + PRIME32_1 + PRIME32_2;
          U32 v2 = seed + PRIME32_2;
          U32 v3 = seed + 0;
          U32 v4 = seed - PRIME32_1;
  
          do
          {
              v1 += XXH_readLE32_align((const U32*)p, endian, align) * PRIME32_2; v1 = XXH_rotl32(v1, 13); v1 *= PRIME32_1; p+=4;
              v2 += XXH_readLE32_align((const U32*)p, endian, align) * PRIME32_2; v2 = XXH_rotl32(v2, 13); v2 *= PRIME32_1; p+=4;
              v3 += XXH_readLE32_align((const U32*)p, endian, align) * PRIME32_2; v3 = XXH_rotl32(v3, 13); v3 *= PRIME32_1; p+=4;
              v4 += XXH_readLE32_align((const U32*)p, endian, align) * PRIME32_2; v4 = XXH_rotl32(v4, 13); v4 *= PRIME32_1; p+=4;
          } while (p<=limit);
  
          h32 = XXH_rotl32(v1, 1) + XXH_rotl32(v2, 7) + XXH_rotl32(v3, 12) + XXH_rotl32(v4, 18);
      }
      else
      {
          h32  = seed + PRIME32_5;
      }
  
      h32 += (U32) len;
  
      while (p<=bEnd-4)
      {
          h32 += XXH_readLE32_align((const U32*)p, endian, align) * PRIME32_3;
          h32  = XXH_rotl32(h32, 17) * PRIME32_4 ;
          p+=4;
      }
  
      while (p<bEnd)
      {
          h32 += (*p) * PRIME32_5;
          h32 = XXH_rotl32(h32, 11) * PRIME32_1 ;
          p++;
      }
  
      h32 ^= h32 >> 15;
      h32 *= PRIME32_2;
      h32 ^= h32 >> 13;
      h32 *= PRIME32_3;
      h32 ^= h32 >> 16;
  
      return h32;
  }
  
  
  U32 XXH32(const void* input, int len, U32 seed)
  {
  #if 0
      // Simple version, good for code maintenance, but unfortunately slow for small inputs
      void* state = XXH32_init(seed);
      XXH32_update(state, input, len);
      return XXH32_digest(state);
  #else
      XXH_endianess endian_detected = (XXH_endianess)XXH_CPU_LITTLE_ENDIAN;
  
  #  if !defined(XXH_USE_UNALIGNED_ACCESS)
      if ((((size_t)input) & 3))   // Input is aligned, let's leverage the speed advantage
      {
          if ((endian_detected==XXH_littleEndian) || XXH_FORCE_NATIVE_FORMAT)
              return XXH32_endian_align(input, len, seed, XXH_littleEndian, XXH_aligned);
          else
              return XXH32_endian_align(input, len, seed, XXH_bigEndian, XXH_aligned);
      }
  #  endif
  
      if ((endian_detected==XXH_littleEndian) || XXH_FORCE_NATIVE_FORMAT)
          return XXH32_endian_align(input, len, seed, XXH_littleEndian, XXH_unaligned);
      else
          return XXH32_endian_align(input, len, seed, XXH_bigEndian, XXH_unaligned);
  #endif
  }
  
  
  //****************************
  // Advanced Hash Functions
  //****************************
  
  struct XXH_state32_t
  {
      U64 total_len;
      U32 seed;
      U32 v1;
      U32 v2;
      U32 v3;
      U32 v4;
      int memsize;
      char memory[16];
  };
  
  
  int XXH32_sizeofState()
  {
      XXH_STATIC_ASSERT(XXH32_SIZEOFSTATE >= sizeof(struct XXH_state32_t));   // A compilation error here means XXH32_SIZEOFSTATE is not large enough
      return sizeof(struct XXH_state32_t);
  }
  
  
  XXH_errorcode XXH32_resetState(void* state_in, U32 seed)
  {
      struct XXH_state32_t * state = (struct XXH_state32_t *) state_in;
      state->seed = seed;
      state->v1 = seed + PRIME32_1 + PRIME32_2;
      state->v2 = seed + PRIME32_2;
      state->v3 = seed + 0;
      state->v4 = seed - PRIME32_1;
      state->total_len = 0;
      state->memsize = 0;
      return XXH_OK;
  }
  
  
  void* XXH32_init (U32 seed)
  {
      void* state = XXH_malloc (sizeof(struct XXH_state32_t));
      XXH32_resetState(state, seed);
      return state;
  }
  
  
  FORCE_INLINE XXH_errorcode XXH32_update_endian (void* state_in, const void* input, int len, XXH_endianess endian)
  {
      struct XXH_state32_t * state = (struct XXH_state32_t *) state_in;
      const BYTE* p = (const BYTE*)input;
      const BYTE* const bEnd = p + len;
  
  #ifdef XXH_ACCEPT_NULL_INPUT_POINTER
      if (input==NULL) return XXH_ERROR;
  #endif
  
      state->total_len += len;
  
      if (state->memsize + len < 16)   // fill in tmp buffer
      {
          XXH_memcpy(state->memory + state->memsize, input, len);
          state->memsize +=  len;
          return XXH_OK;
      }
  
      if (state->memsize)   // some data left from previous update
      {
          XXH_memcpy(state->memory + state->memsize, input, 16-state->memsize);
          {
              const U32* p32 = (const U32*)state->memory;
              state->v1 += XXH_readLE32(p32, endian) * PRIME32_2; state->v1 = XXH_rotl32(state->v1, 13); state->v1 *= PRIME32_1; p32++;
              state->v2 += XXH_readLE32(p32, endian) * PRIME32_2; state->v2 = XXH_rotl32(state->v2, 13); state->v2 *= PRIME32_1; p32++;
              state->v3 += XXH_readLE32(p32, endian) * PRIME32_2; state->v3 = XXH_rotl32(state->v3, 13); state->v3 *= PRIME32_1; p32++;
              state->v4 += XXH_readLE32(p32, endian) * PRIME32_2; state->v4 = XXH_rotl32(state->v4, 13); state->v4 *= PRIME32_1; p32++;
          }
          p += 16-state->memsize;
          state->memsize = 0;
      }
  
      if (p <= bEnd-16)
      {
          const BYTE* const limit = bEnd - 16;
          U32 v1 = state->v1;
          U32 v2 = state->v2;
          U32 v3 = state->v3;
          U32 v4 = state->v4;
  
          do
          {
              v1 += XXH_readLE32((const U32*)p, endian) * PRIME32_2; v1 = XXH_rotl32(v1, 13); v1 *= PRIME32_1; p+=4;
              v2 += XXH_readLE32((const U32*)p, endian) * PRIME32_2; v2 = XXH_rotl32(v2, 13); v2 *= PRIME32_1; p+=4;
              v3 += XXH_readLE32((const U32*)p, endian) * PRIME32_2; v3 = XXH_rotl32(v3, 13); v3 *= PRIME32_1; p+=4;
              v4 += XXH_readLE32((const U32*)p, endian) * PRIME32_2; v4 = XXH_rotl32(v4, 13); v4 *= PRIME32_1; p+=4;
          } while (p<=limit);
  
          state->v1 = v1;
          state->v2 = v2;
          state->v3 = v3;
          state->v4 = v4;
      }
  
      if (p < bEnd)
      {
          XXH_memcpy(state->memory, p, bEnd-p);
          state->memsize = (int)(bEnd-p);
      }
  
      return XXH_OK;
  }
  
  XXH_errorcode XXH32_update (void* state_in, const void* input, int len)
  {
      XXH_endianess endian_detected = (XXH_endianess)XXH_CPU_LITTLE_ENDIAN;
  
      if ((endian_detected==XXH_littleEndian) || XXH_FORCE_NATIVE_FORMAT)
          return XXH32_update_endian(state_in, input, len, XXH_littleEndian);
      else
          return XXH32_update_endian(state_in, input, len, XXH_bigEndian);
  }
  
  
  
  FORCE_INLINE U32 XXH32_intermediateDigest_endian (void* state_in, XXH_endianess endian)
  {
      struct XXH_state32_t * state = (struct XXH_state32_t *) state_in;
      const BYTE * p = (const BYTE*)state->memory;
      BYTE* bEnd = (BYTE*)state->memory + state->memsize;
      U32 h32;
  
      if (state->total_len >= 16)
      {
          h32 = XXH_rotl32(state->v1, 1) + XXH_rotl32(state->v2, 7) + XXH_rotl32(state->v3, 12) + XXH_rotl32(state->v4, 18);
      }
      else
      {
          h32  = state->seed + PRIME32_5;
      }
  
      h32 += (U32) state->total_len;
  
      while (p<=bEnd-4)
      {
          h32 += XXH_readLE32((const U32*)p, endian) * PRIME32_3;
          h32  = XXH_rotl32(h32, 17) * PRIME32_4;
          p+=4;
      }
  
      while (p<bEnd)
      {
          h32 += (*p) * PRIME32_5;
          h32 = XXH_rotl32(h32, 11) * PRIME32_1;
          p++;
      }
  
      h32 ^= h32 >> 15;
      h32 *= PRIME32_2;
      h32 ^= h32 >> 13;
      h32 *= PRIME32_3;
      h32 ^= h32 >> 16;
  
      return h32;
  }
  
  
  U32 XXH32_intermediateDigest (void* state_in)
  {
      XXH_endianess endian_detected = (XXH_endianess)XXH_CPU_LITTLE_ENDIAN;
  
      if ((endian_detected==XXH_littleEndian) || XXH_FORCE_NATIVE_FORMAT)
          return XXH32_intermediateDigest_endian(state_in, XXH_littleEndian);
      else
          return XXH32_intermediateDigest_endian(state_in, XXH_bigEndian);
  }
  
  
  U32 XXH32_digest (void* state_in)
  {
      U32 h32 = XXH32_intermediateDigest(state_in);
  
      XXH_free(state_in);
  
      return h32;
  }
  
  }  // namespace rocksdb
  