murmur3.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2014 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
copies of the Software, and to permit persons to whom the Software is
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The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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******************************************************************************/
 
#ifndef ETL_MURMUR3_INCLUDED
#define ETL_MURMUR3_INCLUDED
 
#include "platform.h"
#include "ihash.h"
#include "iterator.h"
#include "binary.h"
#include "error_handler.h"
 
#include <stdint.h>
 
#if defined(ETL_COMPILER_KEIL)
#pragma diag_suppress 1300
#endif

 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  template <typename THash>
  class murmur3
  {
  public:
 
#if ETL_NOT_USING_64BIT_TYPES
    ETL_STATIC_ASSERT((etl::is_same<THash, uint32_t>::value), "Only 32 bit types supported");
#else
    ETL_STATIC_ASSERT((etl::is_same<THash, uint32_t>::value || etl::is_same<THash, uint64_t>::value), "Only 32 & 64 bit types supported");
#endif
 
    typedef THash value_type;
 
    //*************************************************************************
    //*************************************************************************
    murmur3(value_type seed_ = 0)
      : seed(seed_)
    {
      reset();
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TIterator>
    murmur3(TIterator begin, const TIterator end, value_type seed_ = 0)
      : seed(seed_)
    {
      ETL_STATIC_ASSERT(sizeof(typename etl::iterator_traits<TIterator>::value_type) == 1, "Incompatible type");
 
      reset();
      while (begin != end)
      {
        block |= (*begin) << (block_fill_count * 8U);
        ++begin;
 
        if (++block_fill_count == FULL_BLOCK)
        {
          add_block();
          block_fill_count = 0;
          block = 0;
        }
 
        ++char_count;
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    void reset()
    {
      hash             = seed;
      char_count       = 0;
      block            = 0;
      block_fill_count = 0;
      is_finalised     = false;
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TIterator>
    void add(TIterator begin, const TIterator end)
    {
      ETL_STATIC_ASSERT(sizeof(typename etl::iterator_traits<TIterator>::value_type) == 1, "Incompatible type");
      ETL_ASSERT(!is_finalised, ETL_ERROR(hash_finalised));
 
      while (begin != end)
      {
        block |= (*begin) << (block_fill_count * 8U);
        ++begin;
 
        if (++block_fill_count == FULL_BLOCK)
        {
          add_block();
          block_fill_count = 0;
          block = 0;
        }
 
        ++char_count;
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    void add(uint8_t value_)
    {
      // We can't add to a finalised hash!
      ETL_ASSERT(!is_finalised, ETL_ERROR(hash_finalised));
 
      block |= value_ << (block_fill_count * 8U);
 
      if (++block_fill_count == FULL_BLOCK)
      {
        add_block();
        block_fill_count = 0;
        block = 0;
      }
 
      ++char_count;
    }
 
    //*************************************************************************
    //*************************************************************************
    value_type value()
    {
      finalise();
      return hash;
    }
 
    //*************************************************************************
    //*************************************************************************
    operator value_type ()
    {
      return value();
    }
 
  private:
 
    //*************************************************************************
    //*************************************************************************
    void add_block()
    {
      block *= CONSTANT1;
      block = rotate_left(block, SHIFT1);
      block *= CONSTANT2;
 
      hash ^= block;
      hash = rotate_left(hash, SHIFT2);
      hash = (hash * MULTIPLY) + ADD;
    }
 
    //*************************************************************************
    //*************************************************************************
    void finalise()
    {
      if (!is_finalised)
      {
        block *= CONSTANT1;
        block = rotate_left(block, SHIFT1);
        block *= CONSTANT2;
 
        hash ^= block;
        hash ^= char_count;
        hash ^= (hash >> 16U);
        hash *= 0x85EBCA6BUL;
        hash ^= (hash >> 13U);
        hash *= 0xC2B2AE35UL;
        hash ^= (hash >> 16U);
 
        is_finalised = true;
      }
    }
 
    bool       is_finalised;
    uint8_t    block_fill_count;
    size_t     char_count;
    value_type block;
    value_type hash;
    value_type seed;
 
    static ETL_CONSTANT uint8_t    FULL_BLOCK = 4U;
    static ETL_CONSTANT value_type CONSTANT1  = 0xCC9E2D51UL;
    static ETL_CONSTANT value_type CONSTANT2  = 0x1B873593UL;
    static ETL_CONSTANT value_type SHIFT1     = 15;
    static ETL_CONSTANT value_type SHIFT2     = 13;
    static ETL_CONSTANT value_type MULTIPLY   = 5;
    static ETL_CONSTANT value_type ADD        = 0xE6546B64UL;
  };
}
 
#endif