pearson.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
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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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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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******************************************************************************/
 
#ifndef ETL_PEARSON_INCLUDED
#define ETL_PEARSON_INCLUDED
 
#include "platform.h"
#include "static_assert.h"
#include "type_traits.h"
#include "ihash.h"
#include "array.h"
#include "iterator.h"
 
#include <stdint.h>
 
ETL_STATIC_ASSERT(ETL_USING_8BIT_TYPES, "This file does not currently support targets with no 8bit type");
 
#if defined(ETL_COMPILER_KEIL)
#pragma diag_suppress 1300
#endif

 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  template <size_t HASH_LENGTH>
  class pearson
  {
  public:
 
    typedef etl::array<uint8_t, HASH_LENGTH> value_type;
 
    //*************************************************************************
    //*************************************************************************
    pearson()
      : first(true)
    {
      reset();
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TIterator>
    pearson(TIterator begin, const TIterator end)
      : first(true)
    {
      ETL_STATIC_ASSERT(sizeof(typename etl::iterator_traits<TIterator>::value_type) == 1, "Type not supported");
 
      reset();
      add(begin, end);
    }
 
    //*************************************************************************
    //*************************************************************************
    void reset()
    {
      hash.fill(0);
    }
 
    //*************************************************************************
    //*************************************************************************
    template<typename TIterator>
    void add(TIterator begin, const TIterator end)
    {
      ETL_STATIC_ASSERT(sizeof(typename etl::iterator_traits<TIterator>::value_type) == 1, "Type not supported");
 
      while (begin != end)
      {
        add(*begin);
        ++begin;
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    void add(uint8_t value_)
    {
      static ETL_CONSTANT uint8_t PEARSON_LOOKUP[] =
      {
        228,  39,  61,  95, 227, 187,   0, 197,  31, 189, 161, 222,  34,  15, 221, 246,
        19,  234,   6,  50, 113,   3,  91,  63,  77, 245, 144,   2, 183, 196,  25, 226,
        97,  126,  48,  59, 217,   4, 100, 145,  12,  88, 203, 149,  80, 154,  38,  27,
        224, 218, 158, 115, 202,  79,  53,  83, 242,  36, 139, 131, 136, 191,  42, 170,
        23,  99,  156,  51, 143,  60, 233, 206,  62, 108,  17,  67,  81,  71,  93, 195,
        26,  231, 247,  96,  24, 200, 176, 209, 152, 212, 138, 165,  75, 185, 130, 248,
        125, 110,  10, 116, 201,  90,  69, 204,  85, 251,  78, 157,  47, 184, 169, 141,
        134, 230,  89,  21, 146,  46,  55, 128, 148, 207, 216,  11, 114, 199, 103, 102,
        166, 244,   5, 104, 225, 160, 132,  28, 172,  65, 121, 140, 153, 119, 198, 210,
        58,  87,  117, 177,  33,  22,  13,  37,  49, 174, 109,  40,  73, 211,  18, 167,
        164, 252, 168,  74,  30, 173,  35,  98,  66, 193,  94, 175,  86,  54, 179, 122,
        220, 151, 192,  29, 133, 254, 155, 127, 240, 232, 190, 180,   8,  68, 236,  20,
        137,  92, 219, 208,  52, 250, 147, 142, 111, 112, 120,  45, 135, 255, 123, 229,
        57,  182, 243, 124, 186, 253,   7, 237,   9,  16,  70, 171, 235, 107, 223, 118,
        215, 178, 194, 181,  43, 188, 106, 105,  64, 241,  84, 238, 159,  44,  32,  76,
        213, 163, 150, 101, 129,  14, 249, 205, 214,   1,  41,  56, 162,  72, 239,  82
      };
 
      if (first)
      {
        for (size_t i = 0UL; i < HASH_LENGTH; ++i)
        {
          hash[i] = PEARSON_LOOKUP[(uint32_t(value_) + i) % 256];
        }
 
        first = false;
      }
      else
      {
        for (size_t i = 0UL; i < HASH_LENGTH; ++i)
        {
          hash[i] = PEARSON_LOOKUP[hash[i] ^ value_];
        }
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    value_type value() const
    {
      return hash;
    }
 
    //*************************************************************************
    //*************************************************************************
    operator value_type () const
    {
      return value();
    }
 
  private:
 
    bool first;
    value_type hash;
  };
}
 
#endif