Diff: pearson.h

Revision:

0:b47c2a7920c2

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pearson.h	Fri Mar 16 16:34:18 2018 +0000
@@ -0,0 +1,167 @@
+///\file
+
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+http://www.etlcpp.com
+
+Copyright(c) 2014 jwellbelove
+
+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
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#ifndef __ETL_PEARSON__
+#define __ETL_PEARSON__
+
+#include <stdint.h>
+
+#include "platform.h"
+#include "static_assert.h"
+#include "type_traits.h"
+#include "ihash.h"
+#include "array.h"
+#include "container.h"
+
+STATIC_ASSERT(ETL_8BIT_SUPPORT, "This file does not currently support targets with no 8bit type");
+
+#if defined(ETL_COMPILER_KEIL)
+#pragma diag_suppress 1300
+#endif
+
+///\defgroup pearson Pearson hash calculation
+///\ingroup pearson
+
+namespace etl
+{
+  //***************************************************************************
+  /// Pearson lookup table
+  /// \ingroup pearson
+  //***************************************************************************
+  extern const uint8_t PEARSON_LOOKUP[];
+
+  //***************************************************************************
+  /// Calculates a Pearson hash
+  ///\tparam HASH_LENGTH The number of elements in the hash.
+  /// \ingroup pearson
+  //***************************************************************************
+  template <const size_t HASH_LENGTH>
+  class pearson
+  {
+  public:
+
+    typedef etl::array<uint8_t, HASH_LENGTH> value_type;
+
+    //*************************************************************************
+    /// Default constructor.
+    //*************************************************************************
+    pearson()
+      : first(true)
+    {
+      reset();
+    }
+
+    //*************************************************************************
+    /// Constructor from range.
+    /// \param begin Start of the range.
+    /// \param end   End of the range.
+    //*************************************************************************
+    template<typename TIterator>
+    pearson(TIterator begin, const TIterator end)
+      : first(true)
+    {
+      STATIC_ASSERT(sizeof(typename std::iterator_traits<TIterator>::value_type) == 1, "Type not supported");
+
+      reset();
+      add(begin, end);
+    }
+
+    //*************************************************************************
+    /// Resets the hash to the initial state.
+    //*************************************************************************
+    void reset()
+    {
+      hash.fill(0);
+    }
+
+    //*************************************************************************
+    /// Adds a range.
+    /// \param begin
+    /// \param end
+    //*************************************************************************
+    template<typename TIterator>
+    void add(TIterator begin, const TIterator end)
+    {
+      STATIC_ASSERT(sizeof(typename std::iterator_traits<TIterator>::value_type) == 1, "Type not supported");
+
+      while (begin != end)
+      {
+        add(*begin++);
+      }
+    }
+
+    //*************************************************************************
+    /// \param value The char to add to the hash.
+    //*************************************************************************
+    void add(uint8_t value_)
+    {
+      if (first)
+      {
+        for (size_t i = 0; i < HASH_LENGTH; ++i)
+        {
+          hash[i] = PEARSON_LOOKUP[(uint32_t(value_) + i) % 256];
+        }
+
+        first = false;
+      }
+      else
+      {
+        for (size_t i = 0; i < HASH_LENGTH; ++i)
+        {
+          hash[i] = PEARSON_LOOKUP[hash[i] ^ value_];
+        }
+      }
+    }
+
+    //*************************************************************************
+    /// Gets the hash value.
+    //*************************************************************************
+    value_type value() const
+    {
+      return hash;
+    }
+
+    //*************************************************************************
+    /// Conversion operator to value_type.
+    //*************************************************************************
+    operator value_type () const
+    {
+      return value();
+    }
+
+  private:
+
+    bool first;
+    value_type hash;
+  };
+}
+
+#endif
+