etl/ihash.h

///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl

Copyright(c) 2015 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
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******************************************************************************/

#ifndef __ETL_IHASH__
#define __ETL_IHASH__

#include <stdint.h>
#include <utility>

#include "exception.h"
#include "endian.h"

///\defgroup ihash Base class for all hash type classes.
///\ingroup hash

namespace etl
{
  //***************************************************************************
  ///\ingroup hash
  /// Exception base for hashes.
  //***************************************************************************
  class hash_exception : public exception
  {
  public:

    hash_exception(const char* what)
      : exception(what)
    {}
  };

  //***************************************************************************
  ///\ingroup vector
  /// Hash finalised exception.
  //***************************************************************************
  class hash_finalised : public hash_exception
  {
  public:

    hash_finalised()
      : hash_exception("ihash: finalised")
    {}
  };

  /// For the Americans
  typedef hash_finalised hash_finalized;

  //***************************************************************************
  /// Hash algorithm base class.
  /// \ingroup ihash
  //***************************************************************************
  class ihash
  {
  public:

    /// Generic return type.
    typedef std::pair<const uint8_t*, const uint8_t*> generic_digest;

    //*************************************************************************
    /// Default constructor.
    /// \param endianness The endianness to use for integral types larger than uint8_t.
    //*************************************************************************
    ihash(etl::endian endianness)
      : endianness(endianness)
    {
    }

    //*************************************************************************
    /// \param value The value to add to the hash.
    //*************************************************************************
    template<typename TValue>
    void add(TValue value)
    {
      uint8_t* p_data = reinterpret_cast<uint8_t*>(&value);

      if (endianness == endian::little)
      {
        for (int i = 0; i < sizeof(TValue); ++i)
        {
          add(p_data[i]);
        }
      }
      else
      {
        for (int i = sizeof(TValue) - 1; i >= 0; --i)
        {
          add(p_data[i]);
        }
      }
    }
    
    //*************************************************************************
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    void add(TIterator begin, const TIterator end)
    {
      while (begin != end)
      {
        add(*begin);
        ++begin;
      }
    }

    //*************************************************************************
    /// \param value The value to add to the checksum.
    //*************************************************************************
    template<typename TValue>
    ihash& operator +=(TValue value)
    {
      add(value);
      return *this;
    }

    //*************************************************************************
    /// Get the endianness.
    //*************************************************************************
    etl::endian endian() const
    {
      return endianness;
    }

    //*************************************************************************
    /// Set the endianness.
    //*************************************************************************
    void endian(etl::endian e)
    {
      endianness = e;
    }

    //*************************************************************************
    /// \param value The uint8_t to add to the hash.
    //*************************************************************************
    virtual void add(uint8_t value) = 0;

    //*************************************************************************
    /// Resets the hash to the initial state.
    //*************************************************************************
    virtual void reset() = 0;

    //*************************************************************************
    /// Gets the result as a generic digest.
    //*************************************************************************
    virtual generic_digest digest() = 0;

  protected:

    //*************************************************************************
    /// Gets the result as a generic digest.
    /// Templated for derived class usage.
    //*************************************************************************
    template <typename T>
    generic_digest get_digest(const T& hash) const
    {
      const uint8_t* begin = reinterpret_cast<const uint8_t*>(&hash);

      return generic_digest(begin, begin + sizeof(hash));
    }

  private:

    etl::endian endianness;
  };
}

//*************************************************************************
/// Default streaming operator.
//*************************************************************************
template <typename T>
etl::ihash& operator << (etl::ihash& hash, T value)
{
  hash.add(value);
  return hash;
}

#endif