dlib C++ Library - entropy_encoder_kernel_1.h

// Copyright (C) 2003 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_ENTROPY_ENCODER_KERNEl_1_
#define DLIB_ENTROPY_ENCODER_KERNEl_1_
#include "../algs.h"
#include "entropy_encoder_kernel_abstract.h"
#include <iosfwd>
#include "../uintn.h"
namespace dlib
{
 class entropy_encoder_kernel_1 
 {
 /*!
 GENERAL NOTES
 this encoder is implemented using arithmetic coding
 INITIAL VALUE
 out == 0
 buf_used == 0
 buf == 0
 initial_low == 0x00000001 (slightly more than zero)
 initial_high == 0xffffffff (slightly less than one, 0.99999999976717)
 low == initial_low
 high == initial_high
 CONVENTION
 if (out != 0)
 *out == get_stream()
 true == stream_is_set()
 streambuf == out->rdbuf()
 else
 false == stream_is_set()
 buf == used to accumulate bits before writing them to out. 
 buf_used == the number of low order bits in buf that are currently 
 in use
 low == the low end of the range used for arithmetic encoding.
 this number is used as a 32bit fixed point real number. 
 the point is fixed just before the first bit, so it is
 always in the range [0,1)
 low is also never allowed to be zero to avoid overflow
 in the calculation (high-low+1)/total.
 high == the high end of the range - 1 used for arithmetic encoding.
 this number is used as a 32bit fixed point real number. 
 the point is fixed just before the first bit, so when we
 interpret high as a real number then it is always in the
 range [0,1)
 the range for arithmetic encoding is always 
 [low,high + 0.9999999...) the 0.9999999... is why
 high == real upper range - 1 
 
 !*/
 public:
 entropy_encoder_kernel_1 (
 );
 virtual ~entropy_encoder_kernel_1 (
 );
 void clear(
 );
 void set_stream (
 std::ostream& out
 );
 bool stream_is_set (
 ) const;
 std::ostream& get_stream (
 ) const;
 void encode (
 uint32 low_count,
 uint32 high_count,
 uint32 total
 );
 private:
 void flush ( 
 );
 /*!
 requires
 out != 0 (i.e. there is a stream object to flush the data to 
 !*/
 // restricted functions
 entropy_encoder_kernel_1(entropy_encoder_kernel_1&); // copy constructor
 entropy_encoder_kernel_1& operator=(entropy_encoder_kernel_1&); // assignment operator
 // data members
 const uint32 initial_low;
 const uint32 initial_high;
 std::ostream* out;
 uint32 low;
 uint32 high;
 unsigned char buf; 
 uint32 buf_used; 
 std::streambuf* streambuf;
 }; 
 
}
#ifdef NO_MAKEFILE
#include "entropy_encoder_kernel_1.cpp"
#endif
#endif // DLIB_ENTROPY_ENCODER_KERNEl_1_