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// 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_
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