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// Copyright (C) 2003 Davis E. King ([email protected])
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_ENTROPY_ENCODER_KERNEL_1_CPp_
#define DLIB_ENTROPY_ENCODER_KERNEL_1_CPp_
#include "entropy_encoder_kernel_1.h"
#include <iostream>
#include <streambuf>
namespace dlib
{
// ----------------------------------------------------------------------------------------
entropy_encoder_kernel_1::
entropy_encoder_kernel_1(
) :
initial_low(0x00000001),
initial_high(0xffffffff),
out(0),
low(initial_low),
high(initial_high),
buf(0),
buf_used(0)
{
}
// ----------------------------------------------------------------------------------------
entropy_encoder_kernel_1::
~entropy_encoder_kernel_1 (
)
{
try {
if (out != 0)
{
flush();
}
} catch (...) {}
}
// ----------------------------------------------------------------------------------------
void entropy_encoder_kernel_1::
clear(
)
{
if (out != 0)
{
flush();
}
out = 0;
}
// ----------------------------------------------------------------------------------------
void entropy_encoder_kernel_1::
set_stream (
std::ostream& out_
)
{
if (out != 0)
{
// if a stream is currently set then flush the buffers to it before
// we switch to the new stream
flush();
}
out = &out_;
streambuf = out_.rdbuf();
// reset the encoder state
buf_used = 0;
buf = 0;
low = initial_low;
high = initial_high;
}
// ----------------------------------------------------------------------------------------
bool entropy_encoder_kernel_1::
stream_is_set (
) const
{
if (out != 0)
return true;
else
return false;
}
// ----------------------------------------------------------------------------------------
std::ostream& entropy_encoder_kernel_1::
get_stream (
) const
{
return *out;
}
// ----------------------------------------------------------------------------------------
void entropy_encoder_kernel_1::
encode (
uint32 low_count,
uint32 high_count,
uint32 total
)
{
// note that we must add one because of the convention that
// high == the real upper range minus 1
uint32 r = (high-low+1)/total;
// note that we must subtract 1 to preserve the convention that
// high == the real upper range - 1
high = low + r*high_count-1;
low = low + r*low_count;
while (true)
{
// if the highest order bit in high and low is the same
if ( low >= 0x80000000 || high < 0x80000000)
{
// if buf is full then write it out
if (buf_used == 8)
{
if (streambuf->sputn(reinterpret_cast<char*>(&buf),1)==0)
{
throw std::ios_base::failure("error occurred in the entropy_encoder object");
}
buf = 0;
buf_used = 0;
}
// write the high order bit from low into buf
buf <<= 1;
++buf_used;
if (low&0x80000000)
buf |= 0x1;
// roll off the bit we just wrote to buf
low <<= 1;
high <<= 1;
high |= 1; // note that it is ok to add one to high here because
// of the convention that high == real upper range - 1.
// so that means that if we want to shift the upper range
// left by one then we must shift a one into high also
// since real upper range == high + 0.999999999...
// make sure low is never zero
if (low == 0)
low = 1;
}
// if the distance between high and low is small and there aren't
// any bits we can roll off then round low up or high down.
else if (high-low < 0x10000)
{
if (high == 0x80000000)
high = 0x7fffffff;
else
low = 0x80000000;
}
else
{
break;
}
} // while (true)
}
// ----------------------------------------------------------------------------------------
void entropy_encoder_kernel_1::
flush (
)
{
// flush the next 4 or 5 bytes that are buffered
// thats whatever is contained in buf and then all of low plus any extra
// bits needed to pad that to be an even 4 or 5 bytes
if (buf_used != 8)
{
buf <<= (8-buf_used);
buf |= static_cast<unsigned char>(low>>(24+buf_used));
low <<= (8-buf_used);
}
if (streambuf->sputn(reinterpret_cast<char*>(&buf),1) == 0)
throw std::ios_base::failure("error occurred in the entropy_encoder object");
buf = static_cast<unsigned char>((low >> 24)&0xFF);
if (streambuf->sputn(reinterpret_cast<char*>(&buf),1) == 0)
throw std::ios_base::failure("error occurred in the entropy_encoder object");
buf = static_cast<unsigned char>((low >> 16)&0xFF);
if (streambuf->sputn(reinterpret_cast<char*>(&buf),1)==0)
throw std::ios_base::failure("error occurred in the entropy_encoder object");
buf = static_cast<unsigned char>((low >> 8)&0xFF);
if (streambuf->sputn(reinterpret_cast<char*>(&buf),1)==0)
throw std::ios_base::failure("error occurred in the entropy_encoder object");
if (buf_used != 0)
{
buf = static_cast<unsigned char>((low)&0xFF);
if (streambuf->sputn(reinterpret_cast<char*>(&buf),1)==0)
throw std::ios_base::failure("error occurred in the entropy_encoder object");
}
// make sure the stream buffer flushes to its I/O channel
streambuf->pubsync();
// reset the encoder state
buf_used = 0;
buf = 0;
low = initial_low;
high = initial_high;
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_ENTROPY_ENCODER_KERNEL_1_CPp_
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