File size: 5,833 Bytes
9375c9a |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 |
// Copyright (C) 2003 Davis E. King ([email protected])
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_ENTROPY_DECODER_KERNEL_1_CPp_
#define DLIB_ENTROPY_DECODER_KERNEL_1_CPp_
#include "entropy_decoder_kernel_1.h"
#include <iostream>
#include <streambuf>
#include <sstream>
#include "../assert.h"
namespace dlib
{
// ----------------------------------------------------------------------------------------
entropy_decoder_kernel_1::
entropy_decoder_kernel_1(
) :
initial_low(0x00000001),
initial_high(0xffffffff),
in(0),
low(initial_low),
high(initial_high),
buf(0),
buf_used(0),
target(0x00000000),
r(0)
{
}
// ----------------------------------------------------------------------------------------
entropy_decoder_kernel_1::
~entropy_decoder_kernel_1 (
)
{
}
// ----------------------------------------------------------------------------------------
void entropy_decoder_kernel_1::
clear(
)
{
in = 0;
buf_used = 0;
buf = 0;
r = 0;
low = initial_low;
high = initial_high;
target = 0x00000000;
}
// ----------------------------------------------------------------------------------------
void entropy_decoder_kernel_1::
set_stream (
std::istream& in_
)
{
buf_used = 0;
buf = 0;
r = 0;
low = initial_low;
high = initial_high;
target = 0x00000000;
in = &in_;
streambuf = in_.rdbuf();
unsigned char ch;
streambuf->sgetn((char*)&ch,1);
target = ch;
target <<= 8;
if (streambuf->sgetn((char*)&ch,1))
target += ch;
target <<= 8;
if (streambuf->sgetn((char*)&ch,1))
target += ch;
target <<= 8;
if (streambuf->sgetn((char*)&ch,1))
target += ch;
}
// ----------------------------------------------------------------------------------------
bool entropy_decoder_kernel_1::
stream_is_set (
) const
{
if (in != 0)
return true;
else
return false;
}
// ----------------------------------------------------------------------------------------
std::istream& entropy_decoder_kernel_1::
get_stream (
) const
{
return *in;
}
// ----------------------------------------------------------------------------------------
void entropy_decoder_kernel_1::
decode (
uint32 low_count,
uint32 high_count
)
{
// 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;
r = 0;
while (true)
{
// if the highest order bit in high and low is the same
if ( low >= 0x80000000 || high < 0x80000000)
{
// make sure buf isn't empty
if (buf_used == 0)
{
buf_used = 8;
if (streambuf->sgetn(reinterpret_cast<char*>(&buf),1)==0)
{
// if there isn't anything else in the streambuffer then just
// make buf zero.
buf = 0;
}
}
// we will be taking one bit from buf to replace the one we threw away
--buf_used;
// roll off the bit in target
target <<= 1;
// roll off the bit
high <<= 1;
low <<= 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;
// take a bit from buf to fill in the one we threw away
target += (buf>>buf_used)&0x01;
}
// 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)
}
// ----------------------------------------------------------------------------------------
bool entropy_decoder_kernel_1::
get_target_called (
) const
{
return (r != 0);
}
// ----------------------------------------------------------------------------------------
uint32 entropy_decoder_kernel_1::
get_target (
uint32 total
)
{
// note that we must add one because of the convention that
// high == the real upper range minus 1
r = (high-low+1)/total;
uint32 temp = (target-low)/r;
if (temp < total)
return temp;
else
return total-1;
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_ENTROPY_DECODER_KERNEL_1_CPp_
|