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/*
* $Id: bit_io.c,v 1.14 2010/02/05 23:50:21 simakov Exp $
*
* EPSILON - wavelet image compression library.
* Copyright (C) 2006,2007,2010 Alexander Simakov, <xander@entropyware.info>
*
* This file is part of EPSILON
*
* EPSILON is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* EPSILON is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with EPSILON. If not, see <http://www.gnu.org/licenses/>.
*
* http://epsilon-project.sourceforge.net
*/
#include <common.h>
#include <bit_io.h>
void init_bits(bit_buffer *bb, unsigned char *buf, int size)
{
assert(size > 0);
bb->start = bb->next = buf;
bb->end = bb->start + size;
bb->bits = bb->pending = 0;
}
int write_bits(bit_buffer *bb, int value, int size)
{
assert(size <= 24);
/* No more space available */
if (bb->next >= bb->end) {
return BIT_BUFFER_OVERFLOW;
}
/* Save requested number of bits */
bb->bits |= (value << bb->pending);
bb->pending += size;
/* Write complete octets */
while (bb->pending >= 8) {
if (bb->next >= bb->end) {
return BIT_BUFFER_OVERFLOW;
}
*bb->next++ = (unsigned char) (bb->bits & 0xff);
bb->bits >>= 8;
bb->pending -= 8;
}
return BIT_BUFFER_OK;
}
int read_bits(bit_buffer *bb, int *value, int size)
{
assert(size <= 24);
/* Read missing bytes */
while (bb->pending < size) {
if (bb->next >= bb->end) {
return BIT_BUFFER_UNDERFLOW;
}
bb->bits |= (*bb->next++ << bb->pending);
bb->pending += 8;
}
*value = bb->bits & (~(~0 << size));
bb->bits >>= size;
bb->pending -= size;
return BIT_BUFFER_OK;
}
int flush_bits(bit_buffer *bb)
{
if (bb->pending) {
return write_bits(bb, 0UL, 8);
} else {
return BIT_BUFFER_OK;
}
}
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