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/*****************************************************************************
* bits.h : Bit handling helpers
*****************************************************************************
* Copyright (C) 2003 the VideoLAN team
* $Id: 0f9cbfe93686319fc2285767b8c4019555451f4c $
*
* Authors: Laurent Aimar <fenrir@via.ecp.fr>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
*****************************************************************************/
#ifndef VLC_BITS_H
#define VLC_BITS_H 1
/**
* \file
* This file defines functions, structures for handling streams of bits in vlc
*/
typedef struct bs_s
{
uint8_t *p_start;
uint8_t *p;
uint8_t *p_end;
ssize_t i_left; /* i_count number of available bits */
} bs_t;
static inline void bs_init( bs_t *s, const void *p_data, size_t i_data )
{
s->p_start = (void *)p_data;
s->p = s->p_start;
s->p_end = s->p_start + i_data;
s->i_left = 8;
}
static inline int bs_pos( const bs_t *s )
{
return( 8 * ( s->p - s->p_start ) + 8 - s->i_left );
}
static inline int bs_eof( const bs_t *s )
{
return( s->p >= s->p_end ? 1: 0 );
}
static inline uint32_t bs_read( bs_t *s, int i_count )
{
static const uint32_t i_mask[33] =
{ 0x00,
0x01, 0x03, 0x07, 0x0f,
0x1f, 0x3f, 0x7f, 0xff,
0x1ff, 0x3ff, 0x7ff, 0xfff,
0x1fff, 0x3fff, 0x7fff, 0xffff,
0x1ffff, 0x3ffff, 0x7ffff, 0xfffff,
0x1fffff, 0x3fffff, 0x7fffff, 0xffffff,
0x1ffffff, 0x3ffffff, 0x7ffffff, 0xfffffff,
0x1fffffff,0x3fffffff,0x7fffffff,0xffffffff};
int i_shr;
uint32_t i_result = 0;
while( i_count > 0 )
{
if( s->p >= s->p_end )
{
break;
}
if( ( i_shr = s->i_left - i_count ) >= 0 )
{
/* more in the buffer than requested */
i_result |= ( *s->p >> i_shr )&i_mask[i_count];
s->i_left -= i_count;
if( s->i_left == 0 )
{
s->p++;
s->i_left = 8;
}
return( i_result );
}
else
{
/* less in the buffer than requested */
i_result |= (*s->p&i_mask[s->i_left]) << -i_shr;
i_count -= s->i_left;
s->p++;
s->i_left = 8;
}
}
return( i_result );
}
static inline uint32_t bs_read1( bs_t *s )
{
if( s->p < s->p_end )
{
unsigned int i_result;
s->i_left--;
i_result = ( *s->p >> s->i_left )&0x01;
if( s->i_left == 0 )
{
s->p++;
s->i_left = 8;
}
return i_result;
}
return 0;
}
static inline uint32_t bs_show( bs_t *s, int i_count )
{
bs_t s_tmp = *s;
return bs_read( &s_tmp, i_count );
}
static inline void bs_skip( bs_t *s, ssize_t i_count )
{
s->i_left -= i_count;
if( s->i_left <= 0 )
{
const int i_bytes = ( -s->i_left + 8 ) / 8;
s->p += i_bytes;
s->i_left += 8 * i_bytes;
}
}
static inline void bs_write( bs_t *s, int i_count, uint32_t i_bits )
{
while( i_count > 0 )
{
if( s->p >= s->p_end )
{
break;
}
i_count--;
if( ( i_bits >> i_count )&0x01 )
{
*s->p |= 1 << ( s->i_left - 1 );
}
else
{
*s->p &= ~( 1 << ( s->i_left - 1 ) );
}
s->i_left--;
if( s->i_left == 0 )
{
s->p++;
s->i_left = 8;
}
}
}
static inline void bs_align( bs_t *s )
{
if( s->i_left != 8 )
{
s->i_left = 8;
s->p++;
}
}
static inline void bs_align_0( bs_t *s )
{
if( s->i_left != 8 )
{
bs_write( s, s->i_left, 0 );
}
}
static inline void bs_align_1( bs_t *s )
{
while( s->i_left != 8 )
{
bs_write( s, 1, 1 );
}
}
#endif
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