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/*
* bitstream.c
* Copyright (C) 2000-2002 Michel Lespinasse <walken@zoy.org>
* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
*
* This file is part of a52dec, a free ATSC A-52 stream decoder.
* See http://liba52.sourceforge.net/ for updates.
*
* a52dec 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.
*
* a52dec 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "a52.h"
#include "a52_internal.h"
#include "bitstream.h"
#define BUFFER_SIZE 4096
static uint32_t * buffer_start;
uint32_t a52_bits_left;
uint32_t a52_current_word;
void a52_bitstream_set_ptr (uint8_t * buf)
{
int align;
align = (long)buf & 3;
buffer_start = (uint32_t *) (buf - align);
a52_bits_left = 0;
bitstream_get (align * 8);
}
static inline void
bitstream_fill_current()
{
uint32_t tmp;
tmp = *(buffer_start++);
a52_current_word = swab32 (tmp);
}
/*
* The fast paths for _get is in the
* bitstream.h header file so it can be inlined.
*
* The "bottom half" of this routine is suffixed _bh
*
* -ah
*/
uint32_t
a52_bitstream_get_bh(uint32_t num_bits)
{
uint32_t result;
num_bits -= a52_bits_left;
result = ((a52_current_word << (32 - a52_bits_left)) >>
(32 - a52_bits_left));
bitstream_fill_current();
if(num_bits != 0)
result = (result << num_bits) | (a52_current_word >> (32 - num_bits));
a52_bits_left = 32 - num_bits;
return result;
}
int32_t
a52_bitstream_get_bh_2(uint32_t num_bits)
{
int32_t result;
num_bits -= a52_bits_left;
result = ((((int32_t)a52_current_word) << (32 - a52_bits_left)) >>
(32 - a52_bits_left));
bitstream_fill_current();
if(num_bits != 0)
result = (result << num_bits) | (a52_current_word >> (32 - num_bits));
a52_bits_left = 32 - num_bits;
return result;
}
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