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/*
* bitstream.c
*
* Copyright (C) Aaron Holtzman - Dec 1999
*
* This file is part of ac3dec, a free AC-3 audio decoder
*
* ac3dec 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, or (at your option)
* any later version.
*
* ac3dec 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 GNU Make; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
#include <stdlib.h>
#include <stdio.h>
#include "ac3.h"
#include "ac3_internal.h"
#include "bitstream.h"
#define BUFFER_SIZE 4096
static uint8_t *buffer_start;
uint32_t bits_left;
uint32_t current_word;
void bitstream_set_ptr (uint8_t * buf)
{
buffer_start = buf;
bits_left = 0;
}
static inline void
bitstream_fill_current()
{
#ifdef __sparc__
#warning FIXME: cannot access unaligned pointer on sparc
current_word =
(buffer_start[0] << 24) |
(buffer_start[1] << 16) |
(buffer_start[2] << 8) |
buffer_start[3];
buffer_start += 4;
#else
current_word = *((uint32_t*)buffer_start)++;
current_word = swab32(current_word);
#endif
}
//
// 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
bitstream_get_bh(uint32_t num_bits)
{
uint32_t result;
num_bits -= bits_left;
result = (current_word << (32 - bits_left)) >> (32 - bits_left);
bitstream_fill_current();
if(num_bits != 0)
result = (result << num_bits) | (current_word >> (32 - num_bits));
bits_left = 32 - num_bits;
return result;
}
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