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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 <string.h>
#include "ac3.h"
#include "ac3_internal.h"
#include "bitstream.h"
#define BUFFER_SIZE 4096
static uint_8 buffer[BUFFER_SIZE];
static uint_32 *buffer_start, *buffer_end;
static uint_8 *chunk_start, *chunk_end;
uint_32 bits_left;
uint_32 current_word;
ssize_t (*bitstream_fill_buffer)(uint_8**,uint_8**);
int bitstream_get_byte(void)
{
if(chunk_start == chunk_end)
if (bitstream_fill_buffer(&chunk_start,&chunk_end) <= 0)
return EOF;
return (*chunk_start++);
}
uint_8 *bitstream_get_buffer_start(void)
{
return (uint_8 *) buffer_start;
}
int
bitstream_buffer_frame(uint_32 frame_size)
{
uint_32 bytes_read;
uint_32 num_bytes;
bytes_read = 0;
do
{
if(chunk_start > chunk_end)
printf("argh!\n");
if(chunk_start == chunk_end)
if (bitstream_fill_buffer(&chunk_start,&chunk_end) <= 0)
return EOF;
num_bytes = chunk_end - chunk_start;
if(bytes_read + num_bytes > frame_size)
num_bytes = frame_size - bytes_read;
memcpy(&buffer[bytes_read], chunk_start, num_bytes);
bytes_read += num_bytes;
chunk_start += num_bytes;
}
while (bytes_read != frame_size);
buffer_start = (uint_32 *) buffer;
buffer_end = (uint_32 *) (buffer + frame_size);
bits_left = 0;
return 0;
}
static inline void
bitstream_fill_current()
{
current_word = *buffer_start++;
current_word = swab32(current_word);
}
//
// 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
//
uint_32
bitstream_get_bh(uint_32 num_bits)
{
uint_32 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;
}
void
bitstream_init(ssize_t(*fill_function)(uint_8**,uint_8**))
{
// Setup the buffer fill callback
bitstream_fill_buffer = fill_function;
}
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