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/*
* bitstream.c
* Copyright (C) 2004 Gildas Bazin <gbazin@videolan.org>
* Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
*
* This file is part of libdca, a free DTS Coherent Acoustics stream decoder.
* See http://www.videolan.org/developers/libdca.html for updates.
*
* libdca 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.
*
* libdca 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.
*/
#include "config.h"
#include <stdio.h>
#include <inttypes.h>
#include "dca.h"
#include "dca_internal.h"
#include "bitstream.h"
#define BUFFER_SIZE 4096
void dca_bitstream_init (dca_state_t * state, uint8_t * buf, int word_mode,
int bigendian_mode)
{
intptr_t align;
align = (uintptr_t)buf & 3;
state->buffer_start = (uint32_t *) ((uintptr_t)buf - align);
state->bits_left = 0;
state->current_word = 0;
state->word_mode = word_mode;
state->bigendian_mode = bigendian_mode;
bitstream_get (state, align * 8);
}
static inline void bitstream_fill_current (dca_state_t * state)
{
uint32_t tmp;
tmp = *(state->buffer_start++);
if (state->bigendian_mode)
state->current_word = swab32 (tmp);
else
state->current_word = swable32 (tmp);
if (!state->word_mode)
{
state->current_word = (state->current_word & 0x00003FFF) |
((state->current_word & 0x3FFF0000 ) >> 2);
}
}
/*
* 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 dca_bitstream_get_bh (dca_state_t * state, uint32_t num_bits)
{
uint32_t result = 0;
if (state->bits_left)
{
num_bits -= state->bits_left;
result = ((state->current_word << (32 - state->bits_left)) >>
(32 - state->bits_left));
}
if ( !state->word_mode && num_bits > 28 ) {
bitstream_fill_current (state);
result = (result << 28) | state->current_word;
num_bits -= 28;
}
bitstream_fill_current (state);
if ( state->word_mode )
{
if (num_bits != 0)
result = (result << num_bits) |
(state->current_word >> (32 - num_bits));
state->bits_left = 32 - num_bits;
}
else
{
if (num_bits != 0)
result = (result << num_bits) |
(state->current_word >> (28 - num_bits));
state->bits_left = 28 - num_bits;
}
return result;
}
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