3 * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
4 * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
6 * This file is part of a52dec, a free ATSC A-52 stream decoder.
7 * See http://liba52.sourceforge.net/ for updates.
9 * a52dec is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * a52dec is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 #include "a52_internal.h"
25 #include "bitstream.h"
27 #define BUFFER_SIZE 4096
29 void a52_bitstream_set_ptr (a52_state_t * state, uint8_t * buf)
33 align = (long)buf & 3;
34 state->buffer_start = (uint32_t *) (buf - align);
36 state->current_word = 0;
37 bitstream_get (state, align * 8);
40 static inline void bitstream_fill_current (a52_state_t * state)
44 tmp = *(state->buffer_start++);
45 state->current_word = swab32 (tmp);
49 * The fast paths for _get is in the
50 * bitstream.h header file so it can be inlined.
52 * The "bottom half" of this routine is suffixed _bh
57 uint32_t a52_bitstream_get_bh (a52_state_t * state, uint32_t num_bits)
61 num_bits -= state->bits_left;
62 result = ((state->current_word << (32 - state->bits_left)) >>
63 (32 - state->bits_left));
65 bitstream_fill_current (state);
68 result = (result << num_bits) | (state->current_word >> (32 - num_bits));
70 state->bits_left = 32 - num_bits;
75 int32_t a52_bitstream_get_bh_2 (a52_state_t * state, uint32_t num_bits)
79 num_bits -= state->bits_left;
80 result = ((((int32_t)state->current_word) << (32 - state->bits_left)) >>
81 (32 - state->bits_left));
83 bitstream_fill_current(state);
86 result = (result << num_bits) | (state->current_word >> (32 - num_bits));
88 state->bits_left = 32 - num_bits;