liba52/bitstream.c

   1 /*
   2  * bitstream.c
   3  * Copyright (C) 2000-2002 Michel Lespinasse <walken@zoy.org>
   4  * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
   5  *
   6  * This file is part of a52dec, a free ATSC A-52 stream decoder.
   7  * See http://liba52.sourceforge.net/ for updates.
   8  *
   9  * Modified for use with MPlayer, changes contained in liba52_changes.diff.
  10  * detailed changelog at http://svn.mplayerhq.hu/mplayer/trunk/
  11  * $Id$
  12  *
  13  * a52dec is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  *
  18  * a52dec is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  * GNU General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU General Public License
  24  * along with this program; if not, write to the Free Software
  25  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  26  */
  27
  28 #include "config.h"
  29
  30 #include <inttypes.h>
  31
  32 #include "a52.h"
  33 #include "a52_internal.h"
  34 #include "bitstream.h"
  35
  36 #define BUFFER_SIZE 4096
  37
  38 #ifdef ALT_BITSTREAM_READER
  39 int indx=0;
  40 #endif
  41
  42 void a52_bitstream_set_ptr (a52_state_t * state, uint8_t * buf)
  43 {
  44     int align;
  45
  46     align = (long)buf & 3;
  47     state->buffer_start = (uint32_t *) (buf - align);
  48     state->bits_left = 0;
  49 #ifdef ALT_BITSTREAM_READER
  50     indx=0;
  51 #endif
  52     bitstream_get (state, align * 8);
  53 }
  54
  55 static inline void bitstream_fill_current (a52_state_t * state)
  56 {
  57     uint32_t tmp;
  58
  59     tmp = *(state->buffer_start++);
  60     state->current_word = swab32 (tmp);
  61 }
  62
  63 /*
  64  * The fast paths for _get is in the
  65  * bitstream.h header file so it can be inlined.
  66  *
  67  * The "bottom half" of this routine is suffixed _bh
  68  *
  69  * -ah
  70  */
  71
  72 uint32_t a52_bitstream_get_bh (a52_state_t * state, uint32_t num_bits)
  73 {
  74     uint32_t result;
  75
  76     num_bits -= state->bits_left;
  77     result = ((state->current_word << (32 - state->bits_left)) >>
  78               (32 - state->bits_left));
  79
  80     bitstream_fill_current (state);
  81
  82     if (num_bits != 0)
  83         result = (result << num_bits) | (state->current_word >> (32 - num_bits));
  84
  85     state->bits_left = 32 - num_bits;
  86
  87     return result;
  88 }
  89
  90 int32_t a52_bitstream_get_bh_2 (a52_state_t * state, uint32_t num_bits)
  91 {
  92     int32_t result;
  93
  94     num_bits -= state->bits_left;
  95     result = ((((int32_t)state->current_word) << (32 - state->bits_left)) >>
  96               (32 - state->bits_left));
  97
  98     bitstream_fill_current(state);
  99
 100     if (num_bits != 0)
 101         result = (result << num_bits) | (state->current_word >> (32 - num_bits));
 102
 103     state->bits_left = 32 - num_bits;
 104
 105     return result;
 106 }