liba52/bitstream.h

   1 /*
   2  * bitstream.h
   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 /* code from ffmpeg/libavcodec */
  29 #if defined(__sparc__) || defined(hpux)
  30 /*
  31  * the alt bitstream reader performs unaligned memory accesses; that doesn't work
  32  * on sparc/hpux.  For now, disable ALT_BITSTREAM_READER.
  33  */
  34 #undef  ALT_BITSTREAM_READER
  35 #else
  36 // alternative (faster) bitstram reader (reades upto 3 bytes over the end of the input)
  37 #define ALT_BITSTREAM_READER
  38
  39 /* used to avoid misaligned exceptions on some archs (alpha, ...) */
  40 #if ARCH_X86 || HAVE_ARMV6
  41 #    define unaligned32(a) (*(uint32_t*)(a))
  42 #else
  43 #    ifdef __GNUC__
  44 static inline uint32_t unaligned32(const void *v) {
  45     struct Unaligned {
  46         uint32_t i;
  47     } __attribute__((packed));
  48
  49     return ((const struct Unaligned *) v)->i;
  50 }
  51 #    elif defined(__DECC)
  52 static inline uint32_t unaligned32(const void *v) {
  53     return *(const __unaligned uint32_t *) v;
  54 }
  55 #    else
  56 static inline uint32_t unaligned32(const void *v) {
  57     return *(const uint32_t *) v;
  58 }
  59 #    endif
  60 #endif //!ARCH_X86
  61
  62 #endif
  63
  64 /* (stolen from the kernel) */
  65 #ifdef WORDS_BIGENDIAN
  66
  67 #       define swab32(x) (x)
  68
  69 #else
  70
  71 #       if defined (__i386__)
  72
  73 #       define swab32(x) __i386_swab32(x)
  74         static inline const uint32_t __i386_swab32(uint32_t x)
  75         {
  76                 __asm__("bswap %0" : "=r" (x) : "0" (x));
  77                 return x;
  78         }
  79
  80 #       else
  81
  82 #       define swab32(x) __generic_swab32(x)
  83         static inline const uint32_t __generic_swab32(uint32_t x)
  84         {
  85                 return ((((uint8_t*)&x)[0] << 24) | (((uint8_t*)&x)[1] << 16) |
  86                  (((uint8_t*)&x)[2] << 8)  | (((uint8_t*)&x)[3]));
  87         }
  88 #       endif
  89 #endif
  90
  91 #ifdef ALT_BITSTREAM_READER
  92 extern int indx;
  93 #endif
  94
  95 void a52_bitstream_set_ptr (a52_state_t * state, uint8_t * buf);
  96 uint32_t a52_bitstream_get_bh (a52_state_t * state, uint32_t num_bits);
  97 int32_t a52_bitstream_get_bh_2 (a52_state_t * state, uint32_t num_bits);
  98
  99 static inline uint32_t bitstream_get (a52_state_t * state, uint32_t num_bits)
 100 {
 101 #ifdef ALT_BITSTREAM_READER
 102     uint32_t result= swab32( unaligned32(((uint8_t *)state->buffer_start)+(indx>>3)) );
 103
 104     result<<= (indx&0x07);
 105     result>>= 32 - num_bits;
 106     indx+= num_bits;
 107
 108     return result;
 109 #else
 110     uint32_t result;
 111
 112     if (num_bits < state->bits_left) {
 113         result = (state->current_word << (32 - state->bits_left)) >> (32 - num_bits);
 114         state->bits_left -= num_bits;
 115         return result;
 116     }
 117
 118     return a52_bitstream_get_bh (state, num_bits);
 119 #endif
 120 }
 121
 122 static inline void bitstream_skip(a52_state_t * state, int num_bits)
 123 {
 124 #ifdef ALT_BITSTREAM_READER
 125         indx+= num_bits;
 126 #else
 127         bitstream_get(state, num_bits);
 128 #endif
 129 }
 130
 131 static inline int32_t bitstream_get_2 (a52_state_t * state, uint32_t num_bits)
 132 {
 133 #ifdef ALT_BITSTREAM_READER
 134     int32_t result= swab32( unaligned32(((uint8_t *)state->buffer_start)+(indx>>3)) );
 135
 136     result<<= (indx&0x07);
 137     result>>= 32 - num_bits;
 138     indx+= num_bits;
 139
 140     return result;
 141 #else
 142     int32_t result;
 143
 144     if (num_bits < state->bits_left) {
 145         result = (((int32_t)state->current_word) << (32 - state->bits_left)) >> (32 - num_bits);
 146         state->bits_left -= num_bits;
 147         return result;
 148     }
 149
 150     return a52_bitstream_get_bh_2 (state, num_bits);
 151 #endif
 152 }