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# bitstream.h

    00001 /*
    00002  * bitstream.h
    00003  * Copyright (C) 2000-2002 Michel Lespinasse <walken@zoy.org>
    00004  * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
    00005  *
    00006  * This file is part of a52dec, a free ATSC A-52 stream decoder.
    00007  * See http://liba52.sourceforge.net/ for updates.
    00008  *
    00009  * a52dec is free software; you can redistribute it and/or modify
    00010  * it under the terms of the GNU General Public License as published by
    00011  * the Free Software Foundation; either version 2 of the License, or
    00012  * (at your option) any later version.
    00013  *
    00014  * a52dec is distributed in the hope that it will be useful,
    00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00017  * GNU General Public License for more details.
    00018  *
    00019  * You should have received a copy of the GNU General Public License
    00020  * along with this program; if not, write to the Free Software
    00021  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    00022  */
    00023
    00024 /* (stolen from the kernel) */
    00025 #ifdef WORDS_BIGENDIAN
    00026
    00027 #       define swab32(x) (x)
    00028
    00029 #else
    00030
    00031 #       if 0 && defined (__i386__)
    00032
    00033 #       define swab32(x) __i386_swab32(x)
    00034         static inline const uint32_t __i386_swab32(uint32_t x)
    00035         {
    00036                 __asm__("bswap %0" : "=r" (x) : "0" (x));
    00037                 return x;
    00038         }
    00039
    00040 #       else
    00041
    00042 #       define swab32(x)\
    00043 ((((uint8_t*)&x)[0] << 24) | (((uint8_t*)&x)[1] << 16) |  \
    00044  (((uint8_t*)&x)[2] << 8)  | (((uint8_t*)&x)[3]))
    00045
    00046 #       endif
    00047 #endif
    00048
    00049 void a52_bitstream_set_ptr (a52_state_t * state, uint8_t * buf);
    00050 uint32_t a52_bitstream_get_bh (a52_state_t * state, uint32_t num_bits);
    00051 int32_t a52_bitstream_get_bh_2 (a52_state_t * state, uint32_t num_bits);
    00052
    00053 static inline uint32_t bitstream_get (a52_state_t * state, uint32_t num_bits)
    00054 {
    00055     uint32_t result;
    00056
    00057     if (num_bits < state->bits_left) {
    00058         result = (state->current_word << (32 - state->bits_left)) >> (32 - num_bits);
    00059         state->bits_left -= num_bits;
    00060         return result;
    00061     }
    00062
    00063     return a52_bitstream_get_bh (state, num_bits);
    00064 }
    00065
    00066 static inline int32_t bitstream_get_2 (a52_state_t * state, uint32_t num_bits)
    00067 {
    00068     int32_t result;
    00069
    00070     if (num_bits < state->bits_left) {
    00071         result = (((int32_t)state->current_word) << (32 - state->bits_left)) >> (32 - num_bits);
    00072         state->bits_left -= num_bits;
    00073         return result;
    00074     }
    00075
    00076     return a52_bitstream_get_bh_2 (state, num_bits);
    00077 }