mirror of https://github.com/mpv-player/mpv
121 lines
2.9 KiB
C
121 lines
2.9 KiB
C
/*
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* bitstream.h
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* Copyright (C) 2000-2001 Michel Lespinasse <walken@zoy.org>
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* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
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*
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* This file is part of a52dec, a free ATSC A-52 stream decoder.
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* See http://liba52.sourceforge.net/ for updates.
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*
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* a52dec is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* a52dec is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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// alternative (faster) bitstram reader (reades upto 3 bytes over the end of the input)
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#define ALT_BITSTREAM_READER
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/* (stolen from the kernel) */
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#ifdef WORDS_BIGENDIAN
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# define swab32(x) (x)
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#else
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# if defined (__i386__)
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# define swab32(x) __i386_swab32(x)
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static inline const uint32_t __i386_swab32(uint32_t x)
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{
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__asm__("bswap %0" : "=r" (x) : "0" (x));
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return x;
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}
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# else
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# define swab32(x)\
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((((uint8_t*)&x)[0] << 24) | (((uint8_t*)&x)[1] << 16) | \
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(((uint8_t*)&x)[2] << 8) | (((uint8_t*)&x)[3]))
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# endif
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#endif
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#ifdef ALT_BITSTREAM_READER
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extern uint32_t *buffer_start;
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extern int indx;
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#else
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extern uint32_t bits_left;
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extern uint32_t current_word;
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#endif
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void bitstream_set_ptr (uint8_t * buf);
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uint32_t bitstream_get_bh(uint32_t num_bits);
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int32_t bitstream_get_bh_2(uint32_t num_bits);
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static inline uint32_t
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bitstream_get(uint32_t num_bits) // note num_bits is practically a constant due to inlineing
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{
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#ifdef ALT_BITSTREAM_READER
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uint32_t result= swab32( *(uint32_t *)(((uint8_t *)buffer_start)+(indx>>3)) );
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result<<= (indx&0x07);
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result>>= 32 - num_bits;
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indx+= num_bits;
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return result;
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#else
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uint32_t result;
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if(num_bits < bits_left) {
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result = (current_word << (32 - bits_left)) >> (32 - num_bits);
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bits_left -= num_bits;
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return result;
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}
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return bitstream_get_bh(num_bits);
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#endif
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}
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static inline void bitstream_skip(int num_bits)
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{
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#ifdef ALT_BITSTREAM_READER
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indx+= num_bits;
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#else
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bitstream_get(num_bits);
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#endif
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}
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static inline int32_t
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bitstream_get_2(uint32_t num_bits)
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{
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#ifdef ALT_BITSTREAM_READER
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int32_t result= swab32( *(uint32_t *)(((uint8_t *)buffer_start)+(indx>>3)) );
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result<<= (indx&0x07);
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result>>= 32 - num_bits;
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indx+= num_bits;
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return result;
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#else
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int32_t result;
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if(num_bits < bits_left) {
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result = (((int32_t)current_word) << (32 - bits_left)) >> (32 - num_bits);
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bits_left -= num_bits;
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return result;
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}
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return bitstream_get_bh_2(num_bits);
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#endif
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}
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