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122 lines
3.0 KiB
C
122 lines
3.0 KiB
C
/********************************************************************
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* *
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* THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. *
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* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
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* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
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* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
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* *
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* THE OggTheora SOURCE CODE IS (C) COPYRIGHT 1994-2008 *
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* by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
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* *
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********************************************************************
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function: packing variable sized words into an octet stream
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last mod: $Id: bitpack.c 15400 2008-10-15 12:10:58Z tterribe $
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********************************************************************/
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/*We're 'MSb' endian; if we write a word but read individual bits,
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then we'll read the MSb first.*/
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#include <string.h>
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#include <stdlib.h>
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#include "bitpack.h"
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void theorapackB_readinit(oggpack_buffer *_b,unsigned char *_buf,int _bytes){
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memset(_b,0,sizeof(*_b));
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_b->buffer=_b->ptr=_buf;
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_b->storage=_bytes;
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}
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int theorapackB_look1(oggpack_buffer *_b,long *_ret){
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if(_b->endbyte>=_b->storage){
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*_ret=0L;
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return -1;
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}
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*_ret=(_b->ptr[0]>>7-_b->endbit)&1;
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return 0;
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}
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void theorapackB_adv1(oggpack_buffer *_b){
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if(++(_b->endbit)>7){
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_b->endbit=0;
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_b->ptr++;
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_b->endbyte++;
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}
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}
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/*Here we assume that 0<=_bits&&_bits<=32.*/
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int theorapackB_read(oggpack_buffer *_b,int _bits,long *_ret){
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long ret;
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long m;
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long d;
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int fail;
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m=32-_bits;
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_bits+=_b->endbit;
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d=_b->storage-_b->endbyte;
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if(d<=4){
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/*Not the main path.*/
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if(d*8<_bits){
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*_ret=0L;
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fail=-1;
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goto overflow;
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}
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/*Special case to avoid reading _b->ptr[0], which might be past the end of
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the buffer; also skips some useless accounting.*/
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else if(!_bits){
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*_ret=0L;
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return 0;
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}
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}
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ret=_b->ptr[0]<<24+_b->endbit;
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if(_bits>8){
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ret|=_b->ptr[1]<<16+_b->endbit;
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if(_bits>16){
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ret|=_b->ptr[2]<<8+_b->endbit;
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if(_bits>24){
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ret|=_b->ptr[3]<<_b->endbit;
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if(_bits>32)ret|=_b->ptr[4]>>8-_b->endbit;
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}
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}
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}
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*_ret=((ret&0xFFFFFFFFUL)>>(m>>1))>>(m+1>>1);
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fail=0;
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overflow:
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_b->ptr+=_bits>>3;
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_b->endbyte+=_bits>>3;
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_b->endbit=_bits&7;
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return fail;
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}
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int theorapackB_read1(oggpack_buffer *_b,long *_ret){
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int fail;
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if(_b->endbyte>=_b->storage){
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/*Not the main path.*/
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*_ret=0L;
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fail=-1;
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}
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else{
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*_ret=(_b->ptr[0]>>7-_b->endbit)&1;
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fail=0;
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}
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_b->endbit++;
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if(_b->endbit>7){
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_b->endbit=0;
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_b->ptr++;
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_b->endbyte++;
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}
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return fail;
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}
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long theorapackB_bytes(oggpack_buffer *_b){
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return _b->endbyte+(_b->endbit+7>>3);
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}
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long theorapackB_bits(oggpack_buffer *_b){
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return _b->endbyte*8+_b->endbit;
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}
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unsigned char *theorapackB_get_buffer(oggpack_buffer *_b){
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return _b->buffer;
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}
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