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/********************************************************************
* *
* THIS FILE IS PART OF THE OggVorbis 'TREMOR' CODEC SOURCE CODE. *
* *
* THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2002 *
* BY THE Xiph.Org FOUNDATION http://www.xiph.org/ *
* ALL REDISTRIBUTION RIGHTS RESERVED. *
* *
********************************************************************
function: packing variable sized words into an octet stream
********************************************************************/
/* We're 'LSb' endian; if we write a word but read individual bits,
then we'll read the lsb first */
#include <string.h>
#include <stdlib.h>
#include "ogg.h"
#define BUFFER_INCREMENT 256
static unsigned long mask[]=
{0x00000000,0x00000001,0x00000003,0x00000007,0x0000000f,
0x0000001f,0x0000003f,0x0000007f,0x000000ff,0x000001ff,
0x000003ff,0x000007ff,0x00000fff,0x00001fff,0x00003fff,
0x00007fff,0x0000ffff,0x0001ffff,0x0003ffff,0x0007ffff,
0x000fffff,0x001fffff,0x003fffff,0x007fffff,0x00ffffff,
0x01ffffff,0x03ffffff,0x07ffffff,0x0fffffff,0x1fffffff,
0x3fffffff,0x7fffffff,0xffffffff };
void oggpack_readinit(oggpack_buffer *b,unsigned char *buf,int bytes){
memset(b,0,sizeof(*b));
b->buffer=b->ptr=buf;
b->storage=bytes;
}
/* Read in bits without advancing the bitptr; bits <= 32 */
long oggpack_look(oggpack_buffer *b,int bits){
unsigned long ret;
unsigned long m=mask[bits];
bits+=b->endbit;
if(b->endbyte+4>=b->storage){
/* not the main path */
if(b->endbyte*8+bits>b->storage*8)return(-1);
}
ret=b->ptr[0]>>b->endbit;
if(bits>8){
ret|=b->ptr[1]<<(8-b->endbit);
if(bits>16){
ret|=b->ptr[2]<<(16-b->endbit);
if(bits>24){
ret|=b->ptr[3]<<(24-b->endbit);
if(bits>32 && b->endbit)
ret|=b->ptr[4]<<(32-b->endbit);
}
}
}
return(m&ret);
}
long oggpack_look1(oggpack_buffer *b){
if(b->endbyte>=b->storage)return(-1);
return((b->ptr[0]>>b->endbit)&1);
}
void oggpack_adv(oggpack_buffer *b,int bits){
bits+=b->endbit;
b->ptr+=bits/8;
b->endbyte+=bits/8;
b->endbit=bits&7;
}
void oggpack_adv1(oggpack_buffer *b){
if(++(b->endbit)>7){
b->endbit=0;
b->ptr++;
b->endbyte++;
}
}
/* bits <= 32 */
long oggpack_read(oggpack_buffer *b,int bits){
unsigned long ret;
unsigned long m=mask[bits];
bits+=b->endbit;
if(b->endbyte+4>=b->storage){
/* not the main path */
ret=-1UL;
if(b->endbyte*8+bits>b->storage*8)goto overflow;
}
ret=b->ptr[0]>>b->endbit;
if(bits>8){
ret|=b->ptr[1]<<(8-b->endbit);
if(bits>16){
ret|=b->ptr[2]<<(16-b->endbit);
if(bits>24){
ret|=b->ptr[3]<<(24-b->endbit);
if(bits>32 && b->endbit){
ret|=b->ptr[4]<<(32-b->endbit);
}
}
}
}
ret&=m;
overflow:
b->ptr+=bits/8;
b->endbyte+=bits/8;
b->endbit=bits&7;
return(ret);
}
long oggpack_read1(oggpack_buffer *b){
unsigned long ret;
if(b->endbyte>=b->storage){
/* not the main path */
ret=-1UL;
goto overflow;
}
ret=(b->ptr[0]>>b->endbit)&1;
overflow:
b->endbit++;
if(b->endbit>7){
b->endbit=0;
b->ptr++;
b->endbyte++;
}
return(ret);
}
#undef BUFFER_INCREMENT
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