media/libtheora/lib/dec/bitwise.h

   1 /********************************************************************
   2  *                                                                  *
   3  * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
   4  * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
   5  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
   6  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
   7  *                                                                  *
   8  * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2002             *
   9  * by the Xiph.Org Foundation http://www.xiph.org/                  *
  10  *                                                                  *
  11  ********************************************************************
  12
  13   function: packing variable sized words into an octet stream
  14   last mod: $Id: bitwise.c 7675 2004-09-01 00:34:39Z xiphmont $
  15
  16  ********************************************************************/
  17 #if !defined(_bitwise_H)
  18 # define _bitwise_H (1)
  19 # include <ogg/ogg.h>
  20
  21 void theorapackB_reset(oggpack_buffer *b);
  22 void theorapackB_readinit(oggpack_buffer *b,unsigned char *buf,int bytes);
  23 /* Read in bits without advancing the bitptr; bits <= 32 */
  24 static int theorapackB_look(oggpack_buffer *b,int bits,long *_ret);
  25 int theorapackB_look1(oggpack_buffer *b,long *_ret);
  26 static void theorapackB_adv(oggpack_buffer *b,int bits);
  27 void theorapackB_adv1(oggpack_buffer *b);
  28 /* bits <= 32 */
  29 int theorapackB_read(oggpack_buffer *b,int bits,long *_ret);
  30 int theorapackB_read1(oggpack_buffer *b,long *_ret);
  31 long theorapackB_bytes(oggpack_buffer *b);
  32 long theorapackB_bits(oggpack_buffer *b);
  33 unsigned char *theorapackB_get_buffer(oggpack_buffer *b);
  34
  35 /*These two functions are only used in one place, and declaring them static so
  36    they can be inlined saves considerable function call overhead.*/
  37
  38 /* Read in bits without advancing the bitptr; bits <= 32 */
  39 static int theorapackB_look(oggpack_buffer *b,int bits,long *_ret){
  40   long ret;
  41   long m;
  42   m=32-bits;
  43   bits+=b->endbit;
  44   if(b->endbyte+4>=b->storage){
  45     /* not the main path */
  46     if(b->endbyte>=b->storage){
  47       *_ret=0L;
  48       return -1;
  49     }
  50     /*If we have some bits left, but not enough, return the ones we have.*/
  51     if((b->storage-b->endbyte)*8<bits)bits=(b->storage-b->endbyte)*8;
  52   }
  53   ret=b->ptr[0]<<(24+b->endbit);
  54   if(bits>8){
  55     ret|=b->ptr[1]<<(16+b->endbit);
  56     if(bits>16){
  57       ret|=b->ptr[2]<<(8+b->endbit);
  58       if(bits>24){
  59         ret|=b->ptr[3]<<(b->endbit);
  60         if(bits>32&&b->endbit)
  61           ret|=b->ptr[4]>>(8-b->endbit);
  62       }
  63     }
  64   }
  65   *_ret=((ret&0xffffffff)>>(m>>1))>>((m+1)>>1);
  66   return 0;
  67 }
  68
  69 static void theorapackB_adv(oggpack_buffer *b,int bits){
  70   bits+=b->endbit;
  71   b->ptr+=bits/8;
  72   b->endbyte+=bits/8;
  73   b->endbit=bits&7;
  74 }
  75
  76 #endif