michael@0: /********************************************************************
michael@0:  *                                                                  *
michael@0:  * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE.   *
michael@0:  * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
michael@0:  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
michael@0:  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
michael@0:  *                                                                  *
michael@0:  * THE OggTheora SOURCE CODE IS (C) COPYRIGHT 1994-2009             *
michael@0:  * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
michael@0:  *                                                                  *
michael@0:  ********************************************************************
michael@0: 
michael@0:   function: packing variable sized words into an octet stream
michael@0:   last mod: $Id: bitpack.c 17410 2010-09-21 21:53:48Z tterribe $
michael@0: 
michael@0:  ********************************************************************/
michael@0: #include <string.h>
michael@0: #include <stdlib.h>
michael@0: #include "bitpack.h"
michael@0: 
michael@0: /*We're 'MSb' endian; if we write a word but read individual bits,
michael@0:    then we'll read the MSb first.*/
michael@0: 
michael@0: void oc_pack_readinit(oc_pack_buf *_b,unsigned char *_buf,long _bytes){
michael@0:   memset(_b,0,sizeof(*_b));
michael@0:   _b->ptr=_buf;
michael@0:   _b->stop=_buf+_bytes;
michael@0: }
michael@0: 
michael@0: static oc_pb_window oc_pack_refill(oc_pack_buf *_b,int _bits){
michael@0:   const unsigned char *ptr;
michael@0:   const unsigned char *stop;
michael@0:   oc_pb_window         window;
michael@0:   int                  available;
michael@0:   unsigned             shift;
michael@0:   stop=_b->stop;
michael@0:   ptr=_b->ptr;
michael@0:   window=_b->window;
michael@0:   available=_b->bits;
michael@0:   shift=OC_PB_WINDOW_SIZE-available;
michael@0:   while(7<shift&&ptr<stop){
michael@0:     shift-=8;
michael@0:     window|=(oc_pb_window)*ptr++<<shift;
michael@0:   }
michael@0:   _b->ptr=ptr;
michael@0:   available=OC_PB_WINDOW_SIZE-shift;
michael@0:   if(_bits>available){
michael@0:     if(ptr>=stop){
michael@0:       _b->eof=1;
michael@0:       available=OC_LOTS_OF_BITS;
michael@0:     }
michael@0:     else window|=*ptr>>(available&7);
michael@0:   }
michael@0:   _b->bits=available;
michael@0:   return window;
michael@0: }
michael@0: 
michael@0: int oc_pack_look1(oc_pack_buf *_b){
michael@0:   oc_pb_window window;
michael@0:   int          available;
michael@0:   window=_b->window;
michael@0:   available=_b->bits;
michael@0:   if(available<1)_b->window=window=oc_pack_refill(_b,1);
michael@0:   return window>>OC_PB_WINDOW_SIZE-1;
michael@0: }
michael@0: 
michael@0: void oc_pack_adv1(oc_pack_buf *_b){
michael@0:   _b->window<<=1;
michael@0:   _b->bits--;
michael@0: }
michael@0: 
michael@0: /*Here we assume that 0<=_bits&&_bits<=32.*/
michael@0: long oc_pack_read_c(oc_pack_buf *_b,int _bits){
michael@0:   oc_pb_window window;
michael@0:   int          available;
michael@0:   long         result;
michael@0:   window=_b->window;
michael@0:   available=_b->bits;
michael@0:   if(_bits==0)return 0;
michael@0:   if(available<_bits){
michael@0:     window=oc_pack_refill(_b,_bits);
michael@0:     available=_b->bits;
michael@0:   }
michael@0:   result=window>>OC_PB_WINDOW_SIZE-_bits;
michael@0:   available-=_bits;
michael@0:   window<<=1;
michael@0:   window<<=_bits-1;
michael@0:   _b->window=window;
michael@0:   _b->bits=available;
michael@0:   return result;
michael@0: }
michael@0: 
michael@0: int oc_pack_read1_c(oc_pack_buf *_b){
michael@0:   oc_pb_window window;
michael@0:   int          available;
michael@0:   int          result;
michael@0:   window=_b->window;
michael@0:   available=_b->bits;
michael@0:   if(available<1){
michael@0:     window=oc_pack_refill(_b,1);
michael@0:     available=_b->bits;
michael@0:   }
michael@0:   result=window>>OC_PB_WINDOW_SIZE-1;
michael@0:   available--;
michael@0:   window<<=1;
michael@0:   _b->window=window;
michael@0:   _b->bits=available;
michael@0:   return result;
michael@0: }
michael@0: 
michael@0: long oc_pack_bytes_left(oc_pack_buf *_b){
michael@0:   if(_b->eof)return -1;
michael@0:   return _b->stop-_b->ptr+(_b->bits>>3);
michael@0: }