diff options
Diffstat (limited to 'media/libtheora/lib/bitpack.c')
-rw-r--r-- | media/libtheora/lib/bitpack.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/media/libtheora/lib/bitpack.c b/media/libtheora/lib/bitpack.c new file mode 100644 index 0000000000..5125dde6b0 --- /dev/null +++ b/media/libtheora/lib/bitpack.c @@ -0,0 +1,114 @@ +/******************************************************************** + * * + * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. * + * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS * + * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE * + * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. * + * * + * THE OggTheora SOURCE CODE IS (C) COPYRIGHT 1994-2009 * + * by the Xiph.Org Foundation and contributors http://www.xiph.org/ * + * * + ******************************************************************** + + function: packing variable sized words into an octet stream + last mod: $Id$ + + ********************************************************************/ +#include <string.h> +#include <stdlib.h> +#include "bitpack.h" + +/*We're 'MSb' endian; if we write a word but read individual bits, + then we'll read the MSb first.*/ + +void oc_pack_readinit(oc_pack_buf *_b,unsigned char *_buf,long _bytes){ + memset(_b,0,sizeof(*_b)); + _b->ptr=_buf; + _b->stop=_buf+_bytes; +} + +static oc_pb_window oc_pack_refill(oc_pack_buf *_b,int _bits){ + const unsigned char *ptr; + const unsigned char *stop; + oc_pb_window window; + int available; + unsigned shift; + stop=_b->stop; + ptr=_b->ptr; + window=_b->window; + available=_b->bits; + shift=OC_PB_WINDOW_SIZE-available; + while(7<shift&&ptr<stop){ + shift-=8; + window|=(oc_pb_window)*ptr++<<shift; + } + _b->ptr=ptr; + available=OC_PB_WINDOW_SIZE-shift; + if(_bits>available){ + if(ptr>=stop){ + _b->eof=1; + available=OC_LOTS_OF_BITS; + } + else window|=*ptr>>(available&7); + } + _b->bits=available; + return window; +} + +int oc_pack_look1(oc_pack_buf *_b){ + oc_pb_window window; + int available; + window=_b->window; + available=_b->bits; + if(available<1)_b->window=window=oc_pack_refill(_b,1); + return window>>OC_PB_WINDOW_SIZE-1; +} + +void oc_pack_adv1(oc_pack_buf *_b){ + _b->window<<=1; + _b->bits--; +} + +/*Here we assume that 0<=_bits&&_bits<=32.*/ +long oc_pack_read_c(oc_pack_buf *_b,int _bits){ + oc_pb_window window; + int available; + long result; + window=_b->window; + available=_b->bits; + if(_bits==0)return 0; + if(available<_bits){ + window=oc_pack_refill(_b,_bits); + available=_b->bits; + } + result=window>>OC_PB_WINDOW_SIZE-_bits; + available-=_bits; + window<<=1; + window<<=_bits-1; + _b->window=window; + _b->bits=available; + return result; +} + +int oc_pack_read1_c(oc_pack_buf *_b){ + oc_pb_window window; + int available; + int result; + window=_b->window; + available=_b->bits; + if(available<1){ + window=oc_pack_refill(_b,1); + available=_b->bits; + } + result=window>>OC_PB_WINDOW_SIZE-1; + available--; + window<<=1; + _b->window=window; + _b->bits=available; + return result; +} + +long oc_pack_bytes_left(oc_pack_buf *_b){ + if(_b->eof)return -1; + return _b->stop-_b->ptr+(_b->bits>>3); +} |