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/************************************************************************
*
* getbits.c, bit level routines for tmndecode (H.263 decoder)
* Copyright (C) 1995, 1996 Telenor R&D, Norway
*
* Contacts:
* Robert Danielsen <Robert.Danielsen@nta.no>
*
* Telenor Research and Development http://www.nta.no/brukere/DVC/
* P.O.Box 83 tel.: +47 63 84 84 00
* N-2007 Kjeller, Norway fax.: +47 63 81 00 76
*
* Copyright (C) 1997 University of BC, Canada
* Modified by: Michael Gallant <mikeg@ee.ubc.ca>
* Guy Cote <guyc@ee.ubc.ca>
* Berna Erol <bernae@ee.ubc.ca>
*
* Contacts:
* Michael Gallant <mikeg@ee.ubc.ca>
*
* UBC Image Processing Laboratory http://www.ee.ubc.ca/image
* 2356 Main Mall tel.: +1 604 822 4051
* Vancouver BC Canada V6T1Z4 fax.: +1 604 822 5949
*
************************************************************************/
/* Disclaimer of Warranty
*
* These software programs are available to the user without any license fee
* or royalty on an "as is" basis. The University of British Columbia
* disclaims any and all warranties, whether express, implied, or
* statuary, including any implied warranties or merchantability or of
* fitness for a particular purpose. In no event shall the
* copyright-holder be liable for any incidental, punitive, or
* consequential damages of any kind whatsoever arising from the use of
* these programs.
*
* This disclaimer of warranty extends to the user of these programs and
* user's customers, employees, agents, transferees, successors, and
* assigns.
*
* The University of British Columbia does not represent or warrant that the
* programs furnished hereunder are free of infringement of any
* third-party patents.
*
* Commercial implementations of H.263, including shareware, are subject to
* royalty fees to patent holders. Many of these patents are general
* enough such that they are unavoidable regardless of implementation
* design.
*
*/
/* based on mpeg2decode, (C) 1994, MPEG Software Simulation Group and
* mpeg2play, (C) 1994 Stefan Eckart <stefan@lis.e-technik.tu-muenchen.de>
*
*/
#include <stdlib.h>
#include "config.h"
#include "tmndec.h"
#include "global.h"
#ifdef WIN32
#include <io.h>
#endif
/* to mask the n least significant bits of an integer */
static unsigned int msk[33] =
{
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
};
#ifdef VIC
char *vic_packetbuf;
#endif
/* initialize buffer, call once before first getbits or showbits */
void initbits ()
{
ld->incnt = 0;
ld->rdptr = ld->rdbfr + 2048;
ld->bitcnt = 0;
}
void fillbfr ()
{
int l;
ld->inbfr[0] = ld->inbfr[8];
ld->inbfr[1] = ld->inbfr[9];
ld->inbfr[2] = ld->inbfr[10];
ld->inbfr[3] = ld->inbfr[11];
if (ld->rdptr >= ld->rdbfr + 2048)
{
#ifdef VIC
memcpy(ld->rdbfr, vic_packetbuf, 2048);
vic_packetbuf += 2048;
l = 2048;
#else
l = read (ld->infile, ld->rdbfr, 2048);
#endif
ld->rdptr = ld->rdbfr;
if (l < 2048)
{
if (l < 0)
l = 0;
while (l < 2048) /* Add recognizable sequence end code */
{
ld->rdbfr[l++] = 0;
ld->rdbfr[l++] = 0;
ld->rdbfr[l++] = (1 << 7) | (SE_CODE << 2);
}
}
}
for (l = 0; l < 8; l++)
ld->inbfr[l + 4] = ld->rdptr[l];
ld->rdptr += 8;
ld->incnt += 64;
}
/* return next n bits (right adjusted) without advancing */
unsigned int showbits (int n)
{
unsigned char *v;
unsigned int b;
int c;
if (ld->incnt < n)
fillbfr ();
v = ld->inbfr + ((96 - ld->incnt) >> 3);
b = (v[0] << 24) | (v[1] << 16) | (v[2] << 8) | v[3];
c = ((ld->incnt - 1) & 7) + 25;
return (b >> (c - n)) & msk[n];
}
/* return next bit (could be made faster than getbits(1)) */
unsigned int getbits1 ()
{
return getbits (1);
}
/* advance by n bits */
void flushbits (int n)
{
ld->bitcnt += n;
ld->incnt -= n;
if (ld->incnt < 0)
fillbfr ();
}
/* return next n bits (right adjusted) */
unsigned int getbits (int n)
{
unsigned int l;
l = showbits (n);
flushbits (n);
return l;
}
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