/*

	getbits

	copyright ?-2009 by the mpg123 project - free software under the terms of the LGPL 2.1

	see COPYING and AUTHORS files in distribution or http://mpg123.org

	initially written by Michael Hipp

	All code is in the header to suggest/force inlining of these small often-used functions.

	This indeed has some impact on performance.

*/

#ifndef _MPG123_GETBITS_H_

#define _MPG123_GETBITS_H_

#include "mpg123lib_intern.h"

#define backbits(fr,nob) ((void)( \

  fr->bitindex    -= nob, \

  fr->wordpointer += (fr->bitindex>>3), \

  fr->bitindex    &= 0x7 ))

#define getbitoffset(fr) ((-fr->bitindex)&0x7)

#define getbyte(fr)      (*fr->wordpointer++)

/* There is something wrong with that macro... the function below works also for the layer1 test case. */

#define macro_getbits(fr, nob) ( \

  fr->ultmp = fr->wordpointer[0],\

  fr->ultmp <<= 8, \

  fr->ultmp |= fr->wordpointer[1], \

  fr->ultmp <<= 8, \

  fr->ultmp |= fr->wordpointer[2], \

  fr->ultmp <<= fr->bitindex, \

  fr->ultmp &= 0xffffff, \

  fr->bitindex += nob, \

  fr->ultmp >>= (24-nob), \

  fr->wordpointer += (fr->bitindex>>3), \

  fr->bitindex &= 7, \

  fr->ultmp)

static unsigned int getbits(mpg123_handle *fr, int number_of_bits)

{

  unsigned long rval;

#ifdef DEBUG_GETBITS

fprintf(stderr,"g%d",number_of_bits);

#endif

  /* Safety catch until we got the nasty code fully figured out. */

  /* No, that catch stays here, even if we think we got it figured out! */

  if( (long)(fr->wordpointer-fr->bsbuf)*8

      + fr->bitindex+number_of_bits > (long)fr->framesize*8 )

    return 0;

/*  This is actually slow: if(!number_of_bits)

    return 0; */

#if 0

   check_buffer_range(number_of_bits+fr->bitindex);

#endif

  {

    rval = fr->wordpointer[0];

    rval <<= 8;

    rval |= fr->wordpointer[1];

    rval <<= 8;

    rval |= fr->wordpointer[2];

    rval <<= fr->bitindex;

    rval &= 0xffffff;

    fr->bitindex += number_of_bits;

    rval >>= (24-number_of_bits);

    fr->wordpointer += (fr->bitindex>>3);

    fr->bitindex &= 7;

  }

#ifdef DEBUG_GETBITS

fprintf(stderr,":%lx\n",rval);

#endif

  return rval;

}

#define skipbits(fr, nob) fr->ultmp = ( \

  fr->ultmp = fr->wordpointer[0], fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[1], \

  fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[2], fr->ultmp <<= fr->bitindex, \

  fr->ultmp &= 0xffffff, fr->bitindex += nob, \

  fr->ultmp >>= (24-nob), fr->wordpointer += (fr->bitindex>>3), \

  fr->bitindex &= 7 )

#define getbits_fast(fr, nob) ( \

  fr->ultmp = (unsigned char) (fr->wordpointer[0] << fr->bitindex), \

  fr->ultmp |= ((unsigned long) fr->wordpointer[1]<<fr->bitindex)>>8, \

  fr->ultmp <<= nob, fr->ultmp >>= 8, \

  fr->bitindex += nob, fr->wordpointer += (fr->bitindex>>3), \

  fr->bitindex &= 7, fr->ultmp )

#define get1bit(fr) ( \

  fr->uctmp = *fr->wordpointer << fr->bitindex, fr->bitindex++, \

  fr->wordpointer += (fr->bitindex>>3), fr->bitindex &= 7, fr->uctmp>>7 )

#endif