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/*
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 * Mpeg Layer-1 audio decoder
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 * --------------------------
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 * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
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 * near unoptimzed ...
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 *
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 * may have a few bugs after last optimization ...
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 *
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 */
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#include "mpg123.h"
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void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
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{
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  unsigned int *ba=balloc;
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  unsigned int *sca = (unsigned int *) scale_index;
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  if(fr->stereo) {
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    int i;
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    int jsbound = fr->jsbound;
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    for (i=0;i<jsbound;i++) {
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      *ba++ = getbits(4);
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      *ba++ = getbits(4);
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    }
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    for (i=jsbound;i<SBLIMIT;i++)
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      *ba++ = getbits(4);
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    ba = balloc;
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    for (i=0;i<jsbound;i++) {
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      if ((*ba++))
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        *sca++ = getbits(6);
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      if ((*ba++))
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        *sca++ = getbits(6);
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    }
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    for (i=jsbound;i<SBLIMIT;i++)
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      if ((*ba++)) {
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        *sca++ =  getbits(6);
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        *sca++ =  getbits(6);
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      }
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  }
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  else {
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    int i;
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    for (i=0;i<SBLIMIT;i++)
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      *ba++ = getbits(4);
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    ba = balloc;
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    for (i=0;i<SBLIMIT;i++)
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      if ((*ba++))
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        *sca++ = getbits(6);
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  }
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}
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void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
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        unsigned int scale_index[2][SBLIMIT],struct frame *fr)
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{
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  int i,n;
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  int smpb[2*SBLIMIT]; /* values: 0-65535 */
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  int *sample;
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  register unsigned int *ba;
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  register unsigned int *sca = (unsigned int *) scale_index;
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  if(fr->stereo) {
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    int jsbound = fr->jsbound;
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    register real *f0 = fraction[0];
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    register real *f1 = fraction[1];
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    ba = balloc;
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    for (sample=smpb,i=0;i<jsbound;i++)  {
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      if ((n = *ba++))
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        *sample++ = getbits(n+1);
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      if ((n = *ba++))
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        *sample++ = getbits(n+1);
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    }
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    for (i=jsbound;i<SBLIMIT;i++)
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      if ((n = *ba++))
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        *sample++ = getbits(n+1);
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    ba = balloc;
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    for (sample=smpb,i=0;i<jsbound;i++) {
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      if((n=*ba++))
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        *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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      else
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        *f0++ = 0.0;
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      if((n=*ba++))
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        *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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      else
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        *f1++ = 0.0;
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    }
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    for (sample=smpb,i=jsbound;i<SBLIMIT;i++) {
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      if ((n=*ba++)) {
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        real samp = ( ((-1)<<n) + (*sample++) + 1);
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        *f0++ = samp * muls[n+1][*sca++];
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        *f1++ = samp * muls[n+1][*sca++];
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      }
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      else
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        *f0++ = *f1++ = 0.0;
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    }
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    for(i=SBLIMIT>>fr->down_sample;i<32;i++)
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      fraction[0][i] = fraction[1][i] = 0.0;
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  }
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  else {
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    register real *f0 = fraction[0];
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    ba = balloc;
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    for (sample=smpb,i=0;i<SBLIMIT;i++)
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      if ((n = *ba++))
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        *sample++ = getbits(n+1);
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    ba = balloc;
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    for (sample=smpb,i=0;i<SBLIMIT;i++) {
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      if((n=*ba++))
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        *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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      else
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        *f0++ = 0.0;
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    }
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    for(i=SBLIMIT>>fr->down_sample;i<32;i++)
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      fraction[0][i] = 0.0;
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  }
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}
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int do_layer1(struct frame *fr,int outmode,struct audio_info_struct *ai)
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{
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  int clip=0;
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  int i,stereo = fr->stereo;
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  unsigned int balloc[2*SBLIMIT];
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  unsigned int scale_index[2][SBLIMIT];
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  real fraction[2][SBLIMIT];
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  int single = fr->single;
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  if(stereo == 1 || single == 3)
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    single = 0;
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  I_step_one(balloc,scale_index,fr);
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  for (i=0;i<SCALE_BLOCK;i++)
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  {
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    I_step_two(fraction,balloc,scale_index,fr);
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    if(single >= 0)
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    {
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      clip += (fr->synth_mono)( (real *) fraction[single],pcm_sample+pcm_point);
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    }
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    else {
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        clip += (fr->synth)( (real *) fraction[0],0,pcm_sample+pcm_point);
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        clip += (fr->synth)( (real *) fraction[1],1,pcm_sample+pcm_point);
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    }
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    pcm_point += fr->block_size;
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    if(pcm_point == audiobufsize)
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      audio_flush(outmode,ai);
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  }
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  return clip;
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}
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