text: /*
  	layer2.c: the layer 2 decoder, root of mpg123
  
  	copyright 1994-2021 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
  
  	mpg123 started as mp2 decoder a long time ago...
  	part of this file is required for layer 1, too.
  */
  
  
  #include "mpg123lib_intern.h"
  
  #ifndef NO_LAYER2
  #include "l2tables.h"
  #endif
  
  #include "getbits.h"
  
  #ifndef NO_LAYER12 /* Stuff  needed for layer I and II. */
  
  #include "l12tabs.h"
  
  #ifdef RUNTIME_TABLES
  #include "init_layer12.h"
  #endif
  
  // The layer12_table is already in real format (fixed or float), just needs
  // a little scaling in the MMX/SSE case.
  
  void init_layer12_stuff(mpg123_handle *fr, real* (*init_table)(mpg123_handle *fr, real *table, int m))
  {
  	int k;
  	real *table;
  	for(k=0;k<27;k++)
  	{
  		table = init_table(fr, fr->muls[k], k);
  		*table++ = 0.0;
  	}
  }
  
  real* init_layer12_table(mpg123_handle *fr, real *table, int m)
  {
  	int i;
  	for(i=0;i<63;i++)
  		*table++ = layer12_table[m][i];
  	return table;
  }
  
  #ifdef OPT_MMXORSSE
  real* init_layer12_table_mmx(mpg123_handle *fr, real *table, int m)
  {
  	int i,j;
  	if(!fr->p.down_sample) 
  	{
  		for(j=3,i=0;i<63;i++,j--)
  			*table++ = 16384 * layer12_table[m][i];
  	}
  	else
  	{
  		for(j=3,i=0;i<63;i++,j--)
  			*table++ = layer12_table[m][i];
  	}
  	return table;
  }
  #endif
  
  #endif /* NO_LAYER12 */
  
  /* The rest is the actual decoding of layer II data. */
  
  #ifndef NO_LAYER2
  
  static int II_step_one(unsigned int *bit_alloc,int *scale,mpg123_handle *fr)
  {
  	int stereo = fr->stereo-1;
  	int sblimit = fr->II_sblimit;
  	int jsbound = fr->jsbound;
  	int sblimit2 = fr->II_sblimit<<stereo;
  	const struct al_table *alloc1 = fr->alloc;
  	int i;
  	unsigned int scfsi_buf[64];
  	unsigned int *scfsi,*bita;
  	int sc,step;
  	/* Count the bits needed for getbits_fast(). */
  	unsigned int needbits = 0;
  	unsigned int scale_bits[4] = { 18, 12, 6, 12 };
  
  	bita = bit_alloc;
  	if(stereo)
  	{
  		for(i=jsbound;i;i--,alloc1+=(1<<step))
  		{
  			step=alloc1->bits;
  			bita[0] = (char) getbits(fr, step);
  			bita[1] = (char) getbits(fr, step);
  			needbits += ((bita[0]?1:0)+(bita[1]?1:0))*2;
  			bita+=2;
  		}
  		for(i=sblimit-jsbound;i;i--,alloc1+=(1<<step))
  		{
  			step=alloc1->bits;
  			bita[0] = (char) getbits(fr, step);
  			bita[1] = bita[0];
  			needbits += (bita[0]?1:0)*2*2;
  			bita+=2;
  		}
  		bita = bit_alloc;
  		scfsi=scfsi_buf;
  
  		if(fr->bits_avail < needbits)
  		{
  			if(NOQUIET)
  				error2("need %u bits, have %li", needbits, fr->bits_avail);
  			return -1;
  		}
  		for(i=sblimit2;i;i--)
  		if(*bita++) *scfsi++ = (char) getbits_fast(fr, 2);
  	}
  	else /* mono */
  	{
  		for(i=sblimit;i;i--,alloc1+=(1<<step))
  		{
  			step=alloc1->bits;
  			*bita = (char) getbits(fr, step);
  			if(*bita)
  				needbits += 2;
  			++bita;
  		}
  		bita = bit_alloc;
  		scfsi=scfsi_buf;
  		if(fr->bits_avail < needbits)
  		{
  			if(NOQUIET)
  				error2("need %u bits, have %li", needbits, fr->bits_avail);
  			return -1;
  		}
  		for(i=sblimit;i;i--)
  		if(*bita++) *scfsi++ = (char) getbits_fast(fr, 2);
  	}
  
  	needbits = 0;
  	bita = bit_alloc;
  	scfsi=scfsi_buf;
  	for(i=sblimit2;i;--i)
  		if(*bita++)
  			needbits += scale_bits[*scfsi++];
  	if(fr->bits_avail < needbits)
  	{
  		if(NOQUIET)
  			error2("need %u bits, have %li", needbits, fr->bits_avail);
  		return -1;
  	}
  
  	bita = bit_alloc;
  	scfsi=scfsi_buf;
  	for(i=sblimit2;i;--i)
  	if(*bita++)
  	switch(*scfsi++)
  	{
  		case 0: 
  			*scale++ = getbits_fast(fr, 6);
  			*scale++ = getbits_fast(fr, 6);
  			*scale++ = getbits_fast(fr, 6);
  		break;
  		case 1 : 
  			*scale++ = sc = getbits_fast(fr, 6);
  			*scale++ = sc;
  			*scale++ = getbits_fast(fr, 6);
  		break;
  		case 2: 
  			*scale++ = sc = getbits_fast(fr, 6);
  			*scale++ = sc;
  			*scale++ = sc;
  		break;
  		default:              /* case 3 */
  			*scale++ = getbits_fast(fr, 6);
  			*scale++ = sc = getbits_fast(fr, 6);
  			*scale++ = sc;
  		break;
  	}
  
  	return 0;
  }
  
  
  static void II_step_two(unsigned int *bit_alloc,real fraction[2][4][SBLIMIT],int *scale,mpg123_handle *fr,int x1)
  {
  	int i,j,k,ba;
  	int stereo = fr->stereo;
  	int sblimit = fr->II_sblimit;
  	int jsbound = fr->jsbound;
  	const struct al_table *alloc2,*alloc1 = fr->alloc;
  	unsigned int *bita=bit_alloc;
  	int d1,step;
  
  	for(i=0;i<jsbound;i++,alloc1+=(1<<step))
  	{
  		step = alloc1->bits;
  		for(j=0;j<stereo;j++)
  		{
  			if( (ba=*bita++) ) 
  			{
  				k=(alloc2 = alloc1+ba)->bits;
  				if( (d1=alloc2->d) < 0) 
  				{
  					real cm=fr->muls[k][scale[x1]];
  					fraction[j][0][i] = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1), cm);
  					fraction[j][1][i] = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1), cm);
  					fraction[j][2][i] = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1), cm);
  				}        
  				else 
  				{
  					const unsigned char *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
  					unsigned int m=scale[x1];
  					unsigned int idx = (unsigned int) getbits(fr, k);
  					const unsigned char *tab = table[d1] + idx + idx + idx;
  					fraction[j][0][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m]);
  					fraction[j][1][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m]);
  					fraction[j][2][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m]);  
  				}
  				scale+=3;
  			}
  			else
  			fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = DOUBLE_TO_REAL(0.0);
  			if(fr->bits_avail < 0)
  				return; /* Caller checks that again. */
  		}
  	}
  
  	for(i=jsbound;i<sblimit;i++,alloc1+=(1<<step))
  	{
  		step = alloc1->bits;
  		bita++;	/* channel 1 and channel 2 bitalloc are the same */
  		if( (ba=*bita++) )
  		{
  			k=(alloc2 = alloc1+ba)->bits;
  			if( (d1=alloc2->d) < 0)
  			{
  				real cm;
  				cm=fr->muls[k][scale[x1+3]];
  				fraction[0][0][i] = DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1);
  				fraction[0][1][i] = DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1);
  				fraction[0][2][i] = DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1);
  				fraction[1][0][i] = REAL_MUL_SCALE_LAYER12(fraction[0][0][i], cm);
  				fraction[1][1][i] = REAL_MUL_SCALE_LAYER12(fraction[0][1][i], cm);
  				fraction[1][2][i] = REAL_MUL_SCALE_LAYER12(fraction[0][2][i], cm);
  				cm=fr->muls[k][scale[x1]];
  				fraction[0][0][i] = REAL_MUL_SCALE_LAYER12(fraction[0][0][i], cm);
  				fraction[0][1][i] = REAL_MUL_SCALE_LAYER12(fraction[0][1][i], cm);
  				fraction[0][2][i] = REAL_MUL_SCALE_LAYER12(fraction[0][2][i], cm);
  			}
  			else
  			{
  				const unsigned char *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
  				unsigned int m1 = scale[x1];
  				unsigned int m2 = scale[x1+3];
  				unsigned int idx = (unsigned int) getbits(fr, k);
  				const unsigned char *tab = table[d1] + idx + idx + idx;
  				fraction[0][0][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m1]); fraction[1][0][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m2]);
  				fraction[0][1][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m1]); fraction[1][1][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m2]);
  				fraction[0][2][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m1]); fraction[1][2][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m2]);
  			}
  			scale+=6;
  			if(fr->bits_avail < 0)
  				return; /* Caller checks that again. */
  		}
  		else
  		{
  			fraction[0][0][i] = fraction[0][1][i] = fraction[0][2][i] =
  			fraction[1][0][i] = fraction[1][1][i] = fraction[1][2][i] = DOUBLE_TO_REAL(0.0);
  		}
  /*
  	Historic comment...
  	should we use individual scalefac for channel 2 or
  	is the current way the right one , where we just copy channel 1 to
  	channel 2 ?? 
  	The current 'strange' thing is, that we throw away the scalefac
  	values for the second channel ...!!
  	-> changed .. now we use the scalefac values of channel one !! 
  */
  	}
  
  	if(sblimit > (fr->down_sample_sblimit) )
  	sblimit = fr->down_sample_sblimit;
  
  	for(i=sblimit;i<SBLIMIT;i++)
  	for (j=0;j<stereo;j++)
  	fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = DOUBLE_TO_REAL(0.0);
  }
  
  
  static void II_select_table(mpg123_handle *fr)
  {
  	const int translate[3][2][16] =
  	{
  		{
  			{ 0,2,2,2,2,2,2,0,0,0,1,1,1,1,1,0 },
  			{ 0,2,2,0,0,0,1,1,1,1,1,1,1,1,1,0 }
  		},
  		{
  			{ 0,2,2,2,2,2,2,0,0,0,0,0,0,0,0,0 },
  			{ 0,2,2,0,0,0,0,0,0,0,0,0,0,0,0,0 }
  		},
  		{
  			{ 0,3,3,3,3,3,3,0,0,0,1,1,1,1,1,0 },
  			{ 0,3,3,0,0,0,1,1,1,1,1,1,1,1,1,0 }
  		}
  	};
  
  	int table,sblim;
  	const struct al_table *tables[5] = { alloc_0, alloc_1, alloc_2, alloc_3 , alloc_4 };
  	const int sblims[5] = { 27 , 30 , 8, 12 , 30 };
  
  	if(fr->sampling_frequency >= 3)	/* Or equivalent: (fr->lsf == 1) */
  	table = 4;
  	else
  	table = translate[fr->sampling_frequency][2-fr->stereo][fr->bitrate_index];
  
  	sblim = sblims[table];
  	fr->alloc      = tables[table];
  	fr->II_sblimit = sblim;
  }
  
  
  int do_layer2(mpg123_handle *fr)
  {
  	int clip=0;
  	int i,j;
  	int stereo = fr->stereo;
  	/* pick_table clears unused subbands */
  	/* replacement for real fraction[2][4][SBLIMIT], needs alignment. */
  	real (*fraction)[4][SBLIMIT] = fr->layer2.fraction;
  	unsigned int bit_alloc[64];
  	int scale[192];
  	int single = fr->single;
  
  	II_select_table(fr);
  	fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : fr->II_sblimit;
  
  	if(fr->jsbound > fr->II_sblimit)
  	{
  		fprintf(stderr, "Truncating stereo boundary to sideband limit.\n");
  		fr->jsbound=fr->II_sblimit;
  	}
  
  	/* TODO: What happens with mono mixing, actually? */
  	if(stereo == 1 || single == SINGLE_MIX) /* also, mix not really handled */
  	single = SINGLE_LEFT;
  
  	if(II_step_one(bit_alloc, scale, fr))
  	{
  		if(NOQUIET)
  			error("first step of layer I decoding failed");
  		return clip;
  	}
  
  	for(i=0;i<SCALE_BLOCK;i++)
  	{
  		II_step_two(bit_alloc,fraction,scale,fr,i>>2);
  		if(fr->bits_avail < 0)
  		{
  			if(NOQUIET)
  				error("missing bits in layer II step two");
  			return clip;
  		}
  		for(j=0;j<3;j++) 
  		{
  			if(single != SINGLE_STEREO)
  			clip += (fr->synth_mono)(fraction[single][j], fr);
  			else
  			clip += (fr->synth_stereo)(fraction[0][j], fraction[1][j], fr);
  		}
  	}
  
  	return clip;
  }
  
  #endif /* NO_LAYER2 */
  