/**********************************************************************Copyright (c) 1991 MPEG/audio software simulation group, All Rights Reservedhuffman.c**********************************************************************//********************************************************************** * MPEG/audio coding/decoding software, work in progress              * *   NOT for public distribution until verified and approved by the   * *   MPEG/audio committee.  For further information, please contact   * *   Chad Fogg email: <cfogg@xenon.com>                               * *                                                                    * * VERSION 2.10                                                       * *   changes made since last update:                                  * *   date   programmers                comment                        * *27.2.92   F.O.Witte                  (ITT Intermetall)              * *				       email: otto.witte@itt-sc.de    * *				       tel:   ++49 (761)517-125	      * *				       fax:   ++49 (761)517-880	      * *12.6.92   J. Pineda                  Added sign bit to decoder.     * * 08/24/93 M. Iwadare                 Changed for 1 pass decoding.   * *--------------------------------------------------------------------* *  7/14/94 Juergen Koller      Bug fixes in Layer III code           * *********************************************************************/	#include <string.h>
#include <stdlib.h>
#include "common.h"#include "huffman.h"     HUFFBITS dmask = 1 << (sizeof(HUFFBITS)*8-1);struct huffcodetab ht[HTN];	/* array of all huffcodtable headers	*/
				/* 0..31 Huffman code table 0..31	*/
				/* 32,33 count1-tables			*/
/* read the huffman decoder table */int read_decoder_table(FILE *fi) {  int n,i,nn,t;  unsigned int v0,v1;  char command[100],line[100];  for (n=0;n<HTN;n++) {    /* .table number treelen xlen ylen linbits */     do {      fgets(line,99,fi);    } while ((line[0] == '#') || (line[0] < ' '));         sscanf(line,"%s %s %u %u %u %u",command,ht[n].tablename,           &ht[n].treelen, &ht[n].xlen, &ht[n].ylen, &ht[n].linbits);    if (strcmp(command,".end")==0)      return n;    else if (strcmp(command,".table")!=0) {      fprintf(stderr,"huffman table %u data corrupted\n",n);      return -1;    }    ht[n].linmax = (1<<ht[n].linbits)-1;       sscanf(ht[n].tablename,"%u",&nn);    if (nn != n) {      fprintf(stderr,"wrong table number %u\n",n);      return(-2);    }     do {      fgets(line,99,fi);    } while ((line[0] == '#') || (line[0] < ' '));    sscanf(line,"%s %u",command,&t);    if (strcmp(command,".reference")==0) {      ht[n].ref   = t;      ht[n].val   = ht[t].val;      ht[n].treelen  = ht[t].treelen;      if ( (ht[n].xlen != ht[t].xlen) ||           (ht[n].ylen != ht[t].ylen)  ) {        fprintf(stderr,"wrong table %u reference\n",n);        return (-3);      };      while ((line[0] == '#') || (line[0] < ' ') ) {        fgets(line,99,fi);      }    }        else if (strcmp(command,".treedata")==0) {      ht[n].ref  = -1;      ht[n].val = (unsigned char (*)[2])         calloc(2*(ht[n].treelen),sizeof(unsigned char));      if ((ht[n].val == NULL) && ( ht[n].treelen != 0 )){    	fprintf(stderr, "heaperror at table %d\n",n);    	exit (-10);      }      for (i=0;i<ht[n].treelen; i++) {        fscanf(fi,"%x %x",&v0, &v1);        ht[n].val[i][0]=(unsigned char)v0;        ht[n].val[i][1]=(unsigned char)v1;      }      fgets(line,99,fi); /* read the rest of the line */    }    else {      fprintf(stderr,"huffman decodertable error at table %d\n",n);    }  }  return n;}/* do the huffman-decoding 						*//* note! for counta,countb -the 4 bit value is returned in y, discard x */int huffman_decoder(struct huffcodetab *h, int *x, int *y, int *v, int *w){    HUFFBITS level;  int point = 0;  int error = 1;  level     = dmask;  if (h->val == NULL) return 2;  /* table 0 needs no bits */  if ( h->treelen == 0)  {  *x = *y = 0;     return 0;  }  /* Lookup in Huffman table. */  do {    if (h->val[point][0]==0) {   /*end of tree*/      *x = h->val[point][1] >> 4;      *y = h->val[point][1] & 0xf;      error = 0;      break;    }     if (hget1bit()) {      while (h->val[point][1] >= MXOFF) point += h->val[point][1];       point += h->val[point][1];    }    else {      while (h->val[point][0] >= MXOFF) point += h->val[point][0];       point += h->val[point][0];    }    level >>= 1;  } while (level  || (point < ht->treelen) );    /* Check for error. */    if (error) { /* set x and y to a medium value as a simple concealment */    printf("Illegal Huffman code in data.\n");    *x = (h->xlen-1 << 1);    *y = (h->ylen-1 << 1);  }  /* Process sign encodings for quadruples tables. */  if (h->tablename[0] == '3'      && (h->tablename[1] == '2' || h->tablename[1] == '3')) {     *v = (*y>>3) & 1;     *w = (*y>>2) & 1;     *x = (*y>>1) & 1;     *y = *y & 1;     /* v, w, x and y are reversed in the bitstream.         switch them around to make test bistream work. */     /*   {int i=*v; *v=*y; *y=i; i=*w; *w=*x; *x=i;}  MI */     if (*v)        if (hget1bit() == 1) *v = -*v;     if (*w)        if (hget1bit() == 1) *w = -*w;     if (*x)        if (hget1bit() == 1) *x = -*x;     if (*y)        if (hget1bit() == 1) *y = -*y;     }       /* Process sign and escape encodings for dual tables. */    else {        /* x and y are reversed in the test bitstream.         Reverse x and y here to make test bitstream work. */	 /*    removed 11/11/92 -ag  		{int i=*x; *x=*y; *y=i;} */           if (h->linbits)       if ((h->xlen-1) == *x)          *x += hgetbits(h->linbits);     if (*x)        if (hget1bit() == 1) *x = -*x;     if (h->linbits)	         if ((h->ylen-1) == *y)         *y += hgetbits(h->linbits);     if (*y)        if (hget1bit() == 1) *y = -*y;     }	    return error;  }