/********************************************************************** * MPEG/audio 編碼/解碼軟件              * * VERSION 2.10                                                       * *********************************************************************/	#include <string.h>
#include <stdlib.h>
#include "common.h"#include "huffman.h"     HUFFBITS dmask = 1 << (sizeof(HUFFBITS)*8-1);struct huffcodetab ht[HTN];	/* 所有 huffcodtable headers的數組	*/
				/* 0..31 Huffman code table 0..31	*/
				/* 32,33 count1-tables			*/
/* 讀取 huffman 解碼表 */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++) {        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); /* 讀取剩余行 */    }    else {      fprintf(stderr,"huffman decodertable error at table %d\n",n);    }  }  return n;}/* 進行huffman解碼	*//* 注意! 對counta,countb - 4 bit 值 用 y返回, 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 不需要 bits */  if ( h->treelen == 0)  {  *x = *y = 0;     return 0;  }  /* 查找 Huffman table. */  do {    if (h->val[point][0]==0) {   /*樹的結尾*/      *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) );    /* 檢查錯誤 */    if (error) { /* 設置 x 和 y 為一中間值 */    printf("Illegal Huffman code in data.\n");    *x = (h->xlen-1 << 1);    *y = (h->ylen-1 << 1);  }  /* 處理信號編碼 */  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 和 y 在比特流中是顛倒的，交換他們          */     /*   {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;     }       /* 對dual table情況，處理信號編碼 */    else {        /* 在測試比特流中x 和 y是顛倒的          這里顛倒 x 和 y 使測試比特流正常 */         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;  }