www.pudn.com > ampegsrc.zip > HUFFMAN.C
/**********************************************************************
Copyright (c) 1991 MPEG/audio software simulation group, All Rights Reserved
huffman.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 *
* Davis Pan, 708-538-5671, e-mail: pan@ukraine.corp.mot.com *
* *
* VERSION 4.3 *
* 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 "common.h"
#include "huffman.h"
HUFFBITS dmask = 1 << (sizeof(HUFFBITS)*8-1);
unsigned int hs = sizeof(HUFFBITS)*8;
struct huffcodetab ht[HTN]; /* array of all huffcodtable headers */
/* 0..31 Huffman code table 0..31 */
/* 32,33 count1-tables */
/* read the huffman encode table */
int read_huffcodetab(fi)
FILE *fi;
{
char line[100],command[40],huffdata[40];
unsigned int t,i,j,k,nn,x,y,n=0;
unsigned int xl, yl, len;
HUFFBITS h;
int hsize;
hsize = sizeof(HUFFBITS)*8;
do {
fgets(line,99,fi);
} while ((line[0] == '#') || (line[0] < ' ') );
do {
while ((line[0]=='#') || (line[0] < ' ')) {
fgets(line,99,fi);
}
sscanf(line,"%s %s %u %u %u",command,ht[n].tablename,
&xl,&yl,&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<1)
sscanf(line,"%u %u %u %s",&x, &y, &len,huffdata);
else
sscanf(line,"%u %u %s",&x,&len,huffdata);
h=0;k=0;
while (huffdata[k]) {
h <<= 1;
if (huffdata[k] == '1')
h++;
else if (huffdata[k] != '0'){
fprintf(stderr,"huffman-table %u bit error\n",n);
return (-5);
};
k++;
};
if (k != len) {
fprintf(stderr,
"warning: wrong codelen in table %u, pos [%2u][%2u]\n",
n,i,j);
};
ht[n].table[i*xl+j] = h;
ht[n].hlen[i*xl+j] = (unsigned char) len;
do {
fgets(line,99,fi);
} while ((line[0] == '#') || (line[0] < ' '));
}
}
}
n++;
} while (1);
}
/* read the huffman decoder table */
int read_decoder_table(fi)
FILE *fi;
{
int n,i,nn,t;
unsigned int v0,v1;
char command[100],line[100];
for (n=0;nxlen-1;
unsigned int yl1 = h->ylen-1;
linbitsX = 0;
linbitsY = 0;
if (h->table == NULL) return;
if (((x < xl1) || (xl1==0)) && (y < yl1)) {
huffbits = h->table[x*(h->xlen)+y];
len = h->hlen[x*(h->xlen)+y];
putbits(bs,huffbits,len);
return;
}
else if (x >= xl1) {
linbitsX = x-xl1;
if (linbitsX > h->linmax) {
fprintf(stderr,"warning: Huffman X table overflow\n");
linbitsX= h->linmax;
};
if (y >= yl1) {
huffbits = h->table[(h->ylen)*(h->xlen)-1];
len = h->hlen[(h->ylen)*(h->xlen)-1];
putbits(bs,huffbits,len);
linbitsY = y-yl1;
if (linbitsY > h->linmax) {
fprintf(stderr,"warning: Huffman Y table overflow\n");
linbitsY = h->linmax;
};
if (h->linbits) {
putbits(bs,linbitsX,h->linbits);
putbits(bs,linbitsY,h->linbits);
}
}
else { /* x>= h->xlen, yylen */
huffbits = h->table[(h->ylen)*xl1+y];
len = h->hlen[(h->ylen)*xl1+y];
putbits(bs,huffbits,len);
if (h->linbits) {
putbits(bs,linbitsX,h->linbits);
}
}
}
else { /* ((x < h->xlen) && (y>=h->ylen)) */
huffbits = h->table[(h->ylen)*x+yl1];
len = h->hlen[(h->ylen)*x+yl1];
putbits(bs,huffbits,len);
linbitsY = y-yl1;
if (linbitsY > h->linmax) {
fprintf(stderr,"warning: Huffman Y table overflow\n");
linbitsY = h->linmax;
};
if (h->linbits) {
putbits(bs,linbitsY,h->linbits);
}
}
}
/* do the huffman-decoding */
/* note! for counta,countb -the 4 bit value is returned in y, discard x */
int huffman_decoder(h, x, y, v, w)
struct huffcodetab *h; /* pointer to huffman code record */
/* unsigned */ int *x; /* returns decoded x value */
/* unsigned */ int *y; /* returns decoded y value */
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;
}