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/*
* ARC - Archive utility - ARCUSQ
*
* Version 3.14, created on 07/25/86 at 13:04:19
*
* (C) COPYRIGHT 1985-87 by System Enhancement Associates.
* You may copy and distribute this program freely,
* under the terms of the General Public License.
*
* By: Thom Henderson
*
* Description: This file contains the routines used to expand a file which was
* packed using Huffman squeezing.
*
* Most of this code is taken from an USQ program by Richard Greenlaw, which was
* adapted to CI-C86 by Robert J. Beilstein.
*
* Language: Computer Innovations Optimizing C86
*/
#include <stdio.h>
#include "arc.h"
#include "proto.h"
VOID arcdie();
/* stuff for Huffman unsqueezing */
#define ERROR (-1)
#define SPEOF 256 /* special endfile token */
#define NUMVALS 257 /* 256 data values plus SPEOF */
extern struct nd { /* decoding tree */
int child[2]; /* left, right */
} node[NUMVALS]; /* use large buffer */
extern char *pinbuf;
extern u_char *outbuf, *outbeg, *outend;
static int bpos; /* last bit position read */
extern int curin; /* last byte value read */
static int numnodes; /* number of nodes in decode tree */
extern char *inbeg, *inend;
/* get a 16bit integer */
#define GET_INT(x) \
{ x = (u_char) (*inbeg++); \
x |= *inbeg++ << 8;}
VOID
init_usq(f) /* initialize Huffman unsqueezing */
FILE *f; /* file containing squeezed data */
{
int i; /* node index */
u_int inlen;
bpos = 99; /* force initial read */
inlen = getb_unp(f);
inbeg = pinbuf;
inend = &pinbuf[inlen];
GET_INT(numnodes);
if (numnodes < 0 || numnodes >= NUMVALS)
arcdie("File has an invalid decode tree");
/* initialize for possible empty tree (SPEOF only) */
node[0].child[0] = -(SPEOF + 1);
node[0].child[1] = -(SPEOF + 1);
for (i = 0; i < numnodes; ++i) { /* get decoding tree from
* file */
GET_INT(node[i].child[0]);
GET_INT(node[i].child[1]);
}
}
u_int
getb_usq(f) /* get byte from squeezed file */
FILE *f; /* file containing squeezed data */
{
int i; /* tree index */
u_int j;
outbeg = outbuf;
for (j = 0; j < MYBUF; j++) {
/* follow bit stream in tree to a leaf */
for (i = 0; i >= 0;) { /* work down(up?) from root */
if (++bpos > 7) {
if (inbeg >= inend) {
inend = &pinbuf[getb_unp(f)];
inbeg = pinbuf;
if (inend == inbeg) {
if (!curin)
j--;
return(j);
}
}
curin = *inbeg++;
bpos = 0;
/* move a level deeper in tree */
i = node[i].child[1 & curin];
} else
i = node[i].child[1 & (curin >>= 1)];
}
/* decode fake node index to original data value */
i = -(i + 1);
if (i != SPEOF)
*outbeg++ = i;
else
break;
}
/*NOTREACHED*/
return (j);
}
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