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/*
* $Header: arcusq.c,v 1.2 88/06/02 16:27:44 hyc Locked $
*/
/*
* ARC - Archive utility - ARCUSQ
*
* Version 3.14, created on 07/25/86 at 13:04:19
*
* (C) COPYRIGHT 1985 by System Enhancement Associates; ALL RIGHTS RESERVED
*
* 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"
void abort();
int getc_unp();
/* 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 */
static int bpos; /* last bit position read */
static int curin; /* last byte value read */
static int numnodes; /* number of nodes in decode tree */
static short
get_int(f) /* get a 16bit integer */
FILE *f; /* file to get it from */
{
int i,j;
i = getc_unp(f);
j = getc_unp(f) << 8;
return (i | j) & 0xFFFF;
}
void
init_usq(f) /* initialize Huffman unsqueezing */
FILE *f; /* file containing squeezed data */
{
int i; /* node index */
bpos = 99; /* force initial read */
numnodes = get_int(f);
if (numnodes < 0 || numnodes >= NUMVALS)
abort("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 */
node[i].child[0] = get_int(f);
node[i].child[1] = get_int(f);
}
}
int
getc_usq(f) /* get byte from squeezed file */
FILE *f; /* file containing squeezed data */
{
int i; /* tree index */
/* follow bit stream in tree to a leaf */
for (i = 0; i >= 0;) { /* work down(up?) from root */
if (++bpos > 7) {
if ((curin = getc_unp(f)) == ERROR)
return (ERROR);
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);
/* decode special endfile token to normal EOF */
i = (i == SPEOF) ? EOF : i;
return i;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.