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/*---------------------------------------------------------------------------
unreduce.c
The Reducing algorithm is actually a combination of two distinct algorithms.
The first algorithm compresses repeated byte sequences, and the second al-
gorithm takes the compressed stream from the first algorithm and applies a
probabilistic compression method.
* Copyright 1989 Samuel H. Smith; All rights reserved
*
* Do not distribute modified versions without my permission.
* Do not remove or alter this notice or any other copyright notice.
* If you use this in your own program you must distribute source code.
* Do not use any of this in a commercial product.
See the accompanying file "COPYING" in UnZip source and binary distributions
for further information. This code is NOT used unless USE_SMITH_CODE is
explicitly defined (==> COPYRIGHT_CLEAN is not defined).
---------------------------------------------------------------------------*/
#define UNZIP_INTERNAL
#include "unzip.h" /* defines COPYRIGHT_CLEAN by default */
#ifndef COPYRIGHT_CLEAN
/**************************************/
/* UnReduce Defines, Typedefs, etc. */
/**************************************/
#define DLE 144
typedef uch f_array[64]; /* for followers[256][64] */
/******************************/
/* UnReduce Local Functions */
/******************************/
static void LoadFollowers OF((__GPRO__ f_array *followers, uch *Slen));
/*******************************/
/* UnReduce Global Constants */
/*******************************/
static ZCONST shrint L_table[] =
{0, 0x7f, 0x3f, 0x1f, 0x0f};
static ZCONST shrint D_shift[] =
{0, 0x07, 0x06, 0x05, 0x04};
static ZCONST shrint D_mask[] =
{0, 0x01, 0x03, 0x07, 0x0f};
static ZCONST shrint B_table[] =
{8, 1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8};
/*************************/
/* Function unreduce() */
/*************************/
void unreduce(__G) /* expand probabilistically reduced data */
__GDEF
{
register int lchar = 0;
shrint nchar;
shrint ExState = 0;
shrint V = 0;
shrint Len = 0;
long s = G.ucsize; /* number of bytes left to decompress */
unsigned w = 0; /* position in output window slide[] */
unsigned u = 1; /* true if slide[] unflushed */
uch Slen[256];
f_array *followers = (f_array *)(slide + 0x4000);
int factor = G.lrec.compression_method - 1;
LoadFollowers(__G__ followers, Slen);
while (s > 0 /* && (!zipeof) */) {
if (Slen[lchar] == 0)
READBITS(8, nchar) /* ; */
else {
READBITS(1, nchar) /* ; */
if (nchar != 0)
READBITS(8, nchar) /* ; */
else {
shrint follower;
int bitsneeded = B_table[Slen[lchar]];
READBITS(bitsneeded, follower) /* ; */
nchar = followers[lchar][follower];
}
}
/* expand the resulting byte */
switch (ExState) {
case 0:
if (nchar != DLE) {
s--;
slide[w++] = (uch)nchar;
if (w == 0x4000) {
flush(__G__ slide, (ulg)w, 0);
w = u = 0;
}
}
else
ExState = 1;
break;
case 1:
if (nchar != 0) {
V = nchar;
Len = V & L_table[factor];
if (Len == L_table[factor])
ExState = 2;
else
ExState = 3;
} else {
s--;
slide[w++] = DLE;
if (w == 0x4000)
{
flush(__G__ slide, (ulg)w, 0);
w = u = 0;
}
ExState = 0;
}
break;
case 2:{
Len += nchar;
ExState = 3;
}
break;
case 3:{
register unsigned e;
register unsigned n = Len + 3;
register unsigned d = w - ((((V >> D_shift[factor]) &
D_mask[factor]) << 8) + nchar + 1);
s -= n;
do {
n -= (e = (e = 0x4000 - ((d &= 0x3fff) > w ? d : w)) > n ?
n : e);
if (u && w <= d)
{
memzero(slide + w, e);
w += e;
d += e;
}
else
if (w - d < e) /* (assume unsigned comparison) */
do { /* slow to avoid memcpy() overlap */
slide[w++] = slide[d++];
} while (--e);
else
{
memcpy(slide + w, slide + d, e);
w += e;
d += e;
}
if (w == 0x4000)
{
flush(__G__ slide, (ulg)w, 0);
w = u = 0;
}
} while (n);
ExState = 0;
}
break;
}
/* store character for next iteration */
lchar = nchar;
}
/* flush out slide */
flush(__G__ slide, (ulg)w, 0);
}
/******************************/
/* Function LoadFollowers() */
/******************************/
static void LoadFollowers(__G__ followers, Slen)
__GDEF
f_array *followers;
uch *Slen;
{
register int x;
register int i;
for (x = 255; x >= 0; x--) {
READBITS(6, Slen[x]) /* ; */
for (i = 0; (uch)i < Slen[x]; i++)
READBITS(8, followers[x][i]) /* ; */
}
}
#endif /* !COPYRIGHT_CLEAN */
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