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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.
---------------------------------------------------------------------------*/
#include "unzip.h"
/**************************************/
/* UnReduce Defines, Typedefs, etc. */
/**************************************/
#define DLE 144
typedef uch f_array[64]; /* for followers[256][64] */
static void LoadFollowers __((void));
/*******************************/
/* UnReduce Global Variables */
/*******************************/
#if defined(MALLOC_WORK) || defined(MTS)
f_array *followers; /* shared work space */
#else
f_array *followers = (f_array *) (slide + 0x4000);
#endif
uch Slen[256];
int factor;
int L_table[] =
{0, 0x7f, 0x3f, 0x1f, 0x0f};
int D_shift[] =
{0, 0x07, 0x06, 0x05, 0x04};
int D_mask[] =
{0, 0x01, 0x03, 0x07, 0x0f};
int 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() /* expand probabilistically reduced data */
{
register int lchar = 0;
int nchar;
int ExState = 0;
int V = 0;
int Len = 0;
long s = ucsize; /* number of bytes left to decompress */
unsigned w = 0; /* position in output window slide[] */
unsigned u = 1; /* true if slide[] unflushed */
#if defined(MALLOC_WORK) || defined(MTS)
followers = (f_array *)(slide + 0x4000);
#endif
factor = lrec.compression_method - 1;
LoadFollowers();
while (s > 0 /* && (!zipeof) */) {
if (Slen[lchar] == 0)
READBITS(8, nchar) /* ; */
else {
READBITS(1, nchar) /* ; */
if (nchar != 0)
READBITS(8, nchar) /* ; */
else {
int 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(slide, 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(slide, 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(slide, w, 0);
w = u = 0;
}
} while (n);
ExState = 0;
}
break;
}
/* store character for next iteration */
lchar = nchar;
}
/* flush out slide */
flush(slide, w, 0);
}
/******************************/
/* Function LoadFollowers() */
/******************************/
static void LoadFollowers()
{
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]) /* ; */
}
}
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