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unlzw.c
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unlzw.c
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/* unlzw.c -- decompress files in LZW format.
* The code in this file is directly derived from the public domain 'compress'
* written by Spencer Thomas, Joe Orost, James Woods, Jim McKie, Steve Davies,
* Ken Turkowski, Dave Mack and Peter Jannesen.
*
* This is a temporary version which will be rewritten in some future version
* to accommodate in-memory decompression.
*/
#include <config.h>
#include "tailor.h"
#include <unistd.h>
#include <fcntl.h>
#include "gzip.h"
#include "lzw.h"
typedef unsigned char char_type;
typedef long code_int;
typedef unsigned long count_int;
typedef unsigned short count_short;
typedef unsigned long cmp_code_int;
#define MAXCODE(n) (1L << (n))
#ifndef BYTEORDER
# define BYTEORDER 0000
#endif
#ifndef NOALLIGN
# define NOALLIGN 0
#endif
union bytes {
long word;
struct {
#if BYTEORDER == 4321
char_type b1;
char_type b2;
char_type b3;
char_type b4;
#else
#if BYTEORDER == 1234
char_type b4;
char_type b3;
char_type b2;
char_type b1;
#else
# undef BYTEORDER
int dummy;
#endif
#endif
} bytes;
};
#if BYTEORDER == 4321 && NOALLIGN == 1
# define input(b,o,c,n,m){ \
(c) = (*(long *)(&(b)[(o)>>3])>>((o)&0x7))&(m); \
(o) += (n); \
}
#else
# define input(b,o,c,n,m){ \
char_type *p = &(b)[(o)>>3]; \
(c) = ((((long)(p[0]))|((long)(p[1])<<8)| \
((long)(p[2])<<16))>>((o)&0x7))&(m); \
(o) += (n); \
}
#endif
#ifndef MAXSEG_64K
/* DECLARE(ush, tab_prefix, (1<<BITS)); -- prefix code */
# define tab_prefixof(i) tab_prefix[i]
# define clear_tab_prefixof() memzero(tab_prefix, 256);
#else
/* DECLARE(ush, tab_prefix0, (1<<(BITS-1)); -- prefix for even codes */
/* DECLARE(ush, tab_prefix1, (1<<(BITS-1)); -- prefix for odd codes */
ush *tab_prefix[2];
# define tab_prefixof(i) tab_prefix[(i)&1][(i)>>1]
# define clear_tab_prefixof() \
memzero(tab_prefix0, 128), \
memzero(tab_prefix1, 128);
#endif
#define de_stack ((char_type *)(&d_buf[DIST_BUFSIZE-1]))
#define tab_suffixof(i) tab_suffix[i]
int block_mode = BLOCK_MODE; /* block compress mode -C compatible with 2.0 */
/* ============================================================================
* Decompress in to out. This routine adapts to the codes in the
* file building the "string" table on-the-fly; requiring no table to
* be stored in the compressed file.
* IN assertions: the buffer inbuf contains already the beginning of
* the compressed data, from offsets iptr to insize-1 included.
* The magic header has already been checked and skipped.
* bytes_in and bytes_out have been initialized.
*/
int unlzw(in, out)
int in, out; /* input and output file descriptors */
{
char_type *stackp;
code_int code;
int finchar;
code_int oldcode;
code_int incode;
long inbits;
long posbits;
int outpos;
/* int insize; (global) */
unsigned bitmask;
code_int free_ent;
code_int maxcode;
code_int maxmaxcode;
int n_bits;
int rsize;
#ifdef MAXSEG_64K
tab_prefix[0] = tab_prefix0;
tab_prefix[1] = tab_prefix1;
#endif
maxbits = get_byte();
block_mode = maxbits & BLOCK_MODE;
if ((maxbits & LZW_RESERVED) != 0) {
WARN((stderr, "\n%s: %s: warning, unknown flags 0x%x\n",
program_name, ifname, maxbits & LZW_RESERVED));
}
maxbits &= BIT_MASK;
maxmaxcode = MAXCODE(maxbits);
if (maxbits > BITS) {
fprintf(stderr,
"\n%s: %s: compressed with %d bits, can only handle %d bits\n",
program_name, ifname, maxbits, BITS);
exit_code = ERROR;
return ERROR;
}
rsize = insize;
maxcode = MAXCODE(n_bits = INIT_BITS)-1;
bitmask = (1<<n_bits)-1;
oldcode = -1;
finchar = 0;
outpos = 0;
posbits = inptr<<3;
free_ent = ((block_mode) ? FIRST : 256);
clear_tab_prefixof(); /* Initialize the first 256 entries in the table. */
for (code = 255 ; code >= 0 ; --code) {
tab_suffixof(code) = (char_type)code;
}
do {
int i;
int e;
int o;
resetbuf:
o = posbits >> 3;
e = o <= insize ? insize - o : 0;
for (i = 0 ; i < e ; ++i) {
inbuf[i] = inbuf[i+o];
}
insize = e;
posbits = 0;
if (insize < INBUF_EXTRA) {
rsize = read_buffer (in, (char *) inbuf + insize, INBUFSIZ);
if (rsize == -1) {
read_error();
}
insize += rsize;
bytes_in += (off_t)rsize;
}
inbits = ((rsize != 0) ? ((long)insize - insize%n_bits)<<3 :
((long)insize<<3)-(n_bits-1));
while (inbits > posbits) {
if (free_ent > maxcode) {
posbits = ((posbits-1) +
((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
++n_bits;
if (n_bits == maxbits) {
maxcode = maxmaxcode;
} else {
maxcode = MAXCODE(n_bits)-1;
}
bitmask = (1<<n_bits)-1;
goto resetbuf;
}
input(inbuf,posbits,code,n_bits,bitmask);
Tracev((stderr, "%ld ", code));
if (oldcode == -1) {
if (256 <= code)
gzip_error ("corrupt input.");
outbuf[outpos++] = (char_type)(finchar = (int)(oldcode=code));
continue;
}
if (code == CLEAR && block_mode) {
clear_tab_prefixof();
free_ent = FIRST - 1;
posbits = ((posbits-1) +
((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
maxcode = MAXCODE(n_bits = INIT_BITS)-1;
bitmask = (1<<n_bits)-1;
goto resetbuf;
}
incode = code;
stackp = de_stack;
if (code >= free_ent) { /* Special case for KwKwK string. */
if (code > free_ent) {
#ifdef DEBUG
char_type *p;
posbits -= n_bits;
p = &inbuf[posbits>>3];
fprintf(stderr,
"code:%ld free_ent:%ld n_bits:%d insize:%u\n",
code, free_ent, n_bits, insize);
fprintf(stderr,
"posbits:%ld inbuf:%02X %02X %02X %02X %02X\n",
posbits, p[-1],p[0],p[1],p[2],p[3]);
#endif
if (!test && outpos > 0) {
write_buf(out, (char*)outbuf, outpos);
bytes_out += (off_t)outpos;
}
gzip_error (to_stdout
? "corrupt input."
: "corrupt input. Use zcat to recover some data.");
}
*--stackp = (char_type)finchar;
code = oldcode;
}
while ((cmp_code_int)code >= (cmp_code_int)256) {
/* Generate output characters in reverse order */
*--stackp = tab_suffixof(code);
code = tab_prefixof(code);
}
*--stackp = (char_type)(finchar = tab_suffixof(code));
/* And put them out in forward order */
{
int i;
if (outpos+(i = (de_stack-stackp)) >= OUTBUFSIZ) {
do {
if (i > OUTBUFSIZ-outpos) i = OUTBUFSIZ-outpos;
if (i > 0) {
memcpy(outbuf+outpos, stackp, i);
outpos += i;
}
if (outpos >= OUTBUFSIZ) {
if (!test) {
write_buf(out, (char*)outbuf, outpos);
bytes_out += (off_t)outpos;
}
outpos = 0;
}
stackp+= i;
} while ((i = (de_stack-stackp)) > 0);
} else {
memcpy(outbuf+outpos, stackp, i);
outpos += i;
}
}
if ((code = free_ent) < maxmaxcode) { /* Generate the new entry. */
tab_prefixof(code) = (unsigned short)oldcode;
tab_suffixof(code) = (char_type)finchar;
free_ent = code+1;
}
oldcode = incode; /* Remember previous code. */
}
} while (rsize != 0);
if (!test && outpos > 0) {
write_buf(out, (char*)outbuf, outpos);
bytes_out += (off_t)outpos;
}
return OK;
}