busybox/archival/libunarchive/uncompress.c

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#include "config.h"
#include "libbb.h"
#ifdef CONFIG_FEATURE_UNCOMPRESS
/* uncompress for busybox -- (c) 2002 Robert Griebl
*
* based on the original compress42.c source
* (see disclaimer below)
*/
/* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
*
* Authors:
* Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
* Jim McKie (decvax!mcvax!jim)
* Steve Davies (decvax!vax135!petsd!peora!srd)
* Ken Turkowski (decvax!decwrl!turtlevax!ken)
* James A. Woods (decvax!ihnp4!ames!jaw)
* Joe Orost (decvax!vax135!petsd!joe)
* Dave Mack (csu@alembic.acs.com)
* Peter Jannesen, Network Communication Systems
* (peter@ncs.nl)
*
* marc@suse.de : a small security fix for a buffer overflow
*
* [... History snipped ...]
*
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define IBUFSIZ 2048 /* Defailt input buffer size */
#define OBUFSIZ 2048 /* Default output buffer size */
/* Defines for third byte of header */
#define MAGIC_1 (char_type)'\037'/* First byte of compressed file */
#define MAGIC_2 (char_type)'\235'/* Second byte of compressed file */
#define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
/* Masks 0x20 and 0x40 are free. */
/* I think 0x20 should mean that there is */
/* a fourth header byte (for expansion). */
#define BLOCK_MODE 0x80 /* Block compresssion if table is full and */
/* compression rate is dropping flush tables */
/* the next two codes should not be changed lightly, as they must not */
/* lie within the contiguous general code space. */
#define FIRST 257 /* first free entry */
#define CLEAR 256 /* table clear output code */
#define INIT_BITS 9 /* initial number of bits/code */
/*
* machine variants which require cc -Dmachine: pdp11, z8000, DOS
*/
#define FAST
#define HBITS 17 /* 50% occupancy */
#define HSIZE (1<<HBITS)
#define HMASK (HSIZE-1)
#define HPRIME 9941
#define BITS 16
#undef MAXSEG_64K
typedef long int code_int;
typedef long int count_int;
typedef long int cmp_code_int;
typedef unsigned char char_type;
#define MAXCODE(n) (1L << (n))
int block_mode = BLOCK_MODE;/* Block compress mode -C compatible with 2.0*/
int maxbits = BITS; /* user settable max # bits/code */
int exit_code = -1; /* Exitcode of compress (-1 no file compressed) */
char_type inbuf[IBUFSIZ+64]; /* Input buffer */
char_type outbuf[OBUFSIZ+2048];/* Output buffer */
count_int htab[HSIZE];
unsigned short codetab[HSIZE];
#define htabof(i) htab[i]
#define codetabof(i) codetab[i]
#define tab_prefixof(i) codetabof(i)
#define tab_suffixof(i) ((char_type *)(htab))[i]
#define de_stack ((char_type *)&(htab[HSIZE-1]))
#define clear_htab() memset(htab, -1, sizeof(htab))
#define clear_tab_prefixof() memset(codetab, 0, 256);
/*
* Decompress stdin to stdout. 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. The tables used herein are shared
* with those of the compress() routine. See the definitions above.
*/
extern int uncompress(int fd_in, int fd_out)
{
char_type *stackp;
code_int code;
int finchar;
code_int oldcode;
code_int incode;
int inbits;
int posbits;
int outpos;
int insize;
int bitmask;
code_int free_ent;
code_int maxcode;
code_int maxmaxcode;
int n_bits;
int rsize = 0;
insize = 0;
inbuf [0] = xread_char(fd_in);
maxbits = inbuf[0] & BIT_MASK;
block_mode = inbuf[0] & BLOCK_MODE;
maxmaxcode = MAXCODE(maxbits);
if (maxbits > BITS)
{
fprintf(stderr, "compressed with %d bits, can only handle %d bits\n", maxbits, BITS);
return -1;
}
//fprintf(stderr, "Bits: %d, block_mode: %d\n", maxbits, block_mode );
maxcode = MAXCODE(n_bits = INIT_BITS)-1;
bitmask = (1<<n_bits)-1;
oldcode = -1;
finchar = 0;
outpos = 0;
posbits = 0<<3;
free_ent = ((block_mode) ? FIRST : 256);
clear_tab_prefixof(); /* As above, initialize the first
256 entries in the table. */
for (code = 255 ; code >= 0 ; --code)
tab_suffixof(code) = (char_type)code;
do
{
resetbuf: ;
{
int i;
int e;
int o;
e = insize-(o = (posbits>>3));
for (i = 0 ; i < e ; ++i)
inbuf[i] = inbuf[i+o];
insize = e;
posbits = 0;
}
if (insize < (int) sizeof(inbuf)-IBUFSIZ)
{
xread_all(fd_in, inbuf+insize, IBUFSIZ);
insize += rsize;
}
inbits = ((rsize > 0) ? (insize - insize%n_bits)<<3 :
(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;
}
{
char_type *p = &inbuf[posbits>>3];
code = ((((long)(p[0]))|((long)(p[1])<<8)|((long)(p[2])<<16))>>(posbits&0x7))&bitmask;
}
posbits += n_bits;
if (oldcode == -1)
{
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)
{
char_type *p;
posbits -= n_bits;
p = &inbuf[posbits>>3];
fprintf(stderr, "insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)\n", insize, posbits,
p[-1],p[0],p[1],p[2],p[3], (posbits&07));
fprintf(stderr, "uncompress: corrupt input\n");
return -1;
}
*--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)) >= OBUFSIZ)
{
do
{
if (i > OBUFSIZ-outpos) i = OBUFSIZ-outpos;
if (i > 0)
{
memcpy(outbuf+outpos, stackp, i);
outpos += i;
}
if (outpos >= OBUFSIZ)
{
write(fd_out, outbuf, 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 (outpos > 0) {
write(fd_out, outbuf, outpos);
}
return 0;
}
#endif