1 /* vi: set sw=4 ts=4: */
4 /* uncompress for busybox -- (c) 2002 Robert Griebl
6 * based on the original compress42.c source
7 * (see disclaimer below)
11 /* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
14 * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
15 * Jim McKie (decvax!mcvax!jim)
16 * Steve Davies (decvax!vax135!petsd!peora!srd)
17 * Ken Turkowski (decvax!decwrl!turtlevax!ken)
18 * James A. Woods (decvax!ihnp4!ames!jaw)
19 * Joe Orost (decvax!vax135!petsd!joe)
20 * Dave Mack (csu@alembic.acs.com)
21 * Peter Jannesen, Network Communication Systems
24 * marc@suse.de : a small security fix for a buffer overflow
26 * [... History snipped ...]
33 /* Default input buffer size */
36 /* Default output buffer size */
39 /* Defines for third byte of header */
40 #define MAGIC_1 (char_type)'\037' /* First byte of compressed file */
41 #define MAGIC_2 (char_type)'\235' /* Second byte of compressed file */
42 #define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
43 /* Masks 0x20 and 0x40 are free. */
44 /* I think 0x20 should mean that there is */
45 /* a fourth header byte (for expansion). */
46 #define BLOCK_MODE 0x80 /* Block compresssion if table is full and */
47 /* compression rate is dropping flush tables */
48 /* the next two codes should not be changed lightly, as they must not */
49 /* lie within the contiguous general code space. */
50 #define FIRST 257 /* first free entry */
51 #define CLEAR 256 /* table clear output code */
53 #define INIT_BITS 9 /* initial number of bits/code */
56 /* machine variants which require cc -Dmachine: pdp11, z8000, DOS */
59 #define HBITS 17 /* 50% occupancy */
60 #define HSIZE (1<<HBITS)
61 #define HMASK (HSIZE-1)
65 #define MAXCODE(n) (1L << (n))
67 /* Block compress mode -C compatible with 2.0 */
68 static int block_mode = BLOCK_MODE;
70 /* user settable max # bits/code */
71 static int maxbits = BITS;
73 #define htabof(i) htab[i]
74 #define codetabof(i) codetab[i]
75 #define tab_prefixof(i) codetabof(i)
76 #define tab_suffixof(i) ((unsigned char *)(htab))[i]
77 #define de_stack ((unsigned char *)&(htab[HSIZE-1]))
78 #define clear_htab() memset(htab, -1, HSIZE)
79 #define clear_tab_prefixof() memset(codetab, 0, 256);
83 * Decompress stdin to stdout. This routine adapts to the codes in the
84 * file building the "string" table on-the-fly; requiring no table to
85 * be stored in the compressed file. The tables used herein are shared
86 * with those of the compress() routine. See the definitions above.
89 int uncompress(int fd_in, int fd_out)
91 unsigned char *stackp;
106 RESERVE_CONFIG_UBUFFER(inbuf, IBUFSIZ + 64);
107 RESERVE_CONFIG_UBUFFER(outbuf, OBUFSIZ + 2048);
108 unsigned char htab[HSIZE];
109 unsigned short codetab[HSIZE];
110 memset(inbuf, 0, IBUFSIZ + 64);
111 memset(outbuf, 0, OBUFSIZ + 2048);
115 inbuf[0] = xread_char(fd_in);
117 maxbits = inbuf[0] & BIT_MASK;
118 block_mode = inbuf[0] & BLOCK_MODE;
119 maxmaxcode = MAXCODE(maxbits);
121 if (maxbits > BITS) {
122 bb_error_msg("compressed with %d bits, can only handle %d bits", maxbits,
127 maxcode = MAXCODE(n_bits = INIT_BITS) - 1;
128 bitmask = (1 << n_bits) - 1;
134 free_ent = ((block_mode) ? FIRST : 256);
136 /* As above, initialize the first 256 entries in the table. */
137 clear_tab_prefixof();
139 for (code = 255; code >= 0; --code) {
140 tab_suffixof(code) = (unsigned char) code;
150 e = insize - (o = (posbits >> 3));
152 for (i = 0; i < e; ++i)
153 inbuf[i] = inbuf[i + o];
159 if (insize < (int) (IBUFSIZ + 64) - IBUFSIZ) {
160 rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ);
164 inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
165 (insize << 3) - (n_bits - 1));
167 while (inbits > posbits) {
168 if (free_ent > maxcode) {
172 (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
174 if (n_bits == maxbits) {
175 maxcode = maxmaxcode;
177 maxcode = MAXCODE(n_bits) - 1;
179 bitmask = (1 << n_bits) - 1;
183 unsigned char *p = &inbuf[posbits >> 3];
186 ((((long) (p[0])) | ((long) (p[1]) << 8) |
187 ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask;
193 outbuf[outpos++] = (unsigned char) (finchar =
194 (int) (oldcode = code));
198 if (code == CLEAR && block_mode) {
199 clear_tab_prefixof();
200 free_ent = FIRST - 1;
204 (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
205 maxcode = MAXCODE(n_bits = INIT_BITS) - 1;
206 bitmask = (1 << n_bits) - 1;
213 /* Special case for KwKwK string. */
214 if (code >= free_ent) {
215 if (code > free_ent) {
219 p = &inbuf[posbits >> 3];
222 ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
223 insize, posbits, p[-1], p[0], p[1], p[2], p[3],
225 bb_error_msg("uncompress: corrupt input");
229 *--stackp = (unsigned char) finchar;
233 /* Generate output characters in reverse order */
234 while ((long int) code >= (long int) 256) {
235 *--stackp = tab_suffixof(code);
236 code = tab_prefixof(code);
239 *--stackp = (unsigned char) (finchar = tab_suffixof(code));
241 /* And put them out in forward order */
245 if (outpos + (i = (de_stack - stackp)) >= OBUFSIZ) {
247 if (i > OBUFSIZ - outpos) {
248 i = OBUFSIZ - outpos;
252 memcpy(outbuf + outpos, stackp, i);
256 if (outpos >= OBUFSIZ) {
257 write(fd_out, outbuf, outpos);
261 } while ((i = (de_stack - stackp)) > 0);
263 memcpy(outbuf + outpos, stackp, i);
268 /* Generate the new entry. */
269 if ((code = free_ent) < maxmaxcode) {
270 tab_prefixof(code) = (unsigned short) oldcode;
271 tab_suffixof(code) = (unsigned char) finchar;
275 /* Remember previous code. */
282 write(fd_out, outbuf, outpos);
285 RELEASE_CONFIG_BUFFER(inbuf);
286 RELEASE_CONFIG_BUFFER(outbuf);