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-rw-r--r--libbb/uncompress.c307
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diff --git a/libbb/uncompress.c b/libbb/uncompress.c
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1#include "config.h"
2#include "libbb.h"
3
4#ifdef CONFIG_FEATURE_UNCOMPRESS
5
6/* uncompress for busybox -- (c) 2002 Robert Griebl
7 *
8 * based on the original compress42.c source
9 * (see disclaimer below)
10 */
11
12
13/* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
14 *
15 * Authors:
16 * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
17 * Jim McKie (decvax!mcvax!jim)
18 * Steve Davies (decvax!vax135!petsd!peora!srd)
19 * Ken Turkowski (decvax!decwrl!turtlevax!ken)
20 * James A. Woods (decvax!ihnp4!ames!jaw)
21 * Joe Orost (decvax!vax135!petsd!joe)
22 * Dave Mack (csu@alembic.acs.com)
23 * Peter Jannesen, Network Communication Systems
24 * (peter@ncs.nl)
25 *
26 * marc@suse.de : a small security fix for a buffer overflow
27 *
28 * [... History snipped ...]
29 *
30 */
31#include <stdio.h>
32#include <string.h>
33#include <unistd.h>
34
35#define IBUFSIZ 2048 /* Defailt input buffer size */
36#define OBUFSIZ 2048 /* Default output buffer size */
37
38 /* Defines for third byte of header */
39#define MAGIC_1 (char_type)'\037'/* First byte of compressed file */
40#define MAGIC_2 (char_type)'\235'/* Second byte of compressed file */
41#define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
42 /* Masks 0x20 and 0x40 are free. */
43 /* I think 0x20 should mean that there is */
44 /* a fourth header byte (for expansion). */
45#define BLOCK_MODE 0x80 /* Block compresssion if table is full and */
46 /* compression rate is dropping flush tables */
47
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 */
52
53#define INIT_BITS 9 /* initial number of bits/code */
54
55
56/*
57 * machine variants which require cc -Dmachine: pdp11, z8000, DOS
58 */
59#define FAST
60
61#define HBITS 17 /* 50% occupancy */
62#define HSIZE (1<<HBITS)
63#define HMASK (HSIZE-1)
64#define HPRIME 9941
65#define BITS 16
66#undef MAXSEG_64K
67
68typedef long int code_int;
69
70typedef long int count_int;
71typedef long int cmp_code_int;
72
73typedef unsigned char char_type;
74
75#define MAXCODE(n) (1L << (n))
76
77
78
79int block_mode = BLOCK_MODE;/* Block compress mode -C compatible with 2.0*/
80int maxbits = BITS; /* user settable max # bits/code */
81int exit_code = -1; /* Exitcode of compress (-1 no file compressed) */
82
83char_type inbuf[IBUFSIZ+64]; /* Input buffer */
84char_type outbuf[OBUFSIZ+2048];/* Output buffer */
85
86
87count_int htab[HSIZE];
88unsigned short codetab[HSIZE];
89
90#define htabof(i) htab[i]
91#define codetabof(i) codetab[i]
92#define tab_prefixof(i) codetabof(i)
93#define tab_suffixof(i) ((char_type *)(htab))[i]
94#define de_stack ((char_type *)&(htab[HSIZE-1]))
95#define clear_htab() memset(htab, -1, sizeof(htab))
96#define clear_tab_prefixof() memset(codetab, 0, 256);
97
98
99/*
100 * Decompress stdin to stdout. This routine adapts to the codes in the
101 * file building the "string" table on-the-fly; requiring no table to
102 * be stored in the compressed file. The tables used herein are shared
103 * with those of the compress() routine. See the definitions above.
104 */
105
106extern int uncompress(int fd_in, int fd_out)
107{
108 char_type *stackp;
109 code_int code;
110 int finchar;
111 code_int oldcode;
112 code_int incode;
113 int inbits;
114 int posbits;
115 int outpos;
116 int insize;
117 int bitmask;
118 code_int free_ent;
119 code_int maxcode;
120 code_int maxmaxcode;
121 int n_bits;
122 int rsize = 0;
123
124 insize = 0;
125
126 inbuf [0] = xread_char(fd_in);
127
128 maxbits = inbuf[0] & BIT_MASK;
129 block_mode = inbuf[0] & BLOCK_MODE;
130 maxmaxcode = MAXCODE(maxbits);
131
132 if (maxbits > BITS)
133 {
134 fprintf(stderr, "compressed with %d bits, can only handle %d bits\n", maxbits, BITS);
135 return -1;
136 }
137
138 //fprintf(stderr, "Bits: %d, block_mode: %d\n", maxbits, block_mode );
139
140 maxcode = MAXCODE(n_bits = INIT_BITS)-1;
141 bitmask = (1<<n_bits)-1;
142 oldcode = -1;
143 finchar = 0;
144 outpos = 0;
145 posbits = 0<<3;
146
147 free_ent = ((block_mode) ? FIRST : 256);
148
149 clear_tab_prefixof(); /* As above, initialize the first
150 256 entries in the table. */
151
152 for (code = 255 ; code >= 0 ; --code)
153 tab_suffixof(code) = (char_type)code;
154
155 do
156 {
157resetbuf: ;
158 {
159 int i;
160 int e;
161 int o;
162
163 e = insize-(o = (posbits>>3));
164
165 for (i = 0 ; i < e ; ++i)
166 inbuf[i] = inbuf[i+o];
167
168 insize = e;
169 posbits = 0;
170 }
171
172 if (insize < (int) sizeof(inbuf)-IBUFSIZ)
173 {
174 xread_all(fd_in, inbuf+insize, IBUFSIZ);
175 insize += rsize;
176 }
177
178 inbits = ((rsize > 0) ? (insize - insize%n_bits)<<3 :
179 (insize<<3)-(n_bits-1));
180
181 while (inbits > posbits)
182 {
183 if (free_ent > maxcode)
184 {
185 posbits = ((posbits-1) + ((n_bits<<3) -
186 (posbits-1+(n_bits<<3))%(n_bits<<3)));
187
188 ++n_bits;
189 if (n_bits == maxbits)
190 maxcode = maxmaxcode;
191 else
192 maxcode = MAXCODE(n_bits)-1;
193
194 bitmask = (1<<n_bits)-1;
195 goto resetbuf;
196 }
197
198
199 {
200 char_type *p = &inbuf[posbits>>3];
201 code = ((((long)(p[0]))|((long)(p[1])<<8)|((long)(p[2])<<16))>>(posbits&0x7))&bitmask;
202 }
203 posbits += n_bits;
204
205
206 if (oldcode == -1)
207 {
208 outbuf[outpos++] = (char_type)(finchar = (int)(oldcode = code));
209 continue;
210 }
211
212 if (code == CLEAR && block_mode)
213 {
214 clear_tab_prefixof();
215 free_ent = FIRST - 1;
216 posbits = ((posbits-1) + ((n_bits<<3) -
217 (posbits-1+(n_bits<<3))%(n_bits<<3)));
218 maxcode = MAXCODE(n_bits = INIT_BITS)-1;
219 bitmask = (1<<n_bits)-1;
220 goto resetbuf;
221 }
222
223 incode = code;
224 stackp = de_stack;
225
226 if (code >= free_ent) /* Special case for KwKwK string. */
227 {
228 if (code > free_ent)
229 {
230 char_type *p;
231
232 posbits -= n_bits;
233 p = &inbuf[posbits>>3];
234
235 fprintf(stderr, "insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)\n", insize, posbits,
236 p[-1],p[0],p[1],p[2],p[3], (posbits&07));
237 fprintf(stderr, "uncompress: corrupt input\n");
238 return -1;
239 }
240
241 *--stackp = (char_type)finchar;
242 code = oldcode;
243 }
244
245 while ((cmp_code_int)code >= (cmp_code_int)256)
246 { /* Generate output characters in reverse order */
247 *--stackp = tab_suffixof(code);
248 code = tab_prefixof(code);
249 }
250
251 *--stackp = (char_type)(finchar = tab_suffixof(code));
252
253 /* And put them out in forward order */
254
255 {
256 int i;
257
258 if (outpos+(i = (de_stack-stackp)) >= OBUFSIZ)
259 {
260 do
261 {
262 if (i > OBUFSIZ-outpos) i = OBUFSIZ-outpos;
263
264 if (i > 0)
265 {
266 memcpy(outbuf+outpos, stackp, i);
267 outpos += i;
268 }
269
270 if (outpos >= OBUFSIZ)
271 {
272 write(fd_out, outbuf, outpos);
273 outpos = 0;
274 }
275 stackp+= i;
276 }
277 while ((i = (de_stack-stackp)) > 0);
278 }
279 else
280 {
281 memcpy(outbuf+outpos, stackp, i);
282 outpos += i;
283 }
284 }
285
286 if ((code = free_ent) < maxmaxcode) /* Generate the new entry. */
287 {
288 tab_prefixof(code) = (unsigned short)oldcode;
289 tab_suffixof(code) = (char_type)finchar;
290 free_ent = code+1;
291 }
292
293 oldcode = incode; /* Remember previous code. */
294 }
295
296 }
297 while (rsize > 0);
298
299 if (outpos > 0) {
300 write(fd_out, outbuf, outpos);
301 }
302
303 return 0;
304}
305
306
307#endif
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