1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /* inffast.c -- fast decoding
26 * Copyright (C) 1995-2008, 2010 Mark Adler
27 * For conditions of distribution and use, see copyright notice in zlib.h
28 */
29
30 #include "zutil.h"
31 #include "inftrees.h"
32 #include "inflate.h"
33 #include "inffast.h"
34
35 #ifndef ASMINF
36
37 /* Allow machine dependent optimization for post-increment or pre-increment.
38 Based on testing to date,
39 Pre-increment preferred for:
40 - PowerPC G3 (Adler)
41 - MIPS R5000 (Randers-Pehrson)
42 Post-increment preferred for:
43 - none
44 No measurable difference:
45 - Pentium III (Anderson)
46 - M68060 (Nikl)
47 */
48 #ifdef POSTINC
49 # define OFF 0
50 # define PUP(a) *(a)++
51 #else
52 # define OFF 1
53 # define PUP(a) *++(a)
54 #endif
55
56 /*
57 Decode literal, length, and distance codes and write out the resulting
58 literal and match bytes until either not enough input or output is
59 available, an end-of-block is encountered, or a data error is encountered.
60 When large enough input and output buffers are supplied to inflate(), for
61 example, a 16K input buffer and a 64K output buffer, more than 95% of the
62 inflate execution time is spent in this routine.
63
64 Entry assumptions:
65
66 state->mode == LEN
67 strm->avail_in >= 6
68 strm->avail_out >= 258
69 start >= strm->avail_out
70 state->bits < 8
71
72 On return, state->mode is one of:
73
74 LEN -- ran out of enough output space or enough available input
75 TYPE -- reached end of block code, inflate() to interpret next block
76 BAD -- error in block data
77
78 Notes:
79
80 - The maximum input bits used by a length/distance pair is 15 bits for the
81 length code, 5 bits for the length extra, 15 bits for the distance code,
82 and 13 bits for the distance extra. This totals 48 bits, or six bytes.
83 Therefore if strm->avail_in >= 6, then there is enough input to avoid
84 checking for available input while decoding.
85
86 - The maximum bytes that a single length/distance pair can output is 258
87 bytes, which is the maximum length that can be coded. inflate_fast()
88 requires strm->avail_out >= 258 for each loop to avoid checking for
89 output space.
90 */
91 void ZLIB_INTERNAL inflate_fast(strm, start)
92 z_streamp strm;
93 unsigned start; /* inflate()'s starting value for strm->avail_out */
94 {
95 struct inflate_state FAR *state;
96 unsigned char FAR *in; /* local strm->next_in */
97 unsigned char FAR *last; /* while in < last, enough input available */
98 unsigned char FAR *out; /* local strm->next_out */
99 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */
100 unsigned char FAR *end; /* while out < end, enough space available */
101 #ifdef INFLATE_STRICT
102 unsigned dmax; /* maximum distance from zlib header */
103 #endif
104 unsigned wsize; /* window size or zero if not using window */
105 unsigned whave; /* valid bytes in the window */
106 unsigned wnext; /* window write index */
107 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */
108 unsigned long hold; /* local strm->hold */
109 unsigned bits; /* local strm->bits */
110 code const FAR *lcode; /* local strm->lencode */
111 code const FAR *dcode; /* local strm->distcode */
112 unsigned lmask; /* mask for first level of length codes */
113 unsigned dmask; /* mask for first level of distance codes */
114 code here; /* retrieved table entry */
115 unsigned op; /* code bits, operation, extra bits, or */
116 /* window position, window bytes to copy */
117 unsigned len; /* match length, unused bytes */
118 unsigned dist; /* match distance */
119 unsigned char FAR *from; /* where to copy match from */
120
121 /* copy state to local variables */
122 state = (struct inflate_state FAR *)strm->state;
123 in = strm->next_in - OFF;
124 last = in + (strm->avail_in - 5);
125 out = strm->next_out - OFF;
126 beg = out - (start - strm->avail_out);
127 end = out + (strm->avail_out - 257);
128 #ifdef INFLATE_STRICT
129 dmax = state->dmax;
130 #endif
131 wsize = state->wsize;
132 whave = state->whave;
133 wnext = state->wnext;
134 window = state->window;
135 hold = state->hold;
136 bits = state->bits;
137 lcode = state->lencode;
138 dcode = state->distcode;
139 lmask = (1U << state->lenbits) - 1;
140 dmask = (1U << state->distbits) - 1;
141
142 /* decode literals and length/distances until end-of-block or not enough
143 input data or output space */
144 do {
145 if (bits < 15) {
146 hold += (unsigned long)(PUP(in)) << bits;
147 bits += 8;
148 hold += (unsigned long)(PUP(in)) << bits;
149 bits += 8;
150 }
151 here = lcode[hold & lmask];
152 dolen:
153 op = (unsigned)(here.bits);
154 hold >>= op;
155 bits -= op;
156 op = (unsigned)(here.op);
157 if (op == 0) { /* literal */
158 Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ?
159 "inflate: literal '%c'\n" :
160 "inflate: literal 0x%02x\n", here.val));
161 PUP(out) = (unsigned char)(here.val);
162 }
163 else if (op & 16) { /* length base */
164 len = (unsigned)(here.val);
165 op &= 15; /* number of extra bits */
166 if (op) {
167 if (bits < op) {
168 hold += (unsigned long)(PUP(in)) << bits;
169 bits += 8;
170 }
171 len += (unsigned)hold & ((1U << op) - 1);
172 hold >>= op;
173 bits -= op;
174 }
175 Tracevv((stderr, "inflate: length %u\n", len));
176 if (bits < 15) {
177 hold += (unsigned long)(PUP(in)) << bits;
178 bits += 8;
179 hold += (unsigned long)(PUP(in)) << bits;
180 bits += 8;
181 }
182 here = dcode[hold & dmask];
183 dodist:
184 op = (unsigned)(here.bits);
185 hold >>= op;
186 bits -= op;
187 op = (unsigned)(here.op);
188 if (op & 16) { /* distance base */
189 dist = (unsigned)(here.val);
190 op &= 15; /* number of extra bits */
191 if (bits < op) {
192 hold += (unsigned long)(PUP(in)) << bits;
193 bits += 8;
194 if (bits < op) {
195 hold += (unsigned long)(PUP(in)) << bits;
196 bits += 8;
197 }
198 }
199 dist += (unsigned)hold & ((1U << op) - 1);
200 #ifdef INFLATE_STRICT
201 if (dist > dmax) {
202 strm->msg = (char *)"invalid distance too far back";
203 state->mode = BAD;
204 break;
205 }
206 #endif
207 hold >>= op;
208 bits -= op;
209 Tracevv((stderr, "inflate: distance %u\n", dist));
210 op = (unsigned)(out - beg); /* max distance in output */
211 if (dist > op) { /* see if copy from window */
212 op = dist - op; /* distance back in window */
213 if (op > whave) {
214 if (state->sane) {
215 strm->msg =
216 (char *)"invalid distance too far back";
217 state->mode = BAD;
218 break;
219 }
220 #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
221 if (len <= op - whave) {
222 do {
223 PUP(out) = 0;
224 } while (--len);
225 continue;
226 }
227 len -= op - whave;
228 do {
229 PUP(out) = 0;
230 } while (--op > whave);
231 if (op == 0) {
232 from = out - dist;
233 do {
234 PUP(out) = PUP(from);
235 } while (--len);
236 continue;
237 }
238 #endif
239 }
240 from = window - OFF;
241 if (wnext == 0) { /* very common case */
242 from += wsize - op;
243 if (op < len) { /* some from window */
244 len -= op;
245 do {
246 PUP(out) = PUP(from);
247 } while (--op);
248 from = out - dist; /* rest from output */
249 }
250 }
251 else if (wnext < op) { /* wrap around window */
252 from += wsize + wnext - op;
253 op -= wnext;
254 if (op < len) { /* some from end of window */
255 len -= op;
256 do {
257 PUP(out) = PUP(from);
258 } while (--op);
259 from = window - OFF;
260 if (wnext < len) { /* some from start of window */
261 op = wnext;
262 len -= op;
263 do {
264 PUP(out) = PUP(from);
265 } while (--op);
266 from = out - dist; /* rest from output */
267 }
268 }
269 }
270 else { /* contiguous in window */
271 from += wnext - op;
272 if (op < len) { /* some from window */
273 len -= op;
274 do {
275 PUP(out) = PUP(from);
276 } while (--op);
277 from = out - dist; /* rest from output */
278 }
279 }
280 while (len > 2) {
281 PUP(out) = PUP(from);
282 PUP(out) = PUP(from);
283 PUP(out) = PUP(from);
284 len -= 3;
285 }
286 if (len) {
287 PUP(out) = PUP(from);
288 if (len > 1)
289 PUP(out) = PUP(from);
290 }
291 }
292 else {
293 from = out - dist; /* copy direct from output */
294 do { /* minimum length is three */
295 PUP(out) = PUP(from);
296 PUP(out) = PUP(from);
297 PUP(out) = PUP(from);
298 len -= 3;
299 } while (len > 2);
300 if (len) {
301 PUP(out) = PUP(from);
302 if (len > 1)
303 PUP(out) = PUP(from);
304 }
305 }
306 }
307 else if ((op & 64) == 0) { /* 2nd level distance code */
308 here = dcode[here.val + (hold & ((1U << op) - 1))];
309 goto dodist;
310 }
311 else {
312 strm->msg = (char *)"invalid distance code";
313 state->mode = BAD;
314 break;
315 }
316 }
317 else if ((op & 64) == 0) { /* 2nd level length code */
318 here = lcode[here.val + (hold & ((1U << op) - 1))];
319 goto dolen;
320 }
321 else if (op & 32) { /* end-of-block */
322 Tracevv((stderr, "inflate: end of block\n"));
323 state->mode = TYPE;
324 break;
325 }
326 else {
327 strm->msg = (char *)"invalid literal/length code";
328 state->mode = BAD;
329 break;
330 }
331 } while (in < last && out < end);
332
333 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
334 len = bits >> 3;
335 in -= len;
336 bits -= len << 3;
337 hold &= (1U << bits) - 1;
338
339 /* update state and return */
340 strm->next_in = in + OFF;
341 strm->next_out = out + OFF;
342 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
343 strm->avail_out = (unsigned)(out < end ?
344 257 + (end - out) : 257 - (out - end));
345 state->hold = hold;
346 state->bits = bits;
347 return;
348 }
349
350 /*
351 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
352 - Using bit fields for code structure
353 - Different op definition to avoid & for extra bits (do & for table bits)
354 - Three separate decoding do-loops for direct, window, and wnext == 0
355 - Special case for distance > 1 copies to do overlapped load and store copy
356 - Explicit branch predictions (based on measured branch probabilities)
357 - Deferring match copy and interspersed it with decoding subsequent codes
358 - Swapping literal/length else
359 - Swapping window/direct else
360 - Larger unrolled copy loops (three is about right)
361 - Moving len -= 3 statement into middle of loop
362 */
363
364 #endif /* !ASMINF */