Merge pull request #377 from pcercuei/libretro
[pcsx_rearmed.git] / deps / zlib / inffast.c
CommitLineData
7795edd6
JAS
1/* inffast.c -- fast decoding
2 * Copyright (C) 1995-2008, 2010, 2013 Mark Adler
3 * For conditions of distribution and use, see copyright notice in zlib.h
4 */
5
6#include "zutil.h"
7#include "inftrees.h"
8#include "inflate.h"
9#include "inffast.h"
10
11#ifndef ASMINF
12
13/* Allow machine dependent optimization for post-increment or pre-increment.
14 Based on testing to date,
15 Pre-increment preferred for:
16 - PowerPC G3 (Adler)
17 - MIPS R5000 (Randers-Pehrson)
18 Post-increment preferred for:
19 - none
20 No measurable difference:
21 - Pentium III (Anderson)
22 - M68060 (Nikl)
23 */
24#ifdef POSTINC
25# define OFF 0
26# define PUP(a) *(a)++
27#else
28# define OFF 1
29# define PUP(a) *++(a)
30#endif
31
32/*
33 Decode literal, length, and distance codes and write out the resulting
34 literal and match bytes until either not enough input or output is
35 available, an end-of-block is encountered, or a data error is encountered.
36 When large enough input and output buffers are supplied to inflate(), for
37 example, a 16K input buffer and a 64K output buffer, more than 95% of the
38 inflate execution time is spent in this routine.
39
40 Entry assumptions:
41
42 state->mode == LEN
43 strm->avail_in >= 6
44 strm->avail_out >= 258
45 start >= strm->avail_out
46 state->bits < 8
47
48 On return, state->mode is one of:
49
50 LEN -- ran out of enough output space or enough available input
51 TYPE -- reached end of block code, inflate() to interpret next block
52 BAD -- error in block data
53
54Notes:
55
56- The maximum input bits used by a length/distance pair is 15 bits for the
57length code, 5 bits for the length extra, 15 bits for the distance code,
58and 13 bits for the distance extra. This totals 48 bits, or six bytes.
59Therefore if strm->avail_in >= 6, then there is enough input to avoid
60checking for available input while decoding.
61
62- The maximum bytes that a single length/distance pair can output is 258
63bytes, which is the maximum length that can be coded. inflate_fast()
64requires strm->avail_out >= 258 for each loop to avoid checking for
65output space.
66*/
67void ZLIB_INTERNAL inflate_fast(z_streamp strm, unsigned start)
68{
69 struct inflate_state FAR *state;
70 unsigned char FAR *in; /* local strm->next_in */
71 unsigned char FAR *last; /* have enough input while in < last */
72 unsigned char FAR *out; /* local strm->next_out */
73 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */
74 unsigned char FAR *end; /* while out < end, enough space available */
75#ifdef INFLATE_STRICT
76 unsigned dmax; /* maximum distance from zlib header */
77#endif
78 unsigned wsize; /* window size or zero if not using window */
79 unsigned whave; /* valid bytes in the window */
80 unsigned wnext; /* window write index */
81 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */
82 unsigned long hold; /* local strm->hold */
83 unsigned bits; /* local strm->bits */
84 code const FAR *lcode; /* local strm->lencode */
85 code const FAR *dcode; /* local strm->distcode */
86 unsigned lmask; /* mask for first level of length codes */
87 unsigned dmask; /* mask for first level of distance codes */
88 code here; /* retrieved table entry */
89 unsigned op; /* code bits, operation, extra bits, or */
90 /* window position, window bytes to copy */
91 unsigned len; /* match length, unused bytes */
92 unsigned dist; /* match distance */
93 unsigned char FAR *from; /* where to copy match from */
94
95 /* copy state to local variables */
96 state = (struct inflate_state FAR *)strm->state;
97 in = strm->next_in - OFF;
98 last = in + (strm->avail_in - 5);
99 out = strm->next_out - OFF;
100 beg = out - (start - strm->avail_out);
101 end = out + (strm->avail_out - 257);
102#ifdef INFLATE_STRICT
103 dmax = state->dmax;
104#endif
105 wsize = state->wsize;
106 whave = state->whave;
107 wnext = state->wnext;
108 window = state->window;
109 hold = state->hold;
110 bits = state->bits;
111 lcode = state->lencode;
112 dcode = state->distcode;
113 lmask = (1U << state->lenbits) - 1;
114 dmask = (1U << state->distbits) - 1;
115
116 /* decode literals and length/distances until end-of-block or not enough
117 input data or output space */
118 do {
119 if (bits < 15) {
120 hold += (unsigned long)(PUP(in)) << bits;
121 bits += 8;
122 hold += (unsigned long)(PUP(in)) << bits;
123 bits += 8;
124 }
125 here = lcode[hold & lmask];
126dolen:
127 op = (unsigned)(here.bits);
128 hold >>= op;
129 bits -= op;
130 op = (unsigned)(here.op);
131 if (op == 0) { /* literal */
132 Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ?
133 "inflate: literal '%c'\n" :
134 "inflate: literal 0x%02x\n", here.val));
135 PUP(out) = (unsigned char)(here.val);
136 }
137 else if (op & 16) { /* length base */
138 len = (unsigned)(here.val);
139 op &= 15; /* number of extra bits */
140 if (op) {
141 if (bits < op) {
142 hold += (unsigned long)(PUP(in)) << bits;
143 bits += 8;
144 }
145 len += (unsigned)hold & ((1U << op) - 1);
146 hold >>= op;
147 bits -= op;
148 }
149 Tracevv((stderr, "inflate: length %u\n", len));
150 if (bits < 15) {
151 hold += (unsigned long)(PUP(in)) << bits;
152 bits += 8;
153 hold += (unsigned long)(PUP(in)) << bits;
154 bits += 8;
155 }
156 here = dcode[hold & dmask];
157dodist:
158 op = (unsigned)(here.bits);
159 hold >>= op;
160 bits -= op;
161 op = (unsigned)(here.op);
162 if (op & 16) { /* distance base */
163 dist = (unsigned)(here.val);
164 op &= 15; /* number of extra bits */
165 if (bits < op) {
166 hold += (unsigned long)(PUP(in)) << bits;
167 bits += 8;
168 if (bits < op) {
169 hold += (unsigned long)(PUP(in)) << bits;
170 bits += 8;
171 }
172 }
173 dist += (unsigned)hold & ((1U << op) - 1);
174#ifdef INFLATE_STRICT
175 if (dist > dmax) {
176 strm->msg = (char *)"invalid distance too far back";
177 state->mode = BAD;
178 break;
179 }
180#endif
181 hold >>= op;
182 bits -= op;
183 Tracevv((stderr, "inflate: distance %u\n", dist));
184 op = (unsigned)(out - beg); /* max distance in output */
185 if (dist > op) { /* see if copy from window */
186 op = dist - op; /* distance back in window */
187 if (op > whave) {
188 if (state->sane) {
189 strm->msg =
190 (char *)"invalid distance too far back";
191 state->mode = BAD;
192 break;
193 }
194#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
195 if (len <= op - whave) {
196 do {
197 PUP(out) = 0;
198 } while (--len);
199 continue;
200 }
201 len -= op - whave;
202 do {
203 PUP(out) = 0;
204 } while (--op > whave);
205 if (op == 0) {
206 from = out - dist;
207 do {
208 PUP(out) = PUP(from);
209 } while (--len);
210 continue;
211 }
212#endif
213 }
214 from = window - OFF;
215 if (wnext == 0) { /* very common case */
216 from += wsize - op;
217 if (op < len) { /* some from window */
218 len -= op;
219 do {
220 PUP(out) = PUP(from);
221 } while (--op);
222 from = out - dist; /* rest from output */
223 }
224 }
225 else if (wnext < op) { /* wrap around window */
226 from += wsize + wnext - op;
227 op -= wnext;
228 if (op < len) { /* some from end of window */
229 len -= op;
230 do {
231 PUP(out) = PUP(from);
232 } while (--op);
233 from = window - OFF;
234 if (wnext < len) { /* some from start of window */
235 op = wnext;
236 len -= op;
237 do {
238 PUP(out) = PUP(from);
239 } while (--op);
240 from = out - dist; /* rest from output */
241 }
242 }
243 }
244 else { /* contiguous in window */
245 from += wnext - op;
246 if (op < len) { /* some from window */
247 len -= op;
248 do {
249 PUP(out) = PUP(from);
250 } while (--op);
251 from = out - dist; /* rest from output */
252 }
253 }
254 while (len > 2) {
255 PUP(out) = PUP(from);
256 PUP(out) = PUP(from);
257 PUP(out) = PUP(from);
258 len -= 3;
259 }
260 if (len) {
261 PUP(out) = PUP(from);
262 if (len > 1)
263 PUP(out) = PUP(from);
264 }
265 }
266 else {
267 from = out - dist; /* copy direct from output */
268 do { /* minimum length is three */
269 PUP(out) = PUP(from);
270 PUP(out) = PUP(from);
271 PUP(out) = PUP(from);
272 len -= 3;
273 } while (len > 2);
274 if (len) {
275 PUP(out) = PUP(from);
276 if (len > 1)
277 PUP(out) = PUP(from);
278 }
279 }
280 }
281 else if ((op & 64) == 0) { /* 2nd level distance code */
282 here = dcode[here.val + (hold & ((1U << op) - 1))];
283 goto dodist;
284 }
285 else {
286 strm->msg = (char *)"invalid distance code";
287 state->mode = BAD;
288 break;
289 }
290 }
291 else if ((op & 64) == 0) { /* 2nd level length code */
292 here = lcode[here.val + (hold & ((1U << op) - 1))];
293 goto dolen;
294 }
295 else if (op & 32) { /* end-of-block */
296 Tracevv((stderr, "inflate: end of block\n"));
297 state->mode = TYPE;
298 break;
299 }
300 else {
301 strm->msg = (char *)"invalid literal/length code";
302 state->mode = BAD;
303 break;
304 }
305 } while (in < last && out < end);
306
307 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
308 len = bits >> 3;
309 in -= len;
310 bits -= len << 3;
311 hold &= (1U << bits) - 1;
312
313 /* update state and return */
314 strm->next_in = in + OFF;
315 strm->next_out = out + OFF;
316 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
317 strm->avail_out = (unsigned)(out < end ?
318 257 + (end - out) : 257 - (out - end));
319 state->hold = hold;
320 state->bits = bits;
321 return;
322}
323
324/*
325 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
326 - Using bit fields for code structure
327 - Different op definition to avoid & for extra bits (do & for table bits)
328 - Three separate decoding do-loops for direct, window, and wnext == 0
329 - Special case for distance > 1 copies to do overlapped load and store copy
330 - Explicit branch predictions (based on measured branch probabilities)
331 - Deferring match copy and interspersed it with decoding subsequent codes
332 - Swapping literal/length else
333 - Swapping window/direct else
334 - Larger unrolled copy loops (three is about right)
335 - Moving len -= 3 statement into middle of loop
336 */
337
338#endif /* !ASMINF */