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4f3865fb RP |
1 | /* inffast.c -- fast decoding |
2 | * Copyright (C) 1995-2004 Mark Adler | |
3 | * For conditions of distribution and use, see copyright notice in zlib.h | |
1da177e4 LT |
4 | */ |
5 | ||
6 | #include <linux/zutil.h> | |
ac4c2a3b JT |
7 | #include <asm/unaligned.h> |
8 | #include <asm/byteorder.h> | |
1da177e4 | 9 | #include "inftrees.h" |
4f3865fb | 10 | #include "inflate.h" |
1da177e4 LT |
11 | #include "inffast.h" |
12 | ||
4f3865fb RP |
13 | #ifndef ASMINF |
14 | ||
15 | /* Allow machine dependent optimization for post-increment or pre-increment. | |
16 | Based on testing to date, | |
17 | Pre-increment preferred for: | |
18 | - PowerPC G3 (Adler) | |
19 | - MIPS R5000 (Randers-Pehrson) | |
20 | Post-increment preferred for: | |
21 | - none | |
22 | No measurable difference: | |
23 | - Pentium III (Anderson) | |
24 | - M68060 (Nikl) | |
25 | */ | |
26 | #ifdef POSTINC | |
27 | # define OFF 0 | |
28 | # define PUP(a) *(a)++ | |
ac4c2a3b | 29 | # define UP_UNALIGNED(a) get_unaligned((a)++) |
4f3865fb RP |
30 | #else |
31 | # define OFF 1 | |
32 | # define PUP(a) *++(a) | |
ac4c2a3b | 33 | # define UP_UNALIGNED(a) get_unaligned(++(a)) |
4f3865fb RP |
34 | #endif |
35 | ||
36 | /* | |
37 | Decode literal, length, and distance codes and write out the resulting | |
38 | literal and match bytes until either not enough input or output is | |
39 | available, an end-of-block is encountered, or a data error is encountered. | |
40 | When large enough input and output buffers are supplied to inflate(), for | |
41 | example, a 16K input buffer and a 64K output buffer, more than 95% of the | |
42 | inflate execution time is spent in this routine. | |
43 | ||
44 | Entry assumptions: | |
45 | ||
46 | state->mode == LEN | |
47 | strm->avail_in >= 6 | |
48 | strm->avail_out >= 258 | |
49 | start >= strm->avail_out | |
50 | state->bits < 8 | |
51 | ||
52 | On return, state->mode is one of: | |
53 | ||
54 | LEN -- ran out of enough output space or enough available input | |
55 | TYPE -- reached end of block code, inflate() to interpret next block | |
56 | BAD -- error in block data | |
57 | ||
58 | Notes: | |
59 | ||
60 | - The maximum input bits used by a length/distance pair is 15 bits for the | |
61 | length code, 5 bits for the length extra, 15 bits for the distance code, | |
62 | and 13 bits for the distance extra. This totals 48 bits, or six bytes. | |
63 | Therefore if strm->avail_in >= 6, then there is enough input to avoid | |
64 | checking for available input while decoding. | |
65 | ||
66 | - The maximum bytes that a single length/distance pair can output is 258 | |
67 | bytes, which is the maximum length that can be coded. inflate_fast() | |
68 | requires strm->avail_out >= 258 for each loop to avoid checking for | |
69 | output space. | |
b762450e RD |
70 | |
71 | - @start: inflate()'s starting value for strm->avail_out | |
4f3865fb | 72 | */ |
b762450e | 73 | void inflate_fast(z_streamp strm, unsigned start) |
1da177e4 | 74 | { |
4f3865fb | 75 | struct inflate_state *state; |
8336793b DV |
76 | const unsigned char *in; /* local strm->next_in */ |
77 | const unsigned char *last; /* while in < last, enough input available */ | |
78 | unsigned char *out; /* local strm->next_out */ | |
79 | unsigned char *beg; /* inflate()'s initial strm->next_out */ | |
80 | unsigned char *end; /* while out < end, enough space available */ | |
4f3865fb RP |
81 | #ifdef INFLATE_STRICT |
82 | unsigned dmax; /* maximum distance from zlib header */ | |
83 | #endif | |
84 | unsigned wsize; /* window size or zero if not using window */ | |
85 | unsigned whave; /* valid bytes in the window */ | |
86 | unsigned write; /* window write index */ | |
8336793b | 87 | unsigned char *window; /* allocated sliding window, if wsize != 0 */ |
4f3865fb RP |
88 | unsigned long hold; /* local strm->hold */ |
89 | unsigned bits; /* local strm->bits */ | |
8336793b DV |
90 | code const *lcode; /* local strm->lencode */ |
91 | code const *dcode; /* local strm->distcode */ | |
4f3865fb RP |
92 | unsigned lmask; /* mask for first level of length codes */ |
93 | unsigned dmask; /* mask for first level of distance codes */ | |
94 | code this; /* retrieved table entry */ | |
95 | unsigned op; /* code bits, operation, extra bits, or */ | |
96 | /* window position, window bytes to copy */ | |
97 | unsigned len; /* match length, unused bytes */ | |
98 | unsigned dist; /* match distance */ | |
8336793b | 99 | unsigned char *from; /* where to copy match from */ |
4f3865fb RP |
100 | |
101 | /* copy state to local variables */ | |
102 | state = (struct inflate_state *)strm->state; | |
103 | in = strm->next_in - OFF; | |
104 | last = in + (strm->avail_in - 5); | |
105 | out = strm->next_out - OFF; | |
106 | beg = out - (start - strm->avail_out); | |
107 | end = out + (strm->avail_out - 257); | |
108 | #ifdef INFLATE_STRICT | |
109 | dmax = state->dmax; | |
110 | #endif | |
111 | wsize = state->wsize; | |
112 | whave = state->whave; | |
113 | write = state->write; | |
114 | window = state->window; | |
115 | hold = state->hold; | |
116 | bits = state->bits; | |
117 | lcode = state->lencode; | |
118 | dcode = state->distcode; | |
119 | lmask = (1U << state->lenbits) - 1; | |
120 | dmask = (1U << state->distbits) - 1; | |
121 | ||
122 | /* decode literals and length/distances until end-of-block or not enough | |
123 | input data or output space */ | |
1da177e4 | 124 | do { |
4f3865fb RP |
125 | if (bits < 15) { |
126 | hold += (unsigned long)(PUP(in)) << bits; | |
127 | bits += 8; | |
128 | hold += (unsigned long)(PUP(in)) << bits; | |
129 | bits += 8; | |
130 | } | |
131 | this = lcode[hold & lmask]; | |
132 | dolen: | |
133 | op = (unsigned)(this.bits); | |
134 | hold >>= op; | |
135 | bits -= op; | |
136 | op = (unsigned)(this.op); | |
137 | if (op == 0) { /* literal */ | |
138 | PUP(out) = (unsigned char)(this.val); | |
139 | } | |
140 | else if (op & 16) { /* length base */ | |
141 | len = (unsigned)(this.val); | |
142 | op &= 15; /* number of extra bits */ | |
143 | if (op) { | |
144 | if (bits < op) { | |
145 | hold += (unsigned long)(PUP(in)) << bits; | |
146 | bits += 8; | |
147 | } | |
148 | len += (unsigned)hold & ((1U << op) - 1); | |
149 | hold >>= op; | |
150 | bits -= op; | |
151 | } | |
152 | if (bits < 15) { | |
153 | hold += (unsigned long)(PUP(in)) << bits; | |
154 | bits += 8; | |
155 | hold += (unsigned long)(PUP(in)) << bits; | |
156 | bits += 8; | |
157 | } | |
158 | this = dcode[hold & dmask]; | |
159 | dodist: | |
160 | op = (unsigned)(this.bits); | |
161 | hold >>= op; | |
162 | bits -= op; | |
163 | op = (unsigned)(this.op); | |
164 | if (op & 16) { /* distance base */ | |
165 | dist = (unsigned)(this.val); | |
166 | op &= 15; /* number of extra bits */ | |
167 | if (bits < op) { | |
168 | hold += (unsigned long)(PUP(in)) << bits; | |
169 | bits += 8; | |
170 | if (bits < op) { | |
171 | hold += (unsigned long)(PUP(in)) << bits; | |
172 | bits += 8; | |
173 | } | |
174 | } | |
175 | dist += (unsigned)hold & ((1U << op) - 1); | |
176 | #ifdef INFLATE_STRICT | |
177 | if (dist > dmax) { | |
178 | strm->msg = (char *)"invalid distance too far back"; | |
179 | state->mode = BAD; | |
180 | break; | |
181 | } | |
182 | #endif | |
183 | hold >>= op; | |
184 | bits -= op; | |
185 | op = (unsigned)(out - beg); /* max distance in output */ | |
186 | if (dist > op) { /* see if copy from window */ | |
187 | op = dist - op; /* distance back in window */ | |
188 | if (op > whave) { | |
189 | strm->msg = (char *)"invalid distance too far back"; | |
190 | state->mode = BAD; | |
191 | break; | |
192 | } | |
193 | from = window - OFF; | |
194 | if (write == 0) { /* very common case */ | |
195 | from += wsize - op; | |
196 | if (op < len) { /* some from window */ | |
197 | len -= op; | |
198 | do { | |
199 | PUP(out) = PUP(from); | |
200 | } while (--op); | |
201 | from = out - dist; /* rest from output */ | |
202 | } | |
203 | } | |
204 | else if (write < op) { /* wrap around window */ | |
205 | from += wsize + write - op; | |
206 | op -= write; | |
207 | if (op < len) { /* some from end of window */ | |
208 | len -= op; | |
209 | do { | |
210 | PUP(out) = PUP(from); | |
211 | } while (--op); | |
212 | from = window - OFF; | |
213 | if (write < len) { /* some from start of window */ | |
214 | op = write; | |
215 | len -= op; | |
216 | do { | |
217 | PUP(out) = PUP(from); | |
218 | } while (--op); | |
219 | from = out - dist; /* rest from output */ | |
220 | } | |
221 | } | |
222 | } | |
223 | else { /* contiguous in window */ | |
224 | from += write - op; | |
225 | if (op < len) { /* some from window */ | |
226 | len -= op; | |
227 | do { | |
228 | PUP(out) = PUP(from); | |
229 | } while (--op); | |
230 | from = out - dist; /* rest from output */ | |
231 | } | |
232 | } | |
233 | while (len > 2) { | |
234 | PUP(out) = PUP(from); | |
235 | PUP(out) = PUP(from); | |
236 | PUP(out) = PUP(from); | |
237 | len -= 3; | |
238 | } | |
239 | if (len) { | |
240 | PUP(out) = PUP(from); | |
241 | if (len > 1) | |
242 | PUP(out) = PUP(from); | |
243 | } | |
244 | } | |
245 | else { | |
ac4c2a3b JT |
246 | unsigned short *sout; |
247 | unsigned long loops; | |
248 | ||
4f3865fb | 249 | from = out - dist; /* copy direct from output */ |
ac4c2a3b JT |
250 | /* minimum length is three */ |
251 | /* Align out addr */ | |
252 | if (!((long)(out - 1 + OFF) & 1)) { | |
253 | PUP(out) = PUP(from); | |
254 | len--; | |
255 | } | |
256 | sout = (unsigned short *)(out - OFF); | |
257 | if (dist > 2) { | |
258 | unsigned short *sfrom; | |
259 | ||
260 | sfrom = (unsigned short *)(from - OFF); | |
261 | loops = len >> 1; | |
262 | do | |
263 | PUP(sout) = UP_UNALIGNED(sfrom); | |
264 | while (--loops); | |
265 | out = (unsigned char *)sout + OFF; | |
266 | from = (unsigned char *)sfrom + OFF; | |
267 | } else { /* dist == 1 or dist == 2 */ | |
268 | unsigned short pat16; | |
269 | ||
270 | pat16 = *(sout-2+2*OFF); | |
271 | if (dist == 1) | |
272 | #if defined(__BIG_ENDIAN) | |
273 | pat16 = (pat16 & 0xff) | ((pat16 & 0xff) << 8); | |
274 | #elif defined(__LITTLE_ENDIAN) | |
275 | pat16 = (pat16 & 0xff00) | ((pat16 & 0xff00) >> 8); | |
276 | #else | |
277 | #error __BIG_ENDIAN nor __LITTLE_ENDIAN is defined | |
278 | #endif | |
279 | loops = len >> 1; | |
280 | do | |
281 | PUP(sout) = pat16; | |
282 | while (--loops); | |
283 | out = (unsigned char *)sout + OFF; | |
284 | } | |
285 | if (len & 1) | |
286 | PUP(out) = PUP(from); | |
4f3865fb RP |
287 | } |
288 | } | |
289 | else if ((op & 64) == 0) { /* 2nd level distance code */ | |
290 | this = dcode[this.val + (hold & ((1U << op) - 1))]; | |
291 | goto dodist; | |
1da177e4 | 292 | } |
4f3865fb RP |
293 | else { |
294 | strm->msg = (char *)"invalid distance code"; | |
295 | state->mode = BAD; | |
296 | break; | |
1da177e4 | 297 | } |
4f3865fb RP |
298 | } |
299 | else if ((op & 64) == 0) { /* 2nd level length code */ | |
300 | this = lcode[this.val + (hold & ((1U << op) - 1))]; | |
301 | goto dolen; | |
302 | } | |
303 | else if (op & 32) { /* end-of-block */ | |
304 | state->mode = TYPE; | |
1da177e4 | 305 | break; |
1da177e4 | 306 | } |
4f3865fb RP |
307 | else { |
308 | strm->msg = (char *)"invalid literal/length code"; | |
309 | state->mode = BAD; | |
310 | break; | |
311 | } | |
312 | } while (in < last && out < end); | |
313 | ||
314 | /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ | |
315 | len = bits >> 3; | |
316 | in -= len; | |
317 | bits -= len << 3; | |
318 | hold &= (1U << bits) - 1; | |
319 | ||
320 | /* update state and return */ | |
321 | strm->next_in = in + OFF; | |
322 | strm->next_out = out + OFF; | |
323 | strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); | |
324 | strm->avail_out = (unsigned)(out < end ? | |
325 | 257 + (end - out) : 257 - (out - end)); | |
326 | state->hold = hold; | |
327 | state->bits = bits; | |
328 | return; | |
1da177e4 | 329 | } |
4f3865fb RP |
330 | |
331 | /* | |
332 | inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): | |
333 | - Using bit fields for code structure | |
334 | - Different op definition to avoid & for extra bits (do & for table bits) | |
335 | - Three separate decoding do-loops for direct, window, and write == 0 | |
336 | - Special case for distance > 1 copies to do overlapped load and store copy | |
337 | - Explicit branch predictions (based on measured branch probabilities) | |
338 | - Deferring match copy and interspersed it with decoding subsequent codes | |
339 | - Swapping literal/length else | |
340 | - Swapping window/direct else | |
341 | - Larger unrolled copy loops (three is about right) | |
342 | - Moving len -= 3 statement into middle of loop | |
343 | */ | |
344 | ||
345 | #endif /* !ASMINF */ |