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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> | |
7 | #include "inftrees.h" | |
4f3865fb | 8 | #include "inflate.h" |
1da177e4 LT |
9 | #include "inffast.h" |
10 | ||
4f3865fb RP |
11 | #ifndef ASMINF |
12 | ||
e69eae65 JT |
13 | union uu { |
14 | unsigned short us; | |
15 | unsigned char b[2]; | |
16 | }; | |
17 | ||
05911c5d | 18 | /* Endian independent version */ |
e69eae65 JT |
19 | static inline unsigned short |
20 | get_unaligned16(const unsigned short *p) | |
21 | { | |
22 | union uu mm; | |
23 | unsigned char *b = (unsigned char *)p; | |
24 | ||
25 | mm.b[0] = b[0]; | |
26 | mm.b[1] = b[1]; | |
27 | return mm.us; | |
28 | } | |
29 | ||
4f3865fb RP |
30 | /* |
31 | Decode literal, length, and distance codes and write out the resulting | |
32 | literal and match bytes until either not enough input or output is | |
33 | available, an end-of-block is encountered, or a data error is encountered. | |
34 | When large enough input and output buffers are supplied to inflate(), for | |
35 | example, a 16K input buffer and a 64K output buffer, more than 95% of the | |
36 | inflate execution time is spent in this routine. | |
37 | ||
38 | Entry assumptions: | |
39 | ||
40 | state->mode == LEN | |
41 | strm->avail_in >= 6 | |
42 | strm->avail_out >= 258 | |
43 | start >= strm->avail_out | |
44 | state->bits < 8 | |
45 | ||
46 | On return, state->mode is one of: | |
47 | ||
48 | LEN -- ran out of enough output space or enough available input | |
49 | TYPE -- reached end of block code, inflate() to interpret next block | |
50 | BAD -- error in block data | |
51 | ||
52 | Notes: | |
53 | ||
54 | - The maximum input bits used by a length/distance pair is 15 bits for the | |
55 | length code, 5 bits for the length extra, 15 bits for the distance code, | |
56 | and 13 bits for the distance extra. This totals 48 bits, or six bytes. | |
57 | Therefore if strm->avail_in >= 6, then there is enough input to avoid | |
58 | checking for available input while decoding. | |
59 | ||
60 | - The maximum bytes that a single length/distance pair can output is 258 | |
61 | bytes, which is the maximum length that can be coded. inflate_fast() | |
62 | requires strm->avail_out >= 258 for each loop to avoid checking for | |
63 | output space. | |
b762450e RD |
64 | |
65 | - @start: inflate()'s starting value for strm->avail_out | |
4f3865fb | 66 | */ |
b762450e | 67 | void inflate_fast(z_streamp strm, unsigned start) |
1da177e4 | 68 | { |
4f3865fb | 69 | struct inflate_state *state; |
8336793b DV |
70 | const unsigned char *in; /* local strm->next_in */ |
71 | const unsigned char *last; /* while in < last, enough input available */ | |
72 | unsigned char *out; /* local strm->next_out */ | |
73 | unsigned char *beg; /* inflate()'s initial strm->next_out */ | |
74 | unsigned char *end; /* while out < end, enough space available */ | |
4f3865fb RP |
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 write; /* window write index */ | |
8336793b | 81 | unsigned char *window; /* allocated sliding window, if wsize != 0 */ |
4f3865fb RP |
82 | unsigned long hold; /* local strm->hold */ |
83 | unsigned bits; /* local strm->bits */ | |
8336793b DV |
84 | code const *lcode; /* local strm->lencode */ |
85 | code const *dcode; /* local strm->distcode */ | |
4f3865fb RP |
86 | unsigned lmask; /* mask for first level of length codes */ |
87 | unsigned dmask; /* mask for first level of distance codes */ | |
88 | code this; /* 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 */ | |
8336793b | 93 | unsigned char *from; /* where to copy match from */ |
4f3865fb RP |
94 | |
95 | /* copy state to local variables */ | |
96 | state = (struct inflate_state *)strm->state; | |
acaab733 | 97 | in = strm->next_in; |
4f3865fb | 98 | last = in + (strm->avail_in - 5); |
acaab733 | 99 | out = strm->next_out; |
4f3865fb RP |
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 | write = state->write; | |
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 */ | |
1da177e4 | 118 | do { |
4f3865fb | 119 | if (bits < 15) { |
acaab733 | 120 | hold += (unsigned long)(*in++) << bits; |
4f3865fb | 121 | bits += 8; |
acaab733 | 122 | hold += (unsigned long)(*in++) << bits; |
4f3865fb RP |
123 | bits += 8; |
124 | } | |
125 | this = lcode[hold & lmask]; | |
126 | dolen: | |
127 | op = (unsigned)(this.bits); | |
128 | hold >>= op; | |
129 | bits -= op; | |
130 | op = (unsigned)(this.op); | |
131 | if (op == 0) { /* literal */ | |
acaab733 | 132 | *out++ = (unsigned char)(this.val); |
4f3865fb RP |
133 | } |
134 | else if (op & 16) { /* length base */ | |
135 | len = (unsigned)(this.val); | |
136 | op &= 15; /* number of extra bits */ | |
137 | if (op) { | |
138 | if (bits < op) { | |
acaab733 | 139 | hold += (unsigned long)(*in++) << bits; |
4f3865fb RP |
140 | bits += 8; |
141 | } | |
142 | len += (unsigned)hold & ((1U << op) - 1); | |
143 | hold >>= op; | |
144 | bits -= op; | |
145 | } | |
146 | if (bits < 15) { | |
acaab733 | 147 | hold += (unsigned long)(*in++) << bits; |
4f3865fb | 148 | bits += 8; |
acaab733 | 149 | hold += (unsigned long)(*in++) << bits; |
4f3865fb RP |
150 | bits += 8; |
151 | } | |
152 | this = dcode[hold & dmask]; | |
153 | dodist: | |
154 | op = (unsigned)(this.bits); | |
155 | hold >>= op; | |
156 | bits -= op; | |
157 | op = (unsigned)(this.op); | |
158 | if (op & 16) { /* distance base */ | |
159 | dist = (unsigned)(this.val); | |
160 | op &= 15; /* number of extra bits */ | |
161 | if (bits < op) { | |
acaab733 | 162 | hold += (unsigned long)(*in++) << bits; |
4f3865fb RP |
163 | bits += 8; |
164 | if (bits < op) { | |
acaab733 | 165 | hold += (unsigned long)(*in++) << bits; |
4f3865fb RP |
166 | bits += 8; |
167 | } | |
168 | } | |
169 | dist += (unsigned)hold & ((1U << op) - 1); | |
170 | #ifdef INFLATE_STRICT | |
171 | if (dist > dmax) { | |
172 | strm->msg = (char *)"invalid distance too far back"; | |
173 | state->mode = BAD; | |
174 | break; | |
175 | } | |
176 | #endif | |
177 | hold >>= op; | |
178 | bits -= op; | |
179 | op = (unsigned)(out - beg); /* max distance in output */ | |
180 | if (dist > op) { /* see if copy from window */ | |
181 | op = dist - op; /* distance back in window */ | |
182 | if (op > whave) { | |
183 | strm->msg = (char *)"invalid distance too far back"; | |
184 | state->mode = BAD; | |
185 | break; | |
186 | } | |
acaab733 | 187 | from = window; |
4f3865fb RP |
188 | if (write == 0) { /* very common case */ |
189 | from += wsize - op; | |
190 | if (op < len) { /* some from window */ | |
191 | len -= op; | |
192 | do { | |
acaab733 | 193 | *out++ = *from++; |
4f3865fb RP |
194 | } while (--op); |
195 | from = out - dist; /* rest from output */ | |
196 | } | |
197 | } | |
198 | else if (write < op) { /* wrap around window */ | |
199 | from += wsize + write - op; | |
200 | op -= write; | |
201 | if (op < len) { /* some from end of window */ | |
202 | len -= op; | |
203 | do { | |
acaab733 | 204 | *out++ = *from++; |
4f3865fb | 205 | } while (--op); |
acaab733 | 206 | from = window; |
4f3865fb RP |
207 | if (write < len) { /* some from start of window */ |
208 | op = write; | |
209 | len -= op; | |
210 | do { | |
acaab733 | 211 | *out++ = *from++; |
4f3865fb RP |
212 | } while (--op); |
213 | from = out - dist; /* rest from output */ | |
214 | } | |
215 | } | |
216 | } | |
217 | else { /* contiguous in window */ | |
218 | from += write - op; | |
219 | if (op < len) { /* some from window */ | |
220 | len -= op; | |
221 | do { | |
acaab733 | 222 | *out++ = *from++; |
4f3865fb RP |
223 | } while (--op); |
224 | from = out - dist; /* rest from output */ | |
225 | } | |
226 | } | |
227 | while (len > 2) { | |
acaab733 JH |
228 | *out++ = *from++; |
229 | *out++ = *from++; | |
230 | *out++ = *from++; | |
4f3865fb RP |
231 | len -= 3; |
232 | } | |
233 | if (len) { | |
acaab733 | 234 | *out++ = *from++; |
4f3865fb | 235 | if (len > 1) |
acaab733 | 236 | *out++ = *from++; |
4f3865fb RP |
237 | } |
238 | } | |
239 | else { | |
ac4c2a3b JT |
240 | unsigned short *sout; |
241 | unsigned long loops; | |
242 | ||
4f3865fb | 243 | from = out - dist; /* copy direct from output */ |
ac4c2a3b JT |
244 | /* minimum length is three */ |
245 | /* Align out addr */ | |
acaab733 JH |
246 | if (!((long)(out - 1) & 1)) { |
247 | *out++ = *from++; | |
ac4c2a3b JT |
248 | len--; |
249 | } | |
acaab733 | 250 | sout = (unsigned short *)(out); |
ac4c2a3b JT |
251 | if (dist > 2) { |
252 | unsigned short *sfrom; | |
253 | ||
acaab733 | 254 | sfrom = (unsigned short *)(from); |
ac4c2a3b | 255 | loops = len >> 1; |
b7cd9fa5 PM |
256 | do { |
257 | if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) | |
258 | *sout++ = *sfrom++; | |
259 | else | |
260 | *sout++ = get_unaligned16(sfrom++); | |
261 | } while (--loops); | |
acaab733 JH |
262 | out = (unsigned char *)sout; |
263 | from = (unsigned char *)sfrom; | |
ac4c2a3b JT |
264 | } else { /* dist == 1 or dist == 2 */ |
265 | unsigned short pat16; | |
266 | ||
acaab733 | 267 | pat16 = *(sout-1); |
e69eae65 JT |
268 | if (dist == 1) { |
269 | union uu mm; | |
270 | /* copy one char pattern to both bytes */ | |
271 | mm.us = pat16; | |
272 | mm.b[0] = mm.b[1]; | |
273 | pat16 = mm.us; | |
274 | } | |
ac4c2a3b JT |
275 | loops = len >> 1; |
276 | do | |
acaab733 | 277 | *sout++ = pat16; |
ac4c2a3b | 278 | while (--loops); |
acaab733 | 279 | out = (unsigned char *)sout; |
ac4c2a3b JT |
280 | } |
281 | if (len & 1) | |
acaab733 | 282 | *out++ = *from++; |
4f3865fb RP |
283 | } |
284 | } | |
285 | else if ((op & 64) == 0) { /* 2nd level distance code */ | |
286 | this = dcode[this.val + (hold & ((1U << op) - 1))]; | |
287 | goto dodist; | |
1da177e4 | 288 | } |
4f3865fb RP |
289 | else { |
290 | strm->msg = (char *)"invalid distance code"; | |
291 | state->mode = BAD; | |
292 | break; | |
1da177e4 | 293 | } |
4f3865fb RP |
294 | } |
295 | else if ((op & 64) == 0) { /* 2nd level length code */ | |
296 | this = lcode[this.val + (hold & ((1U << op) - 1))]; | |
297 | goto dolen; | |
298 | } | |
299 | else if (op & 32) { /* end-of-block */ | |
300 | state->mode = TYPE; | |
1da177e4 | 301 | break; |
1da177e4 | 302 | } |
4f3865fb RP |
303 | else { |
304 | strm->msg = (char *)"invalid literal/length code"; | |
305 | state->mode = BAD; | |
306 | break; | |
307 | } | |
308 | } while (in < last && out < end); | |
309 | ||
310 | /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ | |
311 | len = bits >> 3; | |
312 | in -= len; | |
313 | bits -= len << 3; | |
314 | hold &= (1U << bits) - 1; | |
315 | ||
316 | /* update state and return */ | |
acaab733 JH |
317 | strm->next_in = in; |
318 | strm->next_out = out; | |
4f3865fb RP |
319 | strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); |
320 | strm->avail_out = (unsigned)(out < end ? | |
321 | 257 + (end - out) : 257 - (out - end)); | |
322 | state->hold = hold; | |
323 | state->bits = bits; | |
324 | return; | |
1da177e4 | 325 | } |
4f3865fb RP |
326 | |
327 | /* | |
328 | inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): | |
329 | - Using bit fields for code structure | |
330 | - Different op definition to avoid & for extra bits (do & for table bits) | |
331 | - Three separate decoding do-loops for direct, window, and write == 0 | |
332 | - Special case for distance > 1 copies to do overlapped load and store copy | |
333 | - Explicit branch predictions (based on measured branch probabilities) | |
334 | - Deferring match copy and interspersed it with decoding subsequent codes | |
335 | - Swapping literal/length else | |
336 | - Swapping window/direct else | |
337 | - Larger unrolled copy loops (three is about right) | |
338 | - Moving len -= 3 statement into middle of loop | |
339 | */ | |
340 | ||
341 | #endif /* !ASMINF */ |