ia64/linux-2.6.18-xen.hg

view lib/zlib_inflate/inffast.c @ 740:bf8b1ee634e2

balloon: Fix the build by including <linux/init.h>

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Nov 25 11:19:41 2008 +0000 (2008-11-25)
parents 831230e53067
children
line source
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
4 */
6 #include <linux/zutil.h>
7 #include "inftrees.h"
8 #include "inflate.h"
9 #include "inffast.h"
11 #ifndef ASMINF
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
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.
40 Entry assumptions:
42 state->mode == LEN
43 strm->avail_in >= 6
44 strm->avail_out >= 258
45 start >= strm->avail_out
46 state->bits < 8
48 On return, state->mode is one of:
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
54 Notes:
56 - The maximum input bits used by a length/distance pair is 15 bits for the
57 length code, 5 bits for the length extra, 15 bits for the distance code,
58 and 13 bits for the distance extra. This totals 48 bits, or six bytes.
59 Therefore if strm->avail_in >= 6, then there is enough input to avoid
60 checking for available input while decoding.
62 - The maximum bytes that a single length/distance pair can output is 258
63 bytes, which is the maximum length that can be coded. inflate_fast()
64 requires strm->avail_out >= 258 for each loop to avoid checking for
65 output space.
67 - @start: inflate()'s starting value for strm->avail_out
68 */
69 void inflate_fast(z_streamp strm, unsigned start)
70 {
71 struct inflate_state *state;
72 unsigned char *in; /* local strm->next_in */
73 unsigned char *last; /* while in < last, enough input available */
74 unsigned char *out; /* local strm->next_out */
75 unsigned char *beg; /* inflate()'s initial strm->next_out */
76 unsigned char *end; /* while out < end, enough space available */
77 #ifdef INFLATE_STRICT
78 unsigned dmax; /* maximum distance from zlib header */
79 #endif
80 unsigned wsize; /* window size or zero if not using window */
81 unsigned whave; /* valid bytes in the window */
82 unsigned write; /* window write index */
83 unsigned char *window; /* allocated sliding window, if wsize != 0 */
84 unsigned long hold; /* local strm->hold */
85 unsigned bits; /* local strm->bits */
86 code const *lcode; /* local strm->lencode */
87 code const *dcode; /* local strm->distcode */
88 unsigned lmask; /* mask for first level of length codes */
89 unsigned dmask; /* mask for first level of distance codes */
90 code this; /* retrieved table entry */
91 unsigned op; /* code bits, operation, extra bits, or */
92 /* window position, window bytes to copy */
93 unsigned len; /* match length, unused bytes */
94 unsigned dist; /* match distance */
95 unsigned char *from; /* where to copy match from */
97 /* copy state to local variables */
98 state = (struct inflate_state *)strm->state;
99 in = strm->next_in - OFF;
100 last = in + (strm->avail_in - 5);
101 out = strm->next_out - OFF;
102 beg = out - (start - strm->avail_out);
103 end = out + (strm->avail_out - 257);
104 #ifdef INFLATE_STRICT
105 dmax = state->dmax;
106 #endif
107 wsize = state->wsize;
108 whave = state->whave;
109 write = state->write;
110 window = state->window;
111 hold = state->hold;
112 bits = state->bits;
113 lcode = state->lencode;
114 dcode = state->distcode;
115 lmask = (1U << state->lenbits) - 1;
116 dmask = (1U << state->distbits) - 1;
118 /* decode literals and length/distances until end-of-block or not enough
119 input data or output space */
120 do {
121 if (bits < 15) {
122 hold += (unsigned long)(PUP(in)) << bits;
123 bits += 8;
124 hold += (unsigned long)(PUP(in)) << bits;
125 bits += 8;
126 }
127 this = lcode[hold & lmask];
128 dolen:
129 op = (unsigned)(this.bits);
130 hold >>= op;
131 bits -= op;
132 op = (unsigned)(this.op);
133 if (op == 0) { /* literal */
134 PUP(out) = (unsigned char)(this.val);
135 }
136 else if (op & 16) { /* length base */
137 len = (unsigned)(this.val);
138 op &= 15; /* number of extra bits */
139 if (op) {
140 if (bits < op) {
141 hold += (unsigned long)(PUP(in)) << bits;
142 bits += 8;
143 }
144 len += (unsigned)hold & ((1U << op) - 1);
145 hold >>= op;
146 bits -= op;
147 }
148 if (bits < 15) {
149 hold += (unsigned long)(PUP(in)) << bits;
150 bits += 8;
151 hold += (unsigned long)(PUP(in)) << bits;
152 bits += 8;
153 }
154 this = dcode[hold & dmask];
155 dodist:
156 op = (unsigned)(this.bits);
157 hold >>= op;
158 bits -= op;
159 op = (unsigned)(this.op);
160 if (op & 16) { /* distance base */
161 dist = (unsigned)(this.val);
162 op &= 15; /* number of extra bits */
163 if (bits < op) {
164 hold += (unsigned long)(PUP(in)) << bits;
165 bits += 8;
166 if (bits < op) {
167 hold += (unsigned long)(PUP(in)) << bits;
168 bits += 8;
169 }
170 }
171 dist += (unsigned)hold & ((1U << op) - 1);
172 #ifdef INFLATE_STRICT
173 if (dist > dmax) {
174 strm->msg = (char *)"invalid distance too far back";
175 state->mode = BAD;
176 break;
177 }
178 #endif
179 hold >>= op;
180 bits -= op;
181 op = (unsigned)(out - beg); /* max distance in output */
182 if (dist > op) { /* see if copy from window */
183 op = dist - op; /* distance back in window */
184 if (op > whave) {
185 strm->msg = (char *)"invalid distance too far back";
186 state->mode = BAD;
187 break;
188 }
189 from = window - OFF;
190 if (write == 0) { /* very common case */
191 from += wsize - op;
192 if (op < len) { /* some from window */
193 len -= op;
194 do {
195 PUP(out) = PUP(from);
196 } while (--op);
197 from = out - dist; /* rest from output */
198 }
199 }
200 else if (write < op) { /* wrap around window */
201 from += wsize + write - op;
202 op -= write;
203 if (op < len) { /* some from end of window */
204 len -= op;
205 do {
206 PUP(out) = PUP(from);
207 } while (--op);
208 from = window - OFF;
209 if (write < len) { /* some from start of window */
210 op = write;
211 len -= op;
212 do {
213 PUP(out) = PUP(from);
214 } while (--op);
215 from = out - dist; /* rest from output */
216 }
217 }
218 }
219 else { /* contiguous in window */
220 from += write - op;
221 if (op < len) { /* some from window */
222 len -= op;
223 do {
224 PUP(out) = PUP(from);
225 } while (--op);
226 from = out - dist; /* rest from output */
227 }
228 }
229 while (len > 2) {
230 PUP(out) = PUP(from);
231 PUP(out) = PUP(from);
232 PUP(out) = PUP(from);
233 len -= 3;
234 }
235 if (len) {
236 PUP(out) = PUP(from);
237 if (len > 1)
238 PUP(out) = PUP(from);
239 }
240 }
241 else {
242 from = out - dist; /* copy direct from output */
243 do { /* minimum length is three */
244 PUP(out) = PUP(from);
245 PUP(out) = PUP(from);
246 PUP(out) = PUP(from);
247 len -= 3;
248 } while (len > 2);
249 if (len) {
250 PUP(out) = PUP(from);
251 if (len > 1)
252 PUP(out) = PUP(from);
253 }
254 }
255 }
256 else if ((op & 64) == 0) { /* 2nd level distance code */
257 this = dcode[this.val + (hold & ((1U << op) - 1))];
258 goto dodist;
259 }
260 else {
261 strm->msg = (char *)"invalid distance code";
262 state->mode = BAD;
263 break;
264 }
265 }
266 else if ((op & 64) == 0) { /* 2nd level length code */
267 this = lcode[this.val + (hold & ((1U << op) - 1))];
268 goto dolen;
269 }
270 else if (op & 32) { /* end-of-block */
271 state->mode = TYPE;
272 break;
273 }
274 else {
275 strm->msg = (char *)"invalid literal/length code";
276 state->mode = BAD;
277 break;
278 }
279 } while (in < last && out < end);
281 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
282 len = bits >> 3;
283 in -= len;
284 bits -= len << 3;
285 hold &= (1U << bits) - 1;
287 /* update state and return */
288 strm->next_in = in + OFF;
289 strm->next_out = out + OFF;
290 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
291 strm->avail_out = (unsigned)(out < end ?
292 257 + (end - out) : 257 - (out - end));
293 state->hold = hold;
294 state->bits = bits;
295 return;
296 }
298 /*
299 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
300 - Using bit fields for code structure
301 - Different op definition to avoid & for extra bits (do & for table bits)
302 - Three separate decoding do-loops for direct, window, and write == 0
303 - Special case for distance > 1 copies to do overlapped load and store copy
304 - Explicit branch predictions (based on measured branch probabilities)
305 - Deferring match copy and interspersed it with decoding subsequent codes
306 - Swapping literal/length else
307 - Swapping window/direct else
308 - Larger unrolled copy loops (three is about right)
309 - Moving len -= 3 statement into middle of loop
310 */
312 #endif /* !ASMINF */