inffast.c (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2) inffast.c (4f3865fb57a04db7cca068fed1c15badc064a302)
1/* inffast.c -- process literals and length/distance pairs fast
2 * Copyright (C) 1995-1998 Mark Adler
3 * For conditions of distribution and use, see copyright notice in zlib.h
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 */
5
6#include <linux/zutil.h>
7#include "inftrees.h"
4 */
5
6#include <linux/zutil.h>
7#include "inftrees.h"
8#include "infblock.h"
9#include "infcodes.h"
10#include "infutil.h"
8#include "inflate.h"
11#include "inffast.h"
12
9#include "inffast.h"
10
13struct inflate_codes_state;
11#ifndef ASMINF
14
12
15/* simplify the use of the inflate_huft type with some defines */
16#define exop word.what.Exop
17#define bits word.what.Bits
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
18
31
19/* macros for bit input with no checking and for returning unused bytes */
20#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
21#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}
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.
22
39
23/* Called with number of bytes left to write in window at least 258
24 (the maximum string length) and number of input bytes available
25 at least ten. The ten bytes are six bytes for the longest length/
26 distance pair plus four bytes for overloading the bit buffer. */
40 Entry assumptions:
27
41
28int zlib_inflate_fast(
29 uInt bl,
30 uInt bd,
31 inflate_huft *tl,
32 inflate_huft *td, /* need separate declaration for Borland C++ */
33 inflate_blocks_statef *s,
34 z_streamp z
35)
36{
37 inflate_huft *t; /* temporary pointer */
38 uInt e; /* extra bits or operation */
39 uLong b; /* bit buffer */
40 uInt k; /* bits in bit buffer */
41 Byte *p; /* input data pointer */
42 uInt n; /* bytes available there */
43 Byte *q; /* output window write pointer */
44 uInt m; /* bytes to end of window or read pointer */
45 uInt ml; /* mask for literal/length tree */
46 uInt md; /* mask for distance tree */
47 uInt c; /* bytes to copy */
48 uInt d; /* distance back to copy from */
49 Byte *r; /* copy source pointer */
42 state->mode == LEN
43 strm->avail_in >= 6
44 strm->avail_out >= 258
45 start >= strm->avail_out
46 state->bits < 8
50
47
51 /* load input, output, bit values */
52 LOAD
48 On return, state->mode is one of:
53
49
54 /* initialize masks */
55 ml = zlib_inflate_mask[bl];
56 md = zlib_inflate_mask[bd];
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
57
53
58 /* do until not enough input or output space for fast loop */
59 do { /* assume called with m >= 258 && n >= 10 */
60 /* get literal/length code */
61 GRABBITS(20) /* max bits for literal/length code */
62 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
63 {
64 DUMPBITS(t->bits)
65 *q++ = (Byte)t->base;
66 m--;
67 continue;
68 }
69 do {
70 DUMPBITS(t->bits)
71 if (e & 16)
72 {
73 /* get extra bits for length */
74 e &= 15;
75 c = t->base + ((uInt)b & zlib_inflate_mask[e]);
76 DUMPBITS(e)
54 Notes:
77
55
78 /* decode distance base of block to copy */
79 GRABBITS(15); /* max bits for distance code */
80 e = (t = td + ((uInt)b & md))->exop;
81 do {
82 DUMPBITS(t->bits)
83 if (e & 16)
84 {
85 /* get extra bits to add to distance base */
86 e &= 15;
87 GRABBITS(e) /* get extra bits (up to 13) */
88 d = t->base + ((uInt)b & zlib_inflate_mask[e]);
89 DUMPBITS(e)
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.
90
61
91 /* do the copy */
92 m -= c;
93 r = q - d;
94 if (r < s->window) /* wrap if needed */
95 {
96 do {
97 r += s->end - s->window; /* force pointer in window */
98 } while (r < s->window); /* covers invalid distances */
99 e = s->end - r;
100 if (c > e)
101 {
102 c -= e; /* wrapped copy */
103 do {
104 *q++ = *r++;
105 } while (--e);
106 r = s->window;
107 do {
108 *q++ = *r++;
109 } while (--c);
110 }
111 else /* normal copy */
112 {
113 *q++ = *r++; c--;
114 *q++ = *r++; c--;
115 do {
116 *q++ = *r++;
117 } while (--c);
118 }
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.
66 */
67void inflate_fast(strm, start)
68z_streamp strm;
69unsigned start; /* inflate()'s starting value for strm->avail_out */
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 */
96
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;
117
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;
119 }
147 }
120 else /* normal copy */
121 {
122 *q++ = *r++; c--;
123 *q++ = *r++; c--;
124 do {
125 *q++ = *r++;
126 } while (--c);
148 if (bits < 15) {
149 hold += (unsigned long)(PUP(in)) << bits;
150 bits += 8;
151 hold += (unsigned long)(PUP(in)) << bits;
152 bits += 8;
127 }
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;
128 break;
272 break;
129 }
130 else if ((e & 64) == 0)
131 {
132 t += t->base;
133 e = (t += ((uInt)b & zlib_inflate_mask[e]))->exop;
134 }
135 else
136 {
137 z->msg = (char*)"invalid distance code";
138 UNGRAB
139 UPDATE
140 return Z_DATA_ERROR;
141 }
142 } while (1);
143 break;
144 }
145 if ((e & 64) == 0)
146 {
147 t += t->base;
148 if ((e = (t += ((uInt)b & zlib_inflate_mask[e]))->exop) == 0)
149 {
150 DUMPBITS(t->bits)
151 *q++ = (Byte)t->base;
152 m--;
153 break;
154 }
273 }
155 }
156 else if (e & 32)
157 {
158 UNGRAB
159 UPDATE
160 return Z_STREAM_END;
161 }
162 else
163 {
164 z->msg = (char*)"invalid literal/length code";
165 UNGRAB
166 UPDATE
167 return Z_DATA_ERROR;
168 }
169 } while (1);
170 } while (m >= 258 && n >= 10);
274 else {
275 strm->msg = (char *)"invalid literal/length code";
276 state->mode = BAD;
277 break;
278 }
279 } while (in < last && out < end);
171
280
172 /* not enough input or output--restore pointers and return */
173 UNGRAB
174 UPDATE
175 return Z_OK;
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;
286
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;
176}
296}
297
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 */
311
312#endif /* !ASMINF */