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 /* U-Boot: we already included these
7 #include "zutil.h"
8 #include "inftrees.h"
9 #include "inflate.h"
10 #include "inffast.h"
11 */
12
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)++
29 #else
30 # define OFF 1
31 # define PUP(a) *++(a)
32 #endif
33
34 /*
35 Decode literal, length, and distance codes and write out the resulting
36 literal and match bytes until either not enough input or output is
37 available, an end-of-block is encountered, or a data error is encountered.
38 When large enough input and output buffers are supplied to inflate(), for
39 example, a 16K input buffer and a 64K output buffer, more than 95% of the
40 inflate execution time is spent in this routine.
41
42 Entry assumptions:
43
44 state->mode == LEN
45 strm->avail_in >= 6
46 strm->avail_out >= 258
47 start >= strm->avail_out
48 state->bits < 8
49
50 On return, state->mode is one of:
51
52 LEN -- ran out of enough output space or enough available input
53 TYPE -- reached end of block code, inflate() to interpret next block
54 BAD -- error in block data
55
56 Notes:
57
58 - The maximum input bits used by a length/distance pair is 15 bits for the
59 length code, 5 bits for the length extra, 15 bits for the distance code,
60 and 13 bits for the distance extra. This totals 48 bits, or six bytes.
61 Therefore if strm->avail_in >= 6, then there is enough input to avoid
62 checking for available input while decoding.
63
64 - The maximum bytes that a single length/distance pair can output is 258
65 bytes, which is the maximum length that can be coded. inflate_fast()
66 requires strm->avail_out >= 258 for each loop to avoid checking for
67 output space.
68 */
inflate_fast(z_streamp strm,unsigned start)69 void inflate_fast(z_streamp strm, unsigned start)
70 /* start: inflate()'s starting value for strm->avail_out */
71 {
72 struct inflate_state FAR *state;
73 unsigned char FAR *in; /* local strm->next_in */
74 unsigned char FAR *last; /* while in < last, enough input available */
75 unsigned char FAR *out; /* local strm->next_out */
76 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */
77 unsigned char FAR *end; /* while out < end, enough space available */
78 #ifdef INFLATE_STRICT
79 unsigned dmax; /* maximum distance from zlib header */
80 #endif
81 unsigned wsize; /* window size or zero if not using window */
82 unsigned whave; /* valid bytes in the window */
83 unsigned write; /* window write index */
84 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */
85 unsigned long hold; /* local strm->hold */
86 unsigned bits; /* local strm->bits */
87 code const FAR *lcode; /* local strm->lencode */
88 code const FAR *dcode; /* local strm->distcode */
89 unsigned lmask; /* mask for first level of length codes */
90 unsigned dmask; /* mask for first level of distance codes */
91 code this; /* retrieved table entry */
92 unsigned op; /* code bits, operation, extra bits, or */
93 /* window position, window bytes to copy */
94 unsigned len; /* match length, unused bytes */
95 unsigned dist; /* match distance */
96 unsigned char FAR *from; /* where to copy match from */
97
98 /* copy state to local variables */
99 state = (struct inflate_state FAR *)strm->state;
100 in = strm->next_in - OFF;
101 last = in + (strm->avail_in - 5);
102 if (in > last && strm->avail_in > 5) {
103 /*
104 * overflow detected, limit strm->avail_in to the
105 * max. possible size and recalculate last
106 */
107 strm->avail_in = 0xffffffff - (uintptr_t)in;
108 last = in + (strm->avail_in - 5);
109 }
110 out = strm->next_out - OFF;
111 beg = out - (start - strm->avail_out);
112 end = out + (strm->avail_out - 257);
113 #ifdef INFLATE_STRICT
114 dmax = state->dmax;
115 #endif
116 wsize = state->wsize;
117 whave = state->whave;
118 write = state->write;
119 window = state->window;
120 hold = state->hold;
121 bits = state->bits;
122 lcode = state->lencode;
123 dcode = state->distcode;
124 lmask = (1U << state->lenbits) - 1;
125 dmask = (1U << state->distbits) - 1;
126
127 /* decode literals and length/distances until end-of-block or not enough
128 input data or output space */
129 do {
130 if (bits < 15) {
131 hold += (unsigned long)(PUP(in)) << bits;
132 bits += 8;
133 hold += (unsigned long)(PUP(in)) << bits;
134 bits += 8;
135 }
136 this = lcode[hold & lmask];
137 dolen:
138 op = (unsigned)(this.bits);
139 hold >>= op;
140 bits -= op;
141 op = (unsigned)(this.op);
142 if (op == 0) { /* literal */
143 Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ?
144 "inflate: literal '%c'\n" :
145 "inflate: literal 0x%02x\n", this.val));
146 PUP(out) = (unsigned char)(this.val);
147 }
148 else if (op & 16) { /* length base */
149 len = (unsigned)(this.val);
150 op &= 15; /* number of extra bits */
151 if (op) {
152 if (bits < op) {
153 hold += (unsigned long)(PUP(in)) << bits;
154 bits += 8;
155 }
156 len += (unsigned)hold & ((1U << op) - 1);
157 hold >>= op;
158 bits -= op;
159 }
160 Tracevv((stderr, "inflate: length %u\n", len));
161 if (bits < 15) {
162 hold += (unsigned long)(PUP(in)) << bits;
163 bits += 8;
164 hold += (unsigned long)(PUP(in)) << bits;
165 bits += 8;
166 }
167 this = dcode[hold & dmask];
168 dodist:
169 op = (unsigned)(this.bits);
170 hold >>= op;
171 bits -= op;
172 op = (unsigned)(this.op);
173 if (op & 16) { /* distance base */
174 dist = (unsigned)(this.val);
175 op &= 15; /* number of extra bits */
176 if (bits < op) {
177 hold += (unsigned long)(PUP(in)) << bits;
178 bits += 8;
179 if (bits < op) {
180 hold += (unsigned long)(PUP(in)) << bits;
181 bits += 8;
182 }
183 }
184 dist += (unsigned)hold & ((1U << op) - 1);
185 #ifdef INFLATE_STRICT
186 if (dist > dmax) {
187 strm->msg = (char *)"invalid distance too far back";
188 state->mode = BAD;
189 break;
190 }
191 #endif
192 hold >>= op;
193 bits -= op;
194 Tracevv((stderr, "inflate: distance %u\n", dist));
195 op = (unsigned)(out - beg); /* max distance in output */
196 if (dist > op) { /* see if copy from window */
197 op = dist - op; /* distance back in window */
198 if (op > whave) {
199 strm->msg = (char *)"invalid distance too far back";
200 state->mode = BAD;
201 break;
202 }
203 from = window - OFF;
204 if (write == 0) { /* very common case */
205 from += wsize - op;
206 if (op < len) { /* some from window */
207 len -= op;
208 do {
209 PUP(out) = PUP(from);
210 } while (--op);
211 from = out - dist; /* rest from output */
212 }
213 }
214 else if (write < op) { /* wrap around window */
215 from += wsize + write - op;
216 op -= write;
217 if (op < len) { /* some from end of window */
218 len -= op;
219 do {
220 PUP(out) = PUP(from);
221 } while (--op);
222 from = window - OFF;
223 if (write < len) { /* some from start of window */
224 op = write;
225 len -= op;
226 do {
227 PUP(out) = PUP(from);
228 } while (--op);
229 from = out - dist; /* rest from output */
230 }
231 }
232 }
233 else { /* contiguous in window */
234 from += write - op;
235 if (op < len) { /* some from window */
236 len -= op;
237 do {
238 PUP(out) = PUP(from);
239 } while (--op);
240 from = out - dist; /* rest from output */
241 }
242 }
243 while (len > 2) {
244 PUP(out) = PUP(from);
245 PUP(out) = PUP(from);
246 PUP(out) = PUP(from);
247 len -= 3;
248 }
249 if (len) {
250 PUP(out) = PUP(from);
251 if (len > 1)
252 PUP(out) = PUP(from);
253 }
254 }
255 else {
256 unsigned short *sout;
257 unsigned long loops;
258
259 from = out - dist; /* copy direct from output */
260 /* minimum length is three */
261 /* Align out addr */
262 if (!((long)(out - 1 + OFF) & 1)) {
263 PUP(out) = PUP(from);
264 len--;
265 }
266 sout = (unsigned short *)(out - OFF);
267 if (dist > 2 ) {
268 unsigned short *sfrom;
269
270 sfrom = (unsigned short *)(from - OFF);
271 loops = len >> 1;
272 do
273 PUP(sout) = get_unaligned(++sfrom);
274 while (--loops);
275 out = (unsigned char *)sout + OFF;
276 from = (unsigned char *)sfrom + OFF;
277 } else { /* dist == 1 or dist == 2 */
278 unsigned short pat16;
279
280 pat16 = *(sout-2+2*OFF);
281 if (dist == 1)
282 #if defined(__BIG_ENDIAN)
283 pat16 = (pat16 & 0xff) | ((pat16 & 0xff ) << 8);
284 #elif defined(__LITTLE_ENDIAN)
285 pat16 = (pat16 & 0xff00) | ((pat16 & 0xff00 ) >> 8);
286 #else
287 #error __BIG_ENDIAN nor __LITTLE_ENDIAN is defined
288 #endif
289 loops = len >> 1;
290 do
291 PUP(sout) = pat16;
292 while (--loops);
293 out = (unsigned char *)sout + OFF;
294 }
295 if (len & 1)
296 PUP(out) = PUP(from);
297 }
298 }
299 else if ((op & 64) == 0) { /* 2nd level distance code */
300 this = dcode[this.val + (hold & ((1U << op) - 1))];
301 goto dodist;
302 }
303 else {
304 strm->msg = (char *)"invalid distance code";
305 state->mode = BAD;
306 break;
307 }
308 }
309 else if ((op & 64) == 0) { /* 2nd level length code */
310 this = lcode[this.val + (hold & ((1U << op) - 1))];
311 goto dolen;
312 }
313 else if (op & 32) { /* end-of-block */
314 Tracevv((stderr, "inflate: end of block\n"));
315 state->mode = TYPE;
316 break;
317 }
318 else {
319 strm->msg = (char *)"invalid literal/length code";
320 state->mode = BAD;
321 break;
322 }
323 } while (in < last && out < end);
324
325 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
326 len = bits >> 3;
327 in -= len;
328 bits -= len << 3;
329 hold &= (1U << bits) - 1;
330
331 /* update state and return */
332 strm->next_in = in + OFF;
333 strm->next_out = out + OFF;
334 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
335 strm->avail_out = (unsigned)(out < end ?
336 257 + (end - out) : 257 - (out - end));
337 state->hold = hold;
338 state->bits = bits;
339 return;
340 }
341
342 /*
343 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
344 - Using bit fields for code structure
345 - Different op definition to avoid & for extra bits (do & for table bits)
346 - Three separate decoding do-loops for direct, window, and write == 0
347 - Special case for distance > 1 copies to do overlapped load and store copy
348 - Explicit branch predictions (based on measured branch probabilities)
349 - Deferring match copy and interspersed it with decoding subsequent codes
350 - Swapping literal/length else
351 - Swapping window/direct else
352 - Larger unrolled copy loops (three is about right)
353 - Moving len -= 3 statement into middle of loop
354 */
355
356 #endif /* !ASMINF */
357