Lines Matching +full:literal +full:- +full:block
1 /* inffast.c -- fast decoding
2 * Copyright (C) 1995-2017 Mark Adler
12 # pragma message("Assembler code may have bugs -- use at your own risk")
16 Decode literal, length, and distance codes and write out the resulting
17 literal and match bytes until either not enough input or output is
18 available, an end-of-block is encountered, or a data error is encountered.
25 state->mode == LEN
26 strm->avail_in >= 6
27 strm->avail_out >= 258
28 start >= strm->avail_out
29 state->bits < 8
31 On return, state->mode is one of:
33 LEN -- ran out of enough output space or enough available input
34 TYPE -- reached end of block code, inflate() to interpret next block
35 BAD -- error in block data
39 - The maximum input bits used by a length/distance pair is 15 bits for the
42 Therefore if strm->avail_in >= 6, then there is enough input to avoid
45 - The maximum bytes that a single length/distance pair can output is 258
47 requires strm->avail_out >= 258 for each loop to avoid checking for
52 z_const unsigned char FAR *in; /* local strm->next_in */ in inflate_fast()
54 unsigned char FAR *out; /* local strm->next_out */ in inflate_fast()
55 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */ in inflate_fast()
64 unsigned long hold; /* local strm->hold */ in inflate_fast()
65 unsigned bits; /* local strm->bits */ in inflate_fast()
66 code const FAR *lcode; /* local strm->lencode */ in inflate_fast()
67 code const FAR *dcode; /* local strm->distcode */ in inflate_fast()
78 state = (struct inflate_state FAR *)strm->state; in inflate_fast()
79 in = strm->next_in; in inflate_fast()
80 last = in + (strm->avail_in - 5); in inflate_fast()
81 out = strm->next_out; in inflate_fast()
82 beg = out - (start - strm->avail_out); in inflate_fast()
83 end = out + (strm->avail_out - 257); in inflate_fast()
85 dmax = state->dmax; in inflate_fast()
87 wsize = state->wsize; in inflate_fast()
88 whave = state->whave; in inflate_fast()
89 wnext = state->wnext; in inflate_fast()
90 window = state->window; in inflate_fast()
91 hold = state->hold; in inflate_fast()
92 bits = state->bits; in inflate_fast()
93 lcode = state->lencode; in inflate_fast()
94 dcode = state->distcode; in inflate_fast()
95 lmask = (1U << state->lenbits) - 1; in inflate_fast()
96 dmask = (1U << state->distbits) - 1; in inflate_fast()
98 /* decode literals and length/distances until end-of-block or not enough in inflate_fast()
109 op = (unsigned)(here->bits); in inflate_fast()
111 bits -= op; in inflate_fast()
112 op = (unsigned)(here->op); in inflate_fast()
113 if (op == 0) { /* literal */ in inflate_fast()
114 Tracevv((stderr, here->val >= 0x20 && here->val < 0x7f ? in inflate_fast()
115 "inflate: literal '%c'\n" : in inflate_fast()
116 "inflate: literal 0x%02x\n", here->val)); in inflate_fast()
117 *out++ = (unsigned char)(here->val); in inflate_fast()
120 len = (unsigned)(here->val); in inflate_fast()
127 len += (unsigned)hold & ((1U << op) - 1); in inflate_fast()
129 bits -= op; in inflate_fast()
140 op = (unsigned)(here->bits); in inflate_fast()
142 bits -= op; in inflate_fast()
143 op = (unsigned)(here->op); in inflate_fast()
145 dist = (unsigned)(here->val); in inflate_fast()
155 dist += (unsigned)hold & ((1U << op) - 1); in inflate_fast()
158 strm->msg = (char *)"invalid distance too far back"; in inflate_fast()
159 state->mode = BAD; in inflate_fast()
164 bits -= op; in inflate_fast()
166 op = (unsigned)(out - beg); /* max distance in output */ in inflate_fast()
168 op = dist - op; /* distance back in window */ in inflate_fast()
170 if (state->sane) { in inflate_fast()
171 strm->msg = in inflate_fast()
173 state->mode = BAD; in inflate_fast()
177 if (len <= op - whave) { in inflate_fast()
180 } while (--len); in inflate_fast()
183 len -= op - whave; in inflate_fast()
186 } while (--op > whave); in inflate_fast()
188 from = out - dist; in inflate_fast()
191 } while (--len); in inflate_fast()
198 from += wsize - op; in inflate_fast()
200 len -= op; in inflate_fast()
203 } while (--op); in inflate_fast()
204 from = out - dist; /* rest from output */ in inflate_fast()
208 from += wsize + wnext - op; in inflate_fast()
209 op -= wnext; in inflate_fast()
211 len -= op; in inflate_fast()
214 } while (--op); in inflate_fast()
218 len -= op; in inflate_fast()
221 } while (--op); in inflate_fast()
222 from = out - dist; /* rest from output */ in inflate_fast()
227 from += wnext - op; in inflate_fast()
229 len -= op; in inflate_fast()
232 } while (--op); in inflate_fast()
233 from = out - dist; /* rest from output */ in inflate_fast()
240 len -= 3; in inflate_fast()
249 from = out - dist; /* copy direct from output */ in inflate_fast()
254 len -= 3; in inflate_fast()
264 here = dcode + here->val + (hold & ((1U << op) - 1)); in inflate_fast()
268 strm->msg = (char *)"invalid distance code"; in inflate_fast()
269 state->mode = BAD; in inflate_fast()
274 here = lcode + here->val + (hold & ((1U << op) - 1)); in inflate_fast()
277 else if (op & 32) { /* end-of-block */ in inflate_fast()
278 Tracevv((stderr, "inflate: end of block\n")); in inflate_fast()
279 state->mode = TYPE; in inflate_fast()
283 strm->msg = (char *)"invalid literal/length code"; in inflate_fast()
284 state->mode = BAD; in inflate_fast()
291 in -= len; in inflate_fast()
292 bits -= len << 3; in inflate_fast()
293 hold &= (1U << bits) - 1; in inflate_fast()
296 strm->next_in = in; in inflate_fast()
297 strm->next_out = out; in inflate_fast()
298 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); in inflate_fast()
299 strm->avail_out = (unsigned)(out < end ? in inflate_fast()
300 257 + (end - out) : 257 - (out - end)); in inflate_fast()
301 state->hold = hold; in inflate_fast()
302 state->bits = bits; in inflate_fast()
308 - Using bit fields for code structure
309 - Different op definition to avoid & for extra bits (do & for table bits)
310 - Three separate decoding do-loops for direct, window, and wnext == 0
311 - Special case for distance > 1 copies to do overlapped load and store copy
312 - Explicit branch predictions (based on measured branch probabilities)
313 - Deferring match copy and interspersed it with decoding subsequent codes
314 - Swapping literal/length else
315 - Swapping window/direct else
316 - Larger unrolled copy loops (three is about right)
317 - Moving len -= 3 statement into middle of loop