3fcffae4981b19ba4cb498076ab6d0ad2d4876c3
[pdfium.git] / core / src / fxcodec / fx_zlib / zlib_v128 / fx_zlib_inffast.c
1 /* inffast.c -- fast decoding
2  * Copyright (C) 1995-2008, 2010, 2013 Mark Adler
3  * For conditions of distribution and use, see copyright notice in zlib.h
4  */
5
6 #include "zutil.h"
7 #include "inftrees.h"
8 #include "inflate.h"
9 #include "inffast.h"
10
11 #ifndef ASMINF
12
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
31
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.
39
40    Entry assumptions:
41
42         state->mode == LEN
43         strm->avail_in >= 6
44         strm->avail_out >= 258
45         start >= strm->avail_out
46         state->bits < 8
47
48    On return, state->mode is one of:
49
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
53
54    Notes:
55
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.
61
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  */
67 void ZLIB_INTERNAL inflate_fast(
68 z_streamp strm,
69 unsigned start)         /* inflate()'s starting value for strm->avail_out */
70 {
71     struct inflate_state FAR *state;
72     z_const unsigned char FAR *in;      /* local strm->next_in */
73     z_const unsigned char FAR *last;    /* have enough input while in < last */
74     unsigned char FAR *out;     /* local strm->next_out */
75     unsigned char FAR *beg;     /* inflate()'s initial strm->next_out */
76     unsigned char FAR *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 wnext;             /* window write index */
83     unsigned char FAR *window;  /* allocated sliding window, if wsize != 0 */
84     unsigned long hold;         /* local strm->hold */
85     unsigned bits;              /* local strm->bits */
86     code const FAR *lcode;      /* local strm->lencode */
87     code const FAR *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 here;                  /* 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 FAR *from;    /* where to copy match from */
96
97     /* copy state to local variables */
98     state = (struct inflate_state FAR *)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     wnext = state->wnext;
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         here = lcode[hold & lmask];
128       dolen:
129         op = (unsigned)(here.bits);
130         hold >>= op;
131         bits -= op;
132         op = (unsigned)(here.op);
133         if (op == 0) {                          /* literal */
134             Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ?
135                     "inflate:         literal '%c'\n" :
136                     "inflate:         literal 0x%02x\n", here.val));
137             PUP(out) = (unsigned char)(here.val);
138         }
139         else if (op & 16) {                     /* length base */
140             len = (unsigned)(here.val);
141             op &= 15;                           /* number of extra bits */
142             if (op) {
143                 if (bits < op) {
144                     hold += (unsigned long)(PUP(in)) << bits;
145                     bits += 8;
146                 }
147                 len += (unsigned)hold & ((1U << op) - 1);
148                 hold >>= op;
149                 bits -= op;
150             }
151             Tracevv((stderr, "inflate:         length %u\n", len));
152             if (bits < 15) {
153                 hold += (unsigned long)(PUP(in)) << bits;
154                 bits += 8;
155                 hold += (unsigned long)(PUP(in)) << bits;
156                 bits += 8;
157             }
158             here = dcode[hold & dmask];
159           dodist:
160             op = (unsigned)(here.bits);
161             hold >>= op;
162             bits -= op;
163             op = (unsigned)(here.op);
164             if (op & 16) {                      /* distance base */
165                 dist = (unsigned)(here.val);
166                 op &= 15;                       /* number of extra bits */
167                 if (bits < op) {
168                     hold += (unsigned long)(PUP(in)) << bits;
169                     bits += 8;
170                     if (bits < op) {
171                         hold += (unsigned long)(PUP(in)) << bits;
172                         bits += 8;
173                     }
174                 }
175                 dist += (unsigned)hold & ((1U << op) - 1);
176 #ifdef INFLATE_STRICT
177                 if (dist > dmax) {
178                     strm->msg = (char *)"invalid distance too far back";
179                     state->mode = BAD;
180                     break;
181                 }
182 #endif
183                 hold >>= op;
184                 bits -= op;
185                 Tracevv((stderr, "inflate:         distance %u\n", dist));
186                 op = (unsigned)(out - beg);     /* max distance in output */
187                 if (dist > op) {                /* see if copy from window */
188                     op = dist - op;             /* distance back in window */
189                     if (op > whave) {
190                         if (state->sane) {
191                             strm->msg =
192                                 (char *)"invalid distance too far back";
193                             state->mode = BAD;
194                             break;
195                         }
196 #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
197                         if (len <= op - whave) {
198                             do {
199                                 PUP(out) = 0;
200                             } while (--len);
201                             continue;
202                         }
203                         len -= op - whave;
204                         do {
205                             PUP(out) = 0;
206                         } while (--op > whave);
207                         if (op == 0) {
208                             from = out - dist;
209                             do {
210                                 PUP(out) = PUP(from);
211                             } while (--len);
212                             continue;
213                         }
214 #endif
215                     }
216                     from = window - OFF;
217                     if (wnext == 0) {           /* very common case */
218                         from += wsize - op;
219                         if (op < len) {         /* some from window */
220                             len -= op;
221                             do {
222                                 PUP(out) = PUP(from);
223                             } while (--op);
224                             from = out - dist;  /* rest from output */
225                         }
226                     }
227                     else if (wnext < op) {      /* wrap around window */
228                         from += wsize + wnext - op;
229                         op -= wnext;
230                         if (op < len) {         /* some from end of window */
231                             len -= op;
232                             do {
233                                 PUP(out) = PUP(from);
234                             } while (--op);
235                             from = window - OFF;
236                             if (wnext < len) {  /* some from start of window */
237                                 op = wnext;
238                                 len -= op;
239                                 do {
240                                     PUP(out) = PUP(from);
241                                 } while (--op);
242                                 from = out - dist;      /* rest from output */
243                             }
244                         }
245                     }
246                     else {                      /* contiguous in window */
247                         from += wnext - op;
248                         if (op < len) {         /* some from window */
249                             len -= op;
250                             do {
251                                 PUP(out) = PUP(from);
252                             } while (--op);
253                             from = out - dist;  /* rest from output */
254                         }
255                     }
256                     while (len > 2) {
257                         PUP(out) = PUP(from);
258                         PUP(out) = PUP(from);
259                         PUP(out) = PUP(from);
260                         len -= 3;
261                     }
262                     if (len) {
263                         PUP(out) = PUP(from);
264                         if (len > 1)
265                             PUP(out) = PUP(from);
266                     }
267                 }
268                 else {
269                     from = out - dist;          /* copy direct from output */
270                     do {                        /* minimum length is three */
271                         PUP(out) = PUP(from);
272                         PUP(out) = PUP(from);
273                         PUP(out) = PUP(from);
274                         len -= 3;
275                     } while (len > 2);
276                     if (len) {
277                         PUP(out) = PUP(from);
278                         if (len > 1)
279                             PUP(out) = PUP(from);
280                     }
281                 }
282             }
283             else if ((op & 64) == 0) {          /* 2nd level distance code */
284                 here = dcode[here.val + (hold & ((1U << op) - 1))];
285                 goto dodist;
286             }
287             else {
288                 strm->msg = (char *)"invalid distance code";
289                 state->mode = BAD;
290                 break;
291             }
292         }
293         else if ((op & 64) == 0) {              /* 2nd level length code */
294             here = lcode[here.val + (hold & ((1U << op) - 1))];
295             goto dolen;
296         }
297         else if (op & 32) {                     /* end-of-block */
298             Tracevv((stderr, "inflate:         end of block\n"));
299             state->mode = TYPE;
300             break;
301         }
302         else {
303             strm->msg = (char *)"invalid literal/length code";
304             state->mode = BAD;
305             break;
306         }
307     } while (in < last && out < end);
308
309     /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
310     len = bits >> 3;
311     in -= len;
312     bits -= len << 3;
313     hold &= (1U << bits) - 1;
314
315     /* update state and return */
316     strm->next_in = in + OFF;
317     strm->next_out = out + OFF;
318     strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
319     strm->avail_out = (unsigned)(out < end ?
320                                  257 + (end - out) : 257 - (out - end));
321     state->hold = hold;
322     state->bits = bits;
323     return;
324 }
325
326 /*
327    inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
328    - Using bit fields for code structure
329    - Different op definition to avoid & for extra bits (do & for table bits)
330    - Three separate decoding do-loops for direct, window, and wnext == 0
331    - Special case for distance > 1 copies to do overlapped load and store copy
332    - Explicit branch predictions (based on measured branch probabilities)
333    - Deferring match copy and interspersed it with decoding subsequent codes
334    - Swapping literal/length else
335    - Swapping window/direct else
336    - Larger unrolled copy loops (three is about right)
337    - Moving len -= 3 statement into middle of loop
338  */
339
340 #endif /* !ASMINF */