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git.ipfire.org Git - people/ms/u-boot.git/blob - lib/zlib/inffast.c
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
6 /* U-boot: we already included these
15 /* Allow machine dependent optimization for post-increment or pre-increment.
16 Based on testing to date,
17 Pre-increment preferred for:
19 - MIPS R5000 (Randers-Pehrson)
20 Post-increment preferred for:
22 No measurable difference:
23 - Pentium III (Anderson)
28 # define PUP(a) *(a)++
31 # define PUP(a) *++(a)
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.
46 strm->avail_out >= 258
47 start >= strm->avail_out
50 On return, state->mode is one of:
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
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.
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
69 void inflate_fast(strm
, start
)
71 unsigned start
; /* inflate()'s starting value for strm->avail_out */
73 struct inflate_state FAR
*state
;
74 unsigned char FAR
*in
; /* local strm->next_in */
75 unsigned char FAR
*last
; /* while in < last, enough input available */
76 unsigned char FAR
*out
; /* local strm->next_out */
77 unsigned char FAR
*beg
; /* inflate()'s initial strm->next_out */
78 unsigned char FAR
*end
; /* while out < end, enough space available */
80 unsigned dmax
; /* maximum distance from zlib header */
82 unsigned wsize
; /* window size or zero if not using window */
83 unsigned whave
; /* valid bytes in the window */
84 unsigned write
; /* window write index */
85 unsigned char FAR
*window
; /* allocated sliding window, if wsize != 0 */
86 unsigned long hold
; /* local strm->hold */
87 unsigned bits
; /* local strm->bits */
88 code
const FAR
*lcode
; /* local strm->lencode */
89 code
const FAR
*dcode
; /* local strm->distcode */
90 unsigned lmask
; /* mask for first level of length codes */
91 unsigned dmask
; /* mask for first level of distance codes */
92 code
this; /* retrieved table entry */
93 unsigned op
; /* code bits, operation, extra bits, or */
94 /* window position, window bytes to copy */
95 unsigned len
; /* match length, unused bytes */
96 unsigned dist
; /* match distance */
97 unsigned char FAR
*from
; /* where to copy match from */
99 /* copy state to local variables */
100 state
= (struct inflate_state FAR
*)strm
->state
;
101 in
= strm
->next_in
- OFF
;
102 last
= in
+ (strm
->avail_in
- 5);
103 if (in
> last
&& strm
->avail_in
> 5) {
105 * overflow detected, limit strm->avail_in to the
106 * max. possible size and recalculate last
108 strm
->avail_in
= 0xffffffff - (unsigned int)in
;
109 last
= in
+ (strm
->avail_in
- 5);
111 out
= strm
->next_out
- OFF
;
112 beg
= out
- (start
- strm
->avail_out
);
113 end
= out
+ (strm
->avail_out
- 257);
114 #ifdef INFLATE_STRICT
117 wsize
= state
->wsize
;
118 whave
= state
->whave
;
119 write
= state
->write
;
120 window
= state
->window
;
123 lcode
= state
->lencode
;
124 dcode
= state
->distcode
;
125 lmask
= (1U << state
->lenbits
) - 1;
126 dmask
= (1U << state
->distbits
) - 1;
128 /* decode literals and length/distances until end-of-block or not enough
129 input data or output space */
132 hold
+= (unsigned long)(PUP(in
)) << bits
;
134 hold
+= (unsigned long)(PUP(in
)) << bits
;
137 this = lcode
[hold
& lmask
];
139 op
= (unsigned)(this.bits
);
142 op
= (unsigned)(this.op
);
143 if (op
== 0) { /* literal */
144 Tracevv((stderr
, this.val
>= 0x20 && this.val
< 0x7f ?
145 "inflate: literal '%c'\n" :
146 "inflate: literal 0x%02x\n", this.val
));
147 PUP(out
) = (unsigned char)(this.val
);
149 else if (op
& 16) { /* length base */
150 len
= (unsigned)(this.val
);
151 op
&= 15; /* number of extra bits */
154 hold
+= (unsigned long)(PUP(in
)) << bits
;
157 len
+= (unsigned)hold
& ((1U << op
) - 1);
161 Tracevv((stderr
, "inflate: length %u\n", len
));
163 hold
+= (unsigned long)(PUP(in
)) << bits
;
165 hold
+= (unsigned long)(PUP(in
)) << bits
;
168 this = dcode
[hold
& dmask
];
170 op
= (unsigned)(this.bits
);
173 op
= (unsigned)(this.op
);
174 if (op
& 16) { /* distance base */
175 dist
= (unsigned)(this.val
);
176 op
&= 15; /* number of extra bits */
178 hold
+= (unsigned long)(PUP(in
)) << bits
;
181 hold
+= (unsigned long)(PUP(in
)) << bits
;
185 dist
+= (unsigned)hold
& ((1U << op
) - 1);
186 #ifdef INFLATE_STRICT
188 strm
->msg
= (char *)"invalid distance too far back";
195 Tracevv((stderr
, "inflate: distance %u\n", dist
));
196 op
= (unsigned)(out
- beg
); /* max distance in output */
197 if (dist
> op
) { /* see if copy from window */
198 op
= dist
- op
; /* distance back in window */
200 strm
->msg
= (char *)"invalid distance too far back";
205 if (write
== 0) { /* very common case */
207 if (op
< len
) { /* some from window */
210 PUP(out
) = PUP(from
);
212 from
= out
- dist
; /* rest from output */
215 else if (write
< op
) { /* wrap around window */
216 from
+= wsize
+ write
- op
;
218 if (op
< len
) { /* some from end of window */
221 PUP(out
) = PUP(from
);
224 if (write
< len
) { /* some from start of window */
228 PUP(out
) = PUP(from
);
230 from
= out
- dist
; /* rest from output */
234 else { /* contiguous in window */
236 if (op
< len
) { /* some from window */
239 PUP(out
) = PUP(from
);
241 from
= out
- dist
; /* rest from output */
245 PUP(out
) = PUP(from
);
246 PUP(out
) = PUP(from
);
247 PUP(out
) = PUP(from
);
251 PUP(out
) = PUP(from
);
253 PUP(out
) = PUP(from
);
257 unsigned short *sout
;
260 from
= out
- dist
; /* copy direct from output */
261 /* minimum length is three */
263 if (!((long)(out
- 1 + OFF
) & 1)) {
264 PUP(out
) = PUP(from
);
267 sout
= (unsigned short *)(out
- OFF
);
269 unsigned short *sfrom
;
271 sfrom
= (unsigned short *)(from
- OFF
);
274 PUP(sout
) = get_unaligned(++sfrom
);
276 out
= (unsigned char *)sout
+ OFF
;
277 from
= (unsigned char *)sfrom
+ OFF
;
278 } else { /* dist == 1 or dist == 2 */
279 unsigned short pat16
;
281 pat16
= *(sout
-2+2*OFF
);
283 #if defined(__BIG_ENDIAN)
284 pat16
= (pat16
& 0xff) | ((pat16
& 0xff ) << 8);
285 #elif defined(__LITTLE_ENDIAN)
286 pat16
= (pat16
& 0xff00) | ((pat16
& 0xff00 ) >> 8);
288 #error __BIG_ENDIAN nor __LITTLE_ENDIAN is defined
294 out
= (unsigned char *)sout
+ OFF
;
297 PUP(out
) = PUP(from
);
300 else if ((op
& 64) == 0) { /* 2nd level distance code */
301 this = dcode
[this.val
+ (hold
& ((1U << op
) - 1))];
305 strm
->msg
= (char *)"invalid distance code";
310 else if ((op
& 64) == 0) { /* 2nd level length code */
311 this = lcode
[this.val
+ (hold
& ((1U << op
) - 1))];
314 else if (op
& 32) { /* end-of-block */
315 Tracevv((stderr
, "inflate: end of block\n"));
320 strm
->msg
= (char *)"invalid literal/length code";
324 } while (in
< last
&& out
< end
);
326 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
330 hold
&= (1U << bits
) - 1;
332 /* update state and return */
333 strm
->next_in
= in
+ OFF
;
334 strm
->next_out
= out
+ OFF
;
335 strm
->avail_in
= (unsigned)(in
< last
? 5 + (last
- in
) : 5 - (in
- last
));
336 strm
->avail_out
= (unsigned)(out
< end
?
337 257 + (end
- out
) : 257 - (out
- end
));
344 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
345 - Using bit fields for code structure
346 - Different op definition to avoid & for extra bits (do & for table bits)
347 - Three separate decoding do-loops for direct, window, and write == 0
348 - Special case for distance > 1 copies to do overlapped load and store copy
349 - Explicit branch predictions (based on measured branch probabilities)
350 - Deferring match copy and interspersed it with decoding subsequent codes
351 - Swapping literal/length else
352 - Swapping window/direct else
353 - Larger unrolled copy loops (three is about right)
354 - Moving len -= 3 statement into middle of loop