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comparison lib/zlib/inffast.c @ 0:9c0607679772

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author Ritor1
date Sat, 12 Jan 2013 09:45:18 +0600
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-1:000000000000 0:9c0607679772
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
4 */
5
6 #include "zutil.h"
7 #include "inftrees.h"
8 #include "infblock.h"
9 #include "infcodes.h"
10 #include "infutil.h"
11 #include "inffast.h"
12
13 struct inflate_codes_state {int dummy;}; /* for buggy compilers */
14
15 /* simplify the use of the inflate_huft type with some defines */
16 #define exop word.what.Exop
17 #define bits word.what.Bits
18
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;}
22
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. */
27
28 int inflate_fast(bl, bd, tl, td, s, z)
29 uInt bl, bd;
30 inflate_huft *tl;
31 inflate_huft *td; /* need separate declaration for Borland C++ */
32 inflate_blocks_statef *s;
33 z_streamp z;
34 {
35 inflate_huft *t; /* temporary pointer */
36 uInt e; /* extra bits or operation */
37 uLong b; /* bit buffer */
38 uInt k; /* bits in bit buffer */
39 Bytef *p; /* input data pointer */
40 uInt n; /* bytes available there */
41 Bytef *q; /* output window write pointer */
42 uInt m; /* bytes to end of window or read pointer */
43 uInt ml; /* mask for literal/length tree */
44 uInt md; /* mask for distance tree */
45 uInt c; /* bytes to copy */
46 uInt d; /* distance back to copy from */
47 Bytef *r; /* copy source pointer */
48
49 /* load input, output, bit values */
50 LOAD
51
52 /* initialize masks */
53 ml = inflate_mask[bl];
54 md = inflate_mask[bd];
55
56 /* do until not enough input or output space for fast loop */
57 do { /* assume called with m >= 258 && n >= 10 */
58 /* get literal/length code */
59 GRABBITS(20) /* max bits for literal/length code */
60 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
61 {
62 DUMPBITS(t->bits)
63 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
64 "inflate: * literal '%c'\n" :
65 "inflate: * literal 0x%02x\n", t->base));
66 *q++ = (Byte)t->base;
67 m--;
68 continue;
69 }
70 do {
71 DUMPBITS(t->bits)
72 if (e & 16)
73 {
74 /* get extra bits for length */
75 e &= 15;
76 c = t->base + ((uInt)b & inflate_mask[e]);
77 DUMPBITS(e)
78 Tracevv((stderr, "inflate: * length %u\n", c));
79
80 /* decode distance base of block to copy */
81 GRABBITS(15); /* max bits for distance code */
82 e = (t = td + ((uInt)b & md))->exop;
83 do {
84 DUMPBITS(t->bits)
85 if (e & 16)
86 {
87 /* get extra bits to add to distance base */
88 e &= 15;
89 GRABBITS(e) /* get extra bits (up to 13) */
90 d = t->base + ((uInt)b & inflate_mask[e]);
91 DUMPBITS(e)
92 Tracevv((stderr, "inflate: * distance %u\n", d));
93
94 /* do the copy */
95 m -= c;
96 if ((uInt)(q - s->window) >= d) /* offset before dest */
97 { /* just copy */
98 r = q - d;
99 *q++ = *r++; c--; /* minimum count is three, */
100 *q++ = *r++; c--; /* so unroll loop a little */
101 }
102 else /* else offset after destination */
103 {
104 e = d - (uInt)(q - s->window); /* bytes from offset to end */
105 r = s->end - e; /* pointer to offset */
106 if (c > e) /* if source crosses, */
107 {
108 c -= e; /* copy to end of window */
109 do {
110 *q++ = *r++;
111 } while (--e);
112 r = s->window; /* copy rest from start of window */
113 }
114 }
115 do { /* copy all or what's left */
116 *q++ = *r++;
117 } while (--c);
118 break;
119 }
120 else if ((e & 64) == 0)
121 {
122 t += t->base;
123 e = (t += ((uInt)b & inflate_mask[e]))->exop;
124 }
125 else
126 {
127 z->msg = (char*)"invalid distance code";
128 UNGRAB
129 UPDATE
130 return Z_DATA_ERROR;
131 }
132 } while (1);
133 break;
134 }
135 if ((e & 64) == 0)
136 {
137 t += t->base;
138 if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
139 {
140 DUMPBITS(t->bits)
141 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
142 "inflate: * literal '%c'\n" :
143 "inflate: * literal 0x%02x\n", t->base));
144 *q++ = (Byte)t->base;
145 m--;
146 break;
147 }
148 }
149 else if (e & 32)
150 {
151 Tracevv((stderr, "inflate: * end of block\n"));
152 UNGRAB
153 UPDATE
154 return Z_STREAM_END;
155 }
156 else
157 {
158 z->msg = (char*)"invalid literal/length code";
159 UNGRAB
160 UPDATE
161 return Z_DATA_ERROR;
162 }
163 } while (1);
164 } while (m >= 258 && n >= 10);
165
166 /* not enough input or output--restore pointers and return */
167 UNGRAB
168 UPDATE
169 return Z_OK;
170 }