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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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 <linux/zutil.h>
7#include "inftrees.h"
8#include "infblock.h"
9#include "infcodes.h"
10#include "infutil.h"
11#include "inffast.h"
12
13struct inflate_codes_state;
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
28int zlib_inflate_fast(
29 uInt bl,
30 uInt bd,
31 inflate_huft *tl,
32 inflate_huft *td, /* need separate declaration for Borland C++ */
33 inflate_blocks_statef *s,
34 z_streamp z
35)
36{
37 inflate_huft *t; /* temporary pointer */
38 uInt e; /* extra bits or operation */
39 uLong b; /* bit buffer */
40 uInt k; /* bits in bit buffer */
41 Byte *p; /* input data pointer */
42 uInt n; /* bytes available there */
43 Byte *q; /* output window write pointer */
44 uInt m; /* bytes to end of window or read pointer */
45 uInt ml; /* mask for literal/length tree */
46 uInt md; /* mask for distance tree */
47 uInt c; /* bytes to copy */
48 uInt d; /* distance back to copy from */
49 Byte *r; /* copy source pointer */
50
51 /* load input, output, bit values */
52 LOAD
53
54 /* initialize masks */
55 ml = zlib_inflate_mask[bl];
56 md = zlib_inflate_mask[bd];
57
58 /* do until not enough input or output space for fast loop */
59 do { /* assume called with m >= 258 && n >= 10 */
60 /* get literal/length code */
61 GRABBITS(20) /* max bits for literal/length code */
62 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
63 {
64 DUMPBITS(t->bits)
65 *q++ = (Byte)t->base;
66 m--;
67 continue;
68 }
69 do {
70 DUMPBITS(t->bits)
71 if (e & 16)
72 {
73 /* get extra bits for length */
74 e &= 15;
75 c = t->base + ((uInt)b & zlib_inflate_mask[e]);
76 DUMPBITS(e)
77
78 /* decode distance base of block to copy */
79 GRABBITS(15); /* max bits for distance code */
80 e = (t = td + ((uInt)b & md))->exop;
81 do {
82 DUMPBITS(t->bits)
83 if (e & 16)
84 {
85 /* get extra bits to add to distance base */
86 e &= 15;
87 GRABBITS(e) /* get extra bits (up to 13) */
88 d = t->base + ((uInt)b & zlib_inflate_mask[e]);
89 DUMPBITS(e)
90
91 /* do the copy */
92 m -= c;
93 r = q - d;
94 if (r < s->window) /* wrap if needed */
95 {
96 do {
97 r += s->end - s->window; /* force pointer in window */
98 } while (r < s->window); /* covers invalid distances */
99 e = s->end - r;
100 if (c > e)
101 {
102 c -= e; /* wrapped copy */
103 do {
104 *q++ = *r++;
105 } while (--e);
106 r = s->window;
107 do {
108 *q++ = *r++;
109 } while (--c);
110 }
111 else /* normal copy */
112 {
113 *q++ = *r++; c--;
114 *q++ = *r++; c--;
115 do {
116 *q++ = *r++;
117 } while (--c);
118 }
119 }
120 else /* normal copy */
121 {
122 *q++ = *r++; c--;
123 *q++ = *r++; c--;
124 do {
125 *q++ = *r++;
126 } while (--c);
127 }
128 break;
129 }
130 else if ((e & 64) == 0)
131 {
132 t += t->base;
133 e = (t += ((uInt)b & zlib_inflate_mask[e]))->exop;
134 }
135 else
136 {
137 z->msg = (char*)"invalid distance code";
138 UNGRAB
139 UPDATE
140 return Z_DATA_ERROR;
141 }
142 } while (1);
143 break;
144 }
145 if ((e & 64) == 0)
146 {
147 t += t->base;
148 if ((e = (t += ((uInt)b & zlib_inflate_mask[e]))->exop) == 0)
149 {
150 DUMPBITS(t->bits)
151 *q++ = (Byte)t->base;
152 m--;
153 break;
154 }
155 }
156 else if (e & 32)
157 {
158 UNGRAB
159 UPDATE
160 return Z_STREAM_END;
161 }
162 else
163 {
164 z->msg = (char*)"invalid literal/length code";
165 UNGRAB
166 UPDATE
167 return Z_DATA_ERROR;
168 }
169 } while (1);
170 } while (m >= 258 && n >= 10);
171
172 /* not enough input or output--restore pointers and return */
173 UNGRAB
174 UPDATE
175 return Z_OK;
176}