File: /usr/src/linux/fs/cramfs/inflate/inffast.c
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 cramfs_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 = cramfs_inflate_mask[bl];
54 md = cramfs_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 *q++ = (Byte)t->base;
64 m--;
65 continue;
66 }
67 do {
68 DUMPBITS(t->bits)
69 if (e & 16)
70 {
71 /* get extra bits for length */
72 e &= 15;
73 c = t->base + ((uInt)b & cramfs_inflate_mask[e]);
74 DUMPBITS(e)
75
76 /* decode distance base of block to copy */
77 GRABBITS(15); /* max bits for distance code */
78 e = (t = td + ((uInt)b & md))->exop;
79 do {
80 DUMPBITS(t->bits)
81 if (e & 16)
82 {
83 /* get extra bits to add to distance base */
84 e &= 15;
85 GRABBITS(e) /* get extra bits (up to 13) */
86 d = t->base + ((uInt)b & cramfs_inflate_mask[e]);
87 DUMPBITS(e)
88
89 /* do the copy */
90 m -= c;
91 if ((uInt)(q - s->window) >= d) /* offset before dest */
92 { /* just copy */
93 r = q - d;
94 *q++ = *r++; c--; /* minimum count is three, */
95 *q++ = *r++; c--; /* so unroll loop a little */
96 }
97 else /* else offset after destination */
98 {
99 e = d - (uInt)(q - s->window); /* bytes from offset to end */
100 r = s->end - e; /* pointer to offset */
101 if (c > e) /* if source crosses, */
102 {
103 c -= e; /* copy to end of window */
104 do {
105 *q++ = *r++;
106 } while (--e);
107 r = s->window; /* copy rest from start of window */
108 }
109 }
110 do { /* copy all or what's left */
111 *q++ = *r++;
112 } while (--c);
113 break;
114 }
115 else if ((e & 64) == 0)
116 {
117 t += t->base;
118 e = (t += ((uInt)b & cramfs_inflate_mask[e]))->exop;
119 }
120 else
121 {
122 z->msg = (char*)"invalid distance code";
123 UNGRAB
124 UPDATE
125 return Z_DATA_ERROR;
126 }
127 } while (1);
128 break;
129 }
130 if ((e & 64) == 0)
131 {
132 t += t->base;
133 if ((e = (t += ((uInt)b & cramfs_inflate_mask[e]))->exop) == 0)
134 {
135 DUMPBITS(t->bits)
136 *q++ = (Byte)t->base;
137 m--;
138 break;
139 }
140 }
141 else if (e & 32)
142 {
143 UNGRAB
144 UPDATE
145 return Z_STREAM_END;
146 }
147 else
148 {
149 z->msg = (char*)"invalid literal/length code";
150 UNGRAB
151 UPDATE
152 return Z_DATA_ERROR;
153 }
154 } while (1);
155 } while (m >= 258 && n >= 10);
156
157 /* not enough input or output--restore pointers and return */
158 UNGRAB
159 UPDATE
160 return Z_OK;
161 }
162