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comparison zlib/inflate.c @ 3:5a977ccbc7a9 default tip

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author darius
date Sat, 06 Dec 1997 05:41:29 +0000
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2:fba0b6e6cdc7 3:5a977ccbc7a9
1 /* inflate.c -- zlib interface to inflate modules
2 * Copyright (C) 1995 Mark Adler
3 * For conditions of distribution and use, see copyright notice in zlib.h
4 */
5
6 #include "zutil.h"
7 #include "infblock.h"
8
9 struct inflate_blocks_state {int dummy;}; /* for buggy compilers */
10
11 /* inflate private state */
12 struct internal_state {
13
14 /* mode */
15 enum {
16 METHOD, /* waiting for method byte */
17 FLAG, /* waiting for flag byte */
18 BLOCKS, /* decompressing blocks */
19 CHECK4, /* four check bytes to go */
20 CHECK3, /* three check bytes to go */
21 CHECK2, /* two check bytes to go */
22 CHECK1, /* one check byte to go */
23 DONE, /* finished check, done */
24 BAD} /* got an error--stay here */
25 mode; /* current inflate mode */
26
27 /* mode dependent information */
28 union {
29 uInt method; /* if FLAGS, method byte */
30 struct {
31 uLong was; /* computed check value */
32 uLong need; /* stream check value */
33 } check; /* if CHECK, check values to compare */
34 uInt marker; /* if BAD, inflateSync's marker bytes count */
35 } sub; /* submode */
36
37 /* mode independent information */
38 int nowrap; /* flag for no wrapper */
39 uInt wbits; /* log2(window size) (8..15, defaults to 15) */
40 struct inflate_blocks_state
41 *blocks; /* current inflate_blocks state */
42
43 };
44
45
46 int inflateReset(z)
47 z_stream *z;
48 {
49 uLong c;
50
51 if (z == Z_NULL || z->state == Z_NULL)
52 return Z_STREAM_ERROR;
53 z->total_in = z->total_out = 0;
54 z->msg = Z_NULL;
55 z->state->mode = z->state->nowrap ? BLOCKS : METHOD;
56 inflate_blocks_reset(z->state->blocks, z, &c);
57 Trace((stderr, "inflate: reset\n"));
58 return Z_OK;
59 }
60
61
62 int inflateEnd(z)
63 z_stream *z;
64 {
65 uLong c;
66
67 if (z == Z_NULL || z->state == Z_NULL || z->zfree == Z_NULL)
68 return Z_STREAM_ERROR;
69 if (z->state->blocks != Z_NULL)
70 inflate_blocks_free(z->state->blocks, z, &c);
71 ZFREE(z, z->state);
72 z->state = Z_NULL;
73 Trace((stderr, "inflate: end\n"));
74 return Z_OK;
75 }
76
77
78 int inflateInit2(z, w)
79 z_stream *z;
80 int w;
81 {
82 /* initialize state */
83 if (z == Z_NULL)
84 return Z_STREAM_ERROR;
85 if (z->zalloc == Z_NULL) z->zalloc = zcalloc;
86 if (z->zfree == Z_NULL) z->zfree = zcfree;
87 if ((z->state = (struct internal_state *)
88 ZALLOC(z,1,sizeof(struct internal_state))) == Z_NULL)
89 return Z_MEM_ERROR;
90 z->state->blocks = Z_NULL;
91
92 /* handle undocumented nowrap option (no zlib header or check) */
93 z->state->nowrap = 0;
94 if (w < 0)
95 {
96 w = - w;
97 z->state->nowrap = 1;
98 }
99
100 /* set window size */
101 if (w < 8 || w > 15)
102 {
103 inflateEnd(z);
104 return Z_STREAM_ERROR;
105 }
106 z->state->wbits = (uInt)w;
107
108 /* create inflate_blocks state */
109 if ((z->state->blocks =
110 inflate_blocks_new(z, z->state->nowrap ? Z_NULL : adler32, 1 << w))
111 == Z_NULL)
112 {
113 inflateEnd(z);
114 return Z_MEM_ERROR;
115 }
116 Trace((stderr, "inflate: allocated\n"));
117
118 /* reset state */
119 inflateReset(z);
120 return Z_OK;
121 }
122
123
124 int inflateInit(z)
125 z_stream *z;
126 {
127 return inflateInit2(z, DEF_WBITS);
128 }
129
130
131 #define NEEDBYTE {if(z->avail_in==0)return r;r=Z_OK;}
132 #define NEXTBYTE (z->avail_in--,z->total_in++,*z->next_in++)
133
134 int inflate(z, f)
135 z_stream *z;
136 int f;
137 {
138 int r = f; /* to avoid warning about unused f */
139 uInt b;
140
141 if (z == Z_NULL || z->next_in == Z_NULL)
142 return Z_STREAM_ERROR;
143 r = Z_BUF_ERROR;
144 while (1) switch (z->state->mode)
145 {
146 case METHOD:
147 NEEDBYTE
148 if (((z->state->sub.method = NEXTBYTE) & 0xf) != DEFLATED)
149 {
150 z->state->mode = BAD;
151 z->msg = "unknown compression method";
152 z->state->sub.marker = 5; /* can't try inflateSync */
153 break;
154 }
155 if ((z->state->sub.method >> 4) + 8 > z->state->wbits)
156 {
157 z->state->mode = BAD;
158 z->msg = "invalid window size";
159 z->state->sub.marker = 5; /* can't try inflateSync */
160 break;
161 }
162 z->state->mode = FLAG;
163 case FLAG:
164 NEEDBYTE
165 if ((b = NEXTBYTE) & 0x20)
166 {
167 z->state->mode = BAD;
168 z->msg = "invalid reserved bit";
169 z->state->sub.marker = 5; /* can't try inflateSync */
170 break;
171 }
172 if (((z->state->sub.method << 8) + b) % 31)
173 {
174 z->state->mode = BAD;
175 z->msg = "incorrect header check";
176 z->state->sub.marker = 5; /* can't try inflateSync */
177 break;
178 }
179 Trace((stderr, "inflate: zlib header ok\n"));
180 z->state->mode = BLOCKS;
181 case BLOCKS:
182 r = inflate_blocks(z->state->blocks, z, r);
183 if (r == Z_DATA_ERROR)
184 {
185 z->state->mode = BAD;
186 z->state->sub.marker = 0; /* can try inflateSync */
187 break;
188 }
189 if (r != Z_STREAM_END)
190 return r;
191 r = Z_OK;
192 inflate_blocks_reset(z->state->blocks, z, &z->state->sub.check.was);
193 if (z->state->nowrap)
194 {
195 z->state->mode = DONE;
196 break;
197 }
198 z->state->mode = CHECK4;
199 case CHECK4:
200 NEEDBYTE
201 z->state->sub.check.need = (uLong)NEXTBYTE << 24;
202 z->state->mode = CHECK3;
203 case CHECK3:
204 NEEDBYTE
205 z->state->sub.check.need += (uLong)NEXTBYTE << 16;
206 z->state->mode = CHECK2;
207 case CHECK2:
208 NEEDBYTE
209 z->state->sub.check.need += (uLong)NEXTBYTE << 8;
210 z->state->mode = CHECK1;
211 case CHECK1:
212 NEEDBYTE
213 z->state->sub.check.need += (uLong)NEXTBYTE;
214
215 if (z->state->sub.check.was != z->state->sub.check.need)
216 {
217 z->state->mode = BAD;
218 z->msg = "incorrect data check";
219 z->state->sub.marker = 5; /* can't try inflateSync */
220 break;
221 }
222 Trace((stderr, "inflate: zlib check ok\n"));
223 z->state->mode = DONE;
224 case DONE:
225 return Z_STREAM_END;
226 case BAD:
227 return Z_DATA_ERROR;
228 default:
229 return Z_STREAM_ERROR;
230 }
231 }
232
233
234 int inflateSync(z)
235 z_stream *z;
236 {
237 uInt n; /* number of bytes to look at */
238 Byte *p; /* pointer to bytes */
239 uInt m; /* number of marker bytes found in a row */
240 uLong r, w; /* temporaries to save total_in and total_out */
241
242 /* set up */
243 if (z == Z_NULL || z->state == Z_NULL)
244 return Z_STREAM_ERROR;
245 if (z->state->mode != BAD)
246 {
247 z->state->mode = BAD;
248 z->state->sub.marker = 0;
249 }
250 if ((n = z->avail_in) == 0)
251 return Z_BUF_ERROR;
252 p = z->next_in;
253 m = z->state->sub.marker;
254
255 /* search */
256 while (n && m < 4)
257 {
258 if (*p == (Byte)(m < 2 ? 0 : 0xff))
259 m++;
260 else if (*p)
261 m = 0;
262 else
263 m = 4 - m;
264 p++, n--;
265 }
266
267 /* restore */
268 z->total_in += p - z->next_in;
269 z->next_in = p;
270 z->avail_in = n;
271 z->state->sub.marker = m;
272
273 /* return no joy or set up to restart on a new block */
274 if (m != 4)
275 return Z_DATA_ERROR;
276 r = z->total_in; w = z->total_out;
277 inflateReset(z);
278 z->total_in = r; z->total_out = w;
279 z->state->mode = BLOCKS;
280 return Z_OK;
281 }