gzipfs.c revision 82852 
1/*
2 * Copyright (c) 1998 Michael Smith.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: head/lib/libstand/gzipfs.c 82852 2001-09-03 05:57:06Z kris $
27 *
28 */
29
30#include "stand.h"
31
32#include <sys/stat.h>
33#include <string.h>
34#include <zlib.h>
35
36#define Z_BUFSIZE 2048	/* XXX larger? */
37
38struct z_file
39{
40    int			zf_rawfd;
41    z_stream		zf_zstream;
42    char		zf_buf[Z_BUFSIZE];
43};
44
45static int	zf_fill(struct z_file *z);
46static int	zf_open(const char *path, struct open_file *f);
47static int	zf_close(struct open_file *f);
48static int	zf_read(struct open_file *f, void *buf, size_t size, size_t *resid);
49static off_t	zf_seek(struct open_file *f, off_t offset, int where);
50static int	zf_stat(struct open_file *f, struct stat *sb);
51
52struct fs_ops zipfs_fsops = {
53    "zip",
54    zf_open,
55    zf_close,
56    zf_read,
57    null_write,
58    zf_seek,
59    zf_stat,
60    null_readdir
61};
62
63#if 0
64void *
65calloc(int items, size_t size)
66{
67    return(malloc(items * size));
68}
69#endif
70
71static int
72zf_fill(struct z_file *zf)
73{
74    int		result;
75    int		req;
76
77    req = Z_BUFSIZE - zf->zf_zstream.avail_in;
78    result = 0;
79
80    /* If we need more */
81    if (req > 0) {
82	/* move old data to bottom of buffer */
83	if (req < Z_BUFSIZE)
84	    bcopy(zf->zf_buf + req, zf->zf_buf, Z_BUFSIZE - req);
85
86	/* read to fill buffer and update availibility data */
87	result = read(zf->zf_rawfd, zf->zf_buf + zf->zf_zstream.avail_in, req);
88	zf->zf_zstream.next_in = zf->zf_buf;
89	if (result >= 0)
90	    zf->zf_zstream.avail_in += result;
91    }
92    return(result);
93}
94
95/*
96 * Adapted from get_byte/check_header in libz
97 *
98 * Returns 0 if the header is OK, nonzero if not.
99 */
100static int
101get_byte(struct z_file *zf)
102{
103    if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1))
104	return(-1);
105    zf->zf_zstream.avail_in--;
106    return(*(zf->zf_zstream.next_in)++);
107}
108
109static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */
110
111/* gzip flag byte */
112#define ASCII_FLAG	0x01 /* bit 0 set: file probably ascii text */
113#define HEAD_CRC	0x02 /* bit 1 set: header CRC present */
114#define EXTRA_FIELD	0x04 /* bit 2 set: extra field present */
115#define ORIG_NAME	0x08 /* bit 3 set: original file name present */
116#define COMMENT		0x10 /* bit 4 set: file comment present */
117#define RESERVED	0xE0 /* bits 5..7: reserved */
118
119static int
120check_header(struct z_file *zf)
121{
122    int		method; /* method byte */
123    int		flags;  /* flags byte */
124    uInt	len;
125    int		c;
126
127    /* Check the gzip magic header */
128    for (len = 0; len < 2; len++) {
129	c = get_byte(zf);
130	if (c != gz_magic[len]) {
131	    return(1);
132	}
133    }
134    method = get_byte(zf);
135    flags = get_byte(zf);
136    if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
137	return(1);
138    }
139
140    /* Discard time, xflags and OS code: */
141    for (len = 0; len < 6; len++) (void)get_byte(zf);
142
143    if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
144	len  =  (uInt)get_byte(zf);
145	len += ((uInt)get_byte(zf))<<8;
146	/* len is garbage if EOF but the loop below will quit anyway */
147	while (len-- != 0 && get_byte(zf) != -1) ;
148    }
149    if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
150	while ((c = get_byte(zf)) != 0 && c != -1) ;
151    }
152    if ((flags & COMMENT) != 0) {   /* skip the .gz file comment */
153	while ((c = get_byte(zf)) != 0 && c != -1) ;
154    }
155    if ((flags & HEAD_CRC) != 0) {  /* skip the header crc */
156	for (len = 0; len < 2; len++) c = get_byte(zf);
157    }
158    /* if there's data left, we're in business */
159    return((c == -1) ? 1 : 0);
160}
161
162static int
163zf_open(const char *fname, struct open_file *f)
164{
165    static char		*zfname;
166    int			rawfd;
167    struct z_file	*zf;
168    char		*cp;
169    int			error;
170    struct stat		sb;
171
172    /* Have to be in "just read it" mode */
173    if (f->f_flags != F_READ)
174	return(EPERM);
175
176    /* If the name already ends in .gz, ignore it */
177    if ((cp = strrchr(fname, '.')) && !strcmp(cp, ".gz"))
178	return(ENOENT);
179
180    /* Construct new name */
181    zfname = malloc(strlen(fname) + 4);
182    if (zfname == NULL)
183        return(ENOMEM);
184    sprintf(zfname, "%s.gz", fname);
185
186    /* Try to open the compressed datafile */
187    rawfd = open(zfname, O_RDONLY);
188    free(zfname);
189    if (rawfd == -1)
190	return(ENOENT);
191
192    if (fstat(rawfd, &sb) < 0) {
193	printf("zf_open: stat failed\n");
194	close(rawfd);
195	return(ENOENT);
196    }
197    if (!S_ISREG(sb.st_mode)) {
198	printf("zf_open: not a file\n");
199	close(rawfd);
200	return(EISDIR);			/* best guess */
201    }
202
203    /* Allocate a z_file structure, populate it */
204    zf = malloc(sizeof(struct z_file));
205    if (zf == NULL)
206        return(ENOMEM);
207    bzero(zf, sizeof(struct z_file));
208    zf->zf_rawfd = rawfd;
209
210    /* Verify that the file is gzipped (XXX why do this afterwards?) */
211    if (check_header(zf)) {
212	close(zf->zf_rawfd);
213	inflateEnd(&(zf->zf_zstream));
214	free(zf);
215	return(EFTYPE);
216    }
217
218    /* Initialise the inflation engine */
219    if ((error = inflateInit2(&(zf->zf_zstream), -15)) != Z_OK) {
220	printf("zf_open: inflateInit returned %d : %s\n", error, zf->zf_zstream.msg);
221	close(zf->zf_rawfd);
222	free(zf);
223	return(EIO);
224    }
225
226    /* Looks OK, we'll take it */
227    f->f_fsdata = zf;
228    return(0);
229}
230
231static int
232zf_close(struct open_file *f)
233{
234    struct z_file	*zf = (struct z_file *)f->f_fsdata;
235
236    inflateEnd(&(zf->zf_zstream));
237    close(zf->zf_rawfd);
238    free(zf);
239    return(0);
240}
241
242static int
243zf_read(struct open_file *f, void *buf, size_t size, size_t *resid)
244{
245    struct z_file	*zf = (struct z_file *)f->f_fsdata;
246    int			error;
247
248    zf->zf_zstream.next_out = buf;			/* where and how much */
249    zf->zf_zstream.avail_out = size;
250
251    while (zf->zf_zstream.avail_out) {
252	if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1)) {
253	    printf("zf_read: fill error\n");
254	    return(-1);
255	}
256	if (zf->zf_zstream.avail_in == 0) {		/* oops, unexpected EOF */
257	    printf("zf_read: unexpected EOF\n");
258	    break;
259	}
260
261	error = inflate(&zf->zf_zstream, Z_SYNC_FLUSH);	/* decompression pass */
262	if (error == Z_STREAM_END) {			/* EOF, all done */
263	    break;
264	}
265	if (error != Z_OK) {				/* argh, decompression error */
266	    printf("inflate: %s\n", zf->zf_zstream.msg);
267	    errno = EIO;
268	    return(-1);
269	}
270    }
271    if (resid != NULL)
272	*resid = zf->zf_zstream.avail_out;
273    return(0);
274}
275
276static off_t
277zf_seek(struct open_file *f, off_t offset, int where)
278{
279    struct z_file	*zf = (struct z_file *)f->f_fsdata;
280    off_t		target;
281    char		discard[16];
282
283    switch (where) {
284    case SEEK_SET:
285	target = offset;
286	break;
287    case SEEK_CUR:
288	target = offset + zf->zf_zstream.total_out;
289	break;
290    default:
291	target = -1;
292    }
293
294    /* Can we get there from here? */
295    if (target < zf->zf_zstream.total_out) {
296	errno = EOFFSET;
297	return -1;
298    }
299
300    /* skip forwards if required */
301    while (target > zf->zf_zstream.total_out) {
302	if (zf_read(f, discard, min(sizeof(discard), target - zf->zf_zstream.total_out), NULL) == -1)
303	    return(-1);
304    }
305    /* This is where we are (be honest if we overshot) */
306    return (zf->zf_zstream.total_out);
307}
308
309
310static int
311zf_stat(struct open_file *f, struct stat *sb)
312{
313    struct z_file	*zf = (struct z_file *)f->f_fsdata;
314    int			result;
315
316    /* stat as normal, but indicate that size is unknown */
317    if ((result = fstat(zf->zf_rawfd, sb)) == 0)
318	sb->st_size = -1;
319    return(result);
320}
321
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324