read.c revision de8f3a76218255e443ba57dec5d74850180fa75d 
1/*
2 * read.c - read the blkid cache from disk, to avoid scanning all devices
3 *
4 * Copyright (C) 2001, 2003 Theodore Y. Ts'o
5 * Copyright (C) 2001 Andreas Dilger
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the
9 * GNU Lesser General Public License.
10 * %End-Header%
11 */
12
13#include <stdio.h>
14#include <ctype.h>
15#include <string.h>
16#include <time.h>
17#include <sys/types.h>
18#include <sys/stat.h>
19#include <fcntl.h>
20#include <unistd.h>
21#if HAVE_ERRNO_H
22#include <errno.h>
23#endif
24
25#include "blkidP.h"
26#include "uuid/uuid.h"
27
28#ifdef HAVE_STRTOULL
29#define __USE_ISOC9X
30#define STRTOULL strtoull /* defined in stdlib.h if you try hard enough */
31#else
32/* FIXME: need to support real strtoull here */
33#define STRTOULL strtoul
34#endif
35
36#if HAVE_STDLIB_H
37#include <stdlib.h>
38#endif
39
40#ifdef TEST_PROGRAM
41#define blkid_debug_dump_dev(dev)	(debug_dump_dev(dev))
42static void debug_dump_dev(blkid_dev dev);
43#endif
44
45/*
46 * File format:
47 *
48 *	<device [<NAME="value"> ...]>device_name</device>
49 *
50 *	The following tags are required for each entry:
51 *	<ID="id">	unique (within this file) ID number of this device
52 *	<TIME="time">	(ascii time_t) time this entry was last read from disk
53 *	<TYPE="type">	(detected) type of filesystem/data for this partition
54 *
55 *	The following tags may be present, depending on the device contents
56 *	<LABEL="label">	(user supplied) label (volume name, etc)
57 *	<UUID="uuid">	(generated) universally unique identifier (serial no)
58 */
59
60static char *skip_over_blank(char *cp)
61{
62	while (*cp && isspace(*cp))
63		cp++;
64	return cp;
65}
66
67static char *skip_over_word(char *cp)
68{
69	char ch;
70
71	while ((ch = *cp)) {
72		/* If we see a backslash, skip the next character */
73		if (ch == '\\') {
74			cp++;
75			if (*cp == '\0')
76				break;
77			cp++;
78			continue;
79		}
80		if (isspace(ch) || ch == '<' || ch == '>')
81			break;
82		cp++;
83	}
84	return cp;
85}
86
87static char *strip_line(char *line)
88{
89	char	*p;
90
91	line = skip_over_blank(line);
92
93	p = line + strlen(line) - 1;
94
95	while (*line) {
96		if (isspace(*p))
97			*p-- = '\0';
98		else
99			break;
100	}
101
102	return line;
103}
104
105#if 0
106static char *parse_word(char **buf)
107{
108	char *word, *next;
109
110	word = *buf;
111	if (*word == '\0')
112		return NULL;
113
114	word = skip_over_blank(word);
115	next = skip_over_word(word);
116	if (*next) {
117		char *end = next - 1;
118		if (*end == '"' || *end == '\'')
119			*end = '\0';
120		*next++ = '\0';
121	}
122	*buf = next;
123
124	if (*word == '"' || *word == '\'')
125		word++;
126	return word;
127}
128#endif
129
130/*
131 * Start parsing a new line from the cache.
132 *
133 * line starts with "<device" return 1 -> continue parsing line
134 * line starts with "<foo", empty, or # return 0 -> skip line
135 * line starts with other, return -BLKID_ERR_CACHE -> error
136 */
137static int parse_start(char **cp)
138{
139	char *p;
140
141	p = strip_line(*cp);
142
143	/* Skip comment or blank lines.  We can't just NUL the first '#' char,
144	 * in case it is inside quotes, or escaped.
145	 */
146	if (*p == '\0' || *p == '#')
147		return 0;
148
149	if (!strncmp(p, "<device", 7)) {
150		DBG(DEBUG_READ, printf("found device header: %8s\n", p));
151		p += 7;
152
153		*cp = p;
154		return 1;
155	}
156
157	if (*p == '<')
158		return 0;
159
160	return -BLKID_ERR_CACHE;
161}
162
163/* Consume the remaining XML on the line (cosmetic only) */
164static int parse_end(char **cp)
165{
166	*cp = skip_over_blank(*cp);
167
168	if (!strncmp(*cp, "</device>", 9)) {
169		DBG(DEBUG_READ, printf("found device trailer %9s\n", *cp));
170		*cp += 9;
171		return 0;
172	}
173
174	return -BLKID_ERR_CACHE;
175}
176
177/*
178 * Allocate a new device struct with device name filled in.  Will handle
179 * finding the device on lines of the form:
180 * <device foo=bar>devname</device>
181 * <device>devname<foo>bar</foo></device>
182 */
183static int parse_dev(blkid_cache cache, blkid_dev *dev, char **cp)
184{
185	char *start, *tmp, *end, *name;
186	int ret;
187
188	if ((ret = parse_start(cp)) <= 0)
189		return ret;
190
191	start = tmp = strchr(*cp, '>');
192	if (!start) {
193		DBG(DEBUG_READ,
194		    printf("blkid: short line parsing dev: %s\n", *cp));
195		return -BLKID_ERR_CACHE;
196	}
197	start = skip_over_blank(start + 1);
198	end = skip_over_word(start);
199
200	DBG(DEBUG_READ, printf("device should be %*s\n",
201			       (int)(end - start), start));
202
203	if (**cp == '>')
204		*cp = end;
205	else
206		(*cp)++;
207
208	*tmp = '\0';
209
210	if (!(tmp = strrchr(end, '<')) || parse_end(&tmp) < 0) {
211		DBG(DEBUG_READ,
212		    printf("blkid: missing </device> ending: %s\n", end));
213	} else if (tmp)
214		*tmp = '\0';
215
216	if (end - start <= 1) {
217		DBG(DEBUG_READ, printf("blkid: empty device name: %s\n", *cp));
218		return -BLKID_ERR_CACHE;
219	}
220
221	name = blkid_strndup(start, end-start);
222	if (name == NULL)
223		return -BLKID_ERR_MEM;
224
225	DBG(DEBUG_READ, printf("found dev %s\n", name));
226
227	if (!(*dev = blkid_get_dev(cache, name, BLKID_DEV_CREATE))) {
228		free(name);
229		return -BLKID_ERR_MEM;
230	}
231
232	free(name);
233	return 1;
234}
235
236/*
237 * Extract a tag of the form NAME="value" from the line.
238 */
239static int parse_token(char **name, char **value, char **cp)
240{
241	char *end;
242
243	if (!name || !value || !cp)
244		return -BLKID_ERR_PARAM;
245
246	if (!(*value = strchr(*cp, '=')))
247		return 0;
248
249	**value = '\0';
250	*name = strip_line(*cp);
251	*value = skip_over_blank(*value + 1);
252
253	if (**value == '"') {
254		end = strchr(*value + 1, '"');
255		if (!end) {
256			DBG(DEBUG_READ,
257			    printf("unbalanced quotes at: %s\n", *value));
258			*cp = *value;
259			return -BLKID_ERR_CACHE;
260		}
261		(*value)++;
262		*end = '\0';
263		end++;
264	} else {
265		end = skip_over_word(*value);
266		if (*end) {
267			*end = '\0';
268			end++;
269		}
270	}
271	*cp = end;
272
273	return 1;
274}
275
276/*
277 * Extract a tag of the form <NAME>value</NAME> from the line.
278 */
279/*
280static int parse_xml(char **name, char **value, char **cp)
281{
282	char *end;
283
284	if (!name || !value || !cp)
285		return -BLKID_ERR_PARAM;
286
287	*name = strip_line(*cp);
288
289	if ((*name)[0] != '<' || (*name)[1] == '/')
290		return 0;
291
292	FIXME: finish this.
293}
294*/
295
296/*
297 * Extract a tag from the line.
298 *
299 * Return 1 if a valid tag was found.
300 * Return 0 if no tag found.
301 * Return -ve error code.
302 */
303static int parse_tag(blkid_cache cache, blkid_dev dev, char **cp)
304{
305	char *name;
306	char *value;
307	int ret;
308
309	if (!cache || !dev)
310		return -BLKID_ERR_PARAM;
311
312	if ((ret = parse_token(&name, &value, cp)) <= 0 /* &&
313	    (ret = parse_xml(&name, &value, cp)) <= 0 */)
314		return ret;
315
316	/* Some tags are stored directly in the device struct */
317	if (!strcmp(name, "DEVNO"))
318		dev->bid_devno = STRTOULL(value, 0, 0);
319	else if (!strcmp(name, "PRI"))
320		dev->bid_pri = strtol(value, 0, 0);
321	else if (!strcmp(name, "TIME"))
322		/* FIXME: need to parse a long long eventually */
323		dev->bid_time = strtol(value, 0, 0);
324	else
325		ret = blkid_set_tag(dev, name, value, strlen(value));
326
327	DBG(DEBUG_READ, printf("    tag: %s=\"%s\"\n", name, value));
328
329	return ret < 0 ? ret : 1;
330}
331
332/*
333 * Parse a single line of data, and return a newly allocated dev struct.
334 * Add the new device to the cache struct, if one was read.
335 *
336 * Lines are of the form <device [TAG="value" ...]>/dev/foo</device>
337 *
338 * Returns -ve value on error.
339 * Returns 0 otherwise.
340 * If a valid device was read, *dev_p is non-NULL, otherwise it is NULL
341 * (e.g. comment lines, unknown XML content, etc).
342 */
343static int blkid_parse_line(blkid_cache cache, blkid_dev *dev_p, char *cp)
344{
345	blkid_dev dev;
346	int ret;
347
348	if (!cache || !dev_p)
349		return -BLKID_ERR_PARAM;
350
351	*dev_p = NULL;
352
353	DBG(DEBUG_READ, printf("line: %s\n", cp));
354
355	if ((ret = parse_dev(cache, dev_p, &cp)) <= 0)
356		return ret;
357
358	dev = *dev_p;
359
360	while ((ret = parse_tag(cache, dev, &cp)) > 0) {
361		;
362	}
363
364	if (dev->bid_type == NULL) {
365		DBG(DEBUG_READ,
366		    printf("blkid: device %s has no TYPE\n",dev->bid_name));
367		blkid_free_dev(dev);
368	}
369
370	DBG(DEBUG_READ, blkid_debug_dump_dev(dev));
371
372	return ret;
373}
374
375/*
376 * Parse the specified filename, and return the data in the supplied or
377 * a newly allocated cache struct.  If the file doesn't exist, return a
378 * new empty cache struct.
379 */
380void blkid_read_cache(blkid_cache cache)
381{
382	FILE *file;
383	char buf[4096];
384	int fd, lineno = 0;
385	struct stat st;
386
387	if (!cache)
388		return;
389
390	/*
391	 * If the file doesn't exist, then we just return an empty
392	 * struct so that the cache can be populated.
393	 */
394	if ((fd = open(cache->bic_filename, O_RDONLY)) < 0)
395		return;
396	if (fstat(fd, &st) < 0)
397		goto errout;
398	if ((st.st_mtime == cache->bic_ftime) ||
399	    (cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
400		DBG(DEBUG_CACHE, printf("skipping re-read of %s\n",
401					cache->bic_filename));
402		goto errout;
403	}
404
405	DBG(DEBUG_CACHE, printf("reading cache file %s\n",
406				cache->bic_filename));
407
408	file = fdopen(fd, "r");
409	if (!file)
410		goto errout;
411
412	while (fgets(buf, sizeof(buf), file)) {
413		blkid_dev dev;
414		unsigned int end;
415
416		lineno++;
417		if (buf[0] == 0)
418			continue;
419		end = strlen(buf) - 1;
420		/* Continue reading next line if it ends with a backslash */
421		while (buf[end] == '\\' && end < sizeof(buf) - 2 &&
422		       fgets(buf + end, sizeof(buf) - end, file)) {
423			end = strlen(buf) - 1;
424			lineno++;
425		}
426
427		if (blkid_parse_line(cache, &dev, buf) < 0) {
428			DBG(DEBUG_READ,
429			    printf("blkid: bad format on line %d\n", lineno));
430			continue;
431		}
432	}
433	fclose(file);
434
435	/*
436	 * Initially we do not need to write out the cache file.
437	 */
438	cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
439	cache->bic_ftime = st.st_mtime;
440
441	return;
442errout:
443	close(fd);
444	return;
445}
446
447#ifdef TEST_PROGRAM
448static void debug_dump_dev(blkid_dev dev)
449{
450	struct list_head *p;
451
452	if (!dev) {
453		printf("  dev: NULL\n");
454		return;
455	}
456
457	printf("  dev: name = %s\n", dev->bid_name);
458	printf("  dev: DEVNO=\"0x%0llx\"\n", (long long)dev->bid_devno);
459	printf("  dev: TIME=\"%lld\"\n", (long long)dev->bid_time);
460	printf("  dev: PRI=\"%d\"\n", dev->bid_pri);
461	printf("  dev: flags = 0x%08X\n", dev->bid_flags);
462
463	list_for_each(p, &dev->bid_tags) {
464		blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
465		if (tag)
466			printf("    tag: %s=\"%s\"\n", tag->bit_name,
467			       tag->bit_val);
468		else
469			printf("    tag: NULL\n");
470	}
471	printf("\n");
472}
473
474int main(int argc, char**argv)
475{
476	blkid_cache cache = NULL;
477	int ret;
478
479	blkid_debug_mask = DEBUG_ALL;
480	if (argc > 2) {
481		fprintf(stderr, "Usage: %s [filename]\n"
482			"Test parsing of the cache (filename)\n", argv[0]);
483		exit(1);
484	}
485	if ((ret = blkid_get_cache(&cache, argv[1])) < 0)
486		fprintf(stderr, "error %d reading cache file %s\n", ret,
487			argv[1] ? argv[1] : BLKID_CACHE_FILE);
488
489	blkid_put_cache(cache);
490
491	return ret;
492}
493#endif
494