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[git/mjg.git] / symlinks.c
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1 #include "cache.h"
3 /*
4 * Returns the length (on a path component basis) of the longest
5 * common prefix match of 'name_a' and 'name_b'.
6 */
7 static int longest_path_match(const char *name_a, int len_a,
8 const char *name_b, int len_b,
9 int *previous_slash)
11 int max_len, match_len = 0, match_len_prev = 0, i = 0;
13 max_len = len_a < len_b ? len_a : len_b;
14 while (i < max_len && name_a[i] == name_b[i]) {
15 if (name_a[i] == '/') {
16 match_len_prev = match_len;
17 match_len = i;
19 i++;
22 * Is 'name_b' a substring of 'name_a', the other way around,
23 * or is 'name_a' and 'name_b' the exact same string?
25 if (i >= max_len && ((len_a > len_b && name_a[len_b] == '/') ||
26 (len_a < len_b && name_b[len_a] == '/') ||
27 (len_a == len_b))) {
28 match_len_prev = match_len;
29 match_len = i;
31 *previous_slash = match_len_prev;
32 return match_len;
35 static struct cache_def default_cache;
37 static inline void reset_lstat_cache(struct cache_def *cache)
39 cache->path[0] = '\0';
40 cache->len = 0;
41 cache->flags = 0;
43 * The track_flags and prefix_len_stat_func members is only
44 * set by the safeguard rule inside lstat_cache()
48 #define FL_DIR (1 << 0)
49 #define FL_NOENT (1 << 1)
50 #define FL_SYMLINK (1 << 2)
51 #define FL_LSTATERR (1 << 3)
52 #define FL_ERR (1 << 4)
53 #define FL_FULLPATH (1 << 5)
56 * Check if name 'name' of length 'len' has a symlink leading
57 * component, or if the directory exists and is real, or not.
59 * To speed up the check, some information is allowed to be cached.
60 * This can be indicated by the 'track_flags' argument, which also can
61 * be used to indicate that we should check the full path.
63 * The 'prefix_len_stat_func' parameter can be used to set the length
64 * of the prefix, where the cache should use the stat() function
65 * instead of the lstat() function to test each path component.
67 static int lstat_cache(struct cache_def *cache, const char *name, int len,
68 int track_flags, int prefix_len_stat_func)
70 int match_len, last_slash, last_slash_dir, previous_slash;
71 int match_flags, ret_flags, save_flags, max_len, ret;
72 struct stat st;
74 if (cache->track_flags != track_flags ||
75 cache->prefix_len_stat_func != prefix_len_stat_func) {
77 * As a safeguard rule we clear the cache if the
78 * values of track_flags and/or prefix_len_stat_func
79 * does not match with the last supplied values.
81 reset_lstat_cache(cache);
82 cache->track_flags = track_flags;
83 cache->prefix_len_stat_func = prefix_len_stat_func;
84 match_len = last_slash = 0;
85 } else {
87 * Check to see if we have a match from the cache for
88 * the 2 "excluding" path types.
90 match_len = last_slash =
91 longest_path_match(name, len, cache->path, cache->len,
92 &previous_slash);
93 match_flags = cache->flags & track_flags & (FL_NOENT|FL_SYMLINK);
94 if (match_flags && match_len == cache->len)
95 return match_flags;
97 * If we now have match_len > 0, we would know that
98 * the matched part will always be a directory.
100 * Also, if we are tracking directories and 'name' is
101 * a substring of the cache on a path component basis,
102 * we can return immediately.
104 match_flags = track_flags & FL_DIR;
105 if (match_flags && len == match_len)
106 return match_flags;
110 * Okay, no match from the cache so far, so now we have to
111 * check the rest of the path components.
113 ret_flags = FL_DIR;
114 last_slash_dir = last_slash;
115 max_len = len < PATH_MAX ? len : PATH_MAX;
116 while (match_len < max_len) {
117 do {
118 cache->path[match_len] = name[match_len];
119 match_len++;
120 } while (match_len < max_len && name[match_len] != '/');
121 if (match_len >= max_len && !(track_flags & FL_FULLPATH))
122 break;
123 last_slash = match_len;
124 cache->path[last_slash] = '\0';
126 if (last_slash <= prefix_len_stat_func)
127 ret = stat(cache->path, &st);
128 else
129 ret = lstat(cache->path, &st);
131 if (ret) {
132 ret_flags = FL_LSTATERR;
133 if (errno == ENOENT)
134 ret_flags |= FL_NOENT;
135 } else if (S_ISDIR(st.st_mode)) {
136 last_slash_dir = last_slash;
137 continue;
138 } else if (S_ISLNK(st.st_mode)) {
139 ret_flags = FL_SYMLINK;
140 } else {
141 ret_flags = FL_ERR;
143 break;
147 * At the end update the cache. Note that max 3 different
148 * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
149 * for the moment!
151 save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
152 if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
153 cache->path[last_slash] = '\0';
154 cache->len = last_slash;
155 cache->flags = save_flags;
156 } else if ((track_flags & FL_DIR) &&
157 last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
159 * We have a separate test for the directory case,
160 * since it could be that we have found a symlink or a
161 * non-existing directory and the track_flags says
162 * that we cannot cache this fact, so the cache would
163 * then have been left empty in this case.
165 * But if we are allowed to track real directories, we
166 * can still cache the path components before the last
167 * one (the found symlink or non-existing component).
169 cache->path[last_slash_dir] = '\0';
170 cache->len = last_slash_dir;
171 cache->flags = FL_DIR;
172 } else {
173 reset_lstat_cache(cache);
175 return ret_flags;
179 * Invalidate the given 'name' from the cache, if 'name' matches
180 * completely with the cache.
182 void invalidate_lstat_cache(const char *name, int len)
184 int match_len, previous_slash;
185 struct cache_def *cache = &default_cache; /* FIXME */
187 match_len = longest_path_match(name, len, cache->path, cache->len,
188 &previous_slash);
189 if (len == match_len) {
190 if ((cache->track_flags & FL_DIR) && previous_slash > 0) {
191 cache->path[previous_slash] = '\0';
192 cache->len = previous_slash;
193 cache->flags = FL_DIR;
194 } else {
195 reset_lstat_cache(cache);
201 * Completely clear the contents of the cache
203 void clear_lstat_cache(void)
205 struct cache_def *cache = &default_cache; /* FIXME */
206 reset_lstat_cache(cache);
209 #define USE_ONLY_LSTAT 0
212 * Return non-zero if path 'name' has a leading symlink component
214 int threaded_has_symlink_leading_path(struct cache_def *cache, const char *name, int len)
216 return lstat_cache(cache, name, len, FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) & FL_SYMLINK;
220 * Return non-zero if path 'name' has a leading symlink component
222 int has_symlink_leading_path(const char *name, int len)
224 return threaded_has_symlink_leading_path(&default_cache, name, len);
228 * Return non-zero if path 'name' has a leading symlink component or
229 * if some leading path component does not exists.
231 int has_symlink_or_noent_leading_path(const char *name, int len)
233 struct cache_def *cache = &default_cache; /* FIXME */
234 return lstat_cache(cache, name, len,
235 FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
236 (FL_SYMLINK|FL_NOENT);
240 * Return non-zero if all path components of 'name' exists as a
241 * directory. If prefix_len > 0, we will test with the stat()
242 * function instead of the lstat() function for a prefix length of
243 * 'prefix_len', thus we then allow for symlinks in the prefix part as
244 * long as those points to real existing directories.
246 int has_dirs_only_path(const char *name, int len, int prefix_len)
248 struct cache_def *cache = &default_cache; /* FIXME */
249 return lstat_cache(cache, name, len,
250 FL_DIR|FL_FULLPATH, prefix_len) &
251 FL_DIR;
254 static struct removal_def {
255 char path[PATH_MAX];
256 int len;
257 } removal;
259 static void do_remove_scheduled_dirs(int new_len)
261 while (removal.len > new_len) {
262 removal.path[removal.len] = '\0';
263 if (rmdir(removal.path))
264 break;
265 do {
266 removal.len--;
267 } while (removal.len > new_len &&
268 removal.path[removal.len] != '/');
270 removal.len = new_len;
273 void schedule_dir_for_removal(const char *name, int len)
275 int match_len, last_slash, i, previous_slash;
277 match_len = last_slash = i =
278 longest_path_match(name, len, removal.path, removal.len,
279 &previous_slash);
280 /* Find last slash inside 'name' */
281 while (i < len) {
282 if (name[i] == '/')
283 last_slash = i;
284 i++;
288 * If we are about to go down the directory tree, we check if
289 * we must first go upwards the tree, such that we then can
290 * remove possible empty directories as we go upwards.
292 if (match_len < last_slash && match_len < removal.len)
293 do_remove_scheduled_dirs(match_len);
295 * If we go deeper down the directory tree, we only need to
296 * save the new path components as we go down.
298 if (match_len < last_slash) {
299 memcpy(&removal.path[match_len], &name[match_len],
300 last_slash - match_len);
301 removal.len = last_slash;
305 void remove_scheduled_dirs(void)
307 do_remove_scheduled_dirs(0);