Merge branch 'jc/maint-1.6.0-diff-borrow-carefully'
[git.git] / symlinks.c
blob1d6b35b858020300f502e2a9341b82d4fa8a61fd
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 {
36 char path[PATH_MAX + 1];
37 int len;
38 int flags;
39 int track_flags;
40 int prefix_len_stat_func;
41 } cache;
43 static inline void reset_lstat_cache(void)
45 cache.path[0] = '\0';
46 cache.len = 0;
47 cache.flags = 0;
49 * The track_flags and prefix_len_stat_func members is only
50 * set by the safeguard rule inside lstat_cache()
54 #define FL_DIR (1 << 0)
55 #define FL_NOENT (1 << 1)
56 #define FL_SYMLINK (1 << 2)
57 #define FL_LSTATERR (1 << 3)
58 #define FL_ERR (1 << 4)
59 #define FL_FULLPATH (1 << 5)
62 * Check if name 'name' of length 'len' has a symlink leading
63 * component, or if the directory exists and is real, or not.
65 * To speed up the check, some information is allowed to be cached.
66 * This can be indicated by the 'track_flags' argument, which also can
67 * be used to indicate that we should check the full path.
69 * The 'prefix_len_stat_func' parameter can be used to set the length
70 * of the prefix, where the cache should use the stat() function
71 * instead of the lstat() function to test each path component.
73 static int lstat_cache(const char *name, int len,
74 int track_flags, int prefix_len_stat_func)
76 int match_len, last_slash, last_slash_dir, previous_slash;
77 int match_flags, ret_flags, save_flags, max_len, ret;
78 struct stat st;
80 if (cache.track_flags != track_flags ||
81 cache.prefix_len_stat_func != prefix_len_stat_func) {
83 * As a safeguard rule we clear the cache if the
84 * values of track_flags and/or prefix_len_stat_func
85 * does not match with the last supplied values.
87 reset_lstat_cache();
88 cache.track_flags = track_flags;
89 cache.prefix_len_stat_func = prefix_len_stat_func;
90 match_len = last_slash = 0;
91 } else {
93 * Check to see if we have a match from the cache for
94 * the 2 "excluding" path types.
96 match_len = last_slash =
97 longest_path_match(name, len, cache.path, cache.len,
98 &previous_slash);
99 match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
100 if (match_flags && match_len == cache.len)
101 return match_flags;
103 * If we now have match_len > 0, we would know that
104 * the matched part will always be a directory.
106 * Also, if we are tracking directories and 'name' is
107 * a substring of the cache on a path component basis,
108 * we can return immediately.
110 match_flags = track_flags & FL_DIR;
111 if (match_flags && len == match_len)
112 return match_flags;
116 * Okay, no match from the cache so far, so now we have to
117 * check the rest of the path components.
119 ret_flags = FL_DIR;
120 last_slash_dir = last_slash;
121 max_len = len < PATH_MAX ? len : PATH_MAX;
122 while (match_len < max_len) {
123 do {
124 cache.path[match_len] = name[match_len];
125 match_len++;
126 } while (match_len < max_len && name[match_len] != '/');
127 if (match_len >= max_len && !(track_flags & FL_FULLPATH))
128 break;
129 last_slash = match_len;
130 cache.path[last_slash] = '\0';
132 if (last_slash <= prefix_len_stat_func)
133 ret = stat(cache.path, &st);
134 else
135 ret = lstat(cache.path, &st);
137 if (ret) {
138 ret_flags = FL_LSTATERR;
139 if (errno == ENOENT)
140 ret_flags |= FL_NOENT;
141 } else if (S_ISDIR(st.st_mode)) {
142 last_slash_dir = last_slash;
143 continue;
144 } else if (S_ISLNK(st.st_mode)) {
145 ret_flags = FL_SYMLINK;
146 } else {
147 ret_flags = FL_ERR;
149 break;
153 * At the end update the cache. Note that max 3 different
154 * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
155 * for the moment!
157 save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
158 if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
159 cache.path[last_slash] = '\0';
160 cache.len = last_slash;
161 cache.flags = save_flags;
162 } else if ((track_flags & FL_DIR) &&
163 last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
165 * We have a separate test for the directory case,
166 * since it could be that we have found a symlink or a
167 * non-existing directory and the track_flags says
168 * that we cannot cache this fact, so the cache would
169 * then have been left empty in this case.
171 * But if we are allowed to track real directories, we
172 * can still cache the path components before the last
173 * one (the found symlink or non-existing component).
175 cache.path[last_slash_dir] = '\0';
176 cache.len = last_slash_dir;
177 cache.flags = FL_DIR;
178 } else {
179 reset_lstat_cache();
181 return ret_flags;
185 * Invalidate the given 'name' from the cache, if 'name' matches
186 * completely with the cache.
188 void invalidate_lstat_cache(const char *name, int len)
190 int match_len, previous_slash;
192 match_len = longest_path_match(name, len, cache.path, cache.len,
193 &previous_slash);
194 if (len == match_len) {
195 if ((cache.track_flags & FL_DIR) && previous_slash > 0) {
196 cache.path[previous_slash] = '\0';
197 cache.len = previous_slash;
198 cache.flags = FL_DIR;
199 } else
200 reset_lstat_cache();
205 * Completely clear the contents of the cache
207 void clear_lstat_cache(void)
209 reset_lstat_cache();
212 #define USE_ONLY_LSTAT 0
215 * Return non-zero if path 'name' has a leading symlink component
217 int has_symlink_leading_path(const char *name, int len)
219 return lstat_cache(name, len,
220 FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
221 FL_SYMLINK;
225 * Return non-zero if path 'name' has a leading symlink component or
226 * if some leading path component does not exists.
228 int has_symlink_or_noent_leading_path(const char *name, int len)
230 return lstat_cache(name, len,
231 FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
232 (FL_SYMLINK|FL_NOENT);
236 * Return non-zero if all path components of 'name' exists as a
237 * directory. If prefix_len > 0, we will test with the stat()
238 * function instead of the lstat() function for a prefix length of
239 * 'prefix_len', thus we then allow for symlinks in the prefix part as
240 * long as those points to real existing directories.
242 int has_dirs_only_path(const char *name, int len, int prefix_len)
244 return lstat_cache(name, len,
245 FL_DIR|FL_FULLPATH, prefix_len) &
246 FL_DIR;
249 static struct removal_def {
250 char path[PATH_MAX];
251 int len;
252 } removal;
254 static void do_remove_scheduled_dirs(int new_len)
256 while (removal.len > new_len) {
257 removal.path[removal.len] = '\0';
258 if (rmdir(removal.path))
259 break;
260 do {
261 removal.len--;
262 } while (removal.len > new_len &&
263 removal.path[removal.len] != '/');
265 removal.len = new_len;
266 return;
269 void schedule_dir_for_removal(const char *name, int len)
271 int match_len, last_slash, i, previous_slash;
273 match_len = last_slash = i =
274 longest_path_match(name, len, removal.path, removal.len,
275 &previous_slash);
276 /* Find last slash inside 'name' */
277 while (i < len) {
278 if (name[i] == '/')
279 last_slash = i;
280 i++;
284 * If we are about to go down the directory tree, we check if
285 * we must first go upwards the tree, such that we then can
286 * remove possible empty directories as we go upwards.
288 if (match_len < last_slash && match_len < removal.len)
289 do_remove_scheduled_dirs(match_len);
291 * If we go deeper down the directory tree, we only need to
292 * save the new path components as we go down.
294 if (match_len < last_slash) {
295 memcpy(&removal.path[match_len], &name[match_len],
296 last_slash - match_len);
297 removal.len = last_slash;
299 return;
302 void remove_scheduled_dirs(void)
304 do_remove_scheduled_dirs(0);
305 return;