Prepare symlink caching for thread-safety
[git/git.git] / symlinks.c
CommitLineData
f859c846
JH
1#include "cache.h"
2
92604b46
KB
3/*
4 * Returns the length (on a path component basis) of the longest
148bc06b 5 * common prefix match of 'name_a' and 'name_b'.
92604b46 6 */
148bc06b
KB
7static int longest_path_match(const char *name_a, int len_a,
8 const char *name_b, int len_b,
9 int *previous_slash)
c40641b7 10{
aeabab5c 11 int max_len, match_len = 0, match_len_prev = 0, i = 0;
92604b46 12
148bc06b
KB
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] == '/') {
aeabab5c 16 match_len_prev = match_len;
92604b46 17 match_len = i;
aeabab5c 18 }
92604b46
KB
19 i++;
20 }
60b458b7 21 /*
148bc06b
KB
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?
60b458b7 24 */
148bc06b
KB
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))) {
aeabab5c 28 match_len_prev = match_len;
60b458b7 29 match_len = i;
aeabab5c
KB
30 }
31 *previous_slash = match_len_prev;
92604b46 32 return match_len;
c40641b7
LT
33}
34
148bc06b
KB
35static 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;
867f72bf 41} default_cache;
148bc06b 42
867f72bf 43static inline void reset_lstat_cache(struct cache_def *cache)
c40641b7 44{
867f72bf
LT
45 cache->path[0] = '\0';
46 cache->len = 0;
47 cache->flags = 0;
60b458b7
KB
48 /*
49 * The track_flags and prefix_len_stat_func members is only
50 * set by the safeguard rule inside lstat_cache()
51 */
c40641b7
LT
52}
53
92604b46 54#define FL_DIR (1 << 0)
09c93066
KB
55#define FL_NOENT (1 << 1)
56#define FL_SYMLINK (1 << 2)
57#define FL_LSTATERR (1 << 3)
58#define FL_ERR (1 << 4)
bad4a54f 59#define FL_FULLPATH (1 << 5)
92604b46
KB
60
61/*
62 * Check if name 'name' of length 'len' has a symlink leading
09c93066 63 * component, or if the directory exists and is real, or not.
92604b46
KB
64 *
65 * To speed up the check, some information is allowed to be cached.
bad4a54f
KB
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.
68 *
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.
92604b46 72 */
867f72bf 73static int lstat_cache(struct cache_def *cache, const char *name, int len,
bad4a54f 74 int track_flags, int prefix_len_stat_func)
c40641b7 75{
aeabab5c 76 int match_len, last_slash, last_slash_dir, previous_slash;
bad4a54f 77 int match_flags, ret_flags, save_flags, max_len, ret;
c40641b7 78 struct stat st;
f859c846 79
867f72bf
LT
80 if (cache->track_flags != track_flags ||
81 cache->prefix_len_stat_func != prefix_len_stat_func) {
09c93066 82 /*
60b458b7
KB
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.
09c93066 86 */
867f72bf
LT
87 reset_lstat_cache(cache);
88 cache->track_flags = track_flags;
89 cache->prefix_len_stat_func = prefix_len_stat_func;
09c93066
KB
90 match_len = last_slash = 0;
91 } else {
92 /*
93 * Check to see if we have a match from the cache for
94 * the 2 "excluding" path types.
95 */
aeabab5c 96 match_len = last_slash =
867f72bf 97 longest_path_match(name, len, cache->path, cache->len,
148bc06b 98 &previous_slash);
867f72bf
LT
99 match_flags = cache->flags & track_flags & (FL_NOENT|FL_SYMLINK);
100 if (match_flags && match_len == cache->len)
09c93066
KB
101 return match_flags;
102 /*
103 * If we now have match_len > 0, we would know that
104 * the matched part will always be a directory.
105 *
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.
109 */
110 match_flags = track_flags & FL_DIR;
111 if (match_flags && len == match_len)
112 return match_flags;
113 }
c40641b7 114
92604b46
KB
115 /*
116 * Okay, no match from the cache so far, so now we have to
117 * check the rest of the path components.
118 */
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 {
867f72bf 124 cache->path[match_len] = name[match_len];
92604b46
KB
125 match_len++;
126 } while (match_len < max_len && name[match_len] != '/');
bad4a54f 127 if (match_len >= max_len && !(track_flags & FL_FULLPATH))
92604b46
KB
128 break;
129 last_slash = match_len;
867f72bf 130 cache->path[last_slash] = '\0';
f859c846 131
bad4a54f 132 if (last_slash <= prefix_len_stat_func)
867f72bf 133 ret = stat(cache->path, &st);
bad4a54f 134 else
867f72bf 135 ret = lstat(cache->path, &st);
bad4a54f
KB
136
137 if (ret) {
92604b46 138 ret_flags = FL_LSTATERR;
09c93066
KB
139 if (errno == ENOENT)
140 ret_flags |= FL_NOENT;
92604b46
KB
141 } else if (S_ISDIR(st.st_mode)) {
142 last_slash_dir = last_slash;
c40641b7 143 continue;
92604b46
KB
144 } else if (S_ISLNK(st.st_mode)) {
145 ret_flags = FL_SYMLINK;
146 } else {
147 ret_flags = FL_ERR;
f859c846 148 }
c40641b7 149 break;
f859c846 150 }
92604b46
KB
151
152 /*
09c93066
KB
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!
92604b46 156 */
09c93066 157 save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
bad4a54f 158 if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
867f72bf
LT
159 cache->path[last_slash] = '\0';
160 cache->len = last_slash;
161 cache->flags = save_flags;
60b458b7 162 } else if ((track_flags & FL_DIR) &&
bad4a54f 163 last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
92604b46
KB
164 /*
165 * We have a separate test for the directory case,
09c93066
KB
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.
92604b46
KB
170 *
171 * But if we are allowed to track real directories, we
172 * can still cache the path components before the last
09c93066 173 * one (the found symlink or non-existing component).
92604b46 174 */
867f72bf
LT
175 cache->path[last_slash_dir] = '\0';
176 cache->len = last_slash_dir;
177 cache->flags = FL_DIR;
92604b46 178 } else {
867f72bf 179 reset_lstat_cache(cache);
92604b46
KB
180 }
181 return ret_flags;
182}
183
aeabab5c
KB
184/*
185 * Invalidate the given 'name' from the cache, if 'name' matches
186 * completely with the cache.
187 */
57199892 188void invalidate_lstat_cache(const char *name, int len)
aeabab5c
KB
189{
190 int match_len, previous_slash;
867f72bf 191 struct cache_def *cache = &default_cache; /* FIXME */
aeabab5c 192
867f72bf 193 match_len = longest_path_match(name, len, cache->path, cache->len,
148bc06b 194 &previous_slash);
aeabab5c 195 if (len == match_len) {
867f72bf
LT
196 if ((cache->track_flags & FL_DIR) && previous_slash > 0) {
197 cache->path[previous_slash] = '\0';
198 cache->len = previous_slash;
199 cache->flags = FL_DIR;
cb319c36 200 } else {
867f72bf 201 reset_lstat_cache(cache);
cb319c36 202 }
aeabab5c
KB
203 }
204}
205
bda6eb0d
KB
206/*
207 * Completely clear the contents of the cache
208 */
209void clear_lstat_cache(void)
210{
867f72bf
LT
211 struct cache_def *cache = &default_cache; /* FIXME */
212 reset_lstat_cache(cache);
bda6eb0d
KB
213}
214
bad4a54f
KB
215#define USE_ONLY_LSTAT 0
216
92604b46
KB
217/*
218 * Return non-zero if path 'name' has a leading symlink component
219 */
57199892 220int has_symlink_leading_path(const char *name, int len)
92604b46 221{
867f72bf
LT
222 struct cache_def *cache = &default_cache; /* FIXME */
223 return lstat_cache(cache, name, len,
bad4a54f 224 FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
92604b46 225 FL_SYMLINK;
f859c846 226}
09c93066
KB
227
228/*
229 * Return non-zero if path 'name' has a leading symlink component or
230 * if some leading path component does not exists.
231 */
57199892 232int has_symlink_or_noent_leading_path(const char *name, int len)
09c93066 233{
867f72bf
LT
234 struct cache_def *cache = &default_cache; /* FIXME */
235 return lstat_cache(cache, name, len,
bad4a54f 236 FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
09c93066
KB
237 (FL_SYMLINK|FL_NOENT);
238}
bad4a54f
KB
239
240/*
241 * Return non-zero if all path components of 'name' exists as a
242 * directory. If prefix_len > 0, we will test with the stat()
243 * function instead of the lstat() function for a prefix length of
244 * 'prefix_len', thus we then allow for symlinks in the prefix part as
245 * long as those points to real existing directories.
246 */
57199892 247int has_dirs_only_path(const char *name, int len, int prefix_len)
bad4a54f 248{
867f72bf
LT
249 struct cache_def *cache = &default_cache; /* FIXME */
250 return lstat_cache(cache, name, len,
bad4a54f
KB
251 FL_DIR|FL_FULLPATH, prefix_len) &
252 FL_DIR;
253}
78478927
KB
254
255static struct removal_def {
256 char path[PATH_MAX];
257 int len;
258} removal;
259
260static void do_remove_scheduled_dirs(int new_len)
261{
262 while (removal.len > new_len) {
263 removal.path[removal.len] = '\0';
264 if (rmdir(removal.path))
265 break;
266 do {
267 removal.len--;
268 } while (removal.len > new_len &&
269 removal.path[removal.len] != '/');
270 }
271 removal.len = new_len;
78478927
KB
272}
273
274void schedule_dir_for_removal(const char *name, int len)
275{
276 int match_len, last_slash, i, previous_slash;
277
278 match_len = last_slash = i =
279 longest_path_match(name, len, removal.path, removal.len,
280 &previous_slash);
281 /* Find last slash inside 'name' */
282 while (i < len) {
283 if (name[i] == '/')
284 last_slash = i;
285 i++;
286 }
287
288 /*
289 * If we are about to go down the directory tree, we check if
290 * we must first go upwards the tree, such that we then can
291 * remove possible empty directories as we go upwards.
292 */
293 if (match_len < last_slash && match_len < removal.len)
294 do_remove_scheduled_dirs(match_len);
295 /*
296 * If we go deeper down the directory tree, we only need to
297 * save the new path components as we go down.
298 */
299 if (match_len < last_slash) {
300 memcpy(&removal.path[match_len], &name[match_len],
301 last_slash - match_len);
302 removal.len = last_slash;
303 }
78478927
KB
304}
305
306void remove_scheduled_dirs(void)
307{
308 do_remove_scheduled_dirs(0);
78478927 309}