diff options
Diffstat (limited to 'symlinks.c')
| -rw-r--r-- | symlinks.c | 347 |
1 files changed, 347 insertions, 0 deletions
diff --git a/symlinks.c b/symlinks.c new file mode 100644 index 0000000..7dbb6b2 --- /dev/null +++ b/symlinks.c @@ -0,0 +1,347 @@ +#include "cache.h" + +static int threaded_check_leading_path(struct cache_def *cache, const char *name, int len); +static int threaded_has_dirs_only_path(struct cache_def *cache, const char *name, int len, int prefix_len); + +/* + * Returns the length (on a path component basis) of the longest + * common prefix match of 'name_a' and 'name_b'. + */ +static int longest_path_match(const char *name_a, int len_a, + const char *name_b, int len_b, + int *previous_slash) +{ + int max_len, match_len = 0, match_len_prev = 0, i = 0; + + max_len = len_a < len_b ? len_a : len_b; + while (i < max_len && name_a[i] == name_b[i]) { + if (name_a[i] == '/') { + match_len_prev = match_len; + match_len = i; + } + i++; + } + /* + * Is 'name_b' a substring of 'name_a', the other way around, + * or is 'name_a' and 'name_b' the exact same string? + */ + if (i >= max_len && ((len_a > len_b && name_a[len_b] == '/') || + (len_a < len_b && name_b[len_a] == '/') || + (len_a == len_b))) { + match_len_prev = match_len; + match_len = i; + } + *previous_slash = match_len_prev; + return match_len; +} + +static struct cache_def default_cache = CACHE_DEF_INIT; + +static inline void reset_lstat_cache(struct cache_def *cache) +{ + strbuf_reset(&cache->path); + cache->flags = 0; + /* + * The track_flags and prefix_len_stat_func members is only + * set by the safeguard rule inside lstat_cache() + */ +} + +#define FL_DIR (1 << 0) +#define FL_NOENT (1 << 1) +#define FL_SYMLINK (1 << 2) +#define FL_LSTATERR (1 << 3) +#define FL_ERR (1 << 4) +#define FL_FULLPATH (1 << 5) + +/* + * Check if name 'name' of length 'len' has a symlink leading + * component, or if the directory exists and is real, or not. + * + * To speed up the check, some information is allowed to be cached. + * This can be indicated by the 'track_flags' argument, which also can + * be used to indicate that we should check the full path. + * + * The 'prefix_len_stat_func' parameter can be used to set the length + * of the prefix, where the cache should use the stat() function + * instead of the lstat() function to test each path component. + */ +static int lstat_cache_matchlen(struct cache_def *cache, + const char *name, int len, + int *ret_flags, int track_flags, + int prefix_len_stat_func) +{ + int match_len, last_slash, last_slash_dir, previous_slash; + int save_flags, ret; + struct stat st; + + if (cache->track_flags != track_flags || + cache->prefix_len_stat_func != prefix_len_stat_func) { + /* + * As a safeguard rule we clear the cache if the + * values of track_flags and/or prefix_len_stat_func + * does not match with the last supplied values. + */ + reset_lstat_cache(cache); + cache->track_flags = track_flags; + cache->prefix_len_stat_func = prefix_len_stat_func; + match_len = last_slash = 0; + } else { + /* + * Check to see if we have a match from the cache for + * the 2 "excluding" path types. + */ + match_len = last_slash = + longest_path_match(name, len, cache->path.buf, + cache->path.len, &previous_slash); + *ret_flags = cache->flags & track_flags & (FL_NOENT|FL_SYMLINK); + + if (!(track_flags & FL_FULLPATH) && match_len == len) + match_len = last_slash = previous_slash; + + if (*ret_flags && match_len == cache->path.len) + return match_len; + /* + * If we now have match_len > 0, we would know that + * the matched part will always be a directory. + * + * Also, if we are tracking directories and 'name' is + * a substring of the cache on a path component basis, + * we can return immediately. + */ + *ret_flags = track_flags & FL_DIR; + if (*ret_flags && len == match_len) + return match_len; + } + + /* + * Okay, no match from the cache so far, so now we have to + * check the rest of the path components. + */ + *ret_flags = FL_DIR; + last_slash_dir = last_slash; + if (len > cache->path.len) + strbuf_grow(&cache->path, len - cache->path.len); + while (match_len < len) { + do { + cache->path.buf[match_len] = name[match_len]; + match_len++; + } while (match_len < len && name[match_len] != '/'); + if (match_len >= len && !(track_flags & FL_FULLPATH)) + break; + last_slash = match_len; + cache->path.buf[last_slash] = '\0'; + + if (last_slash <= prefix_len_stat_func) + ret = stat(cache->path.buf, &st); + else + ret = lstat(cache->path.buf, &st); + + if (ret) { + *ret_flags = FL_LSTATERR; + if (errno == ENOENT) + *ret_flags |= FL_NOENT; + } else if (S_ISDIR(st.st_mode)) { + last_slash_dir = last_slash; + continue; + } else if (S_ISLNK(st.st_mode)) { + *ret_flags = FL_SYMLINK; + } else { + *ret_flags = FL_ERR; + } + break; + } + + /* + * At the end update the cache. Note that max 3 different + * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached + * for the moment! + */ + save_flags = *ret_flags & track_flags & (FL_NOENT|FL_SYMLINK); + if (save_flags && last_slash > 0) { + cache->path.buf[last_slash] = '\0'; + cache->path.len = last_slash; + cache->flags = save_flags; + } else if ((track_flags & FL_DIR) && last_slash_dir > 0) { + /* + * We have a separate test for the directory case, + * since it could be that we have found a symlink or a + * non-existing directory and the track_flags says + * that we cannot cache this fact, so the cache would + * then have been left empty in this case. + * + * But if we are allowed to track real directories, we + * can still cache the path components before the last + * one (the found symlink or non-existing component). + */ + cache->path.buf[last_slash_dir] = '\0'; + cache->path.len = last_slash_dir; + cache->flags = FL_DIR; + } else { + reset_lstat_cache(cache); + } + return match_len; +} + +static int lstat_cache(struct cache_def *cache, const char *name, int len, + int track_flags, int prefix_len_stat_func) +{ + int flags; + (void)lstat_cache_matchlen(cache, name, len, &flags, track_flags, + prefix_len_stat_func); + return flags; +} + +#define USE_ONLY_LSTAT 0 + +/* + * Return non-zero if path 'name' has a leading symlink component + */ +int threaded_has_symlink_leading_path(struct cache_def *cache, const char *name, int len) +{ + return lstat_cache(cache, name, len, FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) & FL_SYMLINK; +} + +/* + * Return non-zero if path 'name' has a leading symlink component + */ +int has_symlink_leading_path(const char *name, int len) +{ + return threaded_has_symlink_leading_path(&default_cache, name, len); +} + +/* + * Return zero if path 'name' has a leading symlink component or + * if some leading path component does not exists. + * + * Return -1 if leading path exists and is a directory. + * + * Return path length if leading path exists and is neither a + * directory nor a symlink. + */ +int check_leading_path(const char *name, int len) +{ + return threaded_check_leading_path(&default_cache, name, len); +} + +/* + * Return zero if path 'name' has a leading symlink component or + * if some leading path component does not exists. + * + * Return -1 if leading path exists and is a directory. + * + * Return path length if leading path exists and is neither a + * directory nor a symlink. + */ +static int threaded_check_leading_path(struct cache_def *cache, const char *name, int len) +{ + int flags; + int match_len = lstat_cache_matchlen(cache, name, len, &flags, + FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT); + if (flags & FL_NOENT) + return 0; + else if (flags & FL_DIR) + return -1; + else + return match_len; +} + +/* + * Return non-zero if all path components of 'name' exists as a + * directory. If prefix_len > 0, we will test with the stat() + * function instead of the lstat() function for a prefix length of + * 'prefix_len', thus we then allow for symlinks in the prefix part as + * long as those points to real existing directories. + */ +int has_dirs_only_path(const char *name, int len, int prefix_len) +{ + return threaded_has_dirs_only_path(&default_cache, name, len, prefix_len); +} + +/* + * Return non-zero if all path components of 'name' exists as a + * directory. If prefix_len > 0, we will test with the stat() + * function instead of the lstat() function for a prefix length of + * 'prefix_len', thus we then allow for symlinks in the prefix part as + * long as those points to real existing directories. + */ +static int threaded_has_dirs_only_path(struct cache_def *cache, const char *name, int len, int prefix_len) +{ + /* + * Note: this function is used by the checkout machinery, which also + * takes care to properly reset the cache when it performs an operation + * that would leave the cache outdated. If this function starts caching + * anything else besides FL_DIR, remember to also invalidate the cache + * when creating or deleting paths that might be in the cache. + */ + return lstat_cache(cache, name, len, + FL_DIR|FL_FULLPATH, prefix_len) & + FL_DIR; +} + +static struct strbuf removal = STRBUF_INIT; + +static void do_remove_scheduled_dirs(int new_len) +{ + while (removal.len > new_len) { + removal.buf[removal.len] = '\0'; + if (rmdir(removal.buf)) + break; + do { + removal.len--; + } while (removal.len > new_len && + removal.buf[removal.len] != '/'); + } + removal.len = new_len; +} + +void schedule_dir_for_removal(const char *name, int len) +{ + int match_len, last_slash, i, previous_slash; + + match_len = last_slash = i = + longest_path_match(name, len, removal.buf, removal.len, + &previous_slash); + /* Find last slash inside 'name' */ + while (i < len) { + if (name[i] == '/') + last_slash = i; + i++; + } + + /* + * If we are about to go down the directory tree, we check if + * we must first go upwards the tree, such that we then can + * remove possible empty directories as we go upwards. + */ + if (match_len < last_slash && match_len < removal.len) + do_remove_scheduled_dirs(match_len); + /* + * If we go deeper down the directory tree, we only need to + * save the new path components as we go down. + */ + if (match_len < last_slash) + strbuf_add(&removal, &name[match_len], last_slash - match_len); +} + +void remove_scheduled_dirs(void) +{ + do_remove_scheduled_dirs(0); +} + +void invalidate_lstat_cache(void) +{ + reset_lstat_cache(&default_cache); +} + +#undef rmdir +int lstat_cache_aware_rmdir(const char *path) +{ + /* Any change in this function must be made also in `mingw_rmdir()` */ + int ret = rmdir(path); + + if (!ret) + invalidate_lstat_cache(); + + return ret; +} |