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-rw-r--r--symlinks.c303
1 files changed, 303 insertions, 0 deletions
diff --git a/symlinks.c b/symlinks.c
new file mode 100644
index 0000000000..034943bda0
--- /dev/null
+++ b/symlinks.c
@@ -0,0 +1,303 @@
+#include "cache.h"
+
+/*
+ * 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;
+
+static inline void reset_lstat_cache(struct cache_def *cache)
+{
+ cache->path[0] = '\0';
+ cache->len = 0;
+ 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, max_len, 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, cache->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->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;
+ max_len = len < PATH_MAX ? len : PATH_MAX;
+ while (match_len < max_len) {
+ do {
+ cache->path[match_len] = name[match_len];
+ match_len++;
+ } while (match_len < max_len && name[match_len] != '/');
+ if (match_len >= max_len && !(track_flags & FL_FULLPATH))
+ break;
+ last_slash = match_len;
+ cache->path[last_slash] = '\0';
+
+ if (last_slash <= prefix_len_stat_func)
+ ret = stat(cache->path, &st);
+ else
+ ret = lstat(cache->path, &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 && last_slash <= PATH_MAX) {
+ cache->path[last_slash] = '\0';
+ cache->len = last_slash;
+ cache->flags = save_flags;
+ } else if ((track_flags & FL_DIR) &&
+ last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
+ /*
+ * 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[last_slash_dir] = '\0';
+ cache->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)
+{
+ struct cache_def *cache = &default_cache; /* FIXME */
+ 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)
+{
+ struct cache_def *cache = &default_cache; /* FIXME */
+ return lstat_cache(cache, name, len,
+ FL_DIR|FL_FULLPATH, prefix_len) &
+ FL_DIR;
+}
+
+static struct removal_def {
+ char path[PATH_MAX];
+ int len;
+} removal;
+
+static void do_remove_scheduled_dirs(int new_len)
+{
+ while (removal.len > new_len) {
+ removal.path[removal.len] = '\0';
+ if (rmdir(removal.path))
+ break;
+ do {
+ removal.len--;
+ } while (removal.len > new_len &&
+ removal.path[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.path, 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) {
+ memcpy(&removal.path[match_len], &name[match_len],
+ last_slash - match_len);
+ removal.len = last_slash;
+ }
+}
+
+void remove_scheduled_dirs(void)
+{
+ do_remove_scheduled_dirs(0);
+}
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