1 files changed, 125 insertions, 40 deletions

diff --git a/symlinks.c b/symlinks.c
index 5a5e781a15..49fb4d8bc2 100644
--- a/symlinks.c
+++ b/symlinks.c
@@ -1,64 +1,149 @@
 #include "cache.h"
 
-struct pathname {
-	int len;
+static struct cache_def {
 	char path[PATH_MAX];
-};
+	int len;
+	int flags;
+} cache;
 
-/* Return matching pathname prefix length, or zero if not matching */
-static inline int match_pathname(int len, const char *name, struct pathname *match)
+/*
+ * Returns the length (on a path component basis) of the longest
+ * common prefix match of 'name' and the cached path string.
+ */
+static inline int longest_match_lstat_cache(int len, const char *name)
 {
-	int match_len = match->len;
-	return (len > match_len &&
-		name[match_len] == '/' &&
-		!memcmp(name, match->path, match_len)) ? match_len : 0;
+	int max_len, match_len = 0, i = 0;
+
+	max_len = len < cache.len ? len : cache.len;
+	while (i < max_len && name[i] == cache.path[i]) {
+		if (name[i] == '/')
+			match_len = i;
+		i++;
+	}
+	/* Is the cached path string a substring of 'name'? */
+	if (i == cache.len && cache.len < len && name[cache.len] == '/')
+		match_len = cache.len;
+	/* Is 'name' a substring of the cached path string? */
+	else if ((i == len && len < cache.len && cache.path[len] == '/') ||
+		 (i == len && len == cache.len))
+		match_len = len;
+	return match_len;
 }
 
-static inline void set_pathname(int len, const char *name, struct pathname *match)
+static inline void reset_lstat_cache(void)
 {
-	if (len < PATH_MAX) {
-		match->len = len;
-		memcpy(match->path, name, len);
-		match->path[len] = 0;
-	}
+	cache.path[0] = '\0';
+	cache.len = 0;
+	cache.flags = 0;
 }
 
-int has_symlink_leading_path(int len, const char *name)
+#define FL_DIR      (1 << 0)
+#define FL_SYMLINK  (1 << 1)
+#define FL_LSTATERR (1 << 2)
+#define FL_ERR      (1 << 3)
+
+/*
+ * Check if name 'name' of length 'len' has a symlink leading
+ * component, or if the directory exists and is real.
+ *
+ * To speed up the check, some information is allowed to be cached.
+ * This can be indicated by the 'track_flags' argument.
+ */
+static int lstat_cache(int len, const char *name,
+		       int track_flags)
 {
-	static struct pathname link, nonlink;
-	char path[PATH_MAX];
+	int match_len, last_slash, last_slash_dir;
+	int match_flags, ret_flags, save_flags, max_len;
 	struct stat st;
-	char *sp;
-	int known_dir;
 
 	/*
-	 * See if the last known symlink cache matches.
+	 * Check to see if we have a match from the cache for the
+	 * symlink path type.
 	 */
-	if (match_pathname(len, name, &link))
-		return 1;
-
+	match_len = last_slash = longest_match_lstat_cache(len, name);
+	match_flags = cache.flags & track_flags & FL_SYMLINK;
+	if (match_flags && match_len == cache.len)
+		return match_flags;
 	/*
-	 * Get rid of the last known directory part
+	 * 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.
 	 */
-	known_dir = match_pathname(len, name, &nonlink);
+	match_flags = track_flags & FL_DIR;
+	if (match_flags && len == match_len)
+		return match_flags;
 
-	while ((sp = strchr(name + known_dir + 1, '/')) != NULL) {
-		int thislen = sp - name ;
-		memcpy(path, name, thislen);
-		path[thislen] = 0;
+	/*
+	 * 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)
+			break;
+		last_slash = match_len;
+		cache.path[last_slash] = '\0';
 
-		if (lstat(path, &st))
-			return 0;
-		if (S_ISDIR(st.st_mode)) {
-			set_pathname(thislen, path, &nonlink);
-			known_dir = thislen;
+		if (lstat(cache.path, &st)) {
+			ret_flags = FL_LSTATERR;
+		} else if (S_ISDIR(st.st_mode)) {
+			last_slash_dir = last_slash;
 			continue;
-		}
-		if (S_ISLNK(st.st_mode)) {
-			set_pathname(thislen, path, &link);
-			return 1;
+		} else if (S_ISLNK(st.st_mode)) {
+			ret_flags = FL_SYMLINK;
+		} else {
+			ret_flags = FL_ERR;
 		}
 		break;
 	}
-	return 0;
+
+	/*
+	 * At the end update the cache.  Note that max 2 different
+	 * path types, FL_SYMLINK and FL_DIR, can be cached for the
+	 * moment!
+	 */
+	save_flags = ret_flags & track_flags & 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 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 component).
+		 */
+		cache.path[last_slash_dir] = '\0';
+		cache.len = last_slash_dir;
+		cache.flags = FL_DIR;
+	} else {
+		reset_lstat_cache();
+	}
+	return ret_flags;
+}
+
+/*
+ * Return non-zero if path 'name' has a leading symlink component
+ */
+int has_symlink_leading_path(int len, const char *name)
+{
+	return lstat_cache(len, name,
+			   FL_SYMLINK|FL_DIR) &
+		FL_SYMLINK;
 }