1 files changed, 64 insertions, 0 deletions
diff --git a/symlinks.c b/symlinks.c
new file mode 100644
index 0000000000..5a5e781a15
--- /dev/null
+++ b/symlinks.c
@@ -0,0 +1,64 @@
+#include "cache.h"
+
+struct pathname {
+	int len;
+	char path[PATH_MAX];
+};
+
+/* Return matching pathname prefix length, or zero if not matching */
+static inline int match_pathname(int len, const char *name, struct pathname *match)
+{
+	int match_len = match->len;
+	return (len > match_len &&
+		name[match_len] == '/' &&
+		!memcmp(name, match->path, match_len)) ? match_len : 0;
+}
+
+static inline void set_pathname(int len, const char *name, struct pathname *match)
+{
+	if (len < PATH_MAX) {
+		match->len = len;
+		memcpy(match->path, name, len);
+		match->path[len] = 0;
+	}
+}
+
+int has_symlink_leading_path(int len, const char *name)
+{
+	static struct pathname link, nonlink;
+	char path[PATH_MAX];
+	struct stat st;
+	char *sp;
+	int known_dir;
+
+	/*
+	 * See if the last known symlink cache matches.
+	 */
+	if (match_pathname(len, name, &link))
+		return 1;
+
+	/*
+	 * Get rid of the last known directory part
+	 */
+	known_dir = match_pathname(len, name, &nonlink);
+
+	while ((sp = strchr(name + known_dir + 1, '/')) != NULL) {
+		int thislen = sp - name ;
+		memcpy(path, name, thislen);
+		path[thislen] = 0;
+
+		if (lstat(path, &st))
+			return 0;
+		if (S_ISDIR(st.st_mode)) {
+			set_pathname(thislen, path, &nonlink);
+			known_dir = thislen;
+			continue;
+		}
+		if (S_ISLNK(st.st_mode)) {
+			set_pathname(thislen, path, &link);
+			return 1;
+		}
+		break;
+	}
+	return 0;
+}