1 files changed, 217 insertions, 0 deletions
diff --git a/lockfile.c b/lockfile.c
new file mode 100644
index 0000000000..663f18f9c4
--- /dev/null
+++ b/lockfile.c
@@ -0,0 +1,217 @@
+/*
+ * Copyright (c) 2005, Junio C Hamano
+ */
+#include "cache.h"
+
+static struct lock_file *lock_file_list;
+static const char *alternate_index_output;
+
+static void remove_lock_file(void)
+{
+	pid_t me = getpid();
+
+	while (lock_file_list) {
+		if (lock_file_list->owner == me &&
+		    lock_file_list->filename[0]) {
+			if (lock_file_list->fd >= 0)
+				close(lock_file_list->fd);
+			unlink(lock_file_list->filename);
+		}
+		lock_file_list = lock_file_list->next;
+	}
+}
+
+static void remove_lock_file_on_signal(int signo)
+{
+	remove_lock_file();
+	signal(SIGINT, SIG_DFL);
+	raise(signo);
+}
+
+/*
+ * p = absolute or relative path name
+ *
+ * Return a pointer into p showing the beginning of the last path name
+ * element.  If p is empty or the root directory ("/"), just return p.
+ */
+static char *last_path_elm(char *p)
+{
+	/* r starts pointing to null at the end of the string */
+	char *r = strchr(p, '\0');
+
+	if (r == p)
+		return p; /* just return empty string */
+
+	r--; /* back up to last non-null character */
+
+	/* back up past trailing slashes, if any */
+	while (r > p && *r == '/')
+		r--;
+
+	/*
+	 * then go backwards until I hit a slash, or the beginning of
+	 * the string
+	 */
+	while (r > p && *(r-1) != '/')
+		r--;
+	return r;
+}
+
+
+/* We allow "recursive" symbolic links. Only within reason, though */
+#define MAXDEPTH 5
+
+/*
+ * p = path that may be a symlink
+ * s = full size of p
+ *
+ * If p is a symlink, attempt to overwrite p with a path to the real
+ * file or directory (which may or may not exist), following a chain of
+ * symlinks if necessary.  Otherwise, leave p unmodified.
+ *
+ * This is a best-effort routine.  If an error occurs, p will either be
+ * left unmodified or will name a different symlink in a symlink chain
+ * that started with p's initial contents.
+ *
+ * Always returns p.
+ */
+
+static char *resolve_symlink(char *p, size_t s)
+{
+	int depth = MAXDEPTH;
+
+	while (depth--) {
+		char link[PATH_MAX];
+		int link_len = readlink(p, link, sizeof(link));
+		if (link_len < 0) {
+			/* not a symlink anymore */
+			return p;
+		}
+		else if (link_len < sizeof(link))
+			/* readlink() never null-terminates */
+			link[link_len] = '\0';
+		else {
+			warning("%s: symlink too long", p);
+			return p;
+		}
+
+		if (is_absolute_path(link)) {
+			/* absolute path simply replaces p */
+			if (link_len < s)
+				strcpy(p, link);
+			else {
+				warning("%s: symlink too long", p);
+				return p;
+			}
+		} else {
+			/*
+			 * link is a relative path, so I must replace the
+			 * last element of p with it.
+			 */
+			char *r = (char*)last_path_elm(p);
+			if (r - p + link_len < s)
+				strcpy(r, link);
+			else {
+				warning("%s: symlink too long", p);
+				return p;
+			}
+		}
+	}
+	return p;
+}
+
+
+static int lock_file(struct lock_file *lk, const char *path)
+{
+	if (strlen(path) >= sizeof(lk->filename)) return -1;
+	strcpy(lk->filename, path);
+	/*
+	 * subtract 5 from size to make sure there's room for adding
+	 * ".lock" for the lock file name
+	 */
+	resolve_symlink(lk->filename, sizeof(lk->filename)-5);
+	strcat(lk->filename, ".lock");
+	lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
+	if (0 <= lk->fd) {
+		if (!lock_file_list) {
+			signal(SIGINT, remove_lock_file_on_signal);
+			atexit(remove_lock_file);
+		}
+		lk->owner = getpid();
+		if (!lk->on_list) {
+			lk->next = lock_file_list;
+			lock_file_list = lk;
+			lk->on_list = 1;
+		}
+		if (adjust_shared_perm(lk->filename))
+			return error("cannot fix permission bits on %s",
+				     lk->filename);
+	}
+	else
+		lk->filename[0] = 0;
+	return lk->fd;
+}
+
+int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on_error)
+{
+	int fd = lock_file(lk, path);
+	if (fd < 0 && die_on_error)
+		die("unable to create '%s.lock': %s", path, strerror(errno));
+	return fd;
+}
+
+int close_lock_file(struct lock_file *lk)
+{
+	int fd = lk->fd;
+	lk->fd = -1;
+	return close(fd);
+}
+
+int commit_lock_file(struct lock_file *lk)
+{
+	char result_file[PATH_MAX];
+	size_t i;
+	if (lk->fd >= 0 && close_lock_file(lk))
+		return -1;
+	strcpy(result_file, lk->filename);
+	i = strlen(result_file) - 5; /* .lock */
+	result_file[i] = 0;
+	if (rename(lk->filename, result_file))
+		return -1;
+	lk->filename[0] = 0;
+	return 0;
+}
+
+int hold_locked_index(struct lock_file *lk, int die_on_error)
+{
+	return hold_lock_file_for_update(lk, get_index_file(), die_on_error);
+}
+
+void set_alternate_index_output(const char *name)
+{
+	alternate_index_output = name;
+}
+
+int commit_locked_index(struct lock_file *lk)
+{
+	if (alternate_index_output) {
+		if (lk->fd >= 0 && close_lock_file(lk))
+			return -1;
+		if (rename(lk->filename, alternate_index_output))
+			return -1;
+		lk->filename[0] = 0;
+		return 0;
+	}
+	else
+		return commit_lock_file(lk);
+}
+
+void rollback_lock_file(struct lock_file *lk)
+{
+	if (lk->filename[0]) {
+		if (lk->fd >= 0)
+			close(lk->fd);
+		unlink(lk->filename);
+	}
+	lk->filename[0] = 0;
+}