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-rw-r--r--lockfile.c280
1 files changed, 280 insertions, 0 deletions
diff --git a/lockfile.c b/lockfile.c
new file mode 100644
index 0000000000..c6fb77b26f
--- /dev/null
+++ b/lockfile.c
@@ -0,0 +1,280 @@
+/*
+ * Copyright (c) 2005, Junio C Hamano
+ */
+#include "cache.h"
+#include "sigchain.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_or_warn(lock_file_list->filename);
+ }
+ lock_file_list = lock_file_list->next;
+ }
+}
+
+static void remove_lock_file_on_signal(int signo)
+{
+ remove_lock_file();
+ sigchain_pop(signo);
+ 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, int flags)
+{
+ 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
+ */
+ if (!(flags & LOCK_NODEREF))
+ 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) {
+ sigchain_push_common(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;
+}
+
+static char *unable_to_lock_message(const char *path, int err)
+{
+ struct strbuf buf = STRBUF_INIT;
+
+ if (err == EEXIST) {
+ strbuf_addf(&buf, "Unable to create '%s.lock': %s.\n\n"
+ "If no other git process is currently running, this probably means a\n"
+ "git process crashed in this repository earlier. Make sure no other git\n"
+ "process is running and remove the file manually to continue.",
+ absolute_path(path), strerror(err));
+ } else
+ strbuf_addf(&buf, "Unable to create '%s.lock': %s",
+ absolute_path(path), strerror(err));
+ return strbuf_detach(&buf, NULL);
+}
+
+int unable_to_lock_error(const char *path, int err)
+{
+ char *msg = unable_to_lock_message(path, err);
+ error("%s", msg);
+ free(msg);
+ return -1;
+}
+
+NORETURN void unable_to_lock_index_die(const char *path, int err)
+{
+ die("%s", unable_to_lock_message(path, err));
+}
+
+int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags)
+{
+ int fd = lock_file(lk, path, flags);
+ if (fd < 0 && (flags & LOCK_DIE_ON_ERROR))
+ unable_to_lock_index_die(path, errno);
+ return fd;
+}
+
+int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags)
+{
+ int fd, orig_fd;
+
+ fd = lock_file(lk, path, flags);
+ if (fd < 0) {
+ if (flags & LOCK_DIE_ON_ERROR)
+ unable_to_lock_index_die(path, errno);
+ return fd;
+ }
+
+ orig_fd = open(path, O_RDONLY);
+ if (orig_fd < 0) {
+ if (errno != ENOENT) {
+ if (flags & LOCK_DIE_ON_ERROR)
+ die("cannot open '%s' for copying", path);
+ close(fd);
+ return error("cannot open '%s' for copying", path);
+ }
+ } else if (copy_fd(orig_fd, fd)) {
+ if (flags & LOCK_DIE_ON_ERROR)
+ exit(128);
+ close(fd);
+ return -1;
+ }
+ 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
+ ? LOCK_DIE_ON_ERROR
+ : 0);
+}
+
+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_or_warn(lk->filename);
+ }
+ lk->filename[0] = 0;
+}