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/*
* 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]) {
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 (link[0] == '/') {
/* 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 commit_lock_file(struct lock_file *lk)
{
char result_file[PATH_MAX];
int i;
close(lk->fd);
strcpy(result_file, lk->filename);
i = strlen(result_file) - 5; /* .lock */
result_file[i] = 0;
i = rename(lk->filename, result_file);
lk->filename[0] = 0;
return i;
}
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) {
int result = rename(lk->filename, alternate_index_output);
lk->filename[0] = 0;
return result;
}
else
return commit_lock_file(lk);
}
void rollback_lock_file(struct lock_file *lk)
{
if (lk->filename[0]) {
close(lk->fd);
unlink(lk->filename);
}
lk->filename[0] = 0;
}
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