diff options
Diffstat (limited to 'lockfile.c')
| -rw-r--r-- | lockfile.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/lockfile.c b/lockfile.c new file mode 100644 index 0000000000..9a1f64d8d7 --- /dev/null +++ b/lockfile.c @@ -0,0 +1,200 @@ +/* + * 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]) + 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) +{ + int fd; + + 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"); + fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666); + if (0 <= 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 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; + 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]) + unlink(lk->filename); + lk->filename[0] = 0; +} |