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![Michael Haggerty](/assets/img/avatar_default.png)
Allow an existing file to be registered with the tempfile-handling infrastructure; in particular, arrange for it to be deleted on program exit. This can be used if the temporary file has to be created in a more complicated way than just open(). For example: * If the file itself needs to be created via the lockfile API * If it is not a regular file (e.g., a socket) Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
306 lines
8 KiB
C
306 lines
8 KiB
C
/*
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* State diagram and cleanup
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* -------------------------
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*
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* If the program exits while a temporary file is active, we want to
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* make sure that we remove it. This is done by remembering the active
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* temporary files in a linked list, `tempfile_list`. An `atexit(3)`
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* handler and a signal handler are registered, to clean up any active
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* temporary files.
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*
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* Because the signal handler can run at any time, `tempfile_list` and
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* the `tempfile` objects that comprise it must be kept in
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* self-consistent states at all times.
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*
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* The possible states of a `tempfile` object are as follows:
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*
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* - Uninitialized. In this state the object's `on_list` field must be
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* zero but the rest of its contents need not be initialized. As
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* soon as the object is used in any way, it is irrevocably
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* registered in `tempfile_list`, and `on_list` is set.
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*
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* - Active, file open (after `create_tempfile()` or
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* `reopen_tempfile()`). In this state:
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*
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* - the temporary file exists
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* - `active` is set
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* - `filename` holds the filename of the temporary file
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* - `fd` holds a file descriptor open for writing to it
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* - `fp` holds a pointer to an open `FILE` object if and only if
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* `fdopen_tempfile()` has been called on the object
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* - `owner` holds the PID of the process that created the file
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*
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* - Active, file closed (after successful `close_tempfile()`). Same
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* as the previous state, except that the temporary file is closed,
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* `fd` is -1, and `fp` is `NULL`.
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*
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* - Inactive (after `delete_tempfile()`, `rename_tempfile()`, a
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* failed attempt to create a temporary file, or a failed
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* `close_tempfile()`). In this state:
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*
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* - `active` is unset
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* - `filename` is empty (usually, though there are transitory
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* states in which this condition doesn't hold). Client code should
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* *not* rely on the filename being empty in this state.
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* - `fd` is -1 and `fp` is `NULL`
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* - the object is left registered in the `tempfile_list`, and
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* `on_list` is set.
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*
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* A temporary file is owned by the process that created it. The
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* `tempfile` has an `owner` field that records the owner's PID. This
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* field is used to prevent a forked process from deleting a temporary
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* file created by its parent.
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*/
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#include "cache.h"
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#include "tempfile.h"
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#include "sigchain.h"
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static struct tempfile *volatile tempfile_list;
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static void remove_tempfiles(int skip_fclose)
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{
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pid_t me = getpid();
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while (tempfile_list) {
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if (tempfile_list->owner == me) {
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/* fclose() is not safe to call in a signal handler */
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if (skip_fclose)
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tempfile_list->fp = NULL;
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delete_tempfile(tempfile_list);
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}
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tempfile_list = tempfile_list->next;
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}
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}
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static void remove_tempfiles_on_exit(void)
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{
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remove_tempfiles(0);
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}
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static void remove_tempfiles_on_signal(int signo)
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{
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remove_tempfiles(1);
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sigchain_pop(signo);
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raise(signo);
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}
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/*
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* Initialize *tempfile if necessary and add it to tempfile_list.
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*/
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static void prepare_tempfile_object(struct tempfile *tempfile)
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{
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if (!tempfile_list) {
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/* One-time initialization */
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sigchain_push_common(remove_tempfiles_on_signal);
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atexit(remove_tempfiles_on_exit);
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}
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if (tempfile->active)
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die("BUG: prepare_tempfile_object called for active object");
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if (!tempfile->on_list) {
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/* Initialize *tempfile and add it to tempfile_list: */
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tempfile->fd = -1;
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tempfile->fp = NULL;
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tempfile->active = 0;
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tempfile->owner = 0;
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strbuf_init(&tempfile->filename, 0);
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tempfile->next = tempfile_list;
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tempfile_list = tempfile;
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tempfile->on_list = 1;
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} else if (tempfile->filename.len) {
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/* This shouldn't happen, but better safe than sorry. */
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die("BUG: prepare_tempfile_object called for improperly-reset object");
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}
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}
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/* Make sure errno contains a meaningful value on error */
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int create_tempfile(struct tempfile *tempfile, const char *path)
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{
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prepare_tempfile_object(tempfile);
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strbuf_add_absolute_path(&tempfile->filename, path);
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tempfile->fd = open(tempfile->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666);
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if (tempfile->fd < 0) {
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strbuf_reset(&tempfile->filename);
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return -1;
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}
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tempfile->owner = getpid();
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tempfile->active = 1;
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if (adjust_shared_perm(tempfile->filename.buf)) {
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int save_errno = errno;
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error("cannot fix permission bits on %s", tempfile->filename.buf);
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delete_tempfile(tempfile);
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errno = save_errno;
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return -1;
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}
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return tempfile->fd;
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}
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void register_tempfile(struct tempfile *tempfile, const char *path)
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{
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prepare_tempfile_object(tempfile);
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strbuf_add_absolute_path(&tempfile->filename, path);
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tempfile->owner = getpid();
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tempfile->active = 1;
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}
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int mks_tempfile_sm(struct tempfile *tempfile,
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const char *template, int suffixlen, int mode)
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{
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prepare_tempfile_object(tempfile);
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strbuf_add_absolute_path(&tempfile->filename, template);
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tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
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if (tempfile->fd < 0) {
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strbuf_reset(&tempfile->filename);
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return -1;
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}
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tempfile->owner = getpid();
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tempfile->active = 1;
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return tempfile->fd;
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}
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int mks_tempfile_tsm(struct tempfile *tempfile,
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const char *template, int suffixlen, int mode)
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{
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const char *tmpdir;
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prepare_tempfile_object(tempfile);
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tmpdir = getenv("TMPDIR");
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if (!tmpdir)
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tmpdir = "/tmp";
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strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
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tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
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if (tempfile->fd < 0) {
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strbuf_reset(&tempfile->filename);
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return -1;
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}
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tempfile->owner = getpid();
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tempfile->active = 1;
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return tempfile->fd;
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}
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int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
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{
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int fd;
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struct strbuf full_template = STRBUF_INIT;
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strbuf_add_absolute_path(&full_template, template);
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fd = mks_tempfile_m(tempfile, full_template.buf, mode);
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if (fd < 0)
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die_errno("Unable to create temporary file '%s'",
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full_template.buf);
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strbuf_release(&full_template);
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return fd;
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}
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FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
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{
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if (!tempfile->active)
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die("BUG: fdopen_tempfile() called for inactive object");
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if (tempfile->fp)
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die("BUG: fdopen_tempfile() called for open object");
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tempfile->fp = fdopen(tempfile->fd, mode);
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return tempfile->fp;
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}
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const char *get_tempfile_path(struct tempfile *tempfile)
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{
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if (!tempfile->active)
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die("BUG: get_tempfile_path() called for inactive object");
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return tempfile->filename.buf;
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}
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int get_tempfile_fd(struct tempfile *tempfile)
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{
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if (!tempfile->active)
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die("BUG: get_tempfile_fd() called for inactive object");
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return tempfile->fd;
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}
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FILE *get_tempfile_fp(struct tempfile *tempfile)
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{
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if (!tempfile->active)
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die("BUG: get_tempfile_fp() called for inactive object");
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return tempfile->fp;
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}
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int close_tempfile(struct tempfile *tempfile)
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{
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int fd = tempfile->fd;
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FILE *fp = tempfile->fp;
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int err;
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if (fd < 0)
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return 0;
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tempfile->fd = -1;
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if (fp) {
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tempfile->fp = NULL;
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/*
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* Note: no short-circuiting here; we want to fclose()
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* in any case!
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*/
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err = ferror(fp) | fclose(fp);
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} else {
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err = close(fd);
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}
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if (err) {
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int save_errno = errno;
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delete_tempfile(tempfile);
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errno = save_errno;
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return -1;
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}
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return 0;
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}
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int reopen_tempfile(struct tempfile *tempfile)
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{
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if (0 <= tempfile->fd)
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die("BUG: reopen_tempfile called for an open object");
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if (!tempfile->active)
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die("BUG: reopen_tempfile called for an inactive object");
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tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
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return tempfile->fd;
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}
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int rename_tempfile(struct tempfile *tempfile, const char *path)
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{
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if (!tempfile->active)
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die("BUG: rename_tempfile called for inactive object");
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if (close_tempfile(tempfile))
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return -1;
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if (rename(tempfile->filename.buf, path)) {
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int save_errno = errno;
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delete_tempfile(tempfile);
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errno = save_errno;
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return -1;
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}
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tempfile->active = 0;
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strbuf_reset(&tempfile->filename);
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return 0;
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}
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void delete_tempfile(struct tempfile *tempfile)
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{
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if (!tempfile->active)
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return;
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if (!close_tempfile(tempfile)) {
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unlink_or_warn(tempfile->filename.buf);
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tempfile->active = 0;
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strbuf_reset(&tempfile->filename);
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}
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}
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