[thirdparty/git.git] / tempfile.c

/*
 * State diagram and cleanup
 * -------------------------
 *
 * If the program exits while a temporary file is active, we want to
 * make sure that we remove it. This is done by remembering the active
 * temporary files in a linked list, `tempfile_list`. An `atexit(3)`
 * handler and a signal handler are registered, to clean up any active
 * temporary files.
 *
 * Because the signal handler can run at any time, `tempfile_list` and
 * the `tempfile` objects that comprise it must be kept in
 * self-consistent states at all times.
 *
 * The possible states of a `tempfile` object are as follows:
 *
 * - Uninitialized. In this state the object's `on_list` field must be
 *   zero but the rest of its contents need not be initialized. As
 *   soon as the object is used in any way, it is irrevocably
 *   registered in `tempfile_list`, and `on_list` is set.
 *
 * - Active, file open (after `create_tempfile()` or
 *   `reopen_tempfile()`). In this state:
 *
 *   - the temporary file exists
 *   - `active` is set
 *   - `filename` holds the filename of the temporary file
 *   - `fd` holds a file descriptor open for writing to it
 *   - `fp` holds a pointer to an open `FILE` object if and only if
 *     `fdopen_tempfile()` has been called on the object
 *   - `owner` holds the PID of the process that created the file
 *
 * - Active, file closed (after successful `close_tempfile()`). Same
 *   as the previous state, except that the temporary file is closed,
 *   `fd` is -1, and `fp` is `NULL`.
 *
 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, a
 *   failed attempt to create a temporary file, or a failed
 *   `close_tempfile()`). In this state:
 *
 *   - `active` is unset
 *   - `filename` is empty (usually, though there are transitory
 *     states in which this condition doesn't hold). Client code should
 *     *not* rely on the filename being empty in this state.
 *   - `fd` is -1 and `fp` is `NULL`
 *   - the object is left registered in the `tempfile_list`, and
 *     `on_list` is set.
 *
 * A temporary file is owned by the process that created it. The
 * `tempfile` has an `owner` field that records the owner's PID. This
 * field is used to prevent a forked process from deleting a temporary
 * file created by its parent.
 */

#include "cache.h"
#include "tempfile.h"
#include "sigchain.h"

static struct tempfile *volatile tempfile_list;

static void remove_tempfiles(int skip_fclose)
{
	pid_t me = getpid();

	while (tempfile_list) {
		if (tempfile_list->owner == me) {
			/* fclose() is not safe to call in a signal handler */
			if (skip_fclose)
				tempfile_list->fp = NULL;
			delete_tempfile(tempfile_list);
		}
		tempfile_list = tempfile_list->next;
	}
}

static void remove_tempfiles_on_exit(void)
{
	remove_tempfiles(0);
}

static void remove_tempfiles_on_signal(int signo)
{
	remove_tempfiles(1);
	sigchain_pop(signo);
	raise(signo);
}

/*
 * Initialize *tempfile if necessary and add it to tempfile_list.
 */
static void prepare_tempfile_object(struct tempfile *tempfile)
{
	if (!tempfile_list) {
		/* One-time initialization */
		sigchain_push_common(remove_tempfiles_on_signal);
		atexit(remove_tempfiles_on_exit);
	}

	if (tempfile->active)
		die("BUG: prepare_tempfile_object called for active object");
	if (!tempfile->on_list) {
		/* Initialize *tempfile and add it to tempfile_list: */
		tempfile->fd = -1;
		tempfile->fp = NULL;
		tempfile->active = 0;
		tempfile->owner = 0;
		strbuf_init(&tempfile->filename, 0);
		tempfile->next = tempfile_list;
		tempfile_list = tempfile;
		tempfile->on_list = 1;
	} else if (tempfile->filename.len) {
		/* This shouldn't happen, but better safe than sorry. */
		die("BUG: prepare_tempfile_object called for improperly-reset object");
	}
}

/* Make sure errno contains a meaningful value on error */
int create_tempfile(struct tempfile *tempfile, const char *path)
{
	prepare_tempfile_object(tempfile);

	strbuf_add_absolute_path(&tempfile->filename, path);
	tempfile->fd = open(tempfile->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666);
	if (tempfile->fd < 0) {
		strbuf_reset(&tempfile->filename);
		return -1;
	}
	tempfile->owner = getpid();
	tempfile->active = 1;
	if (adjust_shared_perm(tempfile->filename.buf)) {
		int save_errno = errno;
		error("cannot fix permission bits on %s", tempfile->filename.buf);
		delete_tempfile(tempfile);
		errno = save_errno;
		return -1;
	}
	return tempfile->fd;
}

void register_tempfile(struct tempfile *tempfile, const char *path)
{
	prepare_tempfile_object(tempfile);
	strbuf_add_absolute_path(&tempfile->filename, path);
	tempfile->owner = getpid();
	tempfile->active = 1;
}

int mks_tempfile_sm(struct tempfile *tempfile,
		    const char *template, int suffixlen, int mode)
{
	prepare_tempfile_object(tempfile);

	strbuf_add_absolute_path(&tempfile->filename, template);
	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	if (tempfile->fd < 0) {
		strbuf_reset(&tempfile->filename);
		return -1;
	}
	tempfile->owner = getpid();
	tempfile->active = 1;
	return tempfile->fd;
}

int mks_tempfile_tsm(struct tempfile *tempfile,
		     const char *template, int suffixlen, int mode)
{
	const char *tmpdir;

	prepare_tempfile_object(tempfile);

	tmpdir = getenv("TMPDIR");
	if (!tmpdir)
		tmpdir = "/tmp";

	strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	if (tempfile->fd < 0) {
		strbuf_reset(&tempfile->filename);
		return -1;
	}
	tempfile->owner = getpid();
	tempfile->active = 1;
	return tempfile->fd;
}

int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
{
	int fd;
	struct strbuf full_template = STRBUF_INIT;

	strbuf_add_absolute_path(&full_template, template);
	fd = mks_tempfile_m(tempfile, full_template.buf, mode);
	if (fd < 0)
		die_errno("Unable to create temporary file '%s'",
			  full_template.buf);

	strbuf_release(&full_template);
	return fd;
}

FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
{
	if (!tempfile->active)
		die("BUG: fdopen_tempfile() called for inactive object");
	if (tempfile->fp)
		die("BUG: fdopen_tempfile() called for open object");

	tempfile->fp = fdopen(tempfile->fd, mode);
	return tempfile->fp;
}

const char *get_tempfile_path(struct tempfile *tempfile)
{
	if (!tempfile->active)
		die("BUG: get_tempfile_path() called for inactive object");
	return tempfile->filename.buf;
}

int get_tempfile_fd(struct tempfile *tempfile)
{
	if (!tempfile->active)
		die("BUG: get_tempfile_fd() called for inactive object");
	return tempfile->fd;
}

FILE *get_tempfile_fp(struct tempfile *tempfile)
{
	if (!tempfile->active)
		die("BUG: get_tempfile_fp() called for inactive object");
	return tempfile->fp;
}

int close_tempfile(struct tempfile *tempfile)
{
	int fd = tempfile->fd;
	FILE *fp = tempfile->fp;
	int err;

	if (fd < 0)
		return 0;

	tempfile->fd = -1;
	if (fp) {
		tempfile->fp = NULL;

		/*
		 * Note: no short-circuiting here; we want to fclose()
		 * in any case!
		 */
		err = ferror(fp) | fclose(fp);
	} else {
		err = close(fd);
	}

	if (err) {
		int save_errno = errno;
		delete_tempfile(tempfile);
		errno = save_errno;
		return -1;
	}

	return 0;
}

int reopen_tempfile(struct tempfile *tempfile)
{
	if (0 <= tempfile->fd)
		die("BUG: reopen_tempfile called for an open object");
	if (!tempfile->active)
		die("BUG: reopen_tempfile called for an inactive object");
	tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
	return tempfile->fd;
}

int rename_tempfile(struct tempfile *tempfile, const char *path)
{
	if (!tempfile->active)
		die("BUG: rename_tempfile called for inactive object");

	if (close_tempfile(tempfile))
		return -1;

	if (rename(tempfile->filename.buf, path)) {
		int save_errno = errno;
		delete_tempfile(tempfile);
		errno = save_errno;
		return -1;
	}

	tempfile->active = 0;
	strbuf_reset(&tempfile->filename);
	return 0;
}

void delete_tempfile(struct tempfile *tempfile)
{
	if (!tempfile->active)
		return;

	if (!close_tempfile(tempfile)) {
		unlink_or_warn(tempfile->filename.buf);
		tempfile->active = 0;
		strbuf_reset(&tempfile->filename);
	}
}
Commit	Line	Data
1a9d15db MH	1	/*
	2	* State diagram and cleanup
	3	* -------------------------
	4	*
	5	* If the program exits while a temporary file is active, we want to
	6	* make sure that we remove it. This is done by remembering the active
	7	* temporary files in a linked list, `tempfile_list`. An `atexit(3)`
	8	* handler and a signal handler are registered, to clean up any active
	9	* temporary files.
	10	*
	11	* Because the signal handler can run at any time, `tempfile_list` and
	12	* the `tempfile` objects that comprise it must be kept in
	13	* self-consistent states at all times.
	14	*
	15	* The possible states of a `tempfile` object are as follows:
	16	*
	17	* - Uninitialized. In this state the object's `on_list` field must be
	18	* zero but the rest of its contents need not be initialized. As
	19	* soon as the object is used in any way, it is irrevocably
	20	* registered in `tempfile_list`, and `on_list` is set.
	21	*
	22	* - Active, file open (after `create_tempfile()` or
	23	* `reopen_tempfile()`). In this state:
	24	*
	25	* - the temporary file exists
	26	* - `active` is set
	27	* - `filename` holds the filename of the temporary file
	28	* - `fd` holds a file descriptor open for writing to it
	29	* - `fp` holds a pointer to an open `FILE` object if and only if
	30	* `fdopen_tempfile()` has been called on the object
	31	* - `owner` holds the PID of the process that created the file
	32	*
	33	* - Active, file closed (after successful `close_tempfile()`). Same
	34	* as the previous state, except that the temporary file is closed,
	35	* `fd` is -1, and `fp` is `NULL`.
	36	*
	37	* - Inactive (after `delete_tempfile()`, `rename_tempfile()`, a
	38	* failed attempt to create a temporary file, or a failed
	39	* `close_tempfile()`). In this state:
	40	*
	41	* - `active` is unset
	42	* - `filename` is empty (usually, though there are transitory
	43	* states in which this condition doesn't hold). Client code should
	44	* not rely on the filename being empty in this state.
	45	* - `fd` is -1 and `fp` is `NULL`
	46	* - the object is left registered in the `tempfile_list`, and
	47	* `on_list` is set.
	48	*
	49	* A temporary file is owned by the process that created it. The
	50	* `tempfile` has an `owner` field that records the owner's PID. This
	51	* field is used to prevent a forked process from deleting a temporary
	52	* file created by its parent.
	53	*/
	54
	55	#include "cache.h"
	56	#include "tempfile.h"
	57	#include "sigchain.h"
	58
	59	static struct tempfile *volatile tempfile_list;
	60
	61	static void remove_tempfiles(int skip_fclose)
	62	{
	63	pid_t me = getpid();
	64
65	while (tempfile_list) {
66	if (tempfile_list->owner == me) {
67	/* fclose() is not safe to call in a signal handler */
68	if (skip_fclose)
69	tempfile_list->fp = NULL;
70	delete_tempfile(tempfile_list);
71	}
72	tempfile_list = tempfile_list->next;
73	}
74	}
75
76	static void remove_tempfiles_on_exit(void)
77	{
78	remove_tempfiles(0);
79	}
80
81	static void remove_tempfiles_on_signal(int signo)
82	{
83	remove_tempfiles(1);
84	sigchain_pop(signo);
85	raise(signo);
86	}
87
7eba6ce5 MH	88	/*
	89	* Initialize *tempfile if necessary and add it to tempfile_list.
	90	*/
	91	static void prepare_tempfile_object(struct tempfile *tempfile)
1a9d15db	92	{
1a9d15db MH	93	if (!tempfile_list) {
	94	/* One-time initialization */
	95	sigchain_push_common(remove_tempfiles_on_signal);
	96	atexit(remove_tempfiles_on_exit);
	97	}
	98
	99	if (tempfile->active)
7eba6ce5	100	die("BUG: prepare_tempfile_object called for active object");
1a9d15db MH	101	if (!tempfile->on_list) {
	102	/* Initialize tempfile and add it to tempfile_list: /
	103	tempfile->fd = -1;
	104	tempfile->fp = NULL;
	105	tempfile->active = 0;
	106	tempfile->owner = 0;
7eba6ce5	107	strbuf_init(&tempfile->filename, 0);
1a9d15db MH	108	tempfile->next = tempfile_list;
	109	tempfile_list = tempfile;
	110	tempfile->on_list = 1;
	111	} else if (tempfile->filename.len) {
	112	/* This shouldn't happen, but better safe than sorry. */
7eba6ce5	113	die("BUG: prepare_tempfile_object called for improperly-reset object");
1a9d15db	114	}
7eba6ce5 MH	115	}
	116
	117	/* Make sure errno contains a meaningful value on error */
	118	int create_tempfile(struct tempfile tempfile, const char path)
	119	{
	120	prepare_tempfile_object(tempfile);
1a9d15db MH	121
	122	strbuf_add_absolute_path(&tempfile->filename, path);
	123	tempfile->fd = open(tempfile->filename.buf, O_RDWR \| O_CREAT \| O_EXCL, 0666);
	124	if (tempfile->fd < 0) {
	125	strbuf_reset(&tempfile->filename);
	126	return -1;
	127	}
	128	tempfile->owner = getpid();
	129	tempfile->active = 1;
	130	if (adjust_shared_perm(tempfile->filename.buf)) {
	131	int save_errno = errno;
	132	error("cannot fix permission bits on %s", tempfile->filename.buf);
	133	delete_tempfile(tempfile);
	134	errno = save_errno;
	135	return -1;
	136	}
	137	return tempfile->fd;
	138	}
	139
99397152 MH	140	void register_tempfile(struct tempfile tempfile, const char path)
	141	{
	142	prepare_tempfile_object(tempfile);
	143	strbuf_add_absolute_path(&tempfile->filename, path);
	144	tempfile->owner = getpid();
	145	tempfile->active = 1;
	146	}
	147
354ab112 MH	148	int mks_tempfile_sm(struct tempfile *tempfile,
	149	const char *template, int suffixlen, int mode)
	150	{
	151	prepare_tempfile_object(tempfile);
	152
	153	strbuf_add_absolute_path(&tempfile->filename, template);
	154	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	155	if (tempfile->fd < 0) {
	156	strbuf_reset(&tempfile->filename);
	157	return -1;
	158	}
	159	tempfile->owner = getpid();
	160	tempfile->active = 1;
	161	return tempfile->fd;
	162	}
	163
	164	int mks_tempfile_tsm(struct tempfile *tempfile,
	165	const char *template, int suffixlen, int mode)
	166	{
	167	const char *tmpdir;
	168
	169	prepare_tempfile_object(tempfile);
	170
	171	tmpdir = getenv("TMPDIR");
	172	if (!tmpdir)
	173	tmpdir = "/tmp";
	174
	175	strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
	176	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	177	if (tempfile->fd < 0) {
	178	strbuf_reset(&tempfile->filename);
	179	return -1;
	180	}
	181	tempfile->owner = getpid();
	182	tempfile->active = 1;
	183	return tempfile->fd;
	184	}
	185
	186	int xmks_tempfile_m(struct tempfile tempfile, const char template, int mode)
	187	{
	188	int fd;
	189	struct strbuf full_template = STRBUF_INIT;
	190
	191	strbuf_add_absolute_path(&full_template, template);
	192	fd = mks_tempfile_m(tempfile, full_template.buf, mode);
	193	if (fd < 0)
	194	die_errno("Unable to create temporary file '%s'",
	195	full_template.buf);
	196
	197	strbuf_release(&full_template);
	198	return fd;
	199	}
	200
1a9d15db MH	201	FILE fdopen_tempfile(struct tempfile tempfile, const char *mode)
	202	{
	203	if (!tempfile->active)
	204	die("BUG: fdopen_tempfile() called for inactive object");
	205	if (tempfile->fp)
	206	die("BUG: fdopen_tempfile() called for open object");
	207
	208	tempfile->fp = fdopen(tempfile->fd, mode);
	209	return tempfile->fp;
	210	}
	211
	212	const char get_tempfile_path(struct tempfile tempfile)
	213	{
	214	if (!tempfile->active)
	215	die("BUG: get_tempfile_path() called for inactive object");
	216	return tempfile->filename.buf;
	217	}
	218
	219	int get_tempfile_fd(struct tempfile *tempfile)
	220	{
	221	if (!tempfile->active)
	222	die("BUG: get_tempfile_fd() called for inactive object");
	223	return tempfile->fd;
	224	}
	225
	226	FILE get_tempfile_fp(struct tempfile tempfile)
	227	{
	228	if (!tempfile->active)
	229	die("BUG: get_tempfile_fp() called for inactive object");
	230	return tempfile->fp;
	231	}
	232
	233	int close_tempfile(struct tempfile *tempfile)
	234	{
	235	int fd = tempfile->fd;
	236	FILE *fp = tempfile->fp;
	237	int err;
	238
	239	if (fd < 0)
	240	return 0;
	241
	242	tempfile->fd = -1;
	243	if (fp) {
	244	tempfile->fp = NULL;
	245
	246	/*
	247	* Note: no short-circuiting here; we want to fclose()
	248	* in any case!
	249	*/
	250	err = ferror(fp) \| fclose(fp);
	251	} else {
	252	err = close(fd);
	253	}
	254
	255	if (err) {
	256	int save_errno = errno;
	257	delete_tempfile(tempfile);
	258	errno = save_errno;
	259	return -1;
	260	}
	261
	262	return 0;
	263	}
	264
265	int reopen_tempfile(struct tempfile *tempfile)
266	{
267	if (0 <= tempfile->fd)
268	die("BUG: reopen_tempfile called for an open object");
269	if (!tempfile->active)
270	die("BUG: reopen_tempfile called for an inactive object");
271	tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
272	return tempfile->fd;
273	}
274
275	int rename_tempfile(struct tempfile tempfile, const char path)
276	{
277	if (!tempfile->active)
278	die("BUG: rename_tempfile called for inactive object");
279
280	if (close_tempfile(tempfile))
281	return -1;
282
283	if (rename(tempfile->filename.buf, path)) {
284	int save_errno = errno;
285	delete_tempfile(tempfile);
286	errno = save_errno;
287	return -1;
288	}
289
290	tempfile->active = 0;
291	strbuf_reset(&tempfile->filename);
292	return 0;
293	}
294
295	void delete_tempfile(struct tempfile *tempfile)
296	{
297	if (!tempfile->active)
298	return;
299
300	if (!close_tempfile(tempfile)) {
301	unlink_or_warn(tempfile->filename.buf);
302	tempfile->active = 0;
303	strbuf_reset(&tempfile->filename);
304	}
305	}