diff options
Diffstat (limited to 'tempfile.c')
| -rw-r--r-- | tempfile.c | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/tempfile.c b/tempfile.c new file mode 100644 index 0000000000..6843710670 --- /dev/null +++ b/tempfile.c @@ -0,0 +1,311 @@ +/* + * 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 | O_CLOEXEC, 0666); + if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL) + /* Try again w/o O_CLOEXEC: the kernel might not support it */ + 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; + if (ferror(fp)) { + err = -1; + if (!fclose(fp)) + errno = EIO; + } else { + err = 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); + } +} |