git-multimail: update to release 1.2.0
[git.git] / tempfile.h
blob4219fe41bd3e2ad16f0b1caf55eedca0b2d9986e
1 #ifndef TEMPFILE_H
2 #define TEMPFILE_H
4 /*
5 * Handle temporary files.
7 * The tempfile API allows temporary files to be created, deleted, and
8 * atomically renamed. Temporary files that are still active when the
9 * program ends are cleaned up automatically. Lockfiles (see
10 * "lockfile.h") are built on top of this API.
13 * Calling sequence
14 * ----------------
16 * The caller:
18 * * Allocates a `struct tempfile` either as a static variable or on
19 * the heap, initialized to zeros. Once you use the structure to
20 * call `create_tempfile()`, it belongs to the tempfile subsystem
21 * and its storage must remain valid throughout the life of the
22 * program (i.e. you cannot use an on-stack variable to hold this
23 * structure).
25 * * Attempts to create a temporary file by calling
26 * `create_tempfile()`.
28 * * Writes new content to the file by either:
30 * * writing to the file descriptor returned by `create_tempfile()`
31 * (also available via `tempfile->fd`).
33 * * calling `fdopen_tempfile()` to get a `FILE` pointer for the
34 * open file and writing to the file using stdio.
36 * When finished writing, the caller can:
38 * * Close the file descriptor and remove the temporary file by
39 * calling `delete_tempfile()`.
41 * * Close the temporary file and rename it atomically to a specified
42 * filename by calling `rename_tempfile()`. This relinquishes
43 * control of the file.
45 * * Close the file descriptor without removing or renaming the
46 * temporary file by calling `close_tempfile()`, and later call
47 * `delete_tempfile()` or `rename_tempfile()`.
49 * Even after the temporary file is renamed or deleted, the `tempfile`
50 * object must not be freed or altered by the caller. However, it may
51 * be reused; just pass it to another call of `create_tempfile()`.
53 * If the program exits before `rename_tempfile()` or
54 * `delete_tempfile()` is called, an `atexit(3)` handler will close
55 * and remove the temporary file.
57 * If you need to close the file descriptor yourself, do so by calling
58 * `close_tempfile()`. You should never call `close(2)` or `fclose(3)`
59 * yourself, otherwise the `struct tempfile` structure would still
60 * think that the file descriptor needs to be closed, and a later
61 * cleanup would result in duplicate calls to `close(2)`. Worse yet,
62 * if you close and then later open another file descriptor for a
63 * completely different purpose, then the unrelated file descriptor
64 * might get closed.
67 * Error handling
68 * --------------
70 * `create_tempfile()` returns a file descriptor on success or -1 on
71 * failure. On errors, `errno` describes the reason for failure.
73 * `delete_tempfile()`, `rename_tempfile()`, and `close_tempfile()`
74 * return 0 on success. On failure they set `errno` appropriately, do
75 * their best to delete the temporary file, and return -1.
78 struct tempfile {
79 struct tempfile *volatile next;
80 volatile sig_atomic_t active;
81 volatile int fd;
82 FILE *volatile fp;
83 volatile pid_t owner;
84 char on_list;
85 struct strbuf filename;
89 * Attempt to create a temporary file at the specified `path`. Return
90 * a file descriptor for writing to it, or -1 on error. It is an error
91 * if a file already exists at that path.
93 extern int create_tempfile(struct tempfile *tempfile, const char *path);
96 * Register an existing file as a tempfile, meaning that it will be
97 * deleted when the program exits. The tempfile is considered closed,
98 * but it can be worked with like any other closed tempfile (for
99 * example, it can be opened using reopen_tempfile()).
101 extern void register_tempfile(struct tempfile *tempfile, const char *path);
105 * mks_tempfile functions
107 * The following functions attempt to create and open temporary files
108 * with names derived automatically from a template, in the manner of
109 * mkstemps(), and arrange for them to be deleted if the program ends
110 * before they are deleted explicitly. There is a whole family of such
111 * functions, named according to the following pattern:
113 * x?mks_tempfile_t?s?m?()
115 * The optional letters have the following meanings:
117 * x - die if the temporary file cannot be created.
119 * t - create the temporary file under $TMPDIR (as opposed to
120 * relative to the current directory). When these variants are
121 * used, template should be the pattern for the filename alone,
122 * without a path.
124 * s - template includes a suffix that is suffixlen characters long.
126 * m - the temporary file should be created with the specified mode
127 * (otherwise, the mode is set to 0600).
129 * None of these functions modify template. If the caller wants to
130 * know the (absolute) path of the file that was created, it can be
131 * read from tempfile->filename.
133 * On success, the functions return a file descriptor that is open for
134 * writing the temporary file. On errors, they return -1 and set errno
135 * appropriately (except for the "x" variants, which die() on errors).
138 /* See "mks_tempfile functions" above. */
139 extern int mks_tempfile_sm(struct tempfile *tempfile,
140 const char *template, int suffixlen, int mode);
142 /* See "mks_tempfile functions" above. */
143 static inline int mks_tempfile_s(struct tempfile *tempfile,
144 const char *template, int suffixlen)
146 return mks_tempfile_sm(tempfile, template, suffixlen, 0600);
149 /* See "mks_tempfile functions" above. */
150 static inline int mks_tempfile_m(struct tempfile *tempfile,
151 const char *template, int mode)
153 return mks_tempfile_sm(tempfile, template, 0, mode);
156 /* See "mks_tempfile functions" above. */
157 static inline int mks_tempfile(struct tempfile *tempfile,
158 const char *template)
160 return mks_tempfile_sm(tempfile, template, 0, 0600);
163 /* See "mks_tempfile functions" above. */
164 extern int mks_tempfile_tsm(struct tempfile *tempfile,
165 const char *template, int suffixlen, int mode);
167 /* See "mks_tempfile functions" above. */
168 static inline int mks_tempfile_ts(struct tempfile *tempfile,
169 const char *template, int suffixlen)
171 return mks_tempfile_tsm(tempfile, template, suffixlen, 0600);
174 /* See "mks_tempfile functions" above. */
175 static inline int mks_tempfile_tm(struct tempfile *tempfile,
176 const char *template, int mode)
178 return mks_tempfile_tsm(tempfile, template, 0, mode);
181 /* See "mks_tempfile functions" above. */
182 static inline int mks_tempfile_t(struct tempfile *tempfile,
183 const char *template)
185 return mks_tempfile_tsm(tempfile, template, 0, 0600);
188 /* See "mks_tempfile functions" above. */
189 extern int xmks_tempfile_m(struct tempfile *tempfile,
190 const char *template, int mode);
192 /* See "mks_tempfile functions" above. */
193 static inline int xmks_tempfile(struct tempfile *tempfile,
194 const char *template)
196 return xmks_tempfile_m(tempfile, template, 0600);
200 * Associate a stdio stream with the temporary file (which must still
201 * be open). Return `NULL` (*without* deleting the file) on error. The
202 * stream is closed automatically when `close_tempfile()` is called or
203 * when the file is deleted or renamed.
205 extern FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode);
207 static inline int is_tempfile_active(struct tempfile *tempfile)
209 return tempfile->active;
213 * Return the path of the lockfile. The return value is a pointer to a
214 * field within the lock_file object and should not be freed.
216 extern const char *get_tempfile_path(struct tempfile *tempfile);
218 extern int get_tempfile_fd(struct tempfile *tempfile);
219 extern FILE *get_tempfile_fp(struct tempfile *tempfile);
222 * If the temporary file is still open, close it (and the file pointer
223 * too, if it has been opened using `fdopen_tempfile()`) without
224 * deleting the file. Return 0 upon success. On failure to `close(2)`,
225 * return a negative value and delete the file. Usually
226 * `delete_tempfile()` or `rename_tempfile()` should eventually be
227 * called if `close_tempfile()` succeeds.
229 extern int close_tempfile(struct tempfile *tempfile);
232 * Re-open a temporary file that has been closed using
233 * `close_tempfile()` but not yet deleted or renamed. This can be used
234 * to implement a sequence of operations like the following:
236 * * Create temporary file.
238 * * Write new contents to file, then `close_tempfile()` to cause the
239 * contents to be written to disk.
241 * * Pass the name of the temporary file to another program to allow
242 * it (and nobody else) to inspect or even modify the file's
243 * contents.
245 * * `reopen_tempfile()` to reopen the temporary file. Make further
246 * updates to the contents.
248 * * `rename_tempfile()` to move the file to its permanent location.
250 extern int reopen_tempfile(struct tempfile *tempfile);
253 * Close the file descriptor and/or file pointer and remove the
254 * temporary file associated with `tempfile`. It is a NOOP to call
255 * `delete_tempfile()` for a `tempfile` object that has already been
256 * deleted or renamed.
258 extern void delete_tempfile(struct tempfile *tempfile);
261 * Close the file descriptor and/or file pointer if they are still
262 * open, and atomically rename the temporary file to `path`. `path`
263 * must be on the same filesystem as the lock file. Return 0 on
264 * success. On failure, delete the temporary file and return -1, with
265 * `errno` set to the value from the failing call to `close(2)` or
266 * `rename(2)`. It is a bug to call `rename_tempfile()` for a
267 * `tempfile` object that is not currently active.
269 extern int rename_tempfile(struct tempfile *tempfile, const char *path);
271 #endif /* TEMPFILE_H */