tempfile: factor out activation
[git/git.git] / tempfile.c
CommitLineData
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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 *
49bd0fc2 33 * - Active, file closed (after `close_tempfile_gently()`). Same
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34 * as the previous state, except that the temporary file is closed,
35 * `fd` is -1, and `fp` is `NULL`.
36 *
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37 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
38 * failed attempt to create a temporary file). In this state:
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39 *
40 * - `active` is unset
41 * - `filename` is empty (usually, though there are transitory
42 * states in which this condition doesn't hold). Client code should
43 * *not* rely on the filename being empty in this state.
44 * - `fd` is -1 and `fp` is `NULL`
45 * - the object is left registered in the `tempfile_list`, and
46 * `on_list` is set.
47 *
48 * A temporary file is owned by the process that created it. The
49 * `tempfile` has an `owner` field that records the owner's PID. This
50 * field is used to prevent a forked process from deleting a temporary
51 * file created by its parent.
52 */
53
54#include "cache.h"
55#include "tempfile.h"
56#include "sigchain.h"
57
58static struct tempfile *volatile tempfile_list;
59
60static void remove_tempfiles(int skip_fclose)
61{
62 pid_t me = getpid();
63
64 while (tempfile_list) {
65 if (tempfile_list->owner == me) {
66 /* fclose() is not safe to call in a signal handler */
67 if (skip_fclose)
68 tempfile_list->fp = NULL;
69 delete_tempfile(tempfile_list);
70 }
71 tempfile_list = tempfile_list->next;
72 }
73}
74
75static void remove_tempfiles_on_exit(void)
76{
77 remove_tempfiles(0);
78}
79
80static void remove_tempfiles_on_signal(int signo)
81{
82 remove_tempfiles(1);
83 sigchain_pop(signo);
84 raise(signo);
85}
86
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87/*
88 * Initialize *tempfile if necessary and add it to tempfile_list.
89 */
90static void prepare_tempfile_object(struct tempfile *tempfile)
1a9d15db 91{
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92 if (!tempfile_list) {
93 /* One-time initialization */
94 sigchain_push_common(remove_tempfiles_on_signal);
95 atexit(remove_tempfiles_on_exit);
96 }
97
e6fc2673 98 if (is_tempfile_active(tempfile))
9b028aa4 99 BUG("prepare_tempfile_object called for active object");
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100 if (!tempfile->on_list) {
101 /* Initialize *tempfile and add it to tempfile_list: */
102 tempfile->fd = -1;
103 tempfile->fp = NULL;
104 tempfile->active = 0;
105 tempfile->owner = 0;
7eba6ce5 106 strbuf_init(&tempfile->filename, 0);
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107 tempfile->next = tempfile_list;
108 tempfile_list = tempfile;
109 tempfile->on_list = 1;
110 } else if (tempfile->filename.len) {
111 /* This shouldn't happen, but better safe than sorry. */
9b028aa4 112 BUG("prepare_tempfile_object called for improperly-reset object");
1a9d15db 113 }
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114}
115
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116static void activate_tempfile(struct tempfile *tempfile)
117{
118 tempfile->owner = getpid();
119 tempfile->active = 1;
120}
121
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122/* Make sure errno contains a meaningful value on error */
123int create_tempfile(struct tempfile *tempfile, const char *path)
124{
125 prepare_tempfile_object(tempfile);
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126
127 strbuf_add_absolute_path(&tempfile->filename, path);
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128 tempfile->fd = open(tempfile->filename.buf,
129 O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
130 if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
131 /* Try again w/o O_CLOEXEC: the kernel might not support it */
132 tempfile->fd = open(tempfile->filename.buf,
133 O_RDWR | O_CREAT | O_EXCL, 0666);
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134 if (tempfile->fd < 0) {
135 strbuf_reset(&tempfile->filename);
136 return -1;
137 }
2933ebba 138 activate_tempfile(tempfile);
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139 if (adjust_shared_perm(tempfile->filename.buf)) {
140 int save_errno = errno;
141 error("cannot fix permission bits on %s", tempfile->filename.buf);
142 delete_tempfile(tempfile);
143 errno = save_errno;
144 return -1;
145 }
146 return tempfile->fd;
147}
148
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149void register_tempfile(struct tempfile *tempfile, const char *path)
150{
151 prepare_tempfile_object(tempfile);
152 strbuf_add_absolute_path(&tempfile->filename, path);
2933ebba 153 activate_tempfile(tempfile);
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154}
155
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156int mks_tempfile_sm(struct tempfile *tempfile,
157 const char *template, int suffixlen, int mode)
158{
159 prepare_tempfile_object(tempfile);
160
161 strbuf_add_absolute_path(&tempfile->filename, template);
162 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
163 if (tempfile->fd < 0) {
164 strbuf_reset(&tempfile->filename);
165 return -1;
166 }
2933ebba 167 activate_tempfile(tempfile);
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168 return tempfile->fd;
169}
170
171int mks_tempfile_tsm(struct tempfile *tempfile,
172 const char *template, int suffixlen, int mode)
173{
174 const char *tmpdir;
175
176 prepare_tempfile_object(tempfile);
177
178 tmpdir = getenv("TMPDIR");
179 if (!tmpdir)
180 tmpdir = "/tmp";
181
182 strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
183 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
184 if (tempfile->fd < 0) {
185 strbuf_reset(&tempfile->filename);
186 return -1;
187 }
2933ebba 188 activate_tempfile(tempfile);
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189 return tempfile->fd;
190}
191
192int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
193{
194 int fd;
195 struct strbuf full_template = STRBUF_INIT;
196
197 strbuf_add_absolute_path(&full_template, template);
198 fd = mks_tempfile_m(tempfile, full_template.buf, mode);
199 if (fd < 0)
200 die_errno("Unable to create temporary file '%s'",
201 full_template.buf);
202
203 strbuf_release(&full_template);
204 return fd;
205}
206
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207FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
208{
e6fc2673 209 if (!is_tempfile_active(tempfile))
9b028aa4 210 BUG("fdopen_tempfile() called for inactive object");
1a9d15db 211 if (tempfile->fp)
9b028aa4 212 BUG("fdopen_tempfile() called for open object");
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213
214 tempfile->fp = fdopen(tempfile->fd, mode);
215 return tempfile->fp;
216}
217
218const char *get_tempfile_path(struct tempfile *tempfile)
219{
e6fc2673 220 if (!is_tempfile_active(tempfile))
9b028aa4 221 BUG("get_tempfile_path() called for inactive object");
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222 return tempfile->filename.buf;
223}
224
225int get_tempfile_fd(struct tempfile *tempfile)
226{
e6fc2673 227 if (!is_tempfile_active(tempfile))
9b028aa4 228 BUG("get_tempfile_fd() called for inactive object");
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229 return tempfile->fd;
230}
231
232FILE *get_tempfile_fp(struct tempfile *tempfile)
233{
e6fc2673 234 if (!is_tempfile_active(tempfile))
9b028aa4 235 BUG("get_tempfile_fp() called for inactive object");
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236 return tempfile->fp;
237}
238
49bd0fc2 239int close_tempfile_gently(struct tempfile *tempfile)
1a9d15db 240{
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241 int fd;
242 FILE *fp;
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243 int err;
244
f5b4dc76 245 if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
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246 return 0;
247
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248 fd = tempfile->fd;
249 fp = tempfile->fp;
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250 tempfile->fd = -1;
251 if (fp) {
252 tempfile->fp = NULL;
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253 if (ferror(fp)) {
254 err = -1;
255 if (!fclose(fp))
256 errno = EIO;
257 } else {
258 err = fclose(fp);
259 }
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260 } else {
261 err = close(fd);
262 }
263
49bd0fc2 264 return err ? -1 : 0;
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265}
266
267int reopen_tempfile(struct tempfile *tempfile)
268{
e6fc2673 269 if (!is_tempfile_active(tempfile))
9b028aa4 270 BUG("reopen_tempfile called for an inactive object");
f5b4dc76 271 if (0 <= tempfile->fd)
9b028aa4 272 BUG("reopen_tempfile called for an open object");
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273 tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
274 return tempfile->fd;
275}
276
277int rename_tempfile(struct tempfile *tempfile, const char *path)
278{
e6fc2673 279 if (!is_tempfile_active(tempfile))
9b028aa4 280 BUG("rename_tempfile called for inactive object");
1a9d15db 281
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282 if (close_tempfile_gently(tempfile)) {
283 delete_tempfile(tempfile);
1a9d15db 284 return -1;
49bd0fc2 285 }
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286
287 if (rename(tempfile->filename.buf, path)) {
288 int save_errno = errno;
289 delete_tempfile(tempfile);
290 errno = save_errno;
291 return -1;
292 }
293
294 tempfile->active = 0;
295 strbuf_reset(&tempfile->filename);
296 return 0;
297}
298
299void delete_tempfile(struct tempfile *tempfile)
300{
e6fc2673 301 if (!is_tempfile_active(tempfile))
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302 return;
303
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304 close_tempfile_gently(tempfile);
305 unlink_or_warn(tempfile->filename.buf);
306 tempfile->active = 0;
307 strbuf_reset(&tempfile->filename);
1a9d15db 308}