Rename the 'bzr' notes file to 'repo'. For two reasons:
[emacs.git] / lib / tempname.c
blob9b713cb04c94166c50556793fe18ff6f9c234d2d
1 /* tempname.c - generate the name of a temporary file.
3 Copyright (C) 1991-2003, 2005-2007, 2009-2014 Free Software Foundation, Inc.
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 /* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */
20 #if !_LIBC
21 # include <config.h>
22 # include "tempname.h"
23 #endif
25 #include <sys/types.h>
26 #include <assert.h>
28 #include <errno.h>
29 #ifndef __set_errno
30 # define __set_errno(Val) errno = (Val)
31 #endif
33 #include <stdio.h>
34 #ifndef P_tmpdir
35 # define P_tmpdir "/tmp"
36 #endif
37 #ifndef TMP_MAX
38 # define TMP_MAX 238328
39 #endif
40 #ifndef __GT_FILE
41 # define __GT_FILE 0
42 # define __GT_DIR 1
43 # define __GT_NOCREATE 2
44 #endif
45 #if !_LIBC && (GT_FILE != __GT_FILE || GT_DIR != __GT_DIR \
46 || GT_NOCREATE != __GT_NOCREATE)
47 # error report this to bug-gnulib@gnu.org
48 #endif
50 #include <stddef.h>
51 #include <stdlib.h>
52 #include <string.h>
54 #include <fcntl.h>
55 #include <sys/time.h>
56 #include <stdint.h>
57 #include <unistd.h>
59 #include <sys/stat.h>
61 #if _LIBC
62 # define struct_stat64 struct stat64
63 #else
64 # define struct_stat64 struct stat
65 # define __gen_tempname gen_tempname
66 # define __getpid getpid
67 # define __gettimeofday gettimeofday
68 # define __mkdir mkdir
69 # define __open open
70 # define __lxstat64(version, file, buf) lstat (file, buf)
71 # define __secure_getenv secure_getenv
72 #endif
74 #ifdef _LIBC
75 # include <hp-timing.h>
76 # if HP_TIMING_AVAIL
77 # define RANDOM_BITS(Var) \
78 if (__builtin_expect (value == UINT64_C (0), 0)) \
79 { \
80 /* If this is the first time this function is used initialize \
81 the variable we accumulate the value in to some somewhat \
82 random value. If we'd not do this programs at startup time \
83 might have a reduced set of possible names, at least on slow \
84 machines. */ \
85 struct timeval tv; \
86 __gettimeofday (&tv, NULL); \
87 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
88 } \
89 HP_TIMING_NOW (Var)
90 # endif
91 #endif
93 /* Use the widest available unsigned type if uint64_t is not
94 available. The algorithm below extracts a number less than 62**6
95 (approximately 2**35.725) from uint64_t, so ancient hosts where
96 uintmax_t is only 32 bits lose about 3.725 bits of randomness,
97 which is better than not having mkstemp at all. */
98 #if !defined UINT64_MAX && !defined uint64_t
99 # define uint64_t uintmax_t
100 #endif
102 #if _LIBC
103 /* Return nonzero if DIR is an existent directory. */
104 static int
105 direxists (const char *dir)
107 struct_stat64 buf;
108 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
111 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
112 non-null and exists, uses it; otherwise uses the first of $TMPDIR,
113 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
114 for use with mk[s]temp. Will fail (-1) if DIR is non-null and
115 doesn't exist, none of the searched dirs exists, or there's not
116 enough space in TMPL. */
118 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
119 int try_tmpdir)
121 const char *d;
122 size_t dlen, plen;
124 if (!pfx || !pfx[0])
126 pfx = "file";
127 plen = 4;
129 else
131 plen = strlen (pfx);
132 if (plen > 5)
133 plen = 5;
136 if (try_tmpdir)
138 d = __secure_getenv ("TMPDIR");
139 if (d != NULL && direxists (d))
140 dir = d;
141 else if (dir != NULL && direxists (dir))
142 /* nothing */ ;
143 else
144 dir = NULL;
146 if (dir == NULL)
148 if (direxists (P_tmpdir))
149 dir = P_tmpdir;
150 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
151 dir = "/tmp";
152 else
154 __set_errno (ENOENT);
155 return -1;
159 dlen = strlen (dir);
160 while (dlen > 1 && dir[dlen - 1] == '/')
161 dlen--; /* remove trailing slashes */
163 /* check we have room for "${dir}/${pfx}XXXXXX\0" */
164 if (tmpl_len < dlen + 1 + plen + 6 + 1)
166 __set_errno (EINVAL);
167 return -1;
170 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
171 return 0;
173 #endif /* _LIBC */
175 /* These are the characters used in temporary file names. */
176 static const char letters[] =
177 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
179 /* Generate a temporary file name based on TMPL. TMPL must match the
180 rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
181 The name constructed does not exist at the time of the call to
182 __gen_tempname. TMPL is overwritten with the result.
184 KIND may be one of:
185 __GT_NOCREATE: simply verify that the name does not exist
186 at the time of the call.
187 __GT_FILE: create the file using open(O_CREAT|O_EXCL)
188 and return a read-write fd. The file is mode 0600.
189 __GT_DIR: create a directory, which will be mode 0700.
191 We use a clever algorithm to get hard-to-predict names. */
193 __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
195 int len;
196 char *XXXXXX;
197 static uint64_t value;
198 uint64_t random_time_bits;
199 unsigned int count;
200 int fd = -1;
201 int save_errno = errno;
202 struct_stat64 st;
204 /* A lower bound on the number of temporary files to attempt to
205 generate. The maximum total number of temporary file names that
206 can exist for a given template is 62**6. It should never be
207 necessary to try all of these combinations. Instead if a reasonable
208 number of names is tried (we define reasonable as 62**3) fail to
209 give the system administrator the chance to remove the problems. */
210 #define ATTEMPTS_MIN (62 * 62 * 62)
212 /* The number of times to attempt to generate a temporary file. To
213 conform to POSIX, this must be no smaller than TMP_MAX. */
214 #if ATTEMPTS_MIN < TMP_MAX
215 unsigned int attempts = TMP_MAX;
216 #else
217 unsigned int attempts = ATTEMPTS_MIN;
218 #endif
220 len = strlen (tmpl);
221 if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
223 __set_errno (EINVAL);
224 return -1;
227 /* This is where the Xs start. */
228 XXXXXX = &tmpl[len - 6 - suffixlen];
230 /* Get some more or less random data. */
231 #ifdef RANDOM_BITS
232 RANDOM_BITS (random_time_bits);
233 #else
235 struct timeval tv;
236 __gettimeofday (&tv, NULL);
237 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
239 #endif
240 value += random_time_bits ^ __getpid ();
242 for (count = 0; count < attempts; value += 7777, ++count)
244 uint64_t v = value;
246 /* Fill in the random bits. */
247 XXXXXX[0] = letters[v % 62];
248 v /= 62;
249 XXXXXX[1] = letters[v % 62];
250 v /= 62;
251 XXXXXX[2] = letters[v % 62];
252 v /= 62;
253 XXXXXX[3] = letters[v % 62];
254 v /= 62;
255 XXXXXX[4] = letters[v % 62];
256 v /= 62;
257 XXXXXX[5] = letters[v % 62];
259 switch (kind)
261 case __GT_FILE:
262 fd = __open (tmpl,
263 (flags & ~O_ACCMODE)
264 | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
265 break;
267 case __GT_DIR:
268 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
269 break;
271 case __GT_NOCREATE:
272 /* This case is backward from the other three. __gen_tempname
273 succeeds if __xstat fails because the name does not exist.
274 Note the continue to bypass the common logic at the bottom
275 of the loop. */
276 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
278 if (errno == ENOENT)
280 __set_errno (save_errno);
281 return 0;
283 else
284 /* Give up now. */
285 return -1;
287 continue;
289 default:
290 assert (! "invalid KIND in __gen_tempname");
291 abort ();
294 if (fd >= 0)
296 __set_errno (save_errno);
297 return fd;
299 else if (errno != EEXIST)
300 return -1;
303 /* We got out of the loop because we ran out of combinations to try. */
304 __set_errno (EEXIST);
305 return -1;