1 /* tempname.c - generate the name of a temporary file.
3 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
4 2000, 2001, 2002, 2003, 2005, 2006, 2007 Free Software Foundation,
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License along
18 with this program; if not, write to the Free Software Foundation,
19 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
21 /* Extracted from glibc sysdeps/posix/tempname.c. See also tmpdir.c. */
25 # include "tempname.h"
28 #include <sys/types.h>
33 # define __set_errno(Val) errno = (Val)
38 # define P_tmpdir "/tmp"
41 # define TMP_MAX 238328
45 # define __GT_BIGFILE 1
47 # define __GT_NOCREATE 3
62 # define struct_stat64 struct stat64
63 # define small_open __open
64 # define large_open __open64
66 # define struct_stat64 struct stat
67 # define small_open open
68 # define large_open open
69 # define __gen_tempname gen_tempname
70 # define __getpid getpid
71 # define __gettimeofday gettimeofday
72 # define __mkdir mkdir
73 # define __lxstat64(version, file, buf) lstat (file, buf)
74 # define __xstat64(version, file, buf) stat (file, buf)
77 #if ! (HAVE___SECURE_GETENV || _LIBC)
78 # define __secure_getenv getenv
82 # include <hp-timing.h>
84 # define RANDOM_BITS(Var) \
85 if (__builtin_expect (value == UINT64_C (0), 0)) \
87 /* If this is the first time this function is used initialize \
88 the variable we accumulate the value in to some somewhat \
89 random value. If we'd not do this programs at startup time \
90 might have a reduced set of possible names, at least on slow \
93 __gettimeofday (&tv, NULL); \
94 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
100 /* Use the widest available unsigned type if uint64_t is not
101 available. The algorithm below extracts a number less than 62**6
102 (approximately 2**35.725) from uint64_t, so ancient hosts where
103 uintmax_t is only 32 bits lose about 3.725 bits of randomness,
104 which is better than not having mkstemp at all. */
105 #if !defined UINT64_MAX && !defined uint64_t
106 # define uint64_t uintmax_t
110 /* Return nonzero if DIR is an existent directory. */
112 direxists (const char *dir)
115 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
118 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
119 non-null and exists, uses it; otherwise uses the first of $TMPDIR,
120 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
121 for use with mk[s]temp. Will fail (-1) if DIR is non-null and
122 doesn't exist, none of the searched dirs exists, or there's not
123 enough space in TMPL. */
125 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
145 d = __secure_getenv ("TMPDIR");
146 if (d != NULL && direxists (d))
148 else if (dir != NULL && direxists (dir))
155 if (direxists (P_tmpdir))
157 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
161 __set_errno (ENOENT);
167 while (dlen > 1 && dir[dlen - 1] == '/')
168 dlen--; /* remove trailing slashes */
170 /* check we have room for "${dir}/${pfx}XXXXXX\0" */
171 if (tmpl_len < dlen + 1 + plen + 6 + 1)
173 __set_errno (EINVAL);
177 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
182 /* These are the characters used in temporary file names. */
183 static const char letters[] =
184 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
186 /* Generate a temporary file name based on TMPL. TMPL must match the
187 rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed
188 does not exist at the time of the call to __gen_tempname. TMPL is
189 overwritten with the result.
192 __GT_NOCREATE: simply verify that the name does not exist
193 at the time of the call.
194 __GT_FILE: create the file using open(O_CREAT|O_EXCL)
195 and return a read-write fd. The file is mode 0600.
196 __GT_BIGFILE: same as __GT_FILE but use open64().
197 __GT_DIR: create a directory, which will be mode 0700.
199 We use a clever algorithm to get hard-to-predict names. */
201 __gen_tempname (char *tmpl, int kind)
205 static uint64_t value;
206 uint64_t random_time_bits;
209 int save_errno = errno;
212 /* A lower bound on the number of temporary files to attempt to
213 generate. The maximum total number of temporary file names that
214 can exist for a given template is 62**6. It should never be
215 necessary to try all these combinations. Instead if a reasonable
216 number of names is tried (we define reasonable as 62**3) fail to
217 give the system administrator the chance to remove the problems. */
218 #define ATTEMPTS_MIN (62 * 62 * 62)
220 /* The number of times to attempt to generate a temporary file. To
221 conform to POSIX, this must be no smaller than TMP_MAX. */
222 #if ATTEMPTS_MIN < TMP_MAX
223 unsigned int attempts = TMP_MAX;
225 unsigned int attempts = ATTEMPTS_MIN;
229 if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
231 __set_errno (EINVAL);
235 /* This is where the Xs start. */
236 XXXXXX = &tmpl[len - 6];
238 /* Get some more or less random data. */
240 RANDOM_BITS (random_time_bits);
244 __gettimeofday (&tv, NULL);
245 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
248 value += random_time_bits ^ __getpid ();
250 for (count = 0; count < attempts; value += 7777, ++count)
254 /* Fill in the random bits. */
255 XXXXXX[0] = letters[v % 62];
257 XXXXXX[1] = letters[v % 62];
259 XXXXXX[2] = letters[v % 62];
261 XXXXXX[3] = letters[v % 62];
263 XXXXXX[4] = letters[v % 62];
265 XXXXXX[5] = letters[v % 62];
270 fd = small_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
274 fd = large_open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
278 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
282 /* This case is backward from the other three. __gen_tempname
283 succeeds if __xstat fails because the name does not exist.
284 Note the continue to bypass the common logic at the bottom
286 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
290 __set_errno (save_errno);
300 assert (! "invalid KIND in __gen_tempname");
305 __set_errno (save_errno);
308 else if (errno != EEXIST)
312 /* We got out of the loop because we ran out of combinations to try. */
313 __set_errno (EEXIST);