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 Free Software Foundation, Inc.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License along
17 with this program; if not, write to the Free Software Foundation,
18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
24 #include <sys/types.h>
29 # define __set_errno(Val) errno = (Val)
34 # define P_tmpdir "/tmp"
37 # define TMP_MAX 238328
41 # define __GT_BIGFILE 1
43 # define __GT_NOCREATE 3
52 #if HAVE_SYS_TIME_H || _LIBC
53 # include <sys/time.h>
56 #if HAVE_STDINT_H || _LIBC
60 # include <inttypes.h>
68 # define struct_stat64 struct stat64
70 # include "stat-macros.h"
71 # define struct_stat64 struct stat
72 # define __getpid getpid
73 # define __gettimeofday gettimeofday
74 # define __mkdir mkdir
76 # define __open64 open
77 # define __lxstat64(version, file, buf) lstat (file, buf)
78 # define __xstat64(version, file, buf) stat (file, buf)
81 #if ! (HAVE___SECURE_GETENV || _LIBC)
82 # define __secure_getenv getenv
86 # include <hp-timing.h>
88 # define RANDOM_BITS(Var) \
89 if (__builtin_expect (value == UINT64_C (0), 0)) \
91 /* If this is the first time this function is used initialize \
92 the variable we accumulate the value in to some somewhat \
93 random value. If we'd not do this programs at startup time \
94 might have a reduced set of possible names, at least on slow \
97 __gettimeofday (&tv, NULL); \
98 value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
104 /* Use the widest available unsigned type if uint64_t is not
105 available. The algorithm below extracts a number less than 62**6
106 (approximately 2**35.725) from uint64_t, so ancient hosts where
107 uintmax_t is only 32 bits lose about 3.725 bits of randomness,
108 which is better than not having mkstemp at all. */
109 #if !defined UINT64_MAX && !defined uint64_t
110 # define uint64_t uintmax_t
113 /* Return nonzero if DIR is an existent directory. */
115 direxists (const char *dir)
118 return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
121 /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is
122 non-null and exists, uses it; otherwise uses the first of $TMPDIR,
123 P_tmpdir, /tmp that exists. Copies into TMPL a template suitable
124 for use with mk[s]temp. Will fail (-1) if DIR is non-null and
125 doesn't exist, none of the searched dirs exists, or there's not
126 enough space in TMPL. */
128 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
148 d = __secure_getenv ("TMPDIR");
149 if (d != NULL && direxists (d))
151 else if (dir != NULL && direxists (dir))
158 if (direxists (P_tmpdir))
160 else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
164 __set_errno (ENOENT);
170 while (dlen > 1 && dir[dlen - 1] == '/')
171 dlen--; /* remove trailing slashes */
173 /* check we have room for "${dir}/${pfx}XXXXXX\0" */
174 if (tmpl_len < dlen + 1 + plen + 6 + 1)
176 __set_errno (EINVAL);
180 sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
184 /* These are the characters used in temporary file names. */
185 static const char letters[] =
186 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
188 /* Generate a temporary file name based on TMPL. TMPL must match the
189 rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed
190 does not exist at the time of the call to __gen_tempname. TMPL is
191 overwritten with the result.
194 __GT_NOCREATE: simply verify that the name does not exist
195 at the time of the call.
196 __GT_FILE: create the file using open(O_CREAT|O_EXCL)
197 and return a read-write fd. The file is mode 0600.
198 __GT_BIGFILE: same as __GT_FILE but use open64().
199 __GT_DIR: create a directory, which will be mode 0700.
201 We use a clever algorithm to get hard-to-predict names. */
203 __gen_tempname (char *tmpl, int kind)
207 static uint64_t value;
208 uint64_t random_time_bits;
211 int save_errno = errno;
214 /* A lower bound on the number of temporary files to attempt to
215 generate. The maximum total number of temporary file names that
216 can exist for a given template is 62**6. It should never be
217 necessary to try all these combinations. Instead if a reasonable
218 number of names is tried (we define reasonable as 62**3) fail to
219 give the system administrator the chance to remove the problems. */
220 unsigned int attempts_min = 62 * 62 * 62;
222 /* The number of times to attempt to generate a temporary file. To
223 conform to POSIX, this must be no smaller than TMP_MAX. */
224 unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min;
227 if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
229 __set_errno (EINVAL);
233 /* This is where the Xs start. */
234 XXXXXX = &tmpl[len - 6];
236 /* Get some more or less random data. */
238 RANDOM_BITS (random_time_bits);
240 # if HAVE_GETTIMEOFDAY || _LIBC
243 __gettimeofday (&tv, NULL);
244 random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
247 random_time_bits = time (NULL);
250 value += random_time_bits ^ __getpid ();
252 for (count = 0; count < attempts; value += 7777, ++count)
256 /* Fill in the random bits. */
257 XXXXXX[0] = letters[v % 62];
259 XXXXXX[1] = letters[v % 62];
261 XXXXXX[2] = letters[v % 62];
263 XXXXXX[3] = letters[v % 62];
265 XXXXXX[4] = letters[v % 62];
267 XXXXXX[5] = letters[v % 62];
272 fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
276 fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
280 fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
284 /* This case is backward from the other three. __gen_tempname
285 succeeds if __xstat fails because the name does not exist.
286 Note the continue to bypass the common logic at the bottom
288 if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
292 __set_errno (save_errno);
302 assert (! "invalid KIND in __gen_tempname");
307 __set_errno (save_errno);
310 else if (errno != EEXIST)
314 /* We got out of the loop because we ran out of combinations to try. */
315 __set_errno (EEXIST);