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/*
* Replacement for a missing mkstemp.
*
* Provides the same functionality as the library function mkstemp for those
* systems that don't have it.
*
* The canonical version of this file is maintained in the rra-c-util package,
* which can be found at <https://www.eyrie.org/~eagle/software/rra-c-util/>.
*
* Written by Russ Allbery <eagle@eyrie.org>
* Copyright 2009, 2011, 2014
* The Board of Trustees of the Leland Stanford Junior University
*
* Copying and distribution of this file, with or without modification, are
* permitted in any medium without royalty provided the copyright notice and
* this notice are preserved. This file is offered as-is, without any
* warranty.
*
* SPDX-License-Identifier: FSFAP
*/
#include <config.h>
#include <portable/system.h>
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include <time.h>
/*
* If we're running the test suite, rename mkstemp to avoid conflicts with the
* system version. #undef it first because some systems may define it to
* another name.
*/
#if TESTING
# undef mkstemp
# define mkstemp test_mkstemp
int test_mkstemp(char *);
#endif
/* Pick the longest available integer type. */
#if HAVE_LONG_LONG_INT
typedef unsigned long long long_int_type;
#else
typedef unsigned long long_int_type;
#endif
int
mkstemp(char *template)
{
static const char letters[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
size_t length;
char *XXXXXX;
struct timeval tv;
long_int_type randnum, working;
int i, tries, fd;
/*
* Make sure we have a valid template and initialize p to point at the
* beginning of the template portion of the string.
*/
length = strlen(template);
if (length < 6) {
errno = EINVAL;
return -1;
}
XXXXXX = template + length - 6;
if (strcmp(XXXXXX, "XXXXXX") != 0) {
errno = EINVAL;
return -1;
}
/* Get some more-or-less random information. */
gettimeofday(&tv, NULL);
randnum = ((long_int_type) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid();
/*
* Now, try to find a working file name. We try no more than TMP_MAX file
* names.
*/
for (tries = 0; tries < TMP_MAX; tries++) {
for (working = randnum, i = 0; i < 6; i++) {
XXXXXX[i] = letters[working % 62];
working /= 62;
}
fd = open(template, O_RDWR | O_CREAT | O_EXCL, 0600);
if (fd >= 0 || (errno != EEXIST && errno != EISDIR))
return fd;
/*
* This is a relatively random increment. Cut off the tail end of
* tv_usec since it's often predictable.
*/
randnum += (tv.tv_usec >> 10) & 0xfff;
}
errno = EEXIST;
return -1;
}
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