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/* $Id: mkstemp.c 5329 2002-03-17 07:39:14Z rra $
**
** Replacement for a missing mkstemp.
**
** Written by Russ Allbery <rra@stanford.edu>
** This work is hereby placed in the public domain by its author.
**
** Provides the same functionality as the library function mkstemp for those
** systems that don't have it.
*/
#include "config.h"
#include "clibrary.h"
#include "portable/time.h"
#include <errno.h>
#include <fcntl.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
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)
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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