Can anybody point me to the code that implements mkstemp() (C/C++) on Win32, or very close analog?
Must be race-free.
It's supposed to look like
#include <windows.h>
#include <io.h>
// port of mkstemp() to win32. race-free.
// behaviour as described in http://linux.die.net/man/3/mkstemp
//
int mkstemp(char *template) {
...
}
You can use the following function which is extracted from wcecompat
library (from file src/stdlib_extras.cpp
)
/* mkstemp extracted from libc/sysdeps/posix/tempname.c. Copyright
(C) 1991-1999, 2000, 2001, 2006 Free Software Foundation, Inc.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. */
static const char letters[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
/* Generate a temporary file name based on TMPL. TMPL must match the
rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed
does not exist at the time of the call to mkstemp. TMPL is
overwritten with the result. */
int
mkstemp (char *tmpl)
{
int len;
char *XXXXXX;
static unsigned long long value;
unsigned long long random_time_bits;
unsigned int count;
int fd = -1;
int save_errno = errno;
/* A lower bound on the number of temporary files to attempt to
generate. The maximum total number of temporary file names that
can exist for a given template is 62**6. It should never be
necessary to try all these combinations. Instead if a reasonable
number of names is tried (we define reasonable as 62**3) fail to
give the system administrator the chance to remove the problems. */
#define ATTEMPTS_MIN (62 * 62 * 62)
/* The number of times to attempt to generate a temporary file. To
conform to POSIX, this must be no smaller than TMP_MAX. */
#if ATTEMPTS_MIN < TMP_MAX
unsigned int attempts = TMP_MAX;
#else
unsigned int attempts = ATTEMPTS_MIN;
#endif
len = strlen (tmpl);
if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
{
errno = EINVAL;
return -1;
}
/* This is where the Xs start. */
XXXXXX = &tmpl[len - 6];
/* Get some more or less random data. */
{
SYSTEMTIME stNow;
FILETIME ftNow;
// get system time
GetSystemTime(&stNow);
stNow.wMilliseconds = 500;
if (!SystemTimeToFileTime(&stNow, &ftNow))
{
errno = -1;
return -1;
}
random_time_bits = (((unsigned long long)ftNow.dwHighDateTime << 32)
| (unsigned long long)ftNow.dwLowDateTime);
}
value += random_time_bits ^ (unsigned long long)GetCurrentThreadId ();
for (count = 0; count < attempts; value += 7777, ++count)
{
unsigned long long v = value;
/* Fill in the random bits. */
XXXXXX[0] = letters[v % 62];
v /= 62;
XXXXXX[1] = letters[v % 62];
v /= 62;
XXXXXX[2] = letters[v % 62];
v /= 62;
XXXXXX[3] = letters[v % 62];
v /= 62;
XXXXXX[4] = letters[v % 62];
v /= 62;
XXXXXX[5] = letters[v % 62];
fd = open (tmpl, O_RDWR | O_CREAT | O_EXCL, _S_IREAD | _S_IWRITE);
if (fd >= 0)
{
errno = save_errno;
return fd;
}
else if (errno != EEXIST)
return -1;
}
/* We got out of the loop because we ran out of combinations to try. */
errno = EEXIST;
return -1;
}
It defines O_EXCL
as;
#define _O_EXCL 0x0400
#define O_EXCL _O_EXCL
You can rip out mkstemp support out of it easily.