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/* One of many ways to emulate flock() on top of real (good) POSIX locks.
*
* This flock() emulation is based upon source taken from the Red Hat
* implementation used in their imap-2002d SRPM.
*
* $RH: flock.c,v 1.2 2000/08/23 17:07:00 nalin Exp $
*/
/* flock.c
Copyright 2003 Red Hat, Inc.
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#include "winsup.h"
#include "cygerrno.h"
#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>
int
flock (int fd, int operation)
{
int i, cmd;
struct __flock64 l = { 0, 0, 0, 0, 0 };
if (operation & LOCK_NB)
{
cmd = F_SETLK;
}
else
{
cmd = F_SETLKW;
}
l.l_whence = SEEK_SET;
switch (operation & (~LOCK_NB))
{
case LOCK_EX:
l.l_type = F_WRLCK;
i = fcntl_worker (fd, cmd, &l);
if (i == -1)
{
if ((get_errno () == EAGAIN) || (get_errno () == EACCES))
{
set_errno (EWOULDBLOCK);
}
}
break;
case LOCK_SH:
l.l_type = F_RDLCK;
i = fcntl_worker (fd, cmd, &l);
if (i == -1)
{
if ((get_errno () == EAGAIN) || (get_errno () == EACCES))
{
set_errno (EWOULDBLOCK);
}
}
break;
case LOCK_UN:
l.l_type = F_UNLCK;
i = fcntl_worker (fd, cmd, &l);
if (i == -1)
{
if ((get_errno () == EAGAIN) || (get_errno () == EACCES))
{
set_errno (EWOULDBLOCK);
}
}
break;
default:
i = -1;
set_errno (EINVAL);
break;
}
return i;
}
#ifdef FLOCK_EMULATE_IS_MAIN
int
main (int argc, char **argv)
{
int fd = open (argv[1], O_WRONLY);
flock (fd, LOCK_EX);
return 0;
}
#endif
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