Mail Archives: cygwin/2006/10/06/22:52:52
Hello!
I'm finding that I have a need to select on a win32 handle. I found the
function cygwin_attach_handle_to_fd which sounded promising, but I do
not have any luck when I try to use it.
I did look through the sources in winsup, but came to the perhaps
misguided conclusion that there needs to be a new fhandler in order to
support this.
I would not mind to be proved wrong though. :-)
I was hoping that the following program would print "tick" with one
second intervals, but the fd is selectable all the time. If I
uncomment the call to WaitForSingleObject, the output is as I hoped,
so I believe the Win32 parts are correct in the sample.
I have tried various arguments instead of NULL for
cygwin_attach_handle_to_fd, in the hopes of finding a workable
fhandler, but to no avail.
Is there some other approach to select on Win32 handles? Or should
I declare defeat and use get_osfhandle on the fds and WaitFor...
the combined set of fds/objects that way instead?
Cheers,
Peter
-------------8<------------
#include <windows.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/cygwin.h>
int
main(void)
{
HANDLE timer;
LARGE_INTEGER due;
int fd;
fd_set fds;
int i;
int res = 0;
timer = CreateWaitableTimer(NULL, TRUE, NULL);
due.QuadPart = -10000000;
if (!SetWaitableTimer(timer, &due, 0, NULL, NULL, FALSE))
return -1;
fd = cygwin_attach_handle_to_fd(NULL, -1, timer, 1, GENERIC_READ);
if (fd < 0) {
CloseHandle(timer);
return -1;
}
FD_ZERO(&fds);
FD_SET(fd, &fds);
for (i = 0; i < 5; ++i) {
res = select(fd + 1, &fds, NULL, NULL, NULL);
if (res < 0)
break;
printf("tick\n");
/* WaitForSingleObject(timer, INFINITE); */
if (!SetWaitableTimer(timer, &due, 0, NULL, NULL, FALSE)) {
res = -1;
break;
}
}
close(fd);
return res < 0 ? res : 0;
}
-------------8<------------
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