int cgc_fdwait(int nfds, cgc_fd_set *readfds, cgc_fd_set *writefds,
const struct cgc_timeval *timeout, int *readyfds) {
int ret;
if (0 != (ret = cgc_check_timeout(timeout))) {
return ret;
} else if (0 > nfds || nfds > CGC__NFDBITS) {
return CGC_EINVAL;
}
// Don't store any more than the max # fds allowed
// Only one copy of every HANDLE will be stored
HANDLE fd_handles[EXPECTED_MAX_FDS];
DWORD num_handles = 0;
// Copy over fd HANDLEs from the sets
for (unsigned int fd = 0; fd < CGC__NFDBITS; ++fd) {
if((readfds && CGC_FD_ISSET(fd, readfds)) ||
(writefds && CGC_FD_ISSET(fd, writefds))) {
if (fd >= EXPECTED_MAX_FDS) {
return CGC_EBADF;
}
fd_handles[num_handles++] = _get_osfhandle(fd);
}
}
// Get the total wait time in milliseconds
DWORD wait_time = 0;
if (timeout) {
wait_time = timeout->tv_sec * 1000 + timeout->tv_usec / 1000;
}
// Wait for any of the HANDLEs to be signaled
if (WAIT_FAILED == WaitForMultipleObjects(num_handles, fd_handles, FALSE, wait_time)) {
return GetLastError();
}
// Pass over all of the fds again and poll the corresponding HANDLEs
int num_ready = 0;
if (readfds) cgc_poll_fd_set(readfds, &num_ready, TRUE);
if (writefds) cgc_poll_fd_set(writefds, &num_ready, FALSE);
if (readyfds) *readyfds = num_ready;
return 0;
}
/* Marshal a CGC fd set into an OS fd set. */
static int copy_cgc_fd_set(const cgc_fd_set *cgc_fds, fd_set *os_fds, int *num_fds) {
for (unsigned fd = 0; fd < CGC__NFDBITS; ++fd) {
if (CGC_FD_ISSET(fd, cgc_fds)) {
// Shouldn't be using an fd greater than the allowed values
if (fd >= kExpectedMaxFDs) {
return CGC_EBADF;
}
if (fd > NFDBITS) {
continue; /* OS set size is too small. */
}
FD_SET(fd, os_fds);
++*num_fds;
}
}
return 0;
}
/* Poll HANDLEs with no timeout to check if they are signaled */
void cgc_poll_fd_set(cgc_fd_set *fd_set, int *num_ready, BOOL read) {
for (unsigned int fd = 0; fd < EXPECTED_MAX_FDS; ++fd) {
if (CGC_FD_ISSET(fd, fd_set)) {
// Setup a read/write call with an event we can watch
HANDLE hndl = _get_osfhandle(fd);
OVERLAPPED ov = {0};
ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
read ? ReadFile(hndl, NULL, 0, NULL, &ov)
: WriteFile(hndl, NULL, 0, NULL, &ov);
// This event will signal if the HANDLE is available for r/w
if (WAIT_OBJECT_0 == WaitForSingleObject(ov.hEvent, 0)) {
// The HANDLE for this fd was signaled, leave the bit set
++*num_ready;
} else {
// This fd hasn't changed state
CGC_FD_CLR(fd, fd_set);
}
}
}
}
