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#include <errno.h>
#include <sys/select.h>
#include <stdio.h>
static int
countset(int nfds, fd_set *set)
{
int count = 0;
if (set == NULL) return 0;
for (int i = 0; i < nfds; i++) {
if (FD_ISSET(i, set)) {
count++;
}
}
return count;
}
int
select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
{
(void)timeout;
FD_ZERO(exceptfds);
if (countset(nfds, readfds) != 0) {
return errno = ENOSYS, -1;
}
return countset(nfds, writefds); /* assume everything is ready for writing */
}
void FD_CLR(int fd, fd_set *set) {
if (0 <= fd && fd < FD_SETSIZE) {
*set = *set & ~(1<<fd);
}
}
int FD_ISSET(int fd, fd_set *set) {
return 0 <= fd && fd < FD_SETSIZE && (*set & (1 << fd));
}
void FD_SET(int fd, fd_set *set) {
if (0 <= fd && fd < FD_SETSIZE) {
*set = *set | (1<<fd);
}
}
void FD_ZERO(fd_set *set) {
*set = 0;
}
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