WIP: Implement poll as a wrapper of kevent

lib/libc/sys/poll.c

@@ -0,0 +1,58 @@
+#include<sys/poll.h>
+#include<sys/time.h>
+#include<sys/event.h>
+#include<stdlib.h>
+#include<unistd.h>
+#include<errno.h>
+
+int	poll(struct pollfd *fds, nfds_t nfds, int timeout) {
+    int kq;
+    int ret;
+    struct kevent *events;
+    struct timespec timeout_ts;
+    int nevents = 0;
+
+    if (nfds < 0 || nfds > (unsigned int)sysconf(_SC_OPEN_MAX)) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if (timeout >= 0) {
+        timeout_ts.tv_sec = timeout / 1000;
+        timeout_ts.tv_nsec = (timeout % 1000) * 1000000;
+    }
+    else if (timeout < -1) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    kq = kqueue();
+    if (kq < 0)
+        return -1;
+
+    events = malloc(nfds * sizeof(struct kevent));
+    if (!events) {
+        errno = ENOMEM;
+        ret = -1;
+        goto close_kq;
+    }
+
+    for (unsigned int i = 0; i < nfds; i++) {
+        if (fds[i].events | POLLIN)
+            EV_SET(&events[nevents++], fds[i].fd, EVFILT_READ, EV_ADD, 0, 0, 0);
+        if (fds[i].events | POLLOUT)
+            EV_SET(&events[nevents++], fds[i].fd, EVFILT_WRITE, EV_ADD, 0, 0, 0);
+    }
+
+    ret = kevent(kq, events, nevents, events, nevents, timeout == -1 ? NULL : &timeout_ts);
+    if (ret == -1)
+        goto end;
+
+    /* TODO - populate `revents` in elements of `fds` array */
+
+end:
+    free(events);
+close_kq:
+    close(kq);
+    return ret;
+}