LibC: Implement poll() using select

userspace/libraries/LibC/CMakeLists.txt

@@ -12,6 +12,7 @@ set(LIBC_SOURCES
 	malloc.cpp
 	math.cpp
 	netdb.cpp
+	poll.cpp
 	printf_impl.cpp
 	pwd.cpp
 	scanf_impl.cpp

userspace/libraries/LibC/poll.cpp

@@ -0,0 +1,56 @@
+#include <poll.h>
+#include <sys/select.h>
+
+int poll(struct pollfd fds[], nfds_t nfds, int timeout)
+{
+	fd_set rfds, wfds, efds;
+	FD_ZERO(&rfds);
+	FD_ZERO(&wfds);
+	FD_ZERO(&efds);
+
+	for (nfds_t i = 0; i < nfds; i++)
+		fds[i].revents = 0;
+
+	constexpr short rmask = POLLIN | POLLRDNORM | POLLRDBAND | POLLPRI | POLLHUP;
+	constexpr short wmask = POLLOUT | POLLWRNORM | POLLWRBAND;
+	constexpr short emask = POLLERR;
+
+	int max_fd = 0;
+	for (nfds_t i = 0; i < nfds; i++)
+	{
+		if (fds[i].fd < 0)
+			continue;
+
+		if (fds[i].events & rmask)
+			FD_SET(fds[i].fd, &rfds);
+		if (fds[i].events & wmask)
+			FD_SET(fds[i].fd, &wfds);
+		if (fds[i].events & emask)
+			FD_SET(fds[i].fd, &efds);
+
+		if (fds[i].fd > max_fd)
+			max_fd = fds[i].fd;
+	}
+
+	timeval tv;
+	tv.tv_sec = timeout / 1000;
+	tv.tv_usec = timeout % 1000 * 1000;
+	int nselect = select(max_fd + 1, &rfds, &wfds, &efds, &tv);
+	if (nselect == -1)
+		return -1;
+
+	for (nfds_t i = 0; i < nfds; i++)
+	{
+		if (fds[i].fd < 0)
+			continue;
+
+		if (FD_ISSET(fds[i].fd, &rfds))
+			fds[i].revents |= fds[i].events & rmask;
+		if (FD_ISSET(fds[i].fd, &wfds))
+			fds[i].revents |= fds[i].events & wmask;
+		if (FD_ISSET(fds[i].fd, &efds))
+			fds[i].revents |= fds[i].events & emask;
+	}
+
+	return nselect;
+}