Add epoll bindings to std::os::linux + misc (#2350)

* Add epoll to std::os::linux + misc

* Fix import in linux.c3

* epoll: Add unit tests

* epoll: Fix imports in unit tests

* epoll: Add libc import

test/unit/stdlib/os/linux_epoll.c3

@@ -0,0 +1,123 @@
+module std::os::linux @test @if (env::LINUX);
+import std::net::os;
+import std::os::posix;
+import libc;
+
+fn void test_epoll_create()
+{
+	// Test epoll_create with valid size
+	int epoll_fd = epoll_create(1);
+	assert(epoll_fd >= 0, "epoll_create failed");
+	libc::close(epoll_fd);
+
+	// Test epoll_create with size 0 (should work on Linux)
+	epoll_fd = epoll_create1(0);
+	assert(epoll_fd >= 0, "epoll_create1 failed");
+	libc::close(epoll_fd);
+
+	// Test epoll_create with negative size (should fail)
+	epoll_fd = epoll_create(-1);
+	assert(epoll_fd == -1, "epoll_create with negative size should fail");
+}
+
+fn void test_epoll_ctl()
+{
+	int epoll_fd = epoll_create(1);
+	assert(epoll_fd >= 0, "epoll_create failed");
+
+	// Create a socket to monitor
+	int sock_fd = os::socket(os::AF_INET, os::SOCK_STREAM, 0);
+	assert(sock_fd >= 0, "socket creation failed");
+
+	EpollEvent event;
+	event.events = EPOLLIN;
+	event.data.fd = sock_fd;
+
+	// Test EPOLL_CTL_ADD
+	int ret = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, sock_fd, &event);
+	assert(ret == 0, "EPOLL_CTL_ADD failed");
+
+	// Test EPOLL_CTL_MOD
+	event.events = EPOLLIN | EPOLLOUT;
+	ret = epoll_ctl(epoll_fd, EPOLL_CTL_MOD, sock_fd, &event);
+	assert(ret == 0, "EPOLL_CTL_MOD failed");
+
+	// Test EPOLL_CTL_DEL
+	ret = epoll_ctl(epoll_fd, EPOLL_CTL_DEL, sock_fd, null);
+	assert(ret == 0, "EPOLL_CTL_DEL failed");
+
+	// Test invalid operations
+	ret = epoll_ctl(epoll_fd, -1, sock_fd, &event); // invalid op
+	assert(ret == -1, "Invalid operation should fail");
+
+	libc::close(sock_fd);
+	libc::close(epoll_fd);
+}
+
+fn void test_epoll_edge_triggered()
+{
+	int epoll_fd = epoll_create(1);
+	assert(epoll_fd >= 0, "epoll_create failed");
+
+	int[2] pipe_fds;
+	assert(posix::pipe(&pipe_fds) == 0, "pipe creation failed");
+
+	// Set up edge-triggered monitoring
+	EpollEvent event;
+	event.events = EPOLLIN | EPOLLET;
+	event.data.fd = pipe_fds[0];
+	assert(epoll_ctl(epoll_fd, EPOLL_CTL_ADD, pipe_fds[0], &event) == 0,
+		   "epoll_ctl add failed");
+
+	// Write to pipe
+	char[] buf = "test";
+	assert(libc::write(pipe_fds[1], buf, buf.len) == buf.len,
+		   "write to pipe failed");
+
+	// First epoll_wait should get the event
+	EpollEvent[10] events;
+	int num_events = epoll_wait(epoll_fd, &events[0], events.len, 0);
+	assert(num_events == 1, "epoll_wait should return 1 event");
+
+	// Second epoll_wait shouldn't get the same event (edge-triggered behavior)
+	num_events = epoll_wait(epoll_fd, &events[0], events.len, 0);
+	assert(num_events == 0, "epoll_wait should not return event again for edge-triggered");
+
+	libc::close(pipe_fds[0]);
+	libc::close(pipe_fds[1]);
+	libc::close(epoll_fd);
+}
+
+fn void test_epoll_level_triggered()
+{
+	int epoll_fd = epoll_create(1);
+	assert(epoll_fd >= 0, "epoll_create failed");
+
+	int[2] pipe_fds;
+	assert(posix::pipe(&pipe_fds) == 0, "pipe creation failed");
+
+	// Set up level-triggered monitoring
+	EpollEvent event;
+	event.events = EPOLLIN; // Default is level-triggered
+	event.data.fd = pipe_fds[0];
+	assert(epoll_ctl(epoll_fd, EPOLL_CTL_ADD, pipe_fds[0], &event) == 0,
+		   "epoll_ctl add failed");
+
+	// Write to pipe
+	char[] buf = "test";
+	assert(libc::write(pipe_fds[1], buf, buf.len) == buf.len,
+		   "write to pipe failed");
+
+	// First epoll_wait should get the event
+	EpollEvent[10] events;
+	int num_events = epoll_wait(epoll_fd, &events[0], events.len, 0);
+	assert(num_events == 1, "epoll_wait should return 1 event");
+
+	// Second epoll_wait should get the same event again (level-triggered behavior)
+	num_events = epoll_wait(epoll_fd, &events[0], events.len, 0);
+	assert(num_events == 1, "epoll_wait should return event again for level-triggered");
+
+	libc::close(pipe_fds[0]);
+	libc::close(pipe_fds[1]);
+	libc::close(epoll_fd);
+}