add tests to check the poll support

examples/demo/Cargo.toml

@@ -20,6 +20,7 @@ path = "src/matrix_multiplication.rs"
 [dependencies]
 rayon = "1.5"
 num_cpus = "1.13"
+hermit-abi = { path = "../../hermit-abi" }
 
 [target.'cfg(target_os = "hermit")'.dependencies.hermit]
 path = "../../hermit"

examples/demo/src/main.rs

@@ -88,4 +88,9 @@ fn main() {
 		stringify!(thread_creation),
 		test_result(thread_creation())
 	);
+	println!(
+		"Test {} ... {}",
+		stringify!(io_poll),
+		test_result(io_poll())
+	);
 }

examples/demo/src/tests/mod.rs

@@ -151,6 +151,35 @@ pub fn create_file() -> Result<(), std::io::Error> {
 	}
 }
 
+pub fn io_poll() -> Result<(), std::io::Error> {
+	const TIMEOUT: i32 = 5000;
+	let mut fds: [hermit_abi::pollfd; 2] = [Default::default(); 2];
+
+	/* watch stdin for input */
+	fds[0].fd = hermit_abi::STDIN_FILENO;
+	fds[0].events = hermit_abi::POLLIN;
+
+	/* watch stdout for ability to write */
+	fds[1].fd = hermit_abi::STDOUT_FILENO;
+	fds[1].events = hermit_abi::POLLOUT;
+
+	let ret = unsafe { hermit_abi::poll(fds.as_mut_ptr(), 2, TIMEOUT) };
+	if ret < 0 {
+		let kind = std::io::ErrorKind::Other;
+		return Err(std::io::Error::from(kind));
+	}
+
+	if fds[0].revents & hermit_abi::POLLIN == hermit_abi::POLLIN {
+		println!("stdin is readable");
+	}
+
+	if fds[1].revents & hermit_abi::POLLOUT == hermit_abi::POLLOUT {
+		println!("stdout is writable");
+	}
+
+	Ok(())
+}
+
 pub fn print_argv() -> Result<(), ()> {
 	let args = env::args();
 

examples/testtcp/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+hermit-abi = { path = "../../hermit-abi" }
 
 [target.'cfg(target_os = "hermit")'.dependencies.hermit]
 path = "../../hermit"

examples/testtcp/src/main.rs

@@ -3,6 +3,7 @@ use hermit as _;
 
 use std::io::Read;
 use std::net::TcpListener;
+use std::os::hermit::io::AsRawFd;
 
 // demo program to test the tcp interface
 //
@@ -14,8 +15,13 @@ fn main() {
 	let listener = TcpListener::bind("0.0.0.0:9975").unwrap();
 	let (mut socket, _) = listener.accept().unwrap();
 	let mut buf = [0u8; 1000];
+	let mut fds: [hermit_abi::pollfd; 1] = [Default::default(); 1];
+	fds[0].fd = socket.as_raw_fd();
+	fds[0].events = hermit_abi::POLLIN;
 	loop {
 		println!("about to read");
+		let _ret = unsafe { hermit_abi::poll(fds.as_mut_ptr(), 1, -1) };
+		println!("revents {:?}", fds[0]);
 		match socket.read(&mut buf) {
 			Err(e) => {
 				println!("read err {e:?}");