os: create epoll wrapper (#10404)

vlib/os/notify/notify_test.v

@@ -0,0 +1,156 @@
+import os
+import os.notify
+import time
+
+// make a pipe and return the (read, write) file descriptors
+fn make_pipe() ?(int, int) {
+	$if linux {
+		pipefd := [2]int{}
+		if C.pipe(&pipefd[0]) != 0 {
+			return error('error $C.errno: ' + os.posix_get_error_msg(C.errno))
+		}
+		return pipefd[0], pipefd[1]
+	}
+	return -1, -1
+}
+
+fn test_level_trigger() ? {
+	// currently only linux is supported
+	$if linux {
+		mut notifier := notify.new() ?
+		reader, writer := make_pipe() ?
+		defer {
+			os.fd_close(reader)
+			os.fd_close(writer)
+			notifier.close() or {}
+		}
+		notifier.add(reader, .read) ?
+
+		os.fd_write(writer, 'foobar')
+		check_read_event(notifier, reader, 'foo')
+		check_read_event(notifier, reader, 'bar')
+
+		assert notifier.wait(0).len == 0
+	}
+}
+
+fn test_edge_trigger() ? {
+	// currently only linux is supported
+	$if linux {
+		mut notifier := notify.new() ?
+		reader, writer := make_pipe() ?
+		defer {
+			os.fd_close(reader)
+			os.fd_close(writer)
+			notifier.close() or {}
+		}
+		notifier.add(reader, .read, .edge_trigger) ?
+
+		os.fd_write(writer, 'foobar')
+		check_read_event(notifier, reader, 'foo')
+
+		assert notifier.wait(0).len == 0
+
+		os.fd_write(writer, 'baz')
+		// we do not get an event because there is still data
+		// to be read
+		assert notifier.wait(0).len == 0
+	}
+}
+
+fn test_one_shot() ? {
+	$if linux {
+		mut notifier := notify.new() ?
+		reader, writer := make_pipe() ?
+		defer {
+			os.fd_close(reader)
+			os.fd_close(writer)
+			notifier.close() or {}
+		}
+		notifier.add(reader, .read, .one_shot) ?
+
+		os.fd_write(writer, 'foobar')
+		check_read_event(notifier, reader, 'foo')
+		os.fd_write(writer, 'baz')
+
+		assert notifier.wait(0).len == 0
+
+		// rearm
+		notifier.modify(reader, .read) ?
+		check_read_event(notifier, reader, 'barbaz')
+	}
+}
+
+fn test_hangup() ? {
+	$if linux {
+		mut notifier := notify.new() ?
+		reader, writer := make_pipe() ?
+		defer {
+			os.fd_close(reader)
+			notifier.close() or {}
+		}
+		notifier.add(reader, .hangup) ?
+
+		assert notifier.wait(0).len == 0
+
+		// closing on the writer end of the pipe will
+		// cause a hangup on the reader end
+		os.fd_close(writer)
+		events := notifier.wait(0)
+		assert events.len == 1
+		assert events[0].fd == reader
+		assert events[0].kind.has(.hangup)
+	}
+}
+
+fn test_write() ? {
+	$if linux {
+		mut notifier := notify.new() ?
+		reader, writer := make_pipe() ?
+		defer {
+			os.fd_close(reader)
+			os.fd_close(writer)
+			notifier.close() or {}
+		}
+
+		notifier.add(reader, .write) ?
+		assert notifier.wait(0).len == 0
+
+		notifier.add(writer, .write) ?
+		events := notifier.wait(0)
+		assert events.len == 1
+		assert events[0].fd == writer
+		assert events[0].kind.has(.write)
+	}
+}
+
+fn test_remove() ? {
+	$if linux {
+		mut notifier := notify.new() ?
+		reader, writer := make_pipe() ?
+		defer {
+			os.fd_close(reader)
+			os.fd_close(writer)
+			notifier.close() or {}
+		}
+
+		// level triggered - will keep getting events while
+		// there is data to read
+		notifier.add(reader, .read) ?
+		os.fd_write(writer, 'foobar')
+		assert notifier.wait(0).len == 1
+		assert notifier.wait(0).len == 1
+
+		notifier.remove(reader) ?
+		assert notifier.wait(0).len == 0
+	}
+}
+
+fn check_read_event(notifier notify.FdNotifier, reader_fd int, expected string) {
+	events := notifier.wait(0)
+	assert events.len == 1
+	assert events[0].fd == reader_fd
+	assert events[0].kind.has(.read)
+	s, _ := os.fd_read(events[0].fd, expected.len)
+	assert s == expected
+}