[os2]: Implement pipe_has_data procedure

core/os/os2/pipe_linux.odin

@@ -15,3 +15,29 @@ _pipe :: proc() -> (r, w: ^File, err: Error) {
 
 	return
 }
+
+@(require_results)
+_pipe_has_data :: proc(r: ^File) -> (ok: bool, err: Error) {
+	if r == nil || r.impl == nil {
+		return false, nil
+	}
+	fd := linux.Fd((^File_Impl)(r.impl).fd)
+	poll_fds := []linux.Poll_Fd {
+		linux.Poll_Fd {
+			fd = fd,
+			events = {.IN, .HUP},
+		},
+	}
+	n, errno := linux.poll(poll_fds, 0)
+	if n != 1 || errno != nil {
+		return false, _get_platform_error(errno)
+	}
+	pipe_events := poll_fds[0].revents
+	if pipe_events >= {.IN} {
+		return true, nil
+	}
+	if pipe_events >= {.HUP} {
+		return false, .Broken_Pipe
+	}
+	return false, nil
+}