+static int xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+ int ret;
+
+ do
+ ret = poll(fds, nfds, timeout);
+ while (ret < 0 && errno == EINTR);
+ return ret < 0? -ERRNO_TO_PARA_ERROR(errno) : ret;
+}
+
+/**
+ * Check a file descriptor for readability.
+ *
+ * \param fd The file descriptor.
+ *
+ * \return positive if fd is ready for reading, zero if it isn't, negative if
+ * an error occurred.
+ *
+ * \sa \ref write_ok().
+ */
+int read_ok(int fd)
+{
+ struct pollfd pfd = {.fd = fd, .events = POLLIN};
+ int ret = xpoll(&pfd, 1, 0);
+ return ret < 0? ret : pfd.revents & POLLIN;
+}
+