void
ttywrite(const char *s, size_t n)
{
- if (xwrite(cmdfd, s, n) == -1)
- die("write error on tty: %s\n", strerror(errno));
+ fd_set wfd;
+ struct timespec tv;
+ ssize_t r;
+
+ /*
+ * Remember that we are using a pty, which might be a modem line.
+ * Writing too much will clog the line. That's why we are doing this
+ * dance.
+ * FIXME: Migrate the world to Plan 9.
+ */
+ while (n > 0) {
+ FD_ZERO(&wfd);
+ FD_SET(cmdfd, &wfd);
+ tv.tv_sec = 0;
+ tv.tv_nsec = 0;
+
+ /* Check if we can write. */
+ if (pselect(cmdfd+1, NULL, &wfd, NULL, &tv, NULL) < 0) {
+ if (errno == EINTR)
+ continue;
+ die("select failed: %s\n", strerror(errno));
+ }
+ if(!FD_ISSET(cmdfd, &wfd)) {
+ /* No, then free some buffer space. */
+ ttyread();
+ } else {
+ /*
+ * Only write 256 bytes at maximum. This seems to be a
+ * reasonable value for a serial line. Bigger values
+ * might clog the I/O.
+ */
+ r = write(cmdfd, s, (n < 256)? n : 256);
+ if (r < 0) {
+ die("write error on tty: %s\n",
+ strerror(errno));
+ }
+ if (r < n) {
+ /*
+ * We weren't able to write out everything.
+ * This means the buffer is getting full
+ * again. Empty it.
+ */
+ ttyread();
+ n -= r;
+ s += r;
+ } else {
+ /* All bytes have been written. */
+ break;
+ }
+ }
+ }
}
void
