Implement chunked write to the cmdfd.

This is needed so big input like a paste of several megabyte does not clog our
I/O.

diff --git a/st.c b/st.c
index 17e0a65493aeab1b63097b187529a476dc5be13d..e65e9813f5fe635a8cfe35d74d3b20241ffa106f 100644 (file)
--- a/st.c
+++ b/st.c
@@ -1478,8 +1478,57 @@ ttyread(void)
 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