[Dosemu-devel] [PATCH] Retry opening MIDI output FIFO on writes.

[Ryan C. U. <nem...@ic...>]

From: "Ryan C. Underwood" <ne...@ic...>

Now the user can start consuming MIDI data after dosemu has started,
instead of having to start over after realizing he forgot to start
his MIDI-consuming app.

Signed-off-by: Ryan C. Underwood <ne...@ic...>
---
 src/plugin/midimisc/mid_o_pipe.c | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/src/plugin/midimisc/mid_o_pipe.c b/src/plugin/midimisc/mid_o_pipe.c
index eb45f64..633e3eb 100644
--- a/src/plugin/midimisc/mid_o_pipe.c
+++ b/src/plugin/midimisc/mid_o_pipe.c
@@ -41,10 +41,16 @@ static int midopipe_init(void)
     pipe_fd =
 	RPT_SYSCALL(open(name, O_WRONLY | O_CREAT | O_NONBLOCK, 0666));
     if (pipe_fd == -1) {
-	S_printf("%s: unable to open %s for writing: %s\n",
-		 midopipe_name, name, strerror(errno));
-	return 0;
+	int err = errno;
+	S_printf("%s: unable to open %s for writing (%s)%s\n", midopipe_name, name,
+	    strerror(errno), errno == ENXIO ? ", will continue trying" : "");
+	if (err == ENXIO) { /* no FIFO readers */
+	    return 1;
+	} else { /* some other problem */
+	   return 0;
+	}
     }
+    /* open ok */
     return 1;
 }
 
@@ -62,9 +68,28 @@ static void midopipe_reset(void)
 
 static void midopipe_write(unsigned char val)
 {
-    if (pipe_fd == -1)
-	return;
-    write(pipe_fd, &val, 1);
+    /* Try again to open FIFO on each write in case some readers showed up. */
+    if (pipe_fd == -1) {
+	pipe_fd = RPT_SYSCALL(open(DOSEMU_MIDI_PATH, O_WRONLY | O_CREAT | O_NONBLOCK, 0666));
+	if (pipe_fd == -1) {
+	    return;
+	}
+    }
+    int retry = 0;
+    do {
+	if (write(pipe_fd, &val, 1) == -1) {
+	    switch (errno) {
+		case EAGAIN:
+		case EINTR:
+		    retry = 1;
+		default: /* all other errors incl. EPIPE */
+		    close(pipe_fd);
+		    pipe_fd = -1;
+		    retry = 0;
+		    break;
+	    }
+	}
+    } while (retry);
 }
 
 CONSTRUCTOR(static int midopipe_register(void))
-- 
1.9.1