[PATCH 1/2] slcanpty: Improve the reading from pty to avoid incomplete messages in the reading buf[]

[uescher <linux-can_ger.kernel.org@myvdr.de>]

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slcanpty: Improve the reading from pty to avoid incomplete messages in 
the reading buf[]

This Patch ensure that we read the maximum of complete SLCAN messages 
from pty.
Leave messages at the pty if is not possible to read it complete in the buf.

Signed-off-by: Ulrich Escher <git@myvdr.de>


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From 13e8e6ad85e42f68816d14eb74c0f3fabcd28465 Mon Sep 17 00:00:00 2001
From: ulrich <git@myvdr.de>
Date: Sun, 24 Feb 2013 15:55:19 +0100
Subject: [PATCH 1/2] slcanpty: Improve the reading from pty to avoid
 incomplete messages in the reading buf[]

This Patch ensure that we read the maximum of complete SLCAN messages from pty.
Leave messages at the pty if is not possible to read it complete in the buf.

Signed-off-by: Ulrich Escher <git@myvdr.de>
---
 slcanpty.c |   32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/slcanpty.c b/slcanpty.c
index f3628b9..037edf5 100644
--- a/slcanpty.c
+++ b/slcanpty.c
@@ -31,6 +31,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <termios.h>
+#include <poll.h>
 
 #include <net/if.h>
 #include <sys/socket.h>
@@ -74,12 +75,41 @@ int pty2can(int pty, int socket, struct can_filter *fi,
 	struct can_frame frame;
 	int tmp, i;
 
-	nbytes = read(pty, &buf, sizeof(buf)-1);
+	nbytes = read(pty, &buf, sizeof(buf)-SLC_MTU-1);
 	if (nbytes < 0) {
 		perror("read pty");
 		return 1;
 	}
 
+	if (nbytes == sizeof(buf)-SLC_MTU-1) {
+		struct pollfd fds;
+		fds.fd = pty;
+		fds.events = POLLIN;
+
+		while (buf[nbytes-1] != '\r' && nbytes < (sizeof(buf)-1)) {
+			tmp = poll(&fds, 1, 0);
+			if (tmp < 0) {
+				perror("poll pty");
+				return 1;
+			}
+
+			if (fds.revents & POLLIN) {
+				tmp = read(pty, &buf[nbytes++], 1);
+				if (tmp < 0) {
+					perror("read pty");
+					return 1;
+				}
+			} else {
+				/* No further Data available */
+				break;
+			}
+		}
+	}
+
+#ifdef DEBUG
+	printf("read %d bytes from pty\n",nbytes);
+#endif
+
 rx_restart:
 	/* remove trailing '\r' characters to be robust against some apps */
 	while (buf[0] == '\r' && nbytes > 0) {
-- 
1.7.9.5