ignore second newline if 2 are received in rapid succession

1 files changed, 40 insertions, 0 deletions

diff --git a/instr-client.c b/instr-client.c
index 4106852..8a62f13 100644
--- a/instr-client.c
+++ b/instr-client.c
@@ -3,6 +3,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <strings.h>
+#include <sys/time.h>
 
 #include "response.h"
 #include "version.h"
@@ -45,6 +46,8 @@ static gboolean Matches(char *src, char* dst, gssize size)
 	return TRUE;
 }
 
+#define TIMEOUT 100000 // 100000 useconds, 100ms
+#define ONESECONDINUSEC 1000000
 
 //GIOChannel callback
 static gboolean
@@ -57,6 +60,43 @@ stdinAvailable  (GIOChannel *source, GIOCondition condition, gpointer data)
 		return TRUE;
 	}
 
+	// Ignore second \n if two are sent in rapid succession.
+	// This happens when the serial input is terminated with \r\n,
+	// which getty translates to \n\n. The IO handler splits this
+	// into 2 input lines, so we can't use a simple regex to
+	// replace it.
+
+	static struct timeval last = { 0, 0 }; // the time this last ran
+	static struct timeval now; // the time now
+	gettimeofday(&now, NULL );
+
+	if (last.tv_sec != 0) { // shouldn't be zero if we have been in here before
+		if (strcmp(tmp, "\n") == 0) { // is this a newline all on it's own?
+			if (last.tv_sec == now.tv_sec) {
+				// if we're in the same second we can just check the usec field
+				if (now.tv_usec - last.tv_usec < TIMEOUT) {
+					// ignore this \n
+					return TRUE;
+				}
+			}
+			// - check that last and now sec fields are only one second apart
+			// - check that the time elapsed in this second is smaller than the
+			//   timeout, if it isn't we don't need to check the other second
+			// - check that there is less of the last second remaining than the timeout
+			else if (now.tv_sec - last.tv_sec == 1 && now.tv_usec < TIMEOUT && (ONESECONDINUSEC - last.tv_usec) < TIMEOUT) {
+				// and then check the the time left in the last second
+				// plus the time in this second is less than the timeout
+				if ((ONESECONDINUSEC - last.tv_usec) + now.tv_usec < TIMEOUT) {
+					// ignore this \n
+					return TRUE;
+				}
+			}
+		}
+	}
+
+	last = now;
+
+
 	//test if we have an exit word
 	int idx=0;
 	for(idx=0; idx<sizeof(exitTokens)/sizeof(exitTokens[0]); idx++) {