- Added missing file charbychar.c which contains a protocol handler

which writes char by char, thereby waiting for the echo character
  to be received in between.

charbychar.c

@@ -0,0 +1,73 @@
+/*
+ * charbychar.c
+ *
+ *  This is a variation of the standard AsonHandler which implements
+ *  a char by char mode while sending. This means, that the protocol
+ *  handler waits for the echoed character from the device before sending
+ *  the next character.
+ *
+ *  Created on: Apr 1, 2010
+ *      Author: koennecke
+ */
+#include <errno.h>
+#include <ascon.h>
+#include <ascon.i>
+
+/*-----------------------------------------------------------
+ * I am abusing the echo field as a flag if we are reading
+ * an echo char or not
+-----------------------------------------------------------*/
+static int CharByCharHandler(Ascon *a)
+{
+	int ret;
+	char chr;
+
+	switch(a->state){
+	case AsconWriting:
+		if(a->wrPos < GetDynStringLength(a->wrBuffer)){
+			ret = AsconWriteChars(a->fd,GetCharArray(a->wrBuffer)+a->wrPos,1);
+		    if (ret < 0) {
+		      AsconError(a, "ASC4", errno); /* sets state to AsconFailed */
+		      return 0;
+		    } else {
+		      a->wrPos++;
+		      a->private = (void *)1;
+		      a->state = AsconReading;
+		      a->start = DoubleTime();
+		    }
+		    break;
+		} else {
+			a->private = NULL;
+			a->state = AsconWriteDone;
+		}
+		break;
+	case AsconReading:
+		/**
+		 * Here I rely on the fact that the base
+		 * handler, in AsconReadStart, clears the
+		 * rdBuffer of amassed echo characters.
+		 */
+		ret = AsconStdHandler(a);
+		if(ret == 1){
+			if(a->private != NULL){
+				a->state = AsconWriting;
+			}
+		}
+		return ret;
+		break;
+	default:
+		return AsconStdHandler(a);
+	}
+	return 1;
+}
+/*------------------------------------------------------------------------*/
+void AddCharByCharProtocoll()
+{
+  AsconProtocol *prot = NULL;
+
+  prot = calloc(sizeof(AsconProtocol), 1);
+  prot->name = strdup("charbychar");
+  prot->init = AsconStdInit;
+  prot->handler = CharByCharHandler;
+  AsconInsertProtocol(prot);
+}