some fixes related to variable UDH header and Multipart SMS's

reference: https://github.com/larvit/larvitsmpp/issues/1

lib/session.js

@@ -363,22 +363,39 @@ function sendLongSms(smsOptions, callback) {
 
 // Store long smses in the temporary storage
 function longSms(pduObj) {
-	var smsGroupId = pduObj.params.short_message[3],
+	// Fix: UDH values are stored in HEX and decoding them make it garbage. First OCTET contains
-	    smsParts   = pduObj.params.short_message[4],
+	//      the size of UDH data header. If UDH data header size is 0x05 then field 4 i.e. CSMS
-	    longSmsId  = pduObj.params.source_addr + '_' + pduObj.params.destination_addr + '_' + smsGroupId;
+	//      reference number is of one octet otherwise it consists of 2 octets. Other fields can
+	//	be found from below reference.
+	//      reference: https://en.wikipedia.org/wiki/Concatenated_SMS
+	var encodedMessage = utils.encodeMsg(pduObj.params.short_message),
+            udhSize = encodedMessage[0];
+	var smsGroupId, smsParts, partNr;
+        if(udhSize === 0x05) {
+                smsGroupId = encodedMessage[3],
+                smsParts   = encodedMessage[4],
+                partNr     = encodedMessage[5];
+        } else {
+                smsGroupId = (encodedMessage[3] * 256) + encodedMessage[4],
+                smsParts   = encodedMessage[5],
+                partNr     = encodedMessage[6];
+        }
+
+	var longSmsId  = pduObj.params.source_addr + '_' + pduObj.params.destination_addr + '_' + smsGroupId;
 
 	if (this.longSmses[longSmsId] === undefined) {
 		this.longSmses[longSmsId] = {
 			'created': new Date(),
 			'partsCount': parseInt(smsParts),
+			'udhSize': udhSize, // Saving udh size to remove garbage from message
 			'pduObjs': [{
-				'partNr': pduObj.params.short_message[5], // We save this here to easier sort the array later on
+				'partNr': partNr, // We save this here to easier sort the array later on
 				'pduObj': pduObj
 			}]
 		};
 	} else {
 		this.longSmses[longSmsId].pduObjs.push({
-			'partNr': pduObj.params.short_message[5], // We save this here to easier sort the array later on
+			'partNr': partNr, // We save this here to easier sort the array later on
 			'pduObj': pduObj
 		});
 	}
@@ -406,6 +423,7 @@ function checkLongSmses() {
 	var that = this,
 	    smsGroupId,
 	    smsGroup,
+	    udhSize, // UDH Size from longSms() function
 	    smsObj,
 	    i,
 	    curPduObj;
@@ -422,7 +440,7 @@ function checkLongSmses() {
 
 	for (smsGroupId in this.longSmses) {
 		smsGroup = this.longSmses[smsGroupId];
-
+		udhSize = smsGroup.udhSize;
 		// All parts are accounted for! Emit sms event and clear from tmp storage
 		if (smsGroup.partsCount === smsGroup.pduObjs.length) {
 			log.debug('larvitsmpp: lib/session.js: checkLongSmses() - All parts accounted for in smsGroupId "' + smsGroupId + '", emitting sms event.');
@@ -451,7 +469,9 @@ function checkLongSmses() {
 				curPduObj         = smsObj.pduObjs[i].pduObj;
 				curPduObj.session = this;
 
-				smsObj.message += utils.decodeMsg(curPduObj.params.short_message, curPduObj.params.data_coding, curPduObj.params.short_message[0] + 1);
+				// Fix: message in pduObj is already decoded we dont need to do it again. Also removing garbade from original message.
+				//smsObj.message += utils.decodeMsg(curPduObj.params.short_message, curPduObj.params.data_coding, curPduObj.params.short_message[0] + 1);
+				smsObj.message += curPduObj.params.short_message.substring(udhSize + 1);
 
 				i ++;
 			}
@@ -557,7 +577,9 @@ function session(sock) {
 		var smsObj = {};
 
 		// If esm_class is 0x40 it means this is just a part of a larger message
-		if (pduObj.params.esm_class === 0x40) {
+		//if (pduObj.params.esm_class === 0x40) {
+		// Fix: esm_class can be combination of bits. We need to extract 0x40 and then compare
+		if ((pduObj.params.esm_class & 0x40) === 0x40) {
 			log.debug('larvitsmpp: lib/session.js: session() - returnObj.handleCmd.submit_sm() - long sms detected, esm_class 0x40.');
 			returnObj.longSms(pduObj);
 			return; // Long messages should not get handled here at all, so cancel execution here