Merge pull request #134 from alexyu1989/master

Can tolerate rescived publish message formatting errors.

Author: zhangwh

Source/CocoaMQTT.swift

@@ -548,7 +548,9 @@ class CocoaMQTTReader {
             delegate.didReceiveConnAck(self, connack: data[1])
         case .publish:
             let (msgid, message) = unpackPublish()
-            delegate.didReceivePublish(self, message: message, id: msgid)
+            if message != nil {
+                delegate.didReceivePublish(self, message: message!, id: msgid)
+            }
         case .puback:
             delegate.didReceivePubAck(self, msgid: msgid(data))
         case .pubrec:
@@ -570,9 +572,13 @@ class CocoaMQTTReader {
         readHeader()
     }
 
-    private func unpackPublish() -> (UInt16, CocoaMQTTMessage) {
+    private func unpackPublish() -> (UInt16, CocoaMQTTMessage?) {
         let frame = CocoaMQTTFramePublish(header: header, data: data)
         frame.unpack()
+        // if unpack fail
+        if frame.msgid == nil {
+            return (0, nil)
+        }
         let msgid = frame.msgid!
         let qos = CocoaMQTTQOS(rawValue: frame.qos)!
         let message = CocoaMQTTMessage(topic: frame.topic!, payload: frame.payload, qos: qos, retained: frame.retained, dup: frame.dup)

Source/CocoaMQTTFrame.swift

@@ -304,19 +304,35 @@ class CocoaMQTTFramePublish: CocoaMQTTFrame {
 
     func unpack() {
         // topic
+        data![1] = 10
+        if data!.count < 2 {
+            print("Invalid format of rescived message.")
+            return
+        }
         var msb = data![0]
         var lsb = data![1]
         let len = UInt16(msb) << 8 + UInt16(lsb)
         var pos = 2 + Int(len)
-        topic = NSString(bytes: [UInt8](data![2...(pos-1)]), length: Int(len), encoding: String.Encoding.utf8.rawValue) as? String
+        
+        if data!.count < pos {
+            print("Invalid format of rescived message.")
+            return
+        }
+        
+        topic = NSString(bytes: [UInt8](data![2...(pos-1)]), length: Int(len), encoding: String.Encoding.utf8.rawValue) as String?
 
         // msgid
         if qos == 0 {
             msgid = 0
         } else {
-            msb = data![pos]; lsb = data![pos+1]
-            msgid = UInt16(msb) << 8 + UInt16(lsb)
+            if data!.count < pos + 2 {
+                print("Invalid format of rescived message.")
+                return
+            }
+            msb = data![pos]
+            lsb = data![pos+1]
             pos += 2
+            msgid = UInt16(msb) << 8 + UInt16(lsb)
         }
 
         // payload