Ensure data sent via SingleApplication::sendMessage is received completely

Whilst the initial "connect" message is framed with a length header,
this was missing for the user data.

Thus there was no guarantee that the message frame was really received
completely on emitting the "receivedMessage" signal.

This change splits the previous "StageConnected" state into
"StageConnectedHeader" and "StageConnectedBody" and does some
refactoring to allow using the same write and read functions as the
"init" messages.

2 files changed, 58 insertions, 30 deletions

diff --git a/singleapplication_p.cpp b/singleapplication_p.cpp
index 365799e..1339728 100644
--- a/singleapplication_p.cpp
+++ b/singleapplication_p.cpp
@@ -263,29 +263,35 @@ bool SingleApplicationPrivate::connectToPrimary( int msecs, ConnectionType conne
 #endif
     writeStream << checksum;
 
-    // The header indicates the message length that follows
+    return writeConfirmedMessage( static_cast<int>(msecs - time.elapsed()), initMsg );
+}
+
+void SingleApplicationPrivate::writeAck( QLocalSocket *sock ) {
+    sock->putChar('\n');
+}
+
+bool SingleApplicationPrivate::writeConfirmedMessage (int msecs, const QByteArray &msg)
+{
+    QElapsedTimer time;
+    time.start();
+
+    // Frame 1: The header indicates the message length that follows
     QByteArray header;
     QDataStream headerStream(&header, QIODevice::WriteOnly);
 
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
     headerStream.setVersion(QDataStream::Qt_5_6);
 #endif
-    headerStream << static_cast <quint64>( initMsg.length() );
+    headerStream << static_cast <quint64>( msg.length() );
 
-    if( !writeConfirmedMessage( static_cast<int>(msecs - time.elapsed()), header ) )
+    if( ! writeConfirmedFrame( static_cast<int>(msecs - time.elapsed()), header ))
         return false;
 
-    if( !writeConfirmedMessage( static_cast<int>(msecs - time.elapsed()), initMsg ) )
-        return false;
-
-    return true;
-}
-
-void SingleApplicationPrivate::writeAck( QLocalSocket *sock ) {
-    sock->putChar('\n');
+    // Frame 2: The message
+    return writeConfirmedFrame( static_cast<int>(msecs - time.elapsed()), msg );
 }
 
-bool SingleApplicationPrivate::writeConfirmedMessage( int msecs, const QByteArray &msg )
+bool SingleApplicationPrivate::writeConfirmedFrame( int msecs, const QByteArray &msg )
 {
     socket->write( msg );
     socket->flush();
@@ -360,13 +366,16 @@ void SingleApplicationPrivate::slotConnectionEstablished()
         [nextConnSocket, this](){
             auto &info = connectionMap[nextConnSocket];
             switch(info.stage){
-            case StageHeader:
-                readInitMessageHeader(nextConnSocket);
+            case StageInitHeader:
+                readMessageHeader( nextConnSocket, StageInitBody );
                 break;
-            case StageBody:
+            case StageInitBody:
                 readInitMessageBody(nextConnSocket);
                 break;
-            case StageConnected:
+            case StageConnectedHeader:
+                readMessageHeader( nextConnSocket, StageConnectedBody );
+                break;
+            case StageConnectedBody:
                 this->slotDataAvailable( nextConnSocket, info.instanceId );
                 break;
             default:
@@ -376,7 +385,7 @@ void SingleApplicationPrivate::slotConnectionEstablished()
     );
 }
 
-void SingleApplicationPrivate::readInitMessageHeader( QLocalSocket *sock )
+void SingleApplicationPrivate::readMessageHeader( QLocalSocket *sock, SingleApplicationPrivate::ConnectionStage nextStage )
 {
     if (!connectionMap.contains( sock )){
         return;
@@ -396,27 +405,35 @@ void SingleApplicationPrivate::readInitMessageHeader( QLocalSocket *sock )
     quint64 msgLen = 0;
     headerStream >> msgLen;
     ConnectionInfo &info = connectionMap[sock];
-    info.stage = StageBody;
+    info.stage = nextStage;
     info.msgLen = msgLen;
 
     writeAck( sock );
 }
 
-void SingleApplicationPrivate::readInitMessageBody( QLocalSocket *sock )
+bool SingleApplicationPrivate::isFrameComplete( QLocalSocket *sock )
 {
-    Q_Q(SingleApplication);
-
     if (!connectionMap.contains( sock )){
-        return;
+        return false;
     }
 
     ConnectionInfo &info = connectionMap[sock];
     if( sock->bytesAvailable() < ( qint64 )info.msgLen ){
-        return;
+        return false;
     }
 
+    return true;
+}
+
+void SingleApplicationPrivate::readInitMessageBody( QLocalSocket *sock )
+{
+    Q_Q(SingleApplication);
+
+    if( !isFrameComplete( sock ) )
+        return;
+
     // Read the message body
-    QByteArray msgBytes = sock->read(info.msgLen);
+    QByteArray msgBytes = sock->readAll();
     QDataStream readStream(msgBytes);
 
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
@@ -456,8 +473,9 @@ void SingleApplicationPrivate::readInitMessageBody( QLocalSocket *sock )
         return;
     }
 
+    ConnectionInfo &info = connectionMap[sock];
     info.instanceId = instanceId;
-    info.stage = StageConnected;
+    info.stage = StageConnectedHeader;
 
     if( connectionType == NewInstance ||
         ( connectionType == SecondaryInstance &&
@@ -472,9 +490,16 @@ void SingleApplicationPrivate::readInitMessageBody( QLocalSocket *sock )
 void SingleApplicationPrivate::slotDataAvailable( QLocalSocket *dataSocket, quint32 instanceId )
 {
     Q_Q(SingleApplication);
+
+    if ( !isFrameComplete( dataSocket ) )
+        return;
+
     Q_EMIT q->receivedMessage( instanceId, dataSocket->readAll() );
 
     writeAck( dataSocket );
+
+    ConnectionInfo &info = connectionMap[dataSocket];
+    info.stage = StageConnectedHeader;
 }
 
 void SingleApplicationPrivate::slotClientConnectionClosed( QLocalSocket *closedSocket, quint32 instanceId )
diff --git a/singleapplication_p.h b/singleapplication_p.h
index 0777c33..58507cf 100644
--- a/singleapplication_p.h
+++ b/singleapplication_p.h
@@ -61,9 +61,10 @@ public:
         Reconnect = 3
     };
     enum ConnectionStage : quint8 {
-        StageHeader = 0,
-        StageBody = 1,
-        StageConnected = 2,
+        StageInitHeader = 0,
+        StageInitBody = 1,
+        StageConnectedHeader = 2,
+        StageConnectedBody = 3,
     };
     Q_DECLARE_PUBLIC(SingleApplication)
 
@@ -79,10 +80,12 @@ public:
     quint16 blockChecksum() const;
     qint64 primaryPid() const;
     QString primaryUser() const;
-    void readInitMessageHeader(QLocalSocket *socket);
+    bool isFrameComplete(QLocalSocket *sock);
+    void readMessageHeader(QLocalSocket *socket, ConnectionStage nextStage);
     void readInitMessageBody(QLocalSocket *socket);
-    bool writeConfirmedMessage(int msecs, const QByteArray &msg);
     void writeAck(QLocalSocket *sock);
+    bool writeConfirmedFrame(int msecs, const QByteArray &msg);
+    bool writeConfirmedMessage(int msecs, const QByteArray &msg);
     static void randomSleep();
     void addAppData(const QString &data);
     QStringList appData() const;