SingleApplication

client/3rd/SingleApplication/singleapplication.cpp

@@ -0,0 +1,274 @@
+// The MIT License (MIT)
+//
+// Copyright (c) Itay Grudev 2015 - 2020
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#include <QtCore/QElapsedTimer>
+#include <QtCore/QByteArray>
+#include <QtCore/QSharedMemory>
+
+#include "singleapplication.h"
+#include "singleapplication_p.h"
+
+/**
+ * @brief Constructor. Checks and fires up LocalServer or closes the program
+ * if another instance already exists
+ * @param argc
+ * @param argv
+ * @param allowSecondary Whether to enable secondary instance support
+ * @param options Optional flags to toggle specific behaviour
+ * @param timeout Maximum time blocking functions are allowed during app load
+ */
+SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSecondary, Options options, int timeout, const QString &userData )
+    : app_t( argc, argv ), d_ptr( new SingleApplicationPrivate( this ) )
+{
+    Q_D( SingleApplication );
+
+#if defined(Q_OS_ANDROID) || defined(Q_OS_IOS)
+    // On Android and iOS since the library is not supported fallback to
+    // standard QApplication behaviour by simply returning at this point.
+    qWarning() << "SingleApplication is not supported on Android and iOS systems.";
+    return;
+#endif
+
+    // Store the current mode of the program
+    d->options = options;
+
+    // Add any unique user data
+    if ( ! userData.isEmpty() )
+        d->addAppData( userData );
+
+    // Generating an application ID used for identifying the shared memory
+    // block and QLocalServer
+    d->genBlockServerName();
+
+    // To mitigate QSharedMemory issues with large amount of processes
+    // attempting to attach at the same time
+    SingleApplicationPrivate::randomSleep();
+
+#ifdef Q_OS_UNIX
+    // By explicitly attaching it and then deleting it we make sure that the
+    // memory is deleted even after the process has crashed on Unix.
+    d->memory = new QSharedMemory( d->blockServerName );
+    d->memory->attach();
+    delete d->memory;
+#endif
+    // Guarantee thread safe behaviour with a shared memory block.
+    d->memory = new QSharedMemory( d->blockServerName );
+
+    // Create a shared memory block
+    if( d->memory->create( sizeof( InstancesInfo ) )){
+        // Initialize the shared memory block
+        if( ! d->memory->lock() ){
+          qCritical() << "SingleApplication: Unable to lock memory block after create.";
+          abortSafely();
+        }
+        d->initializeMemoryBlock();
+    } else {
+        if( d->memory->error() == QSharedMemory::AlreadyExists ){
+          // Attempt to attach to the memory segment
+          if( ! d->memory->attach() ){
+              qCritical() << "SingleApplication: Unable to attach to shared memory block.";
+              abortSafely();
+          }
+          if( ! d->memory->lock() ){
+            qCritical() << "SingleApplication: Unable to lock memory block after attach.";
+            abortSafely();
+          }
+        } else {
+          qCritical() << "SingleApplication: Unable to create block.";
+          abortSafely();
+        }
+    }
+
+    auto *inst = static_cast<InstancesInfo*>( d->memory->data() );
+    QElapsedTimer time;
+    time.start();
+
+    // Make sure the shared memory block is initialised and in consistent state
+    while( true ){
+      // If the shared memory block's checksum is valid continue
+      if( d->blockChecksum() == inst->checksum ) break;
+
+      // If more than 5s have elapsed, assume the primary instance crashed and
+      // assume it's position
+      if( time.elapsed() > 5000 ){
+          qWarning() << "SingleApplication: Shared memory block has been in an inconsistent state from more than 5s. Assuming primary instance failure.";
+          d->initializeMemoryBlock();
+      }
+
+      // Otherwise wait for a random period and try again. The random sleep here
+      // limits the probability of a collision between two racing apps and
+      // allows the app to initialise faster
+      if( ! d->memory->unlock() ){
+        qDebug() << "SingleApplication: Unable to unlock memory for random wait.";
+        qDebug() << d->memory->errorString();
+      }
+      SingleApplicationPrivate::randomSleep();
+      if( ! d->memory->lock() ){
+        qCritical() << "SingleApplication: Unable to lock memory after random wait.";
+        abortSafely();
+      }
+    }
+
+    if( inst->primary == false ){
+        d->startPrimary();
+        if( ! d->memory->unlock() ){
+          qDebug() << "SingleApplication: Unable to unlock memory after primary start.";
+          qDebug() << d->memory->errorString();
+        }
+        return;
+    }
+
+    // Check if another instance can be started
+    if( allowSecondary ){
+        d->startSecondary();
+        if( d->options & Mode::SecondaryNotification ){
+            d->connectToPrimary( timeout, SingleApplicationPrivate::SecondaryInstance );
+        }
+        if( ! d->memory->unlock() ){
+          qDebug() << "SingleApplication: Unable to unlock memory after secondary start.";
+          qDebug() << d->memory->errorString();
+        }
+        return;
+    }
+
+    if( ! d->memory->unlock() ){
+      qDebug() << "SingleApplication: Unable to unlock memory at end of execution.";
+      qDebug() << d->memory->errorString();
+    }
+
+    d->connectToPrimary( timeout, SingleApplicationPrivate::NewInstance );
+
+    delete d;
+
+    ::exit( EXIT_SUCCESS );
+}
+
+SingleApplication::~SingleApplication()
+{
+    Q_D( SingleApplication );
+    delete d;
+}
+
+/**
+ * Checks if the current application instance is primary.
+ * @return Returns true if the instance is primary, false otherwise.
+ */
+bool SingleApplication::isPrimary() const
+{
+    Q_D( const SingleApplication );
+    return d->server != nullptr;
+}
+
+/**
+ * Checks if the current application instance is secondary.
+ * @return Returns true if the instance is secondary, false otherwise.
+ */
+bool SingleApplication::isSecondary() const
+{
+    Q_D( const SingleApplication );
+    return d->server == nullptr;
+}
+
+/**
+ * Allows you to identify an instance by returning unique consecutive instance
+ * ids. It is reset when the first (primary) instance of your app starts and
+ * only incremented afterwards.
+ * @return Returns a unique instance id.
+ */
+quint32 SingleApplication::instanceId() const
+{
+    Q_D( const SingleApplication );
+    return d->instanceNumber;
+}
+
+/**
+ * Returns the OS PID (Process Identifier) of the process running the primary
+ * instance. Especially useful when SingleApplication is coupled with OS.
+ * specific APIs.
+ * @return Returns the primary instance PID.
+ */
+qint64 SingleApplication::primaryPid() const
+{
+    Q_D( const SingleApplication );
+    return d->primaryPid();
+}
+
+/**
+ * Returns the username the primary instance is running as.
+ * @return Returns the username the primary instance is running as.
+ */
+QString SingleApplication::primaryUser() const
+{
+    Q_D( const SingleApplication );
+    return d->primaryUser();
+}
+
+/**
+ * Returns the username the current instance is running as.
+ * @return Returns the username the current instance is running as.
+ */
+QString SingleApplication::currentUser() const
+{
+    return SingleApplicationPrivate::getUsername();
+}
+
+/**
+ * Sends message to the Primary Instance.
+ * @param message The message to send.
+ * @param timeout the maximum timeout in milliseconds for blocking functions.
+ * @return true if the message was sent successfuly, false otherwise.
+ */
+bool SingleApplication::sendMessage( const QByteArray &message, int timeout )
+{
+    Q_D( SingleApplication );
+
+    // Nobody to connect to
+    if( isPrimary() ) return false;
+
+    // Make sure the socket is connected
+    if( ! d->connectToPrimary( timeout,  SingleApplicationPrivate::Reconnect ) )
+      return false;
+
+    d->socket->write( message );
+    bool dataWritten = d->socket->waitForBytesWritten( timeout );
+    d->socket->flush();
+    return dataWritten;
+}
+
+/**
+ * Cleans up the shared memory block and exits with a failure.
+ * This function halts program execution.
+ */
+void SingleApplication::abortSafely()
+{
+    Q_D( SingleApplication );
+
+    qCritical() << "SingleApplication: " << d->memory->error() << d->memory->errorString();
+    delete d;
+    ::exit( EXIT_FAILURE );
+}
+
+QStringList SingleApplication::userData() const
+{
+    Q_D( const SingleApplication );
+    return d->appData();
+}