use socket for single instance guard

src/core/singleinstanceguard.cpp

@@ -1,184 +1,225 @@
 #include "singleinstanceguard.h"
+
 #include <QDebug>
+#include <QLocalServer>
+#include <QLocalSocket>
+#include <QDataStream>
+#include <QByteArray>
 
 #include <utils/utils.h>
 
 using namespace vnotex;
 
-const QString SingleInstanceGuard::c_memKey = "vnotex_shared_memory";
-const int SingleInstanceGuard::c_magic = 376686683;
+const QString SingleInstanceGuard::c_serverName = "vnote";
 
 SingleInstanceGuard::SingleInstanceGuard()
-    : m_online(false),
-      m_sharedMemory(c_memKey)
 {
+    qInfo() << "guarding is on";
+}
+
+SingleInstanceGuard::~SingleInstanceGuard()
+{
+    qInfo() << "guarding is off";
+    exit();
 }
 
 bool SingleInstanceGuard::tryRun()
 {
-    m_online = false;
+    Q_ASSERT(!m_online);
 
-    // If we can attach to the sharedmemory, there is another instance running.
-    // In Linux, crashes may cause the shared memory segment remains. In this case,
-    // this will attach to the old segment, then exit, freeing the old segment.
-    if (m_sharedMemory.attach()) {
-        qInfo() << "another instance is running";
+#if defined(Q_OS_WIN)
+    // On Windows, multiple servers on the same name are allowed.
+    m_client = tryConnect();
+    if (m_client) {
+        // There is one server running and we are now connected, so we could not continue.
         return false;
     }
 
-    // Try to create it.
-    bool ret = m_sharedMemory.create(sizeof(SharedStruct));
-    if (ret) {
-        // We created it.
-        m_sharedMemory.lock();
-        SharedStruct *str = (SharedStruct *)m_sharedMemory.data();
-        str->m_magic = c_magic;
-        str->m_filesBufIdx = 0;
-        str->m_askedToShow = false;
-        m_sharedMemory.unlock();
+    m_server = tryListen();
+    if (m_server) {
+        // We are the lucky one.
+        qInfo() << "guard succeeds to run";
+    } else {
+        // We still allow the guard to run. There maybe a bug need to fix.
+        qWarning() << "failed to connect to an existing instance or establish a new local server";
+    }
+#else
+    m_server = tryListen();
+    if (m_server) {
+        // We are the lucky one.
+        qInfo() << "guard succeeds to run";
+    } else {
+        // Here we are sure there is another instance running. But we still use a socket to connect to make sure.
+        m_client = tryConnect();
+        if (m_client) {
+            // We are sure there is another instance running.
+            return false;
+        }
+
+        // We still allow the guard to run. There maybe a bug need to fix.
+        qWarning() << "failed to connect to an existing instance or establish a new local server";
+    }
+#endif
+
+    setupServer();
 
     m_online = true;
     return true;
-    } else {
-        qCritical() << "fail to create shared memory segment";
-        return false;
-    }
 }
 
-void SingleInstanceGuard::openExternalFiles(const QStringList &p_files)
+void SingleInstanceGuard::requestOpenFiles(const QStringList &p_files)
 {
     if (p_files.isEmpty()) {
         return;
     }
-
-    if (!m_sharedMemory.isAttached()) {
-        if (!m_sharedMemory.attach()) {
-            qCritical() << "fail to attach to the shared memory segment"
-                        << (m_sharedMemory.error() ? m_sharedMemory.errorString() : "");
-            return;
-        }
-    }
-
-    int idx = 0;
-    int tryCount = 100;
-    while (tryCount--) {
-        m_sharedMemory.lock();
-        SharedStruct *str = (SharedStruct *)m_sharedMemory.data();
-        V_ASSERT(str->m_magic == c_magic);
-        for (; idx < p_files.size(); ++idx) {
-            if (p_files[idx].size() + 1 > FilesBufCount) {
-                // Skip this long long name file.
-                continue;
-            }
-
-            if (!appendFileToBuffer(str, p_files[idx])) {
-                break;
-            }
-        }
-
-        m_sharedMemory.unlock();
-
-        if (idx < p_files.size()) {
-            Utils::sleepWait(500);
-        } else {
-            break;
-        }
-    }
 }
 
-bool SingleInstanceGuard::appendFileToBuffer(SharedStruct *p_str, const QString &p_file)
+void SingleInstanceGuard::requestShow()
 {
-    if (p_file.isEmpty()) {
-        return true;
+    Q_ASSERT(!m_online);
+    if (!m_client || m_client->state() != QLocalSocket::ConnectedState) {
+        qWarning() << "failed to request show" << m_client->errorString();
+        return ;
     }
 
-    int strSize = p_file.size();
-    if (strSize + 1 > FilesBufCount - p_str->m_filesBufIdx) {
-        return false;
-    }
-
-    // Put the size first.
-    p_str->m_filesBuf[p_str->m_filesBufIdx++] = (ushort)strSize;
-    const QChar *data = p_file.constData();
-    for (int i = 0; i < strSize; ++i) {
-        p_str->m_filesBuf[p_str->m_filesBufIdx++] = data[i].unicode();
-    }
-
-    return true;
-}
-
-QStringList SingleInstanceGuard::fetchFilesToOpen()
-{
-    QStringList files;
-
-    if (!m_online) {
-        return files;
-    }
-
-    Q_ASSERT(m_sharedMemory.isAttached());
-    m_sharedMemory.lock();
-    SharedStruct *str = (SharedStruct *)m_sharedMemory.data();
-    V_ASSERT(str->m_magic == c_magic);
-    Q_ASSERT(str->m_filesBufIdx <= FilesBufCount);
-    int idx = 0;
-    while (idx < str->m_filesBufIdx) {
-        int strSize = str->m_filesBuf[idx++];
-        Q_ASSERT(strSize <= str->m_filesBufIdx - idx);
-        QString file;
-        for (int i = 0; i < strSize; ++i) {
-            file.append(QChar(str->m_filesBuf[idx++]));
-        }
-
-        files.append(file);
-    }
-
-    str->m_filesBufIdx = 0;
-    m_sharedMemory.unlock();
-
-    return files;
-}
-
-void SingleInstanceGuard::showInstance()
-{
-    if (!m_sharedMemory.isAttached()) {
-        if (!m_sharedMemory.attach()) {
-            qCritical() << "fail to attach to the shared memory segment"
-                        << (m_sharedMemory.error() ? m_sharedMemory.errorString() : "");
-            return;
-        }
-    }
-
-    m_sharedMemory.lock();
-    SharedStruct *str = (SharedStruct *)m_sharedMemory.data();
-    V_ASSERT(str->m_magic == c_magic);
-    str->m_askedToShow = true;
-    m_sharedMemory.unlock();
-}
-
-bool SingleInstanceGuard::fetchAskedToShow()
-{
-    if (!m_online) {
-        return false;
-    }
-
-    Q_ASSERT(m_sharedMemory.isAttached());
-    m_sharedMemory.lock();
-    SharedStruct *str = (SharedStruct *)m_sharedMemory.data();
-    V_ASSERT(str->m_magic == c_magic);
-    bool ret = str->m_askedToShow;
-    str->m_askedToShow = false;
-    m_sharedMemory.unlock();
-
-    return ret;
+    sendRequest(m_client.data(), OpCode::Show, QString());
 }
 
 void SingleInstanceGuard::exit()
 {
-    if (!m_online) {
+    m_online = false;
+
+    if (m_client) {
+        m_client->disconnectFromServer();
+        m_client.clear();
+    }
+
+    if (m_server) {
+        m_server->close();
+        m_server.clear();
+    }
+}
+
+QSharedPointer<QLocalSocket> SingleInstanceGuard::tryConnect()
+{
+    auto socket = QSharedPointer<QLocalSocket>::create();
+    socket->connectToServer(c_serverName);
+    if (socket->waitForConnected(200)) {
+        // Connected.
+        qDebug() << "socket connected to server" << c_serverName;
+        return socket;
+    } else {
+        qDebug() << "socket connect timeout";
+        return nullptr;
+    }
+}
+
+QSharedPointer<QLocalServer> SingleInstanceGuard::tryListen()
+{
+    auto server = QSharedPointer<QLocalServer>::create();
+    bool ret = server->listen(c_serverName);
+    if (!ret && server->serverError() == QAbstractSocket::AddressInUseError) {
+        // On Unix, a previous crash may leave a server running.
+        // Clean up and try again.
+        QLocalServer::removeServer(c_serverName);
+        ret = server->listen(c_serverName);
+    }
+
+    if (ret) {
+        qDebug() << "local server listening on" << c_serverName;
+        return server;
+    } else {
+        qDebug() << "failed to start local server";
+        return nullptr;
+    }
+}
+
+void SingleInstanceGuard::setupServer()
+{
+    if (!m_server) {
         return;
     }
 
-    Q_ASSERT(m_sharedMemory.isAttached());
-    m_sharedMemory.detach();
-    m_online = false;
+    connect(m_server.data(), &QLocalServer::newConnection,
+            this, [this]() {
+                auto socket = m_server->nextPendingConnection();
+                if (socket) {
+                    qInfo() << "local server receives new connect" << socket;
+                    if (m_ongoingConnect) {
+                        qWarning() << "drop the connection since there is one ongoing connect";
+                        socket->disconnectFromServer();
+                        socket->deleteLater();
+                        return;
+                    }
+
+                    m_ongoingConnect = true;
+                    m_command.clear();
+
+                    connect(socket, &QLocalSocket::disconnected,
+                            this, [this, socket]() {
+                                Q_ASSERT(m_ongoingConnect);
+                                socket->deleteLater();
+                                m_ongoingConnect = false;
+                            });
+                    connect(socket, &QLocalSocket::readyRead,
+                            this, [this, socket]() {
+                                receiveCommand(socket);
+                            });
+                }
+            });
+}
+
+void SingleInstanceGuard::receiveCommand(QLocalSocket *p_socket)
+{
+    QDataStream inStream;
+    inStream.setDevice(p_socket);
+    inStream.setVersion(QDataStream::Qt_5_12);
+
+    if (m_command.m_opCode == OpCode::Null) {
+        // Relies on the fact that QDataStream serializes a quint32 into
+        // sizeof(quint32) bytes.
+        if (p_socket->bytesAvailable() < (int)sizeof(quint32) * 2) {
+            return;
+        }
+
+        quint32 opCode = 0;
+        inStream >> opCode;
+        m_command.m_opCode = static_cast<OpCode>(opCode);
+        inStream >> m_command.m_size;
+    }
+
+    if (p_socket->bytesAvailable() < m_command.m_size) {
+        return;
+    }
+
+    qDebug() << "op code" << m_command.m_opCode << m_command.m_size;
+
+    switch (m_command.m_opCode) {
+    case OpCode::Show:
+        Q_ASSERT(m_command.m_size == 0);
+        emit showRequested();
+        break;
+
+    default:
+        qWarning() << "unknown op code" << m_command.m_opCode;
+        break;
+    }
+}
+
+void SingleInstanceGuard::sendRequest(QLocalSocket *p_socket, OpCode p_code, const QString &p_payload)
+{
+    QByteArray block;
+    QDataStream out(&block, QIODevice::WriteOnly);
+    out.setVersion(QDataStream::Qt_5_12);
+    out << static_cast<quint32>(p_code);
+    out << static_cast<quint32>(p_payload.size());
+    if (p_payload.size() > 0) {
+        out << p_payload;
+    }
+    p_socket->write(block);
+    if (p_socket->waitForBytesWritten(3000)) {
+        qDebug() << "request sent" << p_code << p_payload.size();
+    } else {
+        qWarning() << "failed to send request" << p_code;
+    }
 }

src/core/singleinstanceguard.h

@@ -1,68 +1,83 @@
 #ifndef SINGLEINSTANCEGUARD_H
 #define SINGLEINSTANCEGUARD_H
 
-#include <QSharedMemory>
-#include <QStringList>
+#include <QObject>
+#include <QString>
+#include <QSharedPointer>
+
+class QLocalServer;
+class QLocalSocket;
 
 namespace vnotex
 {
-    class SingleInstanceGuard
+    class SingleInstanceGuard : public QObject
     {
+        Q_OBJECT
     public:
         SingleInstanceGuard();
 
-        // Return ture if this is the only instance of VNote.
+        ~SingleInstanceGuard();
+
+        // Try to run. Return true on success.
         bool tryRun();
 
-        // There is already another instance running.
-        // Call this to ask that instance to open external files passed in
-        // via command line arguments.
-        void openExternalFiles(const QStringList &p_files);
-
-        // Ask another instance to show itself.
-        void showInstance();
-
-        // Fetch files from shared memory to open.
-        // Will clear the shared memory.
-        QStringList fetchFilesToOpen();
-
-        // Whether this instance is asked to show itself.
-        bool fetchAskedToShow();
-
+        // Server API.
+    public:
         // A running instance requests to exit.
         void exit();
 
+        // Clients API.
+    public:
+        void requestOpenFiles(const QStringList &p_files);
+
+        void requestShow();
+
+    signals:
+        void openFilesRequested(const QStringList &p_files);
+
+        void showRequested();
+
     private:
-        // The count of the entries in the buffer to hold the path of the files to open.
-        enum { FilesBufCount = 1024 };
-
-        struct SharedStruct {
-            // A magic number to identify if this struct is initialized
-            int m_magic;
-
-            // Next empty entry in m_filesBuf.
-            int m_filesBufIdx;
-
-            // File paths to be opened.
-            // Encoded in this way with 2 bytes for each size part.
-            // [size of file1][file1][size of file2][file 2]
-            // Unicode representation of QString.
-            ushort m_filesBuf[FilesBufCount];
-
-            // Whether other instances ask to show the legal instance.
-            bool m_askedToShow;
+        enum OpCode
+        {
+            Null = 0,
+            Show
         };
 
-        // Append @p_file to the shared struct files buffer.
-        // Returns true if succeeds or false if there is no enough space.
-        bool appendFileToBuffer(SharedStruct *p_str, const QString &p_file);
+        struct Command
+        {
+            void clear()
+            {
+                m_opCode = OpCode::Null;
+                m_size = 0;
+            }
 
-        bool m_online;
+            OpCode m_opCode = OpCode::Null;
+            int m_size = 0;
+        };
 
-        QSharedMemory m_sharedMemory;
+        QSharedPointer<QLocalSocket> tryConnect();
 
-        static const QString c_memKey;
-        static const int c_magic;
+        QSharedPointer<QLocalServer> tryListen();
+
+        void setupServer();
+
+        void receiveCommand(QLocalSocket *p_socket);
+
+        void sendRequest(QLocalSocket *p_socket, OpCode p_code, const QString &p_payload);
+
+        // Whether succeeded to run.
+        bool m_online = false;
+
+        QSharedPointer<QLocalSocket> m_client;
+
+        QSharedPointer<QLocalServer> m_server;
+
+        bool m_ongoingConnect = false;
+
+        Command m_command;
+
+        static const QString c_serverName;
     };
 } // ns vnotex
 

src/main.cpp

@@ -30,12 +30,6 @@ void initWebEngineSettings();
 
 int main(int argc, char *argv[])
 {
-    SingleInstanceGuard guard;
-    bool canRun = guard.tryRun();
-    if (!canRun) {
-        return 0;
-    }
-
     QTextCodec *codec = QTextCodec::codecForName("UTF8");
     if (codec) {
         QTextCodec::setCodecForLocale(codec);
@@ -75,12 +69,22 @@ int main(int argc, char *argv[])
 
     initWebEngineSettings();
 
+    {
         const QString iconPath = ":/vnotex/data/core/icons/vnote.ico";
         // Make sense only on Windows.
         app.setWindowIcon(QIcon(iconPath));
 
         app.setApplicationName(ConfigMgr::c_appName);
         app.setOrganizationName(ConfigMgr::c_orgName);
+    }
+
+    // Guarding.
+    SingleInstanceGuard guard;
+    bool canRun = guard.tryRun();
+    if (!canRun) {
+        guard.requestShow();
+        return 0;
+    }
 
     try {
         app.setApplicationVersion(ConfigMgr::getInst().getConfig().getVersion());
@@ -125,6 +129,9 @@ int main(int argc, char *argv[])
     window.show();
     VNoteX::getInst().getThemeMgr().setBaseBackground(window.palette().color(QPalette::Base));
 
+    QObject::connect(&guard, &SingleInstanceGuard::showRequested,
+                     &window, &MainWindow::showMainWindow);
+
     window.kickOffOnStart();
 
     int ret = app.exec();