Implemented single-instance support (Part #1).

MediaInfoXP.vcxproj

@@ -125,6 +125,7 @@
     </CustomBuild>
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="src\IPC.cpp" />
     <ClCompile Include="src\Main.cpp" />
     <ClCompile Include="src\MainWindow.cpp" />
     <ClCompile Include="src\ShellExtension.cpp" />
@@ -144,6 +145,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="src\Config.h" />
+    <ClInclude Include="src\IPC.h" />
     <ClInclude Include="src\ShellExtension.h" />
     <ClInclude Include="src\Utils.h" />
   </ItemGroup>

MediaInfoXP.vcxproj.filters

@@ -51,6 +51,9 @@
     <ClCompile Include="src\ShellExtension.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="src\IPC.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="src\Config.h">
@@ -62,6 +65,9 @@
     <ClInclude Include="src\ShellExtension.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="src\IPC.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="MediaInfoXP.rcx" />

src/IPC.cpp

@@ -0,0 +1,219 @@
+///////////////////////////////////////////////////////////////////////////////
+// MediaInfoXP
+// Copyright (C) 2004-2014 LoRd_MuldeR <MuldeR2@GMX.de>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// http://www.gnu.org/licenses/gpl-2.0.txt
+///////////////////////////////////////////////////////////////////////////////
+
+#include "IPC.h"
+
+#include "Utils.h"
+
+#include <QSharedMemory>
+#include <QSystemSemaphore>
+#include <QThread>
+
+static const size_t MAX_STR_LEN = 1024;
+static const size_t MAX_ENTRIES = 16;
+
+static const char *s_key_smemory = "{35DE4BDD-F88C-41E1-8080-2EDC503757F2}";
+static const char *s_key_sema_wr = "{C638D990-7553-4D4D-95E8-9B040BA6AE87}";
+static const char *s_key_sema_rd = "{0C30B0B2-0B03-49D7-8DB3-A7D0DDDEA2B0}";
+
+typedef struct
+{
+	wchar_t data[MAX_ENTRIES][MAX_STR_LEN];
+	size_t posRd;
+	size_t posWr;
+}
+mixp_ipc_t;
+
+IPC::IPC(void)
+{
+	m_initialized  = -1;
+	m_sharedMemory = NULL;
+	m_semaphoreWr  = NULL;
+	m_semaphoreRd  = NULL;
+}
+
+IPC::~IPC(void)
+{
+	MIXP_DELETE_OBJ(m_sharedMemory);
+	MIXP_DELETE_OBJ(m_semaphoreWr);
+	MIXP_DELETE_OBJ(m_semaphoreRd);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+class SendThread : public QThread
+{
+public:
+	SendThread(IPC *ipc, const QString &str) : m_ipc(ipc), m_str(str)
+	{
+		m_result = false;
+	}
+	
+	virtual void run(void)
+	{
+		try
+		{
+			m_result = m_ipc->pushStr(m_str);
+		}
+		catch(...)
+		{
+			m_result = false;
+		}
+	}
+
+	inline bool result(void) { return m_result; }
+
+protected:
+	volatile bool m_result;
+	IPC *const m_ipc;
+	const QString m_str;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+int IPC::init(void)
+{
+	if(m_initialized >= 0)
+	{
+		return m_initialized;
+	}
+
+	m_semaphoreWr = new QSystemSemaphore(s_key_sema_wr, MAX_ENTRIES);
+	m_semaphoreRd = new QSystemSemaphore(s_key_sema_rd, 0);
+
+	if((m_semaphoreWr->error() != QSystemSemaphore::NoError) || (m_semaphoreRd->error() != QSystemSemaphore::NoError))
+	{
+		qWarning("IPC: Failed to created system semaphores!");
+		return -1;
+	}
+
+	m_sharedMemory = new QSharedMemory(s_key_smemory, this);
+
+	if(m_sharedMemory->create(sizeof(mixp_ipc_t)))
+	{
+		memset(m_sharedMemory->data(), 0, sizeof(mixp_ipc_t));
+		m_initialized = 1;
+		return 1;
+	}
+
+	if(m_sharedMemory->error() == QSharedMemory::AlreadyExists)
+	{
+		qDebug("Not the first instance -> attaching to existing shared memory");
+		if(m_sharedMemory->attach())
+		{
+			m_initialized = 0;
+			return 0;
+		}
+	}
+
+	qWarning("IPC: Failed to attach to the shared memory!");
+	return -1;
+}
+
+bool IPC::pushStr(const QString &str)
+{
+	if(m_initialized < 0)
+	{
+		qWarning("Error: IPC not initialized yet!");
+		return false;
+	}
+
+	if(!m_semaphoreWr->acquire())
+	{
+		qWarning("IPC: Failed to acquire semaphore!");
+		return false;
+	}
+
+	if(!m_sharedMemory->lock())
+	{
+		qWarning("IPC: Failed to lock shared memory!");
+		return false;
+	}
+
+	try
+	{
+		mixp_ipc_t *memory = (mixp_ipc_t*) m_sharedMemory->data();
+		wcsncpy_s(memory->data[memory->posWr], MAX_STR_LEN, (wchar_t*)str.utf16(), _TRUNCATE);
+		memory->posWr = (memory->posWr + 1) % MAX_ENTRIES;
+	}
+	catch(...)
+	{
+		/*ignore any exception*/
+	}
+
+	m_sharedMemory->unlock();
+	m_semaphoreRd->release();
+
+	return true;
+}
+
+bool IPC::popStr(QString &str)
+{
+	if(m_initialized < 0)
+	{
+		qWarning("Error: IPC not initialized yet!");
+		return false;
+	}
+
+	if(!m_semaphoreRd->acquire())
+	{
+		qWarning("IPC: Failed to acquire semaphore!");
+		return false;
+	}
+
+	if(!m_sharedMemory->lock())
+	{
+		qWarning("IPC: Failed to lock shared memory!");
+		return false;
+	}
+
+	try
+	{
+		mixp_ipc_t *memory = (mixp_ipc_t*) m_sharedMemory->data();
+		str = QString::fromUtf16((const ushort*)memory->data[memory->posRd]);
+		memory->posRd = (memory->posRd + 1) % MAX_ENTRIES;
+	}
+	catch(...)
+	{
+		/*ignore any exception*/
+	}
+
+	m_sharedMemory->unlock();
+	m_semaphoreWr->release();
+
+	return true;
+}
+
+bool IPC::sendAsync(const QString &str, const int timeout)
+{
+	SendThread sendThread(this, str);
+	sendThread.start();
+
+	if(!sendThread.wait(timeout))
+	{
+		qWarning("IPC send operation encountered timeout!");
+		sendThread.terminate();
+		sendThread.wait();
+		return false;
+	}
+
+	return sendThread.result();
+}

src/IPC.h

@@ -0,0 +1,50 @@
+///////////////////////////////////////////////////////////////////////////////
+// MediaInfoXP
+// Copyright (C) 2004-2014 LoRd_MuldeR <MuldeR2@GMX.de>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// http://www.gnu.org/licenses/gpl-2.0.txt
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include <QObject>
+
+class QSharedMemory;
+class QSystemSemaphore;
+
+class IPC : public QObject
+{
+public:
+	IPC(void);
+	~IPC(void);
+
+	int init(void);
+
+	//async support
+	bool sendAsync(const QString &str, const int timeout = 5000);
+	
+	//blocking operations
+	bool pushStr(const QString &str);
+	bool popStr(QString &str);
+
+protected:
+	int m_initialized;
+
+	QSharedMemory *m_sharedMemory;
+	QSystemSemaphore *m_semaphoreRd;
+	QSystemSemaphore *m_semaphoreWr;
+};

src/Main.cpp

@@ -47,6 +47,7 @@
 
 #include "Config.h"
 #include "MainWindow.h"
+#include "IPC.h"
 #include "Utils.h"
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -101,6 +102,21 @@ int mixp_main(int argc, char* argv[])
 	qDebug("Copyright (c) 2004-%s LoRd_MuldeR <mulder2@gmx.de>. Some rights reserved.", &mixp_buildDate[7]);
 	qDebug("Built with Qt v%s, running with Qt v%s.\n", QT_VERSION_STR, qVersion());
 
+	//Initialize IPC
+	IPC *ipc = new IPC();
+	if(ipc->init() == 0)
+	{
+		ipc->sendAsync("Test Hello World 123!");
+		return 0;
+	}
+
+	QString test;
+	qDebug("Awaiting data from other instance...");
+	if(ipc->popStr(test))
+	{
+		qDebug("Got the data: %s\n", test.toUtf8().constData());
+	}
+
 	QFile *lockFile = NULL;
 
 	//Get temp folder
@@ -108,6 +124,7 @@ int mixp_main(int argc, char* argv[])
 	if(tempFolder.isEmpty())
 	{
 		qFatal("Failed to determine TEMP folder!");
+		MIXP_DELETE_OBJ(ipc);
 		return 1;
 	}
 	
@@ -131,6 +148,7 @@ int mixp_main(int argc, char* argv[])
 	if(lockFile) lockFile->remove();
 	MIXP_DELETE_OBJ(lockFile);
 	mixp_clean_folder(tempFolder);
+	MIXP_DELETE_OBJ(ipc);
 
 	return exit_code;
 }