From 65672d3dfbdf179df520bbaa5e7e7ba28a27db20 Mon Sep 17 00:00:00 2001
From: Konstantinos Sideris <sideris.konstantin@gmail.com>
Date: Thu, 14 Dec 2017 21:55:00 +0200
Subject: Allow only one application instance

fixes #141
---
 src/RunGuard.cc | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 src/RunGuard.cc

(limited to 'src/RunGuard.cc')

diff --git a/src/RunGuard.cc b/src/RunGuard.cc
new file mode 100644
index 00000000..75833eb7
--- /dev/null
+++ b/src/RunGuard.cc
@@ -0,0 +1,84 @@
+#include "RunGuard.h"
+
+#include <QCryptographicHash>
+
+namespace {
+
+QString
+generateKeyHash(const QString &key, const QString &salt)
+{
+        QByteArray data;
+
+        data.append(key.toUtf8());
+        data.append(salt.toUtf8());
+        data = QCryptographicHash::hash(data, QCryptographicHash::Sha1).toHex();
+
+        return data;
+}
+}
+
+RunGuard::RunGuard(const QString &key)
+  : key(key)
+  , memLockKey(generateKeyHash(key, "_memLockKey"))
+  , sharedmemKey(generateKeyHash(key, "_sharedmemKey"))
+  , sharedMem(sharedmemKey)
+  , memLock(memLockKey, 1)
+{
+        memLock.acquire();
+        {
+                // Fix for *nix: http://habrahabr.ru/post/173281/
+                QSharedMemory fix(sharedmemKey);
+                fix.attach();
+        }
+
+        memLock.release();
+}
+
+RunGuard::~RunGuard() { release(); }
+
+bool
+RunGuard::isAnotherRunning()
+{
+        if (sharedMem.isAttached())
+                return false;
+
+        memLock.acquire();
+        const bool isRunning = sharedMem.attach();
+
+        if (isRunning)
+                sharedMem.detach();
+
+        memLock.release();
+
+        return isRunning;
+}
+
+bool
+RunGuard::tryToRun()
+{
+        // Extra check
+        if (isAnotherRunning())
+                return false;
+
+        memLock.acquire();
+        const bool result = sharedMem.create(sizeof(quint64));
+        memLock.release();
+
+        if (!result) {
+                release();
+                return false;
+        }
+
+        return true;
+}
+
+void
+RunGuard::release()
+{
+        memLock.acquire();
+
+        if (sharedMem.isAttached())
+                sharedMem.detach();
+
+        memLock.release();
+}
-- 
cgit 1.5.1