From 6d499d4e3a7c69a1ba5658937d797af1f1b3e97c Mon Sep 17 00:00:00 2001
From: Bim Overbohm <bim.overbohm@googlemail.com>
Date: Mon, 27 May 2013 12:38:39 +0200
Subject: [PATCH] Improve singleton implementation

Still not thread-safe, but a bit better now. Should be made thread-safe
and maybe get converted to a template, if possible.
---
 src/VolumeControl.cpp | 24 ++++++++++++++++++++----
 src/VolumeControl.h   |  6 ++++--
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/VolumeControl.cpp b/src/VolumeControl.cpp
index 45a442e02..95ac7535a 100644
--- a/src/VolumeControl.cpp
+++ b/src/VolumeControl.cpp
@@ -12,7 +12,7 @@
     const char * VolumeControl::mixerCard = "default";
 #endif
 
-std::shared_ptr<VolumeControl> VolumeControl::sInstance;
+std::weak_ptr<VolumeControl> VolumeControl::sInstance;
 
 
 VolumeControl::VolumeControl()
@@ -31,6 +31,20 @@ VolumeControl::VolumeControl()
 	originalVolume = getVolume();
 }
 
+VolumeControl::VolumeControl(const VolumeControl & right)
+{
+	sInstance = right.sInstance;
+}
+
+VolumeControl & VolumeControl::operator=(const VolumeControl & right)
+{
+	if (this != &right) {
+		sInstance = right.sInstance;
+	}
+
+	return *this;
+}
+
 VolumeControl::~VolumeControl()
 {
 	//set original volume levels for system
@@ -42,10 +56,12 @@ VolumeControl::~VolumeControl()
 std::shared_ptr<VolumeControl> & VolumeControl::getInstance()
 {
 	//check if an VolumeControl instance is already created, if not create one
-	if (sInstance == nullptr) {
-		sInstance = std::shared_ptr<VolumeControl>(new VolumeControl);
+	static std::shared_ptr<VolumeControl> sharedInstance = sInstance.lock();
+	if (sharedInstance == nullptr) {
+		sharedInstance.reset(new VolumeControl);
+		sInstance = sharedInstance;
 	}
-	return sInstance;
+	return sharedInstance;
 }
 
 void VolumeControl::init()
diff --git a/src/VolumeControl.h b/src/VolumeControl.h
index abfa4a556..8f35ea2c2 100644
--- a/src/VolumeControl.h
+++ b/src/VolumeControl.h
@@ -39,9 +39,11 @@ class VolumeControl
 	int originalVolume;
 	int internalVolume;
 
-	static std::shared_ptr<VolumeControl> sInstance;
+	static std::weak_ptr<VolumeControl> sInstance;
 
 	VolumeControl();
+	VolumeControl(const VolumeControl & right);
+    VolumeControl & operator=(const VolumeControl & right);
 
 public:
 	static std::shared_ptr<VolumeControl> & getInstance();
@@ -52,5 +54,5 @@ public:
 	int getVolume() const;
 	void setVolume(int volume);
 
-	virtual ~VolumeControl();
+	~VolumeControl();
 };