For some reason, Boost provides no good way to return a scoped lock.

It appears people usually fake it by not using RAII. This tiny bit of
ugliness will make returned scope lock holders work.

ScopedLock.h

@@ -0,0 +1,52 @@
+#ifndef __SCOPEDLOCKHOLDER__
+#define __SCOPEDLOCKHOLDER__
+
+#include "boost/thread/mutex.hpp"
+
+// This is a returnable lock holder.
+// I don't know why Boost doesn't provide a good way to do this.
+
+class ScopedLock
+{
+private:
+    boost::mutex *mMutex;	// parent object has greater scope, so guaranteed valid
+    mutable bool mValid;
+
+    ScopedLock();		// no implementation
+    
+public:
+    ScopedLock(boost::mutex &mutex) : mMutex(&mutex), mValid(true)
+    {
+        mMutex->lock();
+    }
+
+    ~ScopedLock()
+    {
+        if(mValid) mMutex->unlock();
+    }
+
+    ScopedLock(const ScopedLock &sl)
+    {
+    	mMutex=sl.mMutex;
+    	if(sl.mValid)
+    	{
+    		mValid=true;
+    		sl.mValid=false;
+        }
+	else mValid=false;
+    }
+
+    ScopedLock &operator=(const ScopedLock &sl)
+    { // we inherit any lock the other class member had
+        if(mValid) mMutex->unlock();
+        mMutex=sl.mMutex;
+        if(sl.mValid)
+        {
+            if(mValid) mMutex->unlock();
+            mValid=true;
+            sl.mValid=false;
+        }
+    }
+};
+
+#endif