add lock free queue

utils/lfqueue.h

@@ -0,0 +1,91 @@
+#ifndef LFQUEUE_H
+#define LFQUEUE_H
+
+#include <QObject>
+#include <QDebug>
+
+
+/* macros */
+#define IS_EMPTY()  (  mWIdx.load()             == mRIdx.load() )
+#define IS_FULL()   ( (mWIdx.load()+1)%mSize    == mRIdx.load() )
+
+
+template<class T>
+class LFQueue
+{
+public:
+    LFQueue() : mSize(0), mArray(NULL){}
+
+    ~LFQueue() {setSize(0);}
+
+    bool setSize(int size) {
+        if(size<0)
+            return false;
+
+        if(mArray) {
+            delete[] mArray;
+            mArray = NULL;
+        }
+
+        if(size>0) {
+            mArray = new T[size];
+            if(mArray)
+                mSize = size;
+            return ( mArray!=NULL );
+        }
+
+        return true;
+    }
+
+    void flush() {
+        mRIdx.store(0);
+        mWIdx.store(0);
+    }
+
+    T* get() {
+        if(IS_FULL())
+            return NULL;
+
+        return &(mArray[mWIdx.loadAcquire()]); /* prevent memory reordering (belt and braces) */
+    }
+
+
+    void queue() {
+        #ifdef QT_DEBUG
+        if(IS_FULL())
+            qCritical() << "BUG: queueing in full queue";
+        #endif
+
+        int wIdx = mWIdx.load();
+        mWIdx.storeRelease((wIdx+1)%mSize);
+    }
+
+
+    T* peek() {
+        if(IS_EMPTY())
+            return NULL;
+
+        return &(mArray[mRIdx.loadAcquire()]); /* prevent memory reordering (belt and braces) */
+    }
+
+
+    void dequeue() {
+        #ifdef QT_DEBUG
+        if(IS_EMPTY())
+            qCritical() << "BUG: dequeueing an empty queue";
+        #endif
+
+        int rIdx = mRIdx.load();
+        mRIdx.storeRelease((rIdx+1)%mSize);
+    }
+
+
+private:
+    int mSize;
+    T*  mArray;
+
+    QAtomicInt mRIdx;
+    QAtomicInt mWIdx;
+};
+
+#endif // LFQUEUE_H