JavaScriptCore-903.tar.gz

[apple/javascriptcore.git] / heap / Strong.h

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+/*
+ * Copyright (C) 2011 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef Strong_h
+#define Strong_h
+
+#include "Assertions.h"
+#include "Handle.h"
+#include "HandleHeap.h"
+
+namespace JSC {
+
+class JSGlobalData;
+HandleSlot allocateGlobalHandle(JSGlobalData&);
+
+// A strongly referenced handle that prevents the object it points to from being garbage collected.
+template <typename T> class Strong : public Handle<T> {
+    using Handle<T>::slot;
+    using Handle<T>::setSlot;
+
+public:
+    typedef typename Handle<T>::ExternalType ExternalType;
+    
+    Strong()
+        : Handle<T>()
+    {
+    }
+    
+    Strong(JSGlobalData& globalData, ExternalType value = ExternalType())
+        : Handle<T>(allocateGlobalHandle(globalData))
+    {
+        set(value);
+    }
+
+    Strong(JSGlobalData& globalData, Handle<T> handle)
+        : Handle<T>(allocateGlobalHandle(globalData))
+    {
+        set(handle.get());
+    }
+    
+    Strong(const Strong& other)
+        : Handle<T>()
+    {
+        if (!other.slot())
+            return;
+        setSlot(HandleHeap::heapFor(other.slot())->allocate());
+        set(other.get());
+    }
+
+    template <typename U> Strong(const Strong<U>& other)
+        : Handle<T>()
+    {
+        if (!other.slot())
+            return;
+        setSlot(HandleHeap::heapFor(other.slot())->allocate());
+        set(other.get());
+    }
+    
+    enum HashTableDeletedValueTag { HashTableDeletedValue };
+    bool isHashTableDeletedValue() const { return slot() == hashTableDeletedValue(); }
+    Strong(HashTableDeletedValueTag)
+        : Handle<T>(hashTableDeletedValue())
+    {
+    }
+
+    ~Strong()
+    {
+        clear();
+    }
+
+    void swap(Strong& other)
+    {
+        Handle<T>::swap(other);
+    }
+
+    void set(JSGlobalData& globalData, ExternalType value)
+    {
+        if (!slot())
+            setSlot(allocateGlobalHandle(globalData));
+        set(value);
+    }
+
+    template <typename U> Strong& operator=(const Strong<U>& other)
+    {
+        if (!other.slot()) {
+            clear();
+            return *this;
+        }
+
+        set(*HandleHeap::heapFor(other.slot())->globalData(), other.get());
+        return *this;
+    }
+    
+    Strong& operator=(const Strong& other)
+    {
+        if (!other.slot()) {
+            clear();
+            return *this;
+        }
+
+        set(*HandleHeap::heapFor(other.slot())->globalData(), other.get());
+        return *this;
+    }
+
+    void clear()
+    {
+        if (!slot())
+            return;
+        HandleHeap::heapFor(slot())->deallocate(slot());
+        setSlot(0);
+    }
+
+private:
+    static HandleSlot hashTableDeletedValue() { return reinterpret_cast<HandleSlot>(-1); }
+
+    void set(ExternalType externalType)
+    {
+        ASSERT(slot());
+        JSValue value = HandleTypes<T>::toJSValue(externalType);
+        HandleHeap::heapFor(slot())->writeBarrier(slot(), value);
+        *slot() = value;
+    }
+};
+
+template<class T> inline void swap(Strong<T>& a, Strong<T>& b)
+{
+    a.swap(b);
+}
+
+} // namespace JSC
+
+namespace WTF {
+
+template<typename T> struct VectorTraits<JSC::Strong<T> > : SimpleClassVectorTraits {
+    static const bool canCompareWithMemcmp = false;
+};
+
+template<typename P> struct HashTraits<JSC::Strong<P> > : SimpleClassHashTraits<JSC::Strong<P> > { };
+
+}
+
+#endif // Strong_h