Sharing of SharedArrayBuffer via PostMessage transfer

Source/wtf/ArrayBufferContents.h

Index: Source/wtf/ArrayBufferContents.h
diff --git a/Source/wtf/ArrayBufferContents.h b/Source/wtf/ArrayBufferContents.h
index 4bd137f02ce984f0fe9c70f30e1564b269498f7a..b6476aa56c0ee3ddd2b8957907d2c81ff5484995 100644
--- a/Source/wtf/ArrayBufferContents.h
+++ b/Source/wtf/ArrayBufferContents.h
@@ -29,6 +29,8 @@
 
 #include "wtf/ArrayBufferDeallocationObserver.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/RefPtr.h"
+#include "wtf/ThreadSafeRefCounted.h"
 #include "wtf/WTFExport.h"
 
 namespace WTF {
@@ -41,35 +43,38 @@ public:
         DontInitialize
     };
 
+    enum SharingType {
+        NotShared,
+        Shared,
+    };
+
     ArrayBufferContents();
-    ArrayBufferContents(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
+    ArrayBufferContents(unsigned numElements, unsigned elementByteSize, SharingType isShared, ArrayBufferContents::InitializationPolicy);
 
     // Use with care. data must be allocated with allocateMemory.
     // ArrayBufferContents will take ownership of the data and free it (using freeMemory)
     // upon destruction.
     // This constructor will not call observer->StartObserving(), so it is a responsibility
     // of the caller to make sure JS knows about external memory.
-    ArrayBufferContents(void* data, unsigned sizeInBytes, ArrayBufferDeallocationObserver*);
+    ArrayBufferContents(void* data, unsigned sizeInBytes, SharingType isShared, ArrayBufferDeallocationObserver*);
 
     ~ArrayBufferContents();
 
     void clear();
 
-    void* data() const { return m_data; }
-    unsigned sizeInBytes() const { return m_sizeInBytes; }
+    void* data() const { return m_holder ? m_holder->data() : nullptr; }

[haraken, 2015/06/11 05:59:29]

Is it a valid thing to access these fields after the m_holder is cleared? I
guess we can change this to ASSERT(m_holder).

+    unsigned sizeInBytes() const { return m_holder ? m_holder->sizeInBytes() : 0; }
+    bool isShared() const { return m_holder ? m_holder->isShared() : false; }
 
     void setDeallocationObserver(ArrayBufferDeallocationObserver& observer)
     {
-        if (!m_deallocationObserver) {
-            m_deallocationObserver = &observer;
-            m_deallocationObserver->blinkAllocatedMemory(m_sizeInBytes);
-        }
+        ASSERT(m_holder);
+        m_holder->setDeallocationObserver(observer);
     }
     void setDeallocationObserverWithoutAllocationNotification(ArrayBufferDeallocationObserver& observer)
     {
-        if (!m_deallocationObserver) {
-            m_deallocationObserver = &observer;
-        }
+        ASSERT(m_holder);
+        m_holder->setDeallocationObserverWithoutAllocationNotification(observer);
     }
 
     void transfer(ArrayBufferContents& other);
@@ -79,9 +84,30 @@ public:
     static void freeMemory(void*, size_t);
 
 private:
-    void* m_data;
-    unsigned m_sizeInBytes;
-    ArrayBufferDeallocationObserver* m_deallocationObserver;
+    class DataHolder : public ThreadSafeRefCounted<DataHolder> {
+        WTF_MAKE_NONCOPYABLE(DataHolder);
+    public:
+        DataHolder();
+        ~DataHolder();
+
+        void allocateNew(unsigned sizeInBytes, SharingType isShared, InitializationPolicy, ArrayBufferDeallocationObserver*);
+        void adopt(void* data, unsigned sizeInBytes, SharingType isShared, ArrayBufferDeallocationObserver*);
+        void copyMemoryTo(DataHolder& other);
+
+        void* data() const { return m_data; }
+        unsigned sizeInBytes() const { return m_sizeInBytes; }
+        bool isShared() const { return m_isShared == Shared; }
+        void setDeallocationObserver(ArrayBufferDeallocationObserver&);
+        void setDeallocationObserverWithoutAllocationNotification(ArrayBufferDeallocationObserver&);
+
+    private:
+        void* m_data;
+        unsigned m_sizeInBytes;
+        SharingType m_isShared;
+        ArrayBufferDeallocationObserver* m_deallocationObserver;
+    };
+
+    RefPtr<DataHolder> m_holder;
 };
 
 } // namespace WTF