Sharing of SharedArrayBuffer via PostMessage transfer

Source/wtf/ArrayBuffer.h

Index: Source/wtf/ArrayBuffer.h
diff --git a/Source/wtf/ArrayBuffer.h b/Source/wtf/ArrayBuffer.h
index e58f53151817c33a0c7323b2ce89f9d14fcd7416..d13bcb18adf81c3a1106b374ca64d510bbf2c113 100644
--- a/Source/wtf/ArrayBuffer.h
+++ b/Source/wtf/ArrayBuffer.h
@@ -51,6 +51,9 @@ public:
     // (through DOMArrayBuffer::createUninitialized).
     static inline PassRefPtr<ArrayBuffer> createUninitialized(unsigned numElements, unsigned elementByteSize);
 
+    static inline PassRefPtr<ArrayBuffer> createShared(unsigned numElements, unsigned elementByteSize);
+    static inline PassRefPtr<ArrayBuffer> createShared(const void* source, unsigned byteLength);
+
     inline void* data();
     inline const void* data() const;
     inline unsigned byteLength() const;
@@ -64,7 +67,8 @@ public:
     void removeView(ArrayBufferView*);
 
     bool transfer(ArrayBufferContents&);
-    bool isNeutered() { return m_isNeutered; }
+    bool isNeutered() const { return m_isNeutered; }
+    bool isShared() const { return m_contents.isShared(); }
 
     void setDeallocationObserver(ArrayBufferDeallocationObserver& observer)
     {
@@ -83,6 +87,7 @@ protected:
 private:
     static inline PassRefPtr<ArrayBuffer> create(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
     static inline PassRefPtr<ArrayBuffer> createOrNull(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
+    static inline PassRefPtr<ArrayBuffer> createShared(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
 
     inline PassRefPtr<ArrayBuffer> sliceImpl(unsigned begin, unsigned end) const;
     inline unsigned clampIndex(int index) const;
@@ -110,12 +115,14 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::create(unsigned numElements, unsigned eleme
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(ArrayBuffer* other)
 {
+    // TODO(binji): support creating a SharedArrayBuffer by copying another ArrayBuffer?
+    ASSERT(!other->isShared());
     return ArrayBuffer::create(other->data(), other->byteLength());
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(const void* source, unsigned byteLength)
 {
-    ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::ZeroInitialize);
+    ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::NotShared, ArrayBufferContents::ZeroInitialize);
     RELEASE_ASSERT(contents.data());
     RefPtr<ArrayBuffer> buffer = adoptRef(new ArrayBuffer(contents));
     memcpy(buffer->data(), source, byteLength);
@@ -139,19 +146,40 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::createUninitialized(unsigned numElements, u
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
 {
-    ArrayBufferContents contents(numElements, elementByteSize, policy);
+    ArrayBufferContents contents(numElements, elementByteSize, ArrayBufferContents::NotShared, policy);
     RELEASE_ASSERT(contents.data());
     return adoptRef(new ArrayBuffer(contents));
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::createOrNull(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
 {
-    ArrayBufferContents contents(numElements, elementByteSize, policy);
+    ArrayBufferContents contents(numElements, elementByteSize, ArrayBufferContents::NotShared, policy);
     if (!contents.data())
         return nullptr;
     return adoptRef(new ArrayBuffer(contents));
 }
 
+PassRefPtr<ArrayBuffer> ArrayBuffer::createShared(unsigned numElements, unsigned elementByteSize)
+{
+    return createShared(numElements, elementByteSize, ArrayBufferContents::ZeroInitialize);
+}
+
+PassRefPtr<ArrayBuffer> ArrayBuffer::createShared(const void* source, unsigned byteLength)
+{
+    ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::Shared, ArrayBufferContents::ZeroInitialize);
+    RELEASE_ASSERT(contents.data());

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

Any reason to make this a RELEASE assert?

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

Shall we add ASSERT(contents.isShared())?

+    RefPtr<ArrayBuffer> buffer = adoptRef(new ArrayBuffer(contents));
+    memcpy(buffer->data(), source, byteLength);
+    return buffer.release();
+}
+
+PassRefPtr<ArrayBuffer> ArrayBuffer::createShared(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
+{
+    ArrayBufferContents contents(numElements, elementByteSize, ArrayBufferContents::Shared, policy);
+    RELEASE_ASSERT(contents.data());

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

Ditto.

+    return adoptRef(new ArrayBuffer(contents));
+}
+
 ArrayBuffer::ArrayBuffer(ArrayBufferContents& contents)
     : m_firstView(0), m_isNeutered(false)
 {
@@ -185,6 +213,9 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::slice(int begin) const
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::sliceImpl(unsigned begin, unsigned end) const
 {
+    // TODO(binji): Isn't supported by SharedArrayBuffer, but maybe we don't need to assert?
+    // If we do support this, make sure to call createShared instead of create below.

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

I'm just curious but do we need to make the sliced buffer shared? I guess we can
just create a non-shared buffer for the sliced buffer.

+    ASSERT(!isShared());
     unsigned size = begin <= end ? end - begin : 0;
     return ArrayBuffer::create(static_cast<const char*>(data()) + begin, size);
 }