Sharing of SharedArrayBuffer via PostMessage transfer

Source/wtf/ArrayBuffer.h

 /*
  * Copyright (C) 2009 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
@@ skipping 33 matching lines @@
     static inline PassRefPtr<ArrayBuffer> create(const void* source, unsigned byteLength);
     static inline PassRefPtr<ArrayBuffer> create(ArrayBufferContents&);
 
     static inline PassRefPtr<ArrayBuffer> createOrNull(unsigned numElements, unsigned elementByteSize);
 
     // Only for use by Uint8ClampedArray::createUninitialized,
     // XMLHttpRequest::responseArrayBuffer and Internals::serializeObject
     // (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;
 
     // Creates a new ArrayBuffer object with copy of bytes in this object
     // ranging from |begin| upto but not including |end|.
     inline PassRefPtr<ArrayBuffer> slice(int begin, int end) const;
     inline PassRefPtr<ArrayBuffer> slice(int begin) const;
 
     void addView(ArrayBufferView*);
     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)
     {
         m_contents.setDeallocationObserver(observer);
     }
     void setDeallocationObserverWithoutAllocationNotification(ArrayBufferDeallocationObserver& observer)
     {
         m_contents.setDeallocationObserverWithoutAllocationNotification(observer);
     }
 
     ~ArrayBuffer() { }
 
 protected:
     inline explicit ArrayBuffer(ArrayBufferContents&);
 
 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;
     static inline int clampValue(int x, int left, int right);
 
     ArrayBufferContents m_contents;
     ArrayBufferView* m_firstView;
     bool m_isNeutered;
 };
 
 int ArrayBuffer::clampValue(int x, int left, int right)
 {
     ASSERT(left <= right);
     if (x < left)
         x = left;
     if (right < x)
         x = right;
     return x;
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(unsigned numElements, unsigned elementByteSize)
 {
     return create(numElements, elementByteSize, ArrayBufferContents::ZeroInitialize);
 }
 
 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);
     return buffer.release();
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(ArrayBufferContents& contents)
 {
     return adoptRef(new ArrayBuffer(contents));
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::createOrNull(unsigned numElements, unsigned elementByteSize)
 {
     return createOrNull(numElements, elementByteSize, ArrayBufferContents::ZeroInitialize);
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::createUninitialized(unsigned numElements, unsigned elementByteSize)
 {
     return create(numElements, elementByteSize, ArrayBufferContents::DontInitialize);
 }
 
 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)
 {
     contents.transfer(m_contents);
 }
 
 void* ArrayBuffer::data()
 {
     return m_contents.data();
 }
@@ skipping 13 matching lines @@
     return sliceImpl(clampIndex(begin), clampIndex(end));
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::slice(int begin) const
 {
     return sliceImpl(clampIndex(begin), byteLength());
 }
 
 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);
 }
 
 unsigned ArrayBuffer::clampIndex(int index) const
 {
     unsigned currentLength = byteLength();
     if (index < 0)
         index = currentLength + index;
     return clampValue(index, 0, currentLength);
 }
 
 } // namespace WTF
 
 using WTF::ArrayBuffer;
 
 #endif // ArrayBuffer_h