[JSC] Added "user controlled buffer" support to ArrayBuffers, to allo…

…w creating ArrayBuffers "around" user controlled buffer, without copying or freeing them

Source/JavaScriptCore/runtime/ArrayBuffer.cpp

@@ -264,6 +264,7 @@ ArrayBuffer::ArrayBuffer(ArrayBufferContents&& contents)
     , m_pinCount(0)
     , m_isWasmMemory(false)
     , m_locked(false)
+	, m_isApiUserControlledBuffer(false)
 {
 }
 
@@ -297,6 +298,18 @@ void ArrayBuffer::makeWasmMemory()
     m_isWasmMemory = true;
 }
 
+void ArrayBuffer::makeApiUserControlledBuffer()
+{
+	m_isApiUserControlledBuffer = true;
+
+	if (m_contents.m_shared) {
+		m_contents.m_shared->m_destructor = [](void*) {};
+	}
+	else {
+		m_contents.m_destructor = [](void*) {};
+	}
+}
+
 void ArrayBuffer::setSharingMode(ArrayBufferSharingMode newSharingMode)
 {
     if (newSharingMode == sharingMode())

Source/JavaScriptCore/runtime/ArrayBuffer.h

@@ -51,6 +51,8 @@ class SharedArrayBufferContents : public ThreadSafeRefCounted<SharedArrayBufferC
     void* data() const { return m_data.getMayBeNull(); }
 
 private:
+	friend class ArrayBuffer;
+
     CagedPtr<Gigacage::Primitive, void> m_data;
     ArrayBufferDestructorFunction m_destructor;
 };
@@ -138,6 +140,9 @@ class ArrayBuffer : public GCIncomingRefCounted<ArrayBuffer> {
     void makeWasmMemory();
     inline bool isWasmMemory();
 
+	void makeApiUserControlledBuffer();
+	inline bool isApiUserControlledBuffer() const;
+
     JS_EXPORT_PRIVATE bool transferTo(VM&, ArrayBufferContents&);
     JS_EXPORT_PRIVATE bool shareWith(ArrayBufferContents&);
 
@@ -160,12 +165,13 @@ class ArrayBuffer : public GCIncomingRefCounted<ArrayBuffer> {
     void notifyIncommingReferencesOfTransfer(VM&);
 
     ArrayBufferContents m_contents;
-    unsigned m_pinCount : 30;
+    unsigned m_pinCount : 29;
     bool m_isWasmMemory : 1;
     // m_locked == true means that some API user fetched m_contents directly from a TypedArray object,
     // the buffer is backed by a WebAssembly.Memory, or is a SharedArrayBuffer.
     bool m_locked : 1;
-
+	bool m_isApiUserControlledBuffer : 1;
+
 public:
     Weak<JSArrayBuffer> m_wrapper;
 };
@@ -239,6 +245,13 @@ bool ArrayBuffer::isWasmMemory()
     return m_isWasmMemory;
 }
 
+bool ArrayBuffer::isApiUserControlledBuffer() const
+{
+	return m_isApiUserControlledBuffer;
+}
+
+
+
 JS_EXPORT_PRIVATE ASCIILiteral errorMesasgeForTransfer(ArrayBuffer*);
 
 } // namespace JSC