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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsXBLMaybeCompiled_h__
#define nsXBLMaybeCompiled_h__
#include "js/GCAPI.h"
/*
* A union containing either a pointer representing uncompiled source or a
* JSObject* representing the compiled result. The class is templated on the
* source object type.
*
* The purpose of abstracting this as a separate class is to allow it to be
* wrapped in a JS::Heap<T> to correctly handle post-barriering of the JSObject
* pointer, when present.
*
* No implementation of rootKind() is provided, which prevents
* Root<nsXBLMaybeCompiled<UncompiledT>> from being used.
*/
template <class UncompiledT>
class nsXBLMaybeCompiled
{
public:
nsXBLMaybeCompiled() : mUncompiled(BIT_UNCOMPILED) {}
explicit nsXBLMaybeCompiled(UncompiledT* uncompiled)
: mUncompiled(reinterpret_cast<uintptr_t>(uncompiled) | BIT_UNCOMPILED) {}
explicit nsXBLMaybeCompiled(JSObject* compiled) : mCompiled(compiled) {}
bool IsCompiled() const
{
return !(mUncompiled & BIT_UNCOMPILED);
}
UncompiledT* GetUncompiled() const
{
MOZ_ASSERT(!IsCompiled(), "Attempt to get compiled function as uncompiled");
uintptr_t unmasked = mUncompiled & ~BIT_UNCOMPILED;
return reinterpret_cast<UncompiledT*>(unmasked);
}
JSObject* GetJSFunction() const
{
MOZ_ASSERT(IsCompiled(), "Attempt to get uncompiled function as compiled");
if (mCompiled) {
JS::ExposeObjectToActiveJS(mCompiled);
}
return mCompiled;
}
// This is appropriate for use in tracing methods, etc.
JSObject* GetJSFunctionPreserveColor() const
{
MOZ_ASSERT(IsCompiled(), "Attempt to get uncompiled function as compiled");
return mCompiled;
}
private:
JSObject*& UnsafeGetJSFunction()
{
MOZ_ASSERT(IsCompiled(), "Attempt to get uncompiled function as compiled");
return mCompiled;
}
enum { BIT_UNCOMPILED = 1 << 0 };
union
{
// An pointer that represents the function before being compiled, with
// BIT_UNCOMPILED set.
uintptr_t mUncompiled;
// The JS object for the compiled result.
JSObject* mCompiled;
};
friend struct js::BarrierMethods<nsXBLMaybeCompiled<UncompiledT>>;
};
/* Add support for JS::Heap<nsXBLMaybeCompiled>. */
namespace JS {
template <class UncompiledT>
struct GCPolicy<nsXBLMaybeCompiled<UncompiledT>>
{
static nsXBLMaybeCompiled<UncompiledT> initial() { return nsXBLMaybeCompiled<UncompiledT>(); }
};
} // namespace JS
namespace js {
template <class UncompiledT>
struct BarrierMethods<nsXBLMaybeCompiled<UncompiledT>>
{
typedef struct BarrierMethods<JSObject *> Base;
static void postBarrier(nsXBLMaybeCompiled<UncompiledT>* functionp,
nsXBLMaybeCompiled<UncompiledT> prev,
nsXBLMaybeCompiled<UncompiledT> next)
{
if (next.IsCompiled()) {
Base::postBarrier(&functionp->UnsafeGetJSFunction(),
prev.IsCompiled() ? prev.UnsafeGetJSFunction() : nullptr,
next.UnsafeGetJSFunction());
} else if (prev.IsCompiled()) {
Base::postBarrier(&prev.UnsafeGetJSFunction(),
prev.UnsafeGetJSFunction(),
nullptr);
}
}
static void exposeToJS(nsXBLMaybeCompiled<UncompiledT> fun) {
if (fun.IsCompiled()) {
JS::ExposeObjectToActiveJS(fun.UnsafeGetJSFunction());
}
}
};
template <class T>
struct IsHeapConstructibleType<nsXBLMaybeCompiled<T>>
{ // Yes, this is the exception to the rule. Sorry.
static const bool value = true;
};
template <class UncompiledT>
class HeapBase<nsXBLMaybeCompiled<UncompiledT>>
{
const JS::Heap<nsXBLMaybeCompiled<UncompiledT>>& wrapper() const {
return *static_cast<const JS::Heap<nsXBLMaybeCompiled<UncompiledT>>*>(this);
}
JS::Heap<nsXBLMaybeCompiled<UncompiledT>>& wrapper() {
return *static_cast<JS::Heap<nsXBLMaybeCompiled<UncompiledT>>*>(this);
}
const nsXBLMaybeCompiled<UncompiledT>* extract() const {
return wrapper().address();
}
nsXBLMaybeCompiled<UncompiledT>* extract() {
return wrapper().unsafeGet();
}
public:
bool IsCompiled() const { return extract()->IsCompiled(); }
UncompiledT* GetUncompiled() const { return extract()->GetUncompiled(); }
JSObject* GetJSFunction() const { return extract()->GetJSFunction(); }
JSObject* GetJSFunctionPreserveColor() const { return extract()->GetJSFunctionPreserveColor(); }
void SetUncompiled(UncompiledT* source) {
wrapper() = nsXBLMaybeCompiled<UncompiledT>(source);
}
void SetJSFunction(JSObject* function) {
wrapper() = nsXBLMaybeCompiled<UncompiledT>(function);
}
JS::Heap<JSObject*>& AsHeapObject()
{
MOZ_ASSERT(extract()->IsCompiled());
return *reinterpret_cast<JS::Heap<JSObject*>*>(this);
}
};
} /* namespace js */
#endif // nsXBLMaybeCompiled_h__
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