mirror of
https://github.com/darlinghq/darling-JavaScriptCore.git
synced 2024-11-23 12:19:46 +00:00
119 lines
4.0 KiB
C++
119 lines
4.0 KiB
C++
/*
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* Copyright (C) 2016 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "VM.h"
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namespace JSC {
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class JSCell;
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class SlotVisitor;
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class VM;
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// Note that if all you're doing is calling LazyProperty::get(), it's completely safe to bitcast
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// this LazyProperty<JSCell, JSCell>.
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template<typename OwnerType, typename ElementType>
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class LazyProperty {
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public:
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struct Initializer {
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Initializer(OwnerType* owner, LazyProperty& property)
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: vm(*Heap::heap(owner)->vm())
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, owner(owner)
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, property(property)
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{
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}
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void set(ElementType* value) const;
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VM& vm;
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OwnerType* owner;
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LazyProperty& property;
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};
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private:
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typedef ElementType* (*FuncType)(const Initializer&);
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public:
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LazyProperty()
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{
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}
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// Tell the property to run the given callback next time someone tries to get the value
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// using get(). The passed callback must be stateless. For example:
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//
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// property.initLater(
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// [] (const LazyProperty<Foo, Bar>::Initializer& init) {
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// init.set(...things...);
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// });
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//
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// This method is always inlineable and should always compile to a store of a constant
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// pointer no matter how complicated the callback is.
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template<typename Func>
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void initLater(const Func&);
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// This lazily initializes the property. Note that this gracefully supports recursive calls.
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// If this gets called while the property is being initialized, it will simply return null.
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ElementType* get(const OwnerType* owner) const
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{
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ASSERT(!isCompilationThread());
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if (UNLIKELY(m_pointer & lazyTag)) {
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FuncType func = *bitwise_cast<FuncType*>(m_pointer & ~(lazyTag | initializingTag));
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return func(Initializer(const_cast<OwnerType*>(owner), *const_cast<LazyProperty*>(this)));
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}
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return bitwise_cast<ElementType*>(m_pointer);
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}
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ElementType* getConcurrently() const
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{
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uintptr_t pointer = m_pointer;
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if (pointer & lazyTag)
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return nullptr;
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return bitwise_cast<ElementType*>(pointer);
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}
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void setMayBeNull(VM&, const OwnerType* owner, ElementType*);
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void set(VM&, const OwnerType* owner, ElementType*);
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void visit(SlotVisitor&);
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void dump(PrintStream&) const;
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private:
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template<typename Func>
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static ElementType* callFunc(const Initializer&);
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static const uintptr_t lazyTag = 1;
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static const uintptr_t initializingTag = 2;
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uintptr_t m_pointer { 0 };
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};
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// It's valid to bitcast any LazyProperty to LazyCellProperty if you're just going to call get()
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// or getConcurrently().
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typedef LazyProperty<JSCell, JSCell> LazyCellProperty;
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} // namespace JSC
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