056f927861
Tbr: ahaas@chromium.org,leszeks@chromium.org,verwaest@chromium.org Bug: v8:3770 Change-Id: Ia6530fbb70dac05e9972283781c3550d8b50e1eb Reviewed-on: https://chromium-review.googlesource.com/c/1390116 Commit-Queue: Jakob Kummerow <jkummerow@chromium.org> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org> Reviewed-by: Alexei Filippov <alph@chromium.org> Reviewed-by: Jakob Gruber <jgruber@chromium.org> Reviewed-by: Ulan Degenbaev <ulan@chromium.org> Reviewed-by: Sigurd Schneider <sigurds@chromium.org> Cr-Commit-Position: refs/heads/master@{#58470}
122 lines
4.0 KiB
C++
122 lines
4.0 KiB
C++
// Copyright 2011 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_MAYBE_HANDLES_H_
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#define V8_MAYBE_HANDLES_H_
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#include <type_traits>
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#include "src/handles.h"
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namespace v8 {
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namespace internal {
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// ----------------------------------------------------------------------------
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// A Handle can be converted into a MaybeHandle. Converting a MaybeHandle
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// into a Handle requires checking that it does not point to nullptr. This
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// ensures nullptr checks before use.
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//
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// Also note that Handles do not provide default equality comparison or hashing
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// operators on purpose. Such operators would be misleading, because intended
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// semantics is ambiguous between Handle location and object identity.
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template <typename T>
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class MaybeHandle final {
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public:
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V8_INLINE MaybeHandle() = default;
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// Constructor for handling automatic up casting from Handle.
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// Ex. Handle<JSArray> can be passed when MaybeHandle<Object> is expected.
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template <typename S, typename = typename std::enable_if<
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std::is_convertible<S*, T*>::value>::type>
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V8_INLINE MaybeHandle(Handle<S> handle) : location_(handle.location_) {}
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// Constructor for handling automatic up casting.
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// Ex. MaybeHandle<JSArray> can be passed when Handle<Object> is expected.
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template <typename S, typename = typename std::enable_if<
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std::is_convertible<S*, T*>::value>::type>
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V8_INLINE MaybeHandle(MaybeHandle<S> maybe_handle)
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: location_(maybe_handle.location_) {}
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V8_INLINE MaybeHandle(T object, Isolate* isolate);
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V8_INLINE void Assert() const { DCHECK_NOT_NULL(location_); }
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V8_INLINE void Check() const { CHECK_NOT_NULL(location_); }
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V8_INLINE Handle<T> ToHandleChecked() const {
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Check();
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return Handle<T>(location_);
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}
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// Convert to a Handle with a type that can be upcasted to.
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template <typename S>
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V8_INLINE bool ToHandle(Handle<S>* out) const {
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if (location_ == nullptr) {
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*out = Handle<T>::null();
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return false;
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} else {
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*out = Handle<T>(location_);
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return true;
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}
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}
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// Returns the raw address where this handle is stored. This should only be
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// used for hashing handles; do not ever try to dereference it.
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V8_INLINE Address address() const {
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return reinterpret_cast<Address>(location_);
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}
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bool is_null() const { return location_ == nullptr; }
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protected:
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Address* location_ = nullptr;
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// MaybeHandles of different classes are allowed to access each
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// other's location_.
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template <typename>
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friend class MaybeHandle;
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};
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// A handle which contains a potentially weak pointer. Keeps it alive (strongly)
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// while the MaybeObjectHandle is alive.
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class MaybeObjectHandle {
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public:
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inline MaybeObjectHandle();
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inline MaybeObjectHandle(MaybeObject object, Isolate* isolate);
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inline MaybeObjectHandle(Object object, Isolate* isolate);
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inline explicit MaybeObjectHandle(Handle<Object> object);
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static inline MaybeObjectHandle Weak(Object object, Isolate* isolate);
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static inline MaybeObjectHandle Weak(Handle<Object> object);
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inline MaybeObject operator*() const;
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inline MaybeObject operator->() const;
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inline Handle<Object> object() const;
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bool is_identical_to(const MaybeObjectHandle& other) const {
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Handle<Object> this_handle;
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Handle<Object> other_handle;
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return reference_type_ == other.reference_type_ &&
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handle_.ToHandle(&this_handle) ==
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other.handle_.ToHandle(&other_handle) &&
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this_handle.is_identical_to(other_handle);
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}
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bool is_null() const { return handle_.is_null(); }
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private:
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inline MaybeObjectHandle(Object object,
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HeapObjectReferenceType reference_type,
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Isolate* isolate);
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inline MaybeObjectHandle(Handle<Object> object,
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HeapObjectReferenceType reference_type);
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HeapObjectReferenceType reference_type_;
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MaybeHandle<Object> handle_;
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};
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} // namespace internal
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} // namespace v8
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#endif // V8_MAYBE_HANDLES_H_
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