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−/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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− * vim: set ts=8 sts=4 et sw=4 tw=99:
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− * This Source Code Form is subject to the terms of the Mozilla Public
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− * License, v. 2.0. If a copy of the MPL was not distributed with this
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− * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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−
+
−#ifndef vm_TaggedProto_h
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−#define vm_TaggedProto_h
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−
+
−#include "gc/Tracer.h"
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−
+
−namespace js {
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−
+
−// Information about an object prototype, which can be either a particular
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−// object, null, or a lazily generated object. The latter is only used by
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−// certain kinds of proxies.
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−class TaggedProto
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−{
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−  public:
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−    static JSObject * const LazyProto;
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−
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−    TaggedProto() : proto(nullptr) {}
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−    TaggedProto(const TaggedProto& other) : proto(other.proto) {}
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−    explicit TaggedProto(JSObject* proto) : proto(proto) {}
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−
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−    uintptr_t toWord() const { return uintptr_t(proto); }
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−
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−    bool isDynamic() const {
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−        return proto == LazyProto;
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−    }
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−    bool isObject() const {
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−        /* Skip nullptr and LazyProto. */
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−        return uintptr_t(proto) > uintptr_t(TaggedProto::LazyProto);
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−    }
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−    JSObject* toObject() const {
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−        MOZ_ASSERT(isObject());
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−        return proto;
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−    }
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−    JSObject* toObjectOrNull() const {
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−        MOZ_ASSERT(!proto || isObject());
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−        return proto;
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−    }
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−    JSObject* raw() const { return proto; }
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−
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−    bool operator ==(const TaggedProto& other) const { return proto == other.proto; }
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−    bool operator !=(const TaggedProto& other) const { return proto != other.proto; }
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−
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−    HashNumber hashCode() const;
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−
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−    bool hasUniqueId() const;
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−    bool ensureUniqueId() const;
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−    uint64_t uniqueId() const;
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−
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−    void trace(JSTracer* trc) {
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−        if (isObject())
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−            TraceManuallyBarrieredEdge(trc, &proto, "TaggedProto");
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−    }
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−
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−  private:
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−    JSObject* proto;
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−};
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−
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−template <>
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−struct InternalBarrierMethods<TaggedProto>
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−{
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−    static void preBarrier(TaggedProto& proto);
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−
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−    static void postBarrier(TaggedProto* vp, TaggedProto prev, TaggedProto next);
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−
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−    static void readBarrier(const TaggedProto& proto);
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−
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−    static bool isMarkable(const TaggedProto& proto) {
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−        return proto.isObject();
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−    }
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−};
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−
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−template <class Wrapper>
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−class WrappedPtrOperations<TaggedProto, Wrapper>
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−{
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−    const TaggedProto& value() const {
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−        return static_cast<const Wrapper*>(this)->get();
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−    }
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−
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−  public:
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−    uintptr_t toWord() const { return value().toWord(); }
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−    inline bool isDynamic() const { return value().isDynamic(); }
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−    inline bool isObject() const { return value().isObject(); }
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−    inline JSObject* toObject() const { return value().toObject(); }
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−    inline JSObject* toObjectOrNull() const { return value().toObjectOrNull(); }
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−    JSObject* raw() const { return value().raw(); }
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−    HashNumber hashCode() const { return value().hashCode(); }
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−    uint64_t uniqueId() const { return value().uniqueId(); }
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−};
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−
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−// If the TaggedProto is a JSObject pointer, convert to that type and call |f|
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−// with the pointer. If the TaggedProto is lazy, calls F::defaultValue.
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−template <typename F, typename... Args>
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−auto
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−DispatchTyped(F f, const TaggedProto& proto, Args&&... args)
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−  -> decltype(f(static_cast<JSObject*>(nullptr), mozilla::Forward<Args>(args)...))
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−{
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−    if (proto.isObject())
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−        return f(proto.toObject(), mozilla::Forward<Args>(args)...);
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−    return F::defaultValue(proto);
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−}
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−
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−// Since JSObject pointers are either nullptr or a valid object and since the
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−// object layout of TaggedProto is identical to a bare object pointer, we can
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−// safely treat a pointer to an already-rooted object (e.g. HandleObject) as a
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−// pointer to a TaggedProto.
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−inline Handle<TaggedProto>
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−AsTaggedProto(HandleObject obj)
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−{
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−    static_assert(sizeof(JSObject*) == sizeof(TaggedProto),
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−                  "TaggedProto must be binary compatible with JSObject");
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−    return Handle<TaggedProto>::fromMarkedLocation(
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−            reinterpret_cast<TaggedProto const*>(obj.address()));
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−}
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−
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−} // namespace js
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−
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−#endif // vm_TaggedProto_h