third_party/WebKit/Source/platform/CrossThreadCopier.h

/*
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 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
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 */

#ifndef CrossThreadCopier_h
#define CrossThreadCopier_h

#include "platform/PlatformExport.h"
#include "platform/heap/Handle.h"
#include "wtf/Assertions.h"
#include "wtf/Forward.h"
#include "wtf/PassRefPtr.h"
#include "wtf/RefPtr.h"
#include "wtf/ThreadSafeRefCounted.h"
#include "wtf/TypeTraits.h"
#include <memory>

class SkRefCnt;

namespace WTF {

template <typename T>
class PassedWrapper;

}

namespace blink {

class IntRect;
class IntSize;
class KURL;
class ResourceError;
class ResourceRequest;
class ResourceResponse;
struct CrossThreadResourceResponseData;
struct CrossThreadResourceRequestData;

template <typename T>
struct CrossThreadCopierPassThrough {
    STATIC_ONLY(CrossThreadCopierPassThrough);
    typedef T Type;
    static Type copy(const T& parameter)
    {
        return parameter;
    }
};

template <typename T, bool isArithmeticOrEnum, bool isThreadSafeRefCounted>
struct CrossThreadCopierBase;

// Arithmetic values (integers or floats) and enums can be safely copied.
template <typename T, bool isThreadSafeRefCounted>
struct CrossThreadCopierBase<T, true, isThreadSafeRefCounted> : public CrossThreadCopierPassThrough<T> {
    STATIC_ONLY(CrossThreadCopierBase);
};

// Custom copy method for ThreadSafeRefCounted.
template <typename T>
struct CrossThreadCopierBase<T, false, true> {
    STATIC_ONLY(CrossThreadCopierBase);
    typedef typename WTF::RemoveTemplate<T, RefPtr>::Type TypeWithoutRefPtr;
    typedef typename WTF::RemoveTemplate<TypeWithoutRefPtr, PassRefPtr>::Type TypeWithoutPassRefPtr;
    typedef typename std::remove_pointer<TypeWithoutPassRefPtr>::type RefCountedType;

    // Verify that only one of the above did a change.
    static_assert((std::is_same<RefPtr<RefCountedType>, T>::value
        || std::is_same<PassRefPtr<RefCountedType>, T>::value
        || std::is_same<RefCountedType*, T>::value),
        "only one type modification should be allowed");

    typedef PassRefPtr<RefCountedType> Type;
    static Type copy(const T& refPtr)
    {
        return refPtr;
    }
};

template <typename T>
struct CrossThreadCopier : public CrossThreadCopierBase<
    T,
    std::is_arithmetic<T>::value || std::is_enum<T>::value,
    WTF::IsSubclassOfTemplate<typename WTF::RemoveTemplate<T, RefPtr>::Type, ThreadSafeRefCounted>::value
    || WTF::IsSubclassOfTemplate<typename std::remove_pointer<T>::type, ThreadSafeRefCounted>::value
    || WTF::IsSubclassOfTemplate<typename WTF::RemoveTemplate<T, PassRefPtr>::Type, ThreadSafeRefCounted>::value
    || std::is_base_of<SkRefCnt, typename WTF::RemoveTemplate<T, RefPtr>::Type>::value
    || std::is_base_of<SkRefCnt, typename std::remove_pointer<T>::type>::value
    || std::is_base_of<SkRefCnt, typename WTF::RemoveTemplate<T, PassRefPtr>::Type>::value> {
    STATIC_ONLY(CrossThreadCopier);
};

// CrossThreadCopier specializations follow.

// nullptr_t can be passed through without any changes.
template <>
struct CrossThreadCopier<std::nullptr_t> : public CrossThreadCopierPassThrough<std::nullptr_t> {
    STATIC_ONLY(CrossThreadCopier);
};

// To allow a type to be passed across threads using its copy constructor, add a forward declaration of the type and
// provide a specialization of CrossThreadCopier<T> in this file, like IntRect below.
template <>
struct CrossThreadCopier<IntRect> : public CrossThreadCopierPassThrough<IntRect> {
    STATIC_ONLY(CrossThreadCopier);
};

template <>
struct CrossThreadCopier<IntSize> : public CrossThreadCopierPassThrough<IntSize> {
    STATIC_ONLY(CrossThreadCopier);
};

template <typename T, typename Deleter>
struct CrossThreadCopier<std::unique_ptr<T, Deleter>> {
    STATIC_ONLY(CrossThreadCopier);
    using Type = std::unique_ptr<T, Deleter>;
    static std::unique_ptr<T, Deleter> copy(std::unique_ptr<T, Deleter> pointer)
    {
        return pointer; // This is in fact a move.
    }
};

template<typename T>
struct CrossThreadCopier<CrossThreadPersistent<T>> : public CrossThreadCopierPassThrough<CrossThreadPersistent<T>> {
    STATIC_ONLY(CrossThreadCopier);
};

template<typename T>
struct CrossThreadCopier<CrossThreadWeakPersistent<T>> : public CrossThreadCopierPassThrough<CrossThreadWeakPersistent<T>> {
    STATIC_ONLY(CrossThreadCopier);
};

template<typename T>
struct CrossThreadCopier<WTF::UnretainedWrapper<T, WTF::CrossThreadAffinity>> : public CrossThreadCopierPassThrough<WTF::UnretainedWrapper<T, WTF::CrossThreadAffinity>> {
    STATIC_ONLY(CrossThreadCopier);
};

template<typename T>
struct CrossThreadCopier<WeakPtr<T>> : public CrossThreadCopierPassThrough<WeakPtr<T>> {
    STATIC_ONLY(CrossThreadCopier);
};

template <typename T>
struct CrossThreadCopier<WTF::PassedWrapper<T>> {
    STATIC_ONLY(CrossThreadCopier);
    using Type = WTF::PassedWrapper<typename CrossThreadCopier<T>::Type>;
    static Type copy(WTF::PassedWrapper<T>&& value) { return passed(CrossThreadCopier<T>::copy(value.moveOut())); }
};

template <>
struct CrossThreadCopier<KURL> {
    STATIC_ONLY(CrossThreadCopier);
    typedef KURL Type;
    PLATFORM_EXPORT static Type copy(const KURL&);
};

template <>
struct CrossThreadCopier<String> {
    STATIC_ONLY(CrossThreadCopier);
    typedef String Type;
    PLATFORM_EXPORT static Type copy(const String&);
};

template <>
struct CrossThreadCopier<ResourceError> {
    STATIC_ONLY(CrossThreadCopier);
    typedef ResourceError Type;
    PLATFORM_EXPORT static Type copy(const ResourceError&);
};

template <>
struct CrossThreadCopier<ResourceRequest> {
    STATIC_ONLY(CrossThreadCopier);
    typedef WTF::PassedWrapper<std::unique_ptr<CrossThreadResourceRequestData>> Type;
    PLATFORM_EXPORT static Type copy(const ResourceRequest&);
};

template <>
struct CrossThreadCopier<ResourceResponse> {
    STATIC_ONLY(CrossThreadCopier);
    typedef WTF::PassedWrapper<std::unique_ptr<CrossThreadResourceResponseData>> Type;
    PLATFORM_EXPORT static Type copy(const ResourceResponse&);
};

template <typename T>
struct CrossThreadCopier<Member<T>> {
    STATIC_ONLY(CrossThreadCopier);
    static_assert(IsGarbageCollectedType<T>::value, "T must be a garbage-collected type.");
    typedef T* Type;
    static Type copy(const Member<T>& ptr)
    {
        return ptr;
    }
};

} // namespace blink

#endif // CrossThreadCopier_h