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 "third_party/skia/include/core/SkRefCnt.h"
#include "wtf/Assertions.h"
#include "wtf/Forward.h"
#include "wtf/Functional.h"  // FunctionThreadAffinity
#include "wtf/PassRefPtr.h"
#include "wtf/RefPtr.h"
#include "wtf/ThreadSafeRefCounted.h"
#include "wtf/TypeTraits.h"
#include "wtf/WeakPtr.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>
class CrossThreadPersistent;
template <typename T>
class CrossThreadWeakPersistent;

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

template <typename T, bool isArithmeticOrEnum>
struct CrossThreadCopierBase;

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

template <typename T>
struct CrossThreadCopier
    : public CrossThreadCopierBase<T,
                                   std::is_arithmetic<T>::value ||
                                       std::is_enum<T>::value> {
  STATIC_ONLY(CrossThreadCopier);
};

// CrossThreadCopier specializations follow.
template <typename T>
struct CrossThreadCopier<PassRefPtr<T>> {
  STATIC_ONLY(CrossThreadCopier);
  typedef PassRefPtr<T> Type;
  static_assert(WTF::IsSubclassOfTemplate<T, ThreadSafeRefCounted>::value,
                "PassRefPtr<T> can be passed across threads only if T is "
                "ThreadSafeRefCounted.");
  static PassRefPtr<T> copy(PassRefPtr<T>&& pointer) {
    return std::move(pointer);
  }
};
template <typename T>
struct CrossThreadCopier<RefPtr<T>>
    : public CrossThreadCopierPassThrough<RefPtr<T>> {
  STATIC_ONLY(CrossThreadCopier);
  static_assert(WTF::IsSubclassOfTemplate<T, ThreadSafeRefCounted>::value,
                "RefPtr<T> can be passed across threads only if T is "
                "ThreadSafeRefCounted.");
};
template <typename T>
struct CrossThreadCopier<sk_sp<T>>
    : public CrossThreadCopierPassThrough<sk_sp<T>> {
  STATIC_ONLY(CrossThreadCopier);
  static_assert(std::is_base_of<SkRefCnt, T>::value,
                "sk_sp<T> can be passed across threads only if T is SkRefCnt.");
};

// 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&);
};

}  // namespace blink

#endif  // CrossThreadCopier_h