// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef IOS_CHROME_BROWSER_OVERLAYS_MODEL_PUBLIC_OVERLAY_USER_DATA_H_
#define IOS_CHROME_BROWSER_OVERLAYS_MODEL_PUBLIC_OVERLAY_USER_DATA_H_
#include "base/memory/ptr_util.h"
#include "base/supports_user_data.h"
// Macro for OverlayUserData setup [add to .h file]:
// - Declares a static variable inside subclasses. The address of this static
// variable is used as the key to associate the OverlayUserData with its
// user data container.
// - Adds a friend specification for OverlayUserData so it can access
// specializations' private constructors and user data keys.
#define OVERLAY_USER_DATA_SETUP(Type) \
static constexpr int kUserDataKey = 0; \
friend class OverlayUserData<Type>
// Macro for OverlayUserData setup implementation [add to .cc/.mm file]:
// - Instantiates the static variable declared by the previous macro. It must
// live in a .cc/.mm file to ensure that there is only one instantiation of
// the static variable.
#define OVERLAY_USER_DATA_SETUP_IMPL(Type) const int Type::kUserDataKey
// A base class for classes attached to, and scoped to, the lifetime of a user
// data container (e.g. OverlayRequest, OverlayResponse).
//
// --- in data.h ---
// class Data : public OverlayUserData<Data> {
// public:
// ~Data() override;
// // ... more public stuff here ...
// private:
// OVERLAY_USER_DATA_SETUP(Data);
// explicit Data( \* ANY ARGUMENT LIST SUPPORTED *\);
// // ... more private stuff here ...
// };
//
// --- in data.cc ---
// OVERLAY_USER_DATA_SETUP_IMPL(Data);
template <class DataType>
class OverlayUserData : public base::SupportsUserData::Data {
public:
// Creates an OverlayUserData of type DataType and adds it to `user_data`
// under its key. The DataType instance is constructed using the arguments
// passed after the key to this function. If a DataType instance already
// exists in `user_data`, no new object is created. For example, if the
// constructor for an OverlayUserData of type StringData takes a string, one
// can be created using:
//
// StringData::CreateForUserData(user_data, "string");
template <typename... Args>
static void CreateForUserData(base::SupportsUserData* user_data,
Args&&... args) {
if (!FromUserData(user_data)) {
std::unique_ptr<DataType> data =
base::WrapUnique(new DataType(std::forward<Args>(args)...));
data->CreateAuxiliaryData(user_data);
user_data->SetUserData(UserDataKey(), std::move(data));
}
}
// Retrieves the instance of type DataType that was attached to the specified
// user data container and returns it. If no instance of the type was
// attached, returns nullptr.
static DataType* FromUserData(base::SupportsUserData* user_data) {
return static_cast<DataType*>(user_data->GetUserData(UserDataKey()));
}
static const DataType* FromUserData(const base::SupportsUserData* user_data) {
return static_cast<const DataType*>(user_data->GetUserData(UserDataKey()));
}
// The key under which to store the user data.
static const void* UserDataKey() { return &DataType::kUserDataKey; }
protected:
// Adds auxilliary OverlayUserData to `data`. Used to allow multiple
// OverlayUserData templates to share common functionality in a separate data
// stored in `user_data`.
virtual void CreateAuxiliaryData(base::SupportsUserData* user_data) {}
};
#endif // IOS_CHROME_BROWSER_OVERLAYS_MODEL_PUBLIC_OVERLAY_USER_DATA_H_
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