99 lines
3.2 KiB
C
99 lines
3.2 KiB
C
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// Copyright (c) 2012 The Chromium 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 BASE_SUPPORTS_USER_DATA_H_
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#define BASE_SUPPORTS_USER_DATA_H_
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#include <map>
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#include <memory>
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#include "base/base_export.h"
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#include "base/macros.h"
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#include "base/memory/ref_counted.h"
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#include "base/sequence_checker.h"
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namespace base {
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// This is a helper for classes that want to allow users to stash random data by
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// key. At destruction all the objects will be destructed.
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class BASE_EXPORT SupportsUserData {
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public:
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SupportsUserData();
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SupportsUserData(SupportsUserData&&);
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SupportsUserData& operator=(SupportsUserData&&);
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// Derive from this class and add your own data members to associate extra
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// information with this object. Alternatively, add this as a public base
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// class to any class with a virtual destructor.
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class BASE_EXPORT Data {
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public:
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virtual ~Data() = default;
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// Returns a copy of |this|; null if copy is not supported.
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virtual std::unique_ptr<Data> Clone();
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};
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// The user data allows the clients to associate data with this object.
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// |key| must not be null--that value is too vulnerable for collision.
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// NOTE: SetUserData() with an empty unique_ptr behaves the same as
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// RemoveUserData().
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Data* GetUserData(const void* key) const;
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void SetUserData(const void* key, std::unique_ptr<Data> data);
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void RemoveUserData(const void* key);
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// Adds all data from |other|, that is clonable, to |this|. That is, this
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// iterates over the data in |other|, and any data that returns non-null from
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// Clone() is added to |this|.
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void CloneDataFrom(const SupportsUserData& other);
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// SupportsUserData is not thread-safe, and on debug build will assert it is
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// only used on one execution sequence. Calling this method allows the caller
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// to hand the SupportsUserData instance across execution sequences. Use only
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// if you are taking full control of the synchronization of that hand over.
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void DetachFromSequence();
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protected:
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virtual ~SupportsUserData();
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// Clear all user data from this object. This can be used if the subclass
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// needs to provide reset functionality.
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void ClearAllUserData();
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private:
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using DataMap = std::map<const void*, std::unique_ptr<Data>>;
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// Externally-defined data accessible by key.
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DataMap user_data_;
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// Guards usage of |user_data_|
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SequenceChecker sequence_checker_;
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DISALLOW_COPY_AND_ASSIGN(SupportsUserData);
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};
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// Adapter class that releases a refcounted object when the
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// SupportsUserData::Data object is deleted.
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template <typename T>
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class UserDataAdapter : public SupportsUserData::Data {
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public:
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static T* Get(const SupportsUserData* supports_user_data, const void* key) {
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UserDataAdapter* data =
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static_cast<UserDataAdapter*>(supports_user_data->GetUserData(key));
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return data ? static_cast<T*>(data->object_.get()) : nullptr;
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}
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explicit UserDataAdapter(T* object) : object_(object) {}
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~UserDataAdapter() override = default;
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T* release() { return object_.release(); }
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private:
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scoped_refptr<T> const object_;
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DISALLOW_COPY_AND_ASSIGN(UserDataAdapter);
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};
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} // namespace base
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#endif // BASE_SUPPORTS_USER_DATA_H_
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