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88 lines
2.8 KiB
C++
88 lines
2.8 KiB
C++
// 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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// TODO(gab): Removing this include causes IWYU failures in other headers,
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// remove it in a follow- up CL.
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#include "base/threading/thread_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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// 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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};
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// The user data allows the clients to associate data with this object.
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// Multiple user data values can be stored under different keys.
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// This object will TAKE OWNERSHIP of the given data pointer, and will
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// delete the object if it is changed or the object is destroyed.
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// |key| must not be null--that value is too vulnerable for collision.
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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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// 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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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 base::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()) : NULL;
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}
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UserDataAdapter(T* object) : object_(object) {}
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T* release() { return object_.release(); }
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private:
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scoped_refptr<T> 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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