Move PropertyBag to base. Originally this was in chrome\common because only chrome used it. Now t...

content/common/property_bag.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_COMMON_PROPERTY_BAG_H_
-#define CONTENT_COMMON_PROPERTY_BAG_H_
-#pragma once
-
-#include <map>
-
-#include "base/basictypes.h"
-#include "content/common/content_export.h"
-
-template <typename T>
-class linked_ptr;
-class PropertyAccessorBase;
-
-// A property bag holds a generalized list of arbitrary metadata called
-// properties. Each property is a class type derived from PropertyBag::Prop
-// that can be set and retrieved.
-//
-// The property bag is not read or written directly. Instead, callers go
-// through a PropertyAccessor. The Accessor generates the unique IDs that
-// identify different properties. The Accessor is templatized to also provide
-// typesafety to the callers.
-//
-// Example:
-//   // Note: you don't want to use Singleton for your Accessor if you're using
-//   // a simple type like int or string as the data, since it will enforce that
-//   // there is only one singleton for that type, which will conflict. If
-//   // you're putting in some struct that's unique to you, go ahead.
-//   PropertyAccessor<int>* my_accessor() const {
-//     static PropertyAccessor<int>* accessor = NULL;
-//     if (!accessor) accessor = new PropertyAccessor<int>;
-//     return accessor;
-//   }
-//
-//   void doit(SomeObjectThatImplementsPropertyBag* object) {
-//     PropertyAccessor<int>* accessor = my_accessor();
-//     int* property = accessor->GetProperty(object);
-//     if (property)
-//       ... use property ...
-//
-//     accessor->SetProperty(object, 22);
-//   }
-class CONTENT_EXPORT PropertyBag {
- public:
-  // The type that uniquely identifies a property type.
-  typedef int PropID;
-  enum { NULL_PROP_ID = -1 };  // Invalid property ID.
-
-  // Properties are all derived from this class. They must be deletable and
-  // copyable
-  class Prop {
-   public:
-    virtual ~Prop() {}
-
-    // Copies the property and returns a pointer to the new one. The caller is
-    // responsible for managing the lifetime.
-    virtual Prop* copy() = 0;
-  };
-
-  PropertyBag();
-  PropertyBag(const PropertyBag& other);
-  virtual ~PropertyBag();
-
-  PropertyBag& operator=(const PropertyBag& other);
-
- private:
-  friend class PropertyAccessorBase;
-
-  typedef std::map<PropID, linked_ptr<Prop> > PropertyMap;
-
-  // Used by the PropertyAccessor to set the property with the given ID.
-  // Ownership of the given pointer will be transferred to us. Any existing
-  // property matching the given ID will be deleted.
-  void SetProperty(PropID id, Prop* prop);
-
-  // Used by the PropertyAccessor to retrieve the property with the given ID.
-  // The returned pointer will be NULL if there is no match. Ownership of the
-  // pointer will stay with the property bag.
-  Prop* GetProperty(PropID id);
-  const Prop* GetProperty(PropID id) const;
-
-  // Deletes the property with the given ID from the bag if it exists.
-  void DeleteProperty(PropID id);
-
-  PropertyMap props_;
-
-  // Copy and assign is explicitly allowed for this class.
-};
-
-// PropertyAccessorBase -------------------------------------------------------
-
-// Manages getting the unique IDs to identify a property. Callers should use
-// PropertyAccessor below instead.
-class CONTENT_EXPORT PropertyAccessorBase {
- public:
-  PropertyAccessorBase();
-  virtual ~PropertyAccessorBase() {}
-
-  // Removes our property, if any, from the given property bag.
-  void DeleteProperty(PropertyBag* bag) {
-    bag->DeleteProperty(prop_id_);
-  }
-
- protected:
-  void SetPropertyInternal(PropertyBag* bag, PropertyBag::Prop* prop) {
-    bag->SetProperty(prop_id_, prop);
-  }
-  PropertyBag::Prop* GetPropertyInternal(PropertyBag* bag) {
-    return bag->GetProperty(prop_id_);
-  }
-  const PropertyBag::Prop* GetPropertyInternal(const PropertyBag* bag) const {
-    return bag->GetProperty(prop_id_);
-  }
-
- private:
-  // Identifier for this property.
-  PropertyBag::PropID prop_id_;
-
-  DISALLOW_COPY_AND_ASSIGN(PropertyAccessorBase);
-};
-
-// PropertyAccessor -----------------------------------------------------------
-
-// Provides typesafe accessor functions for a property bag, and manages the
-// unique identifiers for properties via the PropertyAccessorBase.
-template<class T>
-class PropertyAccessor : public PropertyAccessorBase {
- public:
-  PropertyAccessor() : PropertyAccessorBase() {}
-  virtual ~PropertyAccessor() {}
-
-  // Makes a copy of the |prop| object for storage.
-  void SetProperty(PropertyBag* bag, const T& prop) {
-    SetPropertyInternal(bag, new Container(prop));
-  }
-
-  // Returns our property in the given bag or NULL if there is no match. The
-  // returned pointer's ownership will stay with the property bag.
-  T* GetProperty(PropertyBag* bag) {
-    PropertyBag::Prop* prop = GetPropertyInternal(bag);
-    if (!prop)
-      return NULL;
-    return static_cast<Container*>(prop)->get();
-  }
-  const T* GetProperty(const PropertyBag* bag) const {
-    const PropertyBag::Prop* prop = GetPropertyInternal(bag);
-    if (!prop)
-      return NULL;
-    return static_cast<const Container*>(prop)->get();
-  }
-
-  // See also DeleteProperty on thn PropertyAccessorBase.
-
- private:
-  class Container : public PropertyBag::Prop {
-   public:
-    explicit Container(const T& data) : data_(data) {}
-
-    T* get() { return &data_; }
-    const T* get() const { return &data_; }
-
-   private:
-    virtual Prop* copy() {
-      return new Container(data_);
-    }
-
-    T data_;
-  };
-
-  DISALLOW_COPY_AND_ASSIGN(PropertyAccessor);
-};
-
-#endif  // CONTENT_COMMON_PROPERTY_BAG_H_