chrome/common/notification_details.h

// Copyright (c) 2006-2008 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.

// This file defines the type used to provide details for NotificationService
// notifications.

#ifndef CHROME_COMMON_NOTIFICATION_DETAILS_H__
#define CHROME_COMMON_NOTIFICATION_DETAILS_H__

#include "base/basictypes.h"

// Do not declare a NotificationDetails directly--use either
// "Details<detailsclassname>(detailsclasspointer)" or
// NotificationService::NoDetails().
class NotificationDetails {
 public:
  NotificationDetails();
  NotificationDetails(const NotificationDetails& other);
  ~NotificationDetails();

  // NotificationDetails can be used as the index for a map; this method
  // returns the pointer to the current details as an identifier, for use as a
  // map index.
  uintptr_t map_key() const { return reinterpret_cast<uintptr_t>(ptr_); }

  bool operator!=(const NotificationDetails& other) const {
    return ptr_ != other.ptr_;
  }

  bool operator==(const NotificationDetails& other) const {
    return ptr_ == other.ptr_;
  }

 protected:
  explicit NotificationDetails(const void* ptr);

  // Declaring this const allows Details<T> to be used with both T = Foo and
  // T = const Foo.
  const void* ptr_;
};

template <class T>
class Details : public NotificationDetails {
 public:
  // TODO(erg): Our code hard relies on implicit conversion
  Details(T* ptr) : NotificationDetails(ptr) {}  // NOLINT
  Details(const NotificationDetails& other)      // NOLINT
    : NotificationDetails(other) {}

  T* operator->() const { return ptr(); }
  // The casts here allow this to compile with both T = Foo and T = const Foo.
  T* ptr() const { return static_cast<T*>(const_cast<void*>(ptr_)); }
};

#endif  // CHROME_COMMON_NOTIFICATION_DETAILS_H__