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/*
* Copyright 2009, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef O3D_CORE_CROSS_SERVICE_LOCATOR_H_
#define O3D_CORE_CROSS_SERVICE_LOCATOR_H_
#include <list>
#include <map>
#include "base/logging.h"
#include "base/basictypes.h"
#include "core/cross/service_interface_traits.h"
namespace o3d {
template <typename Interface>
class ServiceImplementation;
template <typename Interface>
class ServiceDependency;
// No virtual destructor for IServiceDependency because it is never destroyed
// through this class and because if forces the destructor in derived template
// classes to be instantiated early, causing a compilation error in some cases.
class IServiceDependency {
friend class ServiceLocator;
private:
virtual void Update(void* newService) = 0;
};
// A ServiceLocator tracks a number of services and connects them together
// through their ServiceDependencies. When a service is constucted, one or
// more ServiceImplementation member variables cause the service to be
// registered for each implemented service interface. Then zero or more
// ServiceDependency member variables register themselves as needing references
// to other services. When these services become available, the dependencies
// are updated to reference them. When these services are not available, the
// dependencies report their reference as NULL.
class ServiceLocator {
template <typename Interface>
friend class ServiceImplementation;
template <typename Interface>
friend class ServiceDependency;
typedef std::list<IServiceDependency*> DependencyList;
typedef std::map<InterfaceId, DependencyList> DependencyMap;
typedef std::map<InterfaceId, void*> ServiceMap;
public:
ServiceLocator() {}
// Returns whether a given service is available.
template <typename Interface>
bool IsAvailable() const {
ServiceMap::const_iterator it = services_.find(Interface::kInterfaceId);
return it != services_.end();
}
// Get a pointer to a service added to the service locator. Consider using a
// ServiceDependency instead.
template <typename Interface>
Interface* GetService() const {
ServiceMap::const_iterator it = services_.find(Interface::kInterfaceId);
if (it != services_.end()) {
return static_cast<Interface*>(it->second);
} else {
DCHECK(false);
return NULL;
}
}
private:
// Add service to list of those available through the service locator
// For any services previously added that are dependent on this one, update
// their dependency pointer to point here. This cannot be invoked directly.
// Use ServiceImplementation class.
void AddService(InterfaceId interfaceId, void* service);
// Remove an existing service from the service locator. Update any existing
// dependencies referencing this service to NULL. This cannot be invoked
// directly. Use ServiceImplementation class.
void RemoveService(InterfaceId interfaceId, void* service);
// Add a service dependency to the service locator. If the service has already
// been added then just modify the dependency parameter to reference the
// known service. Otherwise, set the dependency to NULL and add it to a list
// of those that will be resolved as soon as the necessary service is added.
// This cannot be invoked directly. Use ServiceDependency class.
void AddDependency(InterfaceId interfaceId, IServiceDependency* dependency);
// Remove a service dependency from the service locator.
// This cannot be invoked directly. Use ServiceDependency class.
void RemoveDependency(InterfaceId interfaceId,
IServiceDependency* dependency);
DependencyMap dependencies_;
ServiceMap services_;
DISALLOW_COPY_AND_ASSIGN(ServiceLocator);
};
} // namespace o3d
#endif // O3D_CORE_CROSS_SERVICE_LOCATOR_H_
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