Fawkes API  Fawkes Development Version
unique.h
00001 
00002 /***************************************************************************
00003  *  unique.h - Uniqueness constraint
00004  *
00005  *  Created: Sun Feb 24 13:07:25 2008
00006  *  Copyright  2007-2008  Tim Niemueller [www.niemueller.de]
00007  *
00008  ****************************************************************************/
00009 
00010 /*  This program is free software; you can redistribute it and/or modify
00011  *  it under the terms of the GNU General Public License as published by
00012  *  the Free Software Foundation; either version 2 of the License, or
00013  *  (at your option) any later version. A runtime exception applies to
00014  *  this software (see LICENSE.GPL_WRE file mentioned below for details).
00015  *
00016  *  This program is distributed in the hope that it will be useful,
00017  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  *  GNU Library General Public License for more details.
00020  *
00021  *  Read the full text in the LICENSE.GPL_WRE file in the doc directory.
00022  */
00023 
00024 #ifndef __UTILS_CONSTRAINTS_UNIQUE_H_
00025 #define __UTILS_CONSTRAINTS_UNIQUE_H_
00026 
00027 #include <core/exception.h>
00028 #include <cstddef>
00029 
00030 namespace fawkes {
00031 
00032 
00033 /** @class UniquenessViolationException <utils/constraints/unique.h>
00034  * Uniqueness violation exception.
00035  * Thrown if an operation is tried which would violate the uniqueness
00036  * constraint.
00037  * @see UniquenessConstraint
00038  * @ingroup Exceptions
00039  * @author Tim Niemueller
00040  */
00041 
00042 class UniquenessViolationException : public Exception
00043 {
00044  public:
00045   /** Contructor.
00046    * @param msg message
00047    */
00048   UniquenessViolationException(const char *msg) : Exception(msg) {}
00049 };
00050 
00051 
00052 /** @class UniquenessConstraint <utils/constraints/unique.h>
00053  * Uniqueness constraint.
00054  * This constraint keeps track of a resource that may exist at most once.
00055  *
00056  * The resource can only be added if no resource has been added and not been
00057  * removed before. A resource can always be removed.
00058  *
00059  * @author Tim Niemueller
00060  */
00061 
00062 template <class ResourceType>
00063   class UniquenessConstraint
00064 {
00065  public:
00066   UniquenessConstraint();
00067 
00068   void add(ResourceType *r);
00069   void remove(ResourceType *p);
00070 
00071   ResourceType *             resource();
00072 
00073  private:
00074   ResourceType *_resource;
00075 };
00076 
00077 
00078 /** Constructor. */
00079 template <class ResourceType>
00080   UniquenessConstraint<ResourceType>::UniquenessConstraint()
00081 {
00082   _resource = NULL;
00083 }
00084 
00085 
00086 /** Add resource.
00087  * This will add the resources or throw an exception if there is already a resource.
00088  * @param r resource object to add
00089  * @exception UniquenessViolationException thrown, if a second resource is added
00090  */
00091 template <class ResourceType>
00092 void
00093 UniquenessConstraint<ResourceType>::add(ResourceType *r)
00094 {
00095   if ( (_resource != NULL) && (r != _resource) ) {
00096     throw UniquenessViolationException("Different resource has already been added.");
00097   } else {
00098     _resource = r;
00099   }
00100 }
00101 
00102 
00103 /** Remove resource.
00104  * @param r resource object to remove
00105  */
00106 template <class ResourceType>
00107 void
00108 UniquenessConstraint<ResourceType>::remove(ResourceType *r)
00109 {
00110   if ( r == _resource )  _resource = NULL;
00111 }
00112 
00113 /** Get resource.
00114  * @return resource if set, NULL otherwise
00115  */
00116 template <class ResourceType>
00117 ResourceType *
00118 UniquenessConstraint<ResourceType>::resource()
00119 {
00120   return _resource;
00121 }
00122 
00123 
00124 } // end namespace fawkes
00125 
00126 #endif