00001 /* 00002 libwftk - Worldforge Toolkit - a widget library 00003 Copyright (C) 2003 Ron Steinke <rsteinke@w-link.net> 00004 00005 This library is free software; you can redistribute it and/or 00006 modify it under the terms of the GNU Lesser General Public 00007 License as published by the Free Software Foundation; either 00008 version 2.1 of the License, or (at your option) any later version. 00009 00010 This library is distributed in the hope that it will be useful, 00011 but WITHOUT ANY WARRANTY; without even the implied warranty of 00012 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00013 Lesser General Public License for more details. 00014 00015 You should have received a copy of the GNU Lesser General Public 00016 License along with this library; if not, write to the 00017 Free Software Foundation, Inc., 59 Temple Place - Suite 330, 00018 Boston, MA 02111-1307, SA. 00019 */ 00020 00021 #ifndef _REF_MAP_H_ 00022 #define _REF_MAP_H_ 00023 00024 #include <map> 00025 #include <cassert> 00026 00027 namespace wftk { 00028 00029 // This is a map which keeps single instances of its value 00030 // type available for refcounted keys. You write the create() 00031 // function which is used when an unknown key is ref'ed 00032 // for the first time. 00033 00034 template<class Key, class T, class Cmp = std::less<Key> > 00035 class RefMap 00036 { 00037 public: 00038 RefMap(bool autodelete = true) : autodelete_(autodelete) {} 00039 virtual ~RefMap() 00040 { 00041 // We can't delete elements from the map if other things 00042 // still have references to them. The best we can do 00043 // is assert that all references have been dropped, and 00044 // rely on the users of this class to handle that. 00045 assert(map_.empty()); 00046 } 00047 00048 T* ref(const Key& key) 00049 { 00050 ValType& val = map_[key]; // find, and create if not already present 00051 if(!val.value) // must be newly created element, from new key 00052 val.value = create(key); 00053 ++val.refcount; 00054 return val.value; 00055 } 00056 00057 void unref(const Key& key) 00058 { 00059 typename MapType::iterator I = map_.find(key); 00060 assert(I != map_.end()); 00061 if(--I->second.refcount == 0) { 00062 delete I->second.value; 00063 map_.erase(I); 00064 if(autodelete_ && map_.empty()) 00065 delete this; 00066 } 00067 } 00068 00069 bool empty() const {return map_.empty();} 00070 00071 private: 00072 virtual T* create(const Key&) = 0; 00073 00074 struct ValType 00075 { 00076 ValType() : value(0), refcount(0) {} 00077 00078 T* value; 00079 unsigned long refcount; 00080 }; 00081 typedef std::map<Key, ValType, Cmp> MapType; 00082 MapType map_; 00083 00084 bool autodelete_; 00085 }; 00086 00087 } // namespace 00088 00089 #endif
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