Standard Portable Library: spl/Null.h Source File

00001 /*
00002  *   This file is part of the Standard Portable Library (SPL).
00003  *
00004  *   SPL is free software: you can redistribute it and/or modify
00005  *   it under the terms of the GNU General Public License as published by
00006  *   the Free Software Foundation, either version 3 of the License, or
00007  *   (at your option) any later version.
00008  *
00009  *   SPL is distributed in the hope that it will be useful,
00010  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
00011  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00012  *   GNU General Public License for more details.
00013  *
00014  *   You should have received a copy of the GNU General Public License
00015  *   along with SPL.  If not, see <http://www.gnu.org/licenses/>.
00016  */
00017 #ifndef _null_h
00018 #define _null_h
00019 
00020 #include <spl/types.h>
00021 #include <spl/Debug.h>
00022 
00029 #define NULL_MAJIC 0            //< Majic number for ASSERT's in Compare and Convert
00030 
00034 class Null : public IComparable
00035 {
00036 protected:
00037         static Null m_instance;
00038 
00039 public:
00040         Null();
00041         virtual ~Null();
00042 
00043         virtual bool Equals( const IComparable *a ) const;
00044         virtual int Compare( const IComparable *a ) const;
00045         virtual bool Equals( const IComparable& a ) const;
00046         virtual int Compare( const IComparable& a ) const;
00047 
00050         virtual int32 MajicNumber() const;
00051 
00052         virtual int32 HashCode() const;
00053 
00054         inline operator void *() const { return NULL; }
00055 
00056         inline static Null& Instance() { return m_instance; }
00057 };
00058 
00059 inline void ValidateType( const Null& u ) {}
00060 inline void ValidateType( const Null *u ) {}
00061 
00062 REGISTER_TYPEOF( 571, Null );
00063 
00066 #endif