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csutil/typetraits.h
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00001 /*
00002   Copyright (C) 2006 by Marten Svanfeldt
00003 
00004   This library is free software; you can redistribute it and/or
00005   modify it under the terms of the GNU Library General Public
00006   License as published by the Free Software Foundation; either
00007   version 2 of the License, or (at your option) any later version.
00008 
00009   This library 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 GNU
00012   Library General Public License for more details.
00013 
00014   You should have received a copy of the GNU Library General Public
00015   License along with this library; if not, write to the Free
00016   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00017 */
00018 
00019 #ifndef __CSUTIL_TYPETRAITS_H__
00020 #define __CSUTIL_TYPETRAITS_H__
00021 
00027 namespace CS
00028 {
00029   namespace Meta
00030   {
00031     namespace Implementation
00032     {
00033       // Types for checking yes/no
00034 
00036       typedef char YesType;
00037 
00039       struct NoType
00040       {
00041         char padding[8];
00042       };
00043 
00045       template <class T>
00046       struct Wrap { Wrap () {} };
00047 
00048       template <class T> T&(* IsReferenceHelper1(Wrap<T>) )(Wrap<T>);
00049       char IsReferenceHelper1(...);
00050 
00051       template <class T> NoType IsReferenceHelper2(T&(*)(Wrap<T>));
00052       YesType IsReferenceHelper2(...);
00053 
00054       template <class T>
00055       struct IsReferenceImpl
00056       {
00057         static const bool value = sizeof(IsReferenceHelper2 (
00058           IsReferenceHelper1 (Wrap<T>()))) == 1;
00059       };
00060 
00061 
00062       template <bool b1, bool b2, bool b3 = true, bool b4 = true, bool b5 = true, 
00063                 bool b6 = true, bool b7 = true>
00064       struct TraitAnd;
00065 
00066       template <bool b1, bool b2, bool b3, bool b4, bool b5, bool b6, bool b7>
00067       struct TraitAnd
00068       {
00069         static const bool value = false;
00070       };
00071 
00072       template <>
00073       struct TraitAnd<true, true, true, true, true, true, true>
00074       {
00075         static const bool value = true;
00076       };
00077 
00078       template <bool b1, bool b2, bool b3 = false, bool b4 = false, bool b5 = false,
00079                 bool b6 = false, bool b7 = false>
00080       struct TraitOr;
00081 
00082       template <bool b1, bool b2, bool b3, bool b4, bool b5, bool b6, bool b7>
00083       struct TraitOr
00084       {
00085         static const bool value = true;
00086       };
00087 
00088       template<>
00089       struct TraitOr<false, false, false, false, false, false, false>
00090       {
00091         static const bool value = false;
00092       };
00093 
00094       template <class T>
00095       YesType IsSameTester(T*, T*);
00096 
00097       NoType IsSameTester(...);
00098 
00099       template <class T, class U>
00100       struct IsSameImpl
00101       {
00102         static T* t;
00103         static U* u;
00104 
00105         static const bool value = TraitAnd<
00106           sizeof(YesType) == sizeof(IsSameTester(t, u)),
00107           IsReferenceImpl<T>::value == IsReferenceImpl<U>::value,
00108           sizeof(T) == sizeof(U)>::value;
00109       };
00110 
00111       template<typename B, typename D>
00112       struct IsBaseOfHelper
00113       {
00114         operator const B*() const;
00115         operator const D*();
00116       };
00117 
00118       template<typename B, typename D>
00119       struct IsBaseOfImpl
00120       {
00121         template<typename T>
00122         static YesType Test(const D*,T);
00123         static NoType Test(const B*,int);
00124         static const bool value = TraitOr<
00125           sizeof(YesType) == sizeof(Test(IsBaseOfHelper<B,D>(),0)),
00126           IsSameImpl<B,D>::value>::value;
00127       };
00128     } // namespace Implementation
00129 
00130 
00134     template <class Type>
00135     struct IsReference
00136     {
00137       static const bool value = CS::Meta::Implementation
00138         ::IsReferenceImpl<Type>::value;
00139     };
00140 
00144     template <class Type1, class Type2>
00145     struct IsSame
00146     {
00147       static const bool value = CS::Meta::Implementation
00148         ::IsSameImpl<Type1, Type2>::value;
00149     };
00150 
00154     template <class Type1, class Type2>
00155     struct IsBaseOf
00156     {
00157       static const bool value = CS::Meta::Implementation
00158         ::IsBaseOfImpl<Type1, Type2>::value;
00159     };
00160   } // namespace TypeTraits
00161 
00162 } // namespace CS
00163 
00164 #endif 

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