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// **************************************************************************
// * This file is part of the zenXML project. It is distributed under the *
// * Boost Software License, Version 1.0. See accompanying file *
// * LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt. *
// * Copyright (C) 2011 ZenJu (zhnmju123 AT gmx.de) *
// **************************************************************************
#ifndef STRING_TRAITS_HEADER_813274321443234
#define STRING_TRAITS_HEADER_813274321443234
#include "type_tools.h"
#include "assert_static.h"
//uniform access to string-like types: classes and character arrays
namespace zen
{
/*
strBegin():
std::wstring str(L"dummy");
char array[] = "dummy";
const wchar_t* iter = strBegin(str); //returns str.c_str()
const char* iter2 = strBegin(array); //returns array
strLength():
strLength(str); //equals str.size()
strLength(array); //equals cStringLength(array)
StringTraits<>::CharType:
StringTraits<std::wstring>::CharType //equals wchar_t
StringTraits<wchar_t[5]> ::CharType //equals wchar_t
StringTraits<>::isStringLike:
StringTraits<const wchar_t*>::isStringLike; //equals "true"
StringTraits<const int*> ::isStringLike; //equals "false"
StringTraits<>::isStringClass:
StringTraits<std::wstring>::isStringClass //equals "true"
StringTraits<wchar_t[5]> ::isStringClass //equals "false"
*/
//---------------------- implementation ----------------------
namespace implementation
{
template<typename T>
class HasValueTypedef
{
typedef char Yes[1];
typedef char No [2];
template <typename U> class HelperTp {};
//detect presence of a member type called value_type
template <class U> static Yes& hasMemberValueType(HelperTp<typename U::value_type>*);
template <class U> static No& hasMemberValueType(...);
public:
enum { result = sizeof(hasMemberValueType<T>(NULL)) == sizeof(Yes)
};
};
template<typename T, bool isClassType>
class HasStringMembers
{
public:
enum { result = false };
};
template<typename T>
class HasStringMembers<T, true>
{
typedef char Yes[1];
typedef char No [2];
//detect presence of member functions (without specific restriction on return type, within T or one of it's base classes)
template <typename U, U t> class HelperFn {};
struct Fallback
{
int c_str;
int length;
};
template <class U>
struct Helper2 : public U, public Fallback {}; //U must be a class-type!
//we don't know the exact declaration of the member attribute (may be in base class), but we know what NOT to expect:
template <class U> static No& hasMemberCstr(HelperFn<int Fallback::*, &Helper2<U>::c_str>*);
template <class U> static Yes& hasMemberCstr(...);
template <class U> static No& hasMemberLength(HelperFn<int Fallback::*, &Helper2<U>::length>*);
template <class U> static Yes& hasMemberLength(...);
public:
enum { result = sizeof(hasMemberCstr <T>(NULL)) == sizeof(Yes) &&
sizeof(hasMemberLength<T>(NULL)) == sizeof(Yes)
};
};
template <class S, bool isStringClass> struct StringTraits2 { typedef EmptyType Result; }; //"StringTraits2": fix some VS bug with namespace and partial template specialization
template <class S> struct StringTraits2<S, true > { typedef typename S::value_type Result; };
template <> struct StringTraits2<char, false> { typedef char Result; };
template <> struct StringTraits2<wchar_t, false> { typedef wchar_t Result; };
}
template <class S>
struct StringTraits
{
private:
typedef typename RemoveRef <S >::Result NonRefType;
typedef typename RemoveConst <NonRefType >::Result NonConstType;
typedef typename RemoveArray <NonConstType>::Result NonArrayType;
typedef typename RemovePointer<NonArrayType>::Result NonPtrType;
typedef typename RemoveConst <NonPtrType >::Result UndecoratedType; //handle "const char* const"
public:
enum
{
isStringClass = implementation::HasStringMembers<NonConstType, implementation::HasValueTypedef<NonConstType>::result>::result
};
typedef typename implementation::StringTraits2<UndecoratedType, isStringClass>::Result CharType;
enum
{
isStringLike = IsSameType<CharType, char>::result || IsSameType<CharType, wchar_t>::result
};
};
namespace implementation
{
template <class C> inline
size_t cStringLength(const C* str) //strlen()
{
assert_static((IsSameType<C, char>::result || IsSameType<C, wchar_t>::result));
size_t len = 0;
while (*str++ != 0)
++len;
return len;
}
}
template <class S> inline
const typename StringTraits<S>::CharType* strBegin(const S& str, typename S::value_type dummy = 0) { return str.c_str(); } //SFINAE: T must be a "string"
template <class Char>
inline const typename StringTraits<Char>::CharType* strBegin(const Char* str) { return str; }
inline const char* strBegin(const char& ch) { return &ch; }
inline const wchar_t* strBegin(const wchar_t& ch) { return &ch; }
template <class S> inline
size_t strLength(const S& str, typename S::value_type dummy = 0) { return str.length(); } //SFINAE: T must be a "string"
template <class Char>
inline size_t strLength(const Char* str) { return implementation::cStringLength(str); }
inline size_t strLength(char) { return 1; }
inline size_t strLength(wchar_t) { return 1; }
}
#endif //STRING_TRAITS_HEADER_813274321443234
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