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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 "type_traits.h"
#include "assert_static.h"
//uniform access to string-like types, both classes and character arrays
namespace zen
{
/*
IsStringLike<>::result:
IsStringLike<const wchar_t*>::result; //equals "true"
IsStringLike<const int*> ::result; //equals "false"
GetCharType<>::Result:
GetCharType<std::wstring>::Result //equals wchar_t
GetCharType<wchar_t[5]> ::Result //equals wchar_t
strBegin():
std::wstring str(L"dummy");
char array[] = "dummy";
strBegin(str); //returns str.c_str()
strBegin(array); //returns array
strLength():
strLength(str); //equals str.length()
strLength(array); //equals cStringLength(array)
*/
//wrap a sub-string or a char* as an intermediate string class when the length is already known
template <class Char>
class StringProxy
{
public:
StringProxy(const Char* cstr, size_t len ) : cstr_(cstr), length_(len) {}
StringProxy(const Char* cstrBegin, const Char* cstrEnd) : cstr_(cstrBegin), length_(cstrEnd - cstrBegin) {}
const Char* c_str() const { return cstr_; }
size_t length() const { return length_; }
private:
const Char* cstr_;
size_t length_;
};
//---------------------- implementation ----------------------
namespace implementation
{
ZEN_INIT_DETECT_MEMBER(c_str) //we don't know the exact declaration of the member attribute and it may be in a base class!
ZEN_INIT_DETECT_MEMBER(length) //
template<typename T, bool isClassType>
struct HasStringMembers { enum { result = false }; };
template<typename T>
struct HasStringMembers<T, true> //Note: we can apply non-typed member-check on class types only!
{
enum { result = HasMember_c_str <T>::result &&
HasMember_length<T>::result
};
};
template<class S, class Char> //test if result of S::c_str() can convert to const Char*
class HasConversion
{
typedef char Yes[1];
typedef char No [2];
static Yes& hasConversion(const Char*);
static No& hasConversion(...);
static S createInstance();
public:
enum { result = sizeof(hasConversion(createInstance().c_str())) == sizeof(Yes) };
};
template <class S, bool isStringClass> struct GetCharTypeImpl { typedef EmptyType Result; };
template <class S> struct GetCharTypeImpl<S, true >
{
//typedef typename S::value_type Result;
/*DON'T use S::value_type:
1. support Glib::ustring: value_type is "unsigned int" but c_str() returns "const char*"
2. wxString, wxWidgets v2.9, has some questionable string design: wxString::c_str() returns a proxy (wxCStrData) which
is implicitly convertible to *both* "const char*" and "const wchar_t*" while wxString::value_type is a wrapper around an unsigned int
*/
typedef typename SelectIf<HasConversion<S, wchar_t>::result, wchar_t,
typename SelectIf<HasConversion<S, char>::result, char, EmptyType>::Result
>::Result Result;
};
template <> struct GetCharTypeImpl<char, false> { typedef char Result; };
template <> struct GetCharTypeImpl<wchar_t, false> { typedef wchar_t Result; };
ZEN_INIT_DETECT_MEMBER_TYPE(value_type);
template <class S>
class StringTraits
{
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 = HasStringMembers<NonConstType, HasMemberType_value_type<NonConstType>::result>::result
};
typedef typename GetCharTypeImpl<UndecoratedType, isStringClass>::Result CharType;
enum
{
isStringLike = IsSameType<CharType, char>::result ||
IsSameType<CharType, wchar_t>::result
};
};
}
template <class T>
struct IsStringLike { enum { result = implementation::StringTraits<T>::isStringLike }; };
template <class T>
struct GetCharType { typedef typename implementation::StringTraits<T>::CharType 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 GetCharType<S>::Result* strBegin(const S& str, typename EnableIf<implementation::StringTraits<S>::isStringClass>::Result* = NULL) //SFINAE: T must be a "string"
{
return str.c_str();
}
inline const char* strBegin(const char* str) { return str; }
inline const wchar_t* strBegin(const wchar_t* 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 EnableIf<implementation::StringTraits<S>::isStringClass>::Result* = NULL) //SFINAE: T must be a "string"
{
return str.length();
}
inline size_t strLength(const char* str) { return implementation::cStringLength(str); }
inline size_t strLength(const wchar_t* 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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