C ++ 0x中的新unicode字符 [英] New unicode characters in C++0x

问题描述

我正在建立一个API，允许我以各种编码提取字符串，包括utf8，utf16，utf32和wchar_t（根据操作系统可能是utf32或utf16）。

1. 新C ++标准引入了 char16_t 和 char32_t 但是问题是，会干扰与正常的 uint16_t code>， uint32_t ， wchar_t 类型不允许重载，因为它们可能引用同一类型？

     class some_class {
    public：
    void set（std :: string）; // utf8 string 
    void set（std :: wstring）; // wchar string utf16 or utf32根据
    //到sizeof（wchar_t）
    void set（std :: basic_string< uint16_t>）
    // wchar independent utf16 string 
    void set （std :: basic_string< uint32_t>）; 
    // wchar independent utf32 string 
    
    
    #ifdef HAVE_NEW_UNICODE_CHARRECTERS 
    void set（std :: basic_string< char16_t>）
    // new standard utf16 string 
    void set（std :: basic_string< char32_t>）; 
    // new standard utf32 string 
    #endif 
   }; 
     

   所以我可以写：

     foo.set（USome utf32 String）; 
    foo.set（uSome utf16 string）; 
     




2. std :: basic_string< char16_t& 和 std :: basic_string< char32_t> ：

     typedef basic_string< wchar_t> wstring。 
     

   我找不到任何参考。

   
   
   

   Edit：根据gcc-4.4的标题，引入了这些新类型：

     typedef basic_string< char16_t> u16string; 
    typedef basic_string< char32_t> u32string; 
     

   我只是想确保这是实际的标准要求，而不是gcc-ism。

1） char16_t 和 char32_t 将是不同的新类型，因此可以对它们进行重载。





http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2018.html\">ISO/IEC JTC1 SC22 WG21 N2018 ：




定义 char16_t 为
distinct新类型的typedef，名称为
_Char16_t 与 uint_least16_t 具有相同的大小和表示。
同样，定义 char32_t 为
typedef到一个不同的新类型，
名称 _Char32_t 与
uint_least32_t 具有相同的
大小和表示。




进一步说明（摘自devx.com文章为Unicode革命做准备 ）：




您可能想知道为什么
_Char16_t uint_least16_t 时，需要code>和 _Char32_t
uint_least32_t 已可用。
新类型
解决的主要问题是重载。现在
可能重载
采用 _Char16_t 和 _Char32_t
参数，并创建与
std不同的专用化
，例如 std :: basic_string< _Char16_t>
：basic_string< wchar_t> 。




2） u16string 和 u32string 确实是C ++ 0x的一部分，而不仅仅是GCC主题，因为它们在各种标准草案。它们将包含在新的< string> 头中。同一篇文章的引用：




标准库还将提供
_Char16_t 和 _Char32_t typedefs，类似于typedefs wstring ，
wcout 等，用于以下标准类：





filebuf，streambuf，streampos，streamoff，ios，istream， ostream，fstream，
ifstream，ofstream，stringstream，istringstream，ostringstream， string





I'm buiding an API that allows me to fetch strings in various encodings, including utf8, utf16, utf32 and wchar_t (that may be utf32 or utf16 according to OS).

1. New C++ standard had introduced new types char16_t and char32_t that do not have this sizeof ambiguity and should be used in future, so I would like to support them as well, but the question is, would they interfere with normal uint16_t, uint32_t, wchar_t types not allowing overload because they may refer to same type?

   class some_class {
   public:
       void set(std::string); // utf8 string
       void set(std::wstring); // wchar string utf16 or utf32 according
                                // to sizeof(wchar_t)
       void set(std::basic_string<uint16_t>)
                            // wchar independent utf16 string
       void set(std::basic_string<uint32_t>);
                            // wchar independent utf32 string
   
   
   #ifdef HAVE_NEW_UNICODE_CHARRECTERS
       void set(std::basic_string<char16_t>)
                            // new standard utf16 string
       void set(std::basic_string<char32_t>);
                            // new standard utf32 string
   #endif
   };
   

   So I can just write:

   foo.set(U"Some utf32 String");
   foo.set(u"Some utf16 string");
   

2. What are the typedef of std::basic_string<char16_t> and std::basic_string<char32_t> as there is today:

   typedef basic_string<wchar_t> wstring.
   

   I can't find any reference.

   Edit: according to headers of gcc-4.4, that introduced these new types:

   typedef basic_string<char16_t> u16string;
   typedef basic_string<char32_t> u32string;
   

   I just want to make sure that this is actual standard requirement and not gcc-ism.

解决方案

1) char16_t and char32_t will be distinct new types, so overloading on them will be possible.

Quote from ISO/IEC JTC1 SC22 WG21 N2018:

Define char16_t to be a typedef to a distinct new type, with the name _Char16_t that has the same size and representation as uint_least16_t. Likewise, define char32_t to be a typedef to a distinct new type, with the name _Char32_t that has the same size and representation as uint_least32_t.

Further explanation (from a devx.com article "Prepare Yourself for the Unicode Revolution"):

You're probably wondering why the _Char16_t and _Char32_t types and keywords are needed in the first place when the typedefs uint_least16_t and uint_least32_t are already available. The main problem that the new types solve is overloading. It's now possible to overload functions that take _Char16_t and _Char32_t arguments, and create specializations such as std::basic_string<_Char16_t> that are distinct from std::basic_string <wchar_t>.

2) u16string and u32string are indeed part of C++0x and not just GCC'isms, as they are mentioned in various standard draft papers. They will be included in the new <string> header. Quote from the same article:

The Standard Library will also provide _Char16_t and _Char32_t typedefs, in analogy to the typedefs wstring, wcout, etc., for the following standard classes:

filebuf, streambuf, streampos, streamoff, ios, istream, ostream, fstream, ifstream, ofstream, stringstream, istringstream, ostringstream, string

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