c++ - C++0x 中的新 unicode 字符

Question

我正在构建一个 API，它允许我获取各种编码的字符串，包括 utf8、utf16、utf32 和 wchar_t(根据操作系统可能是 utf32 或 utf16)。

1. 新的 C++ 标准引入了新的类型 char16_t和 char32_t没有这种大小的歧义，应该在将来使用，所以我也想支持它们，但问题是，它们会干扰正常的uint16_t吗？ , uint32_t , wchar_t类型不允许重载，因为它们可能引用相同的类型？

   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
   };
   

   所以我可以写:

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

2. std::basic_string<char16_t> 的 typedef 是什么？和 std::basic_string<char32_t>就像今天一样:

   typedef basic_string<wchar_t> wstring.
   

   我找不到任何引用资料。

   编辑: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。

Answer 1

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。

引自 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.

进一步解释(来自 devx.com 文章“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和 u32string确实是 C++0x 的一部分，而不仅仅是 GCC 主义，正如 various standard draft papers 中提到的那样.它们将包含在新的 <string> 中标题。引用同一篇文章:

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