C++ 将 std::string 编码/解码为 UTF-16
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Encode/Decode std::string to UTF-16
提问by Peter
I have to handle a file format (both read from and write to it) in which strings are encoded in UTF-16 (2 bytes per character). Since characters out of the ASCII table are rarely used in the application domain, all of the strings in my C++ model classes are stored in instances of std::string (UTF-8 encoded).
我必须处理一种文件格式（读取和写入），其中字符串以 UTF-16 编码（每个字符 2 个字节）。由于 ASCII 表中的字符很少在应用程序域中使用，因此我的 C++ 模型类中的所有字符串都存储在 std::string（UTF-8 编码）的实例中。
I'm looking for a library (searched in STL and Boost with no luck) or a set of C/C++ functions to handle this std::string <-> UTF-16 conversion when loading from or saving to file format (actually modeled as a bytestream) including the generation/recognition of surrogate pairs and all that Unicode stuffs (I'm admittedly no expert with)...
我正在寻找一个库（在 STL 和 Boost 中搜索但没有运气）或一组 C/C++ 函数来处理这个 std::string <-> UTF-16 转换时从文件格式加载或保存到文件格式（实际建模作为字节流）包括代理对的生成/识别和所有 Unicode 的东西（我承认我不是专家）......
Any suggestions? Thanks!
有什么建议？谢谢！
EDIT: forgot to mention it should be cross-platform (Win / Mac) and cannot use C++11.
编辑：忘了提到它应该是跨平台的（Win/Mac）并且不能使用 C++11。
回答by bames53
C++11 has this functionality:
C++11 有这个功能：
std::string s = u8"Hello, World!";
// #include <codecvt>
std::wstring_convert<std::codecvt<char16_t,char,std::mbstate_t>,char16_t> convert;
std::u16string u16 = convert.from_bytes(s);
std::string u8 = convert.to_bytes(u16);
However to my knowledge the only implementation that has this so far is libc++. C++11 also has std::codecvt_utf8_utf16<char16_t>which some other implementations have. Specifically, codecvt_utf8_utf16works in VS 2010 and above, and since wchar_t is used by Windows to represent UTF-16 you can use this to convert between UTF-8 and Windows' native encoding.
然而，据我所知，迄今为止唯一具有此功能的实现是 libc++。C++11 也具有std::codecvt_utf8_utf16<char16_t>其他一些实现所具有的特性。具体来说，codecvt_utf8_utf16适用于 VS 2010 及更高版本，并且由于 Windows 使用 wchar_t 来表示 UTF-16，因此您可以使用它在 UTF-8 和 Windows 的本机编码之间进行转换。
The specialization
codecvt<char16_t, char, mbstate_t>converts between the UTF-16 and UTF-8 encoding schemes, and the specializationcodecvt<char32_t, char, mbstate_t>converts between the UTF-32 and UTF-8 encoding schemes.— [locale.codecvt] 22.4.1.4/3
特化
codecvt<char16_t, char, mbstate_t>在 UTF-16 和 UTF-8 编码方案codecvt<char32_t, char, mbstate_t>之间转换，特化在 UTF-32 和 UTF-8 编码方案之间转换。— [locale.codecvt] 22.4.1.4/3
Oh, and std::codecvt specializations have protected destructors, and wstring_convert requires access to the destructor so you really need an adapter:
哦，std::codecvt 特化有受保护的析构函数，而 wstring_convert 需要访问析构函数，所以你真的需要一个适配器：
template <class Facet>
class usable_facet : public Facet {
public:
using Facet::Facet; // inherit constructors
~usable_facet() {}
// workaround for compilers without inheriting constructors:
// template <class ...Args> usable_facet(Args&& ...args) : Facet(std::forward<Args>(args)...) {}
};
template<typename internT, typename externT, typename stateT>
using codecvt = usable_facet<std::codecvt<internT, externT, stateT>>;
std::wstring_convert<codecvt<char16_t,char,std::mbstate_t>> convert;
回答by thehouse
Did you look at Boost.Locale? This page, in particular, describes how to do UTF to UTF conversions and how to integrate it with IOStreams.
你看过Boost.Locale吗？ 本页特别介绍了如何进行 UTF 到 UTF 转换以及如何将其与 IOStreams 集成。
回答by JYG
I would suggest having a look at:
我建议看看：
Convert C++ std::string to UTF-16-LE encoded string
将 C++ std::string 转换为 UTF-16-LE 编码的字符串
And check out the iconv function. It's a C library, no requirements for C++11.
并查看 iconv 函数。它是一个 C 库，对 C++11 没有要求。
There's also a Win32 specific iconv library at https://github.com/win-iconv/win-iconv.
在https://github.com/win-iconv/win-iconv上还有一个 Win32 特定的 iconv 库。
