C++ 如何将 UTF-8 std::string 转换为 UTF-16 std::wstring？
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How to convert UTF-8 std::string to UTF-16 std::wstring?
提问by aliakbarian
If I have a UTF-8 std::stringhow do I convert it to a UTF-16 std::wstring? Actually, I want to compare two Persian words.
如果我有一个 UTF-8std::string我如何将它转换为一个 UTF-16 std::wstring？实际上，我想比较两个波斯语单词。
回答by Yuchen Zhong
This is how you do it with C++11:
这就是你如何使用C++11做到这一点：
std::string str = "your string in utf8";
std::wstring_convert<std::codecvt_utf8_utf16<char16_t>> converter;
std::wstring wstr = converter.from_bytes(str);
And these are the headers you need:
这些是您需要的标题：
#include <iostream>
#include <string>
#include <locale>
#include <codecvt>
A more complete example available here: http://en.cppreference.com/w/cpp/locale/wstring_convert/from_bytes
此处提供更完整的示例：http: //en.cppreference.com/w/cpp/locale/wstring_convert/from_bytes
回答by john
Here's some code. Only lightly tested and there's probably a few improvements. Call this function to convert a UTF-8 string to a UTF-16 wstring. If it thinks the input string is not UTF-8 then it will throw an exception, otherwise it returns the equivalent UTF-16 wstring.
这是一些代码。仅经过轻微测试，可能会有一些改进。调用此函数可将 UTF-8 字符串转换为 UTF-16 wstring。如果它认为输入字符串不是 UTF-8 则它会抛出异常，否则它返回等效的 UTF-16 wstring。
std::wstring utf8_to_utf16(const std::string& utf8)
{
std::vector<unsigned long> unicode;
size_t i = 0;
while (i < utf8.size())
{
unsigned long uni;
size_t todo;
bool error = false;
unsigned char ch = utf8[i++];
if (ch <= 0x7F)
{
uni = ch;
todo = 0;
}
else if (ch <= 0xBF)
{
throw std::logic_error("not a UTF-8 string");
}
else if (ch <= 0xDF)
{
uni = ch&0x1F;
todo = 1;
}
else if (ch <= 0xEF)
{
uni = ch&0x0F;
todo = 2;
}
else if (ch <= 0xF7)
{
uni = ch&0x07;
todo = 3;
}
else
{
throw std::logic_error("not a UTF-8 string");
}
for (size_t j = 0; j < todo; ++j)
{
if (i == utf8.size())
throw std::logic_error("not a UTF-8 string");
unsigned char ch = utf8[i++];
if (ch < 0x80 || ch > 0xBF)
throw std::logic_error("not a UTF-8 string");
uni <<= 6;
uni += ch & 0x3F;
}
if (uni >= 0xD800 && uni <= 0xDFFF)
throw std::logic_error("not a UTF-8 string");
if (uni > 0x10FFFF)
throw std::logic_error("not a UTF-8 string");
unicode.push_back(uni);
}
std::wstring utf16;
for (size_t i = 0; i < unicode.size(); ++i)
{
unsigned long uni = unicode[i];
if (uni <= 0xFFFF)
{
utf16 += (wchar_t)uni;
}
else
{
uni -= 0x10000;
utf16 += (wchar_t)((uni >> 10) + 0xD800);
utf16 += (wchar_t)((uni & 0x3FF) + 0xDC00);
}
}
return utf16;
}
回答by Soren
There are some relevant Q&A hereand herewhich is worth a read.
Basically you need to convert the string to a common format -- my preference is always to convert to UTF-8, but your mileage may wary.
基本上，您需要将字符串转换为通用格式——我的偏好始终是转换为 UTF-8，但您的里程数可能会很谨慎。
There have been lots of software written for doing the conversion -- the conversion is straigth forwards and can be written in a few hours -- however why not pick up something already done such as the UTF-8 CPP
有很多软件是为进行转换而编写的——转换是直接进行的，可以在几个小时内完成——但是为什么不选择一些已经完成的东西，比如 UTF-8 CPP
回答by jj1
This page also seems useful: http://www.codeproject.com/KB/string/UtfConverter.aspx
此页面似乎也很有用：http: //www.codeproject.com/KB/string/UtfConverter.aspx
In the comment section of that page, there are also some interesting suggestions for this task like:
在该页面的评论部分，还有一些针对此任务的有趣建议，例如：
// Get en ASCII std::string from anywhere
std::string sLogLevelA = "Hello ASCII-world!";
std::wstringstream ws;
ws << sLogLevelA.c_str();
std::wstring sLogLevel = ws.str();
Or
或者
// To std::string:
str.assign(ws.begin(), ws.end());
// To std::wstring
ws.assign(str.begin(), str.end());
Though I'm not sure the validity of these approaches...
虽然我不确定这些方法的有效性......
回答by Yochai Timmer
To convert between the 2 types, you should use: std::codecvt_utf8_utf16< wchar_t>
Note the string prefixes I use to define UTF16 (L) and UTF8 (u8).
要在这两种类型之间进行转换，您应该使用：std::codecvt_utf8_utf16< wchar_t>
请注意我用来定义 UTF16 ( L) 和 UTF8 ( u8)的字符串前缀。
#include <string>
#include <codecvt>
int main()
{
std::string original8 = u8"???";
std::wstring original16 = L"???";
//C++11 format converter
std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> convert;
//convert to UTF8 and std::string
std::string utf8NativeString = convert.to_bytes(original16);
std::wstring utf16NativeString = convert.from_bytes(original8);
assert(utf8NativeString == original8);
assert(utf16NativeString == original16);
return 0;
}
