c ++从字符串制作unicode char

Question

我有这样的字符串

string s = "0081";

我需要像这样制作一个单字符的字符串

string c = "\u0081"

如何从长度为 4 的原始字符串中生成长度为 1 的字符串？

编辑：我的错误，“\u0081”不是 char（1 字节）而是 2 字节 character/string？所以我输入的是二进制 1000 0001，即 0x81，这就是我的字符串“0081”的来源。从这个 0x81 到一个字符串 c = "\u0081" 不管那个值是什么会更容易吗？感谢大家的帮助

Answer 1

给你：

unsigned int x;
std::stringstream ss;
ss << std::hex << "1081";
ss >> x;

wchar_t wc1 = x;
wchar_t wc2 = L'\u1081';

assert(wc1 == wc2);

std::wstring ws(1, wc);

Answer 2

这是整个过程，基于我在其他地方的评论中链接到的一些代码。

string s = "0081";
long codepoint = strtol(s.c_str(), NULL, 16);
string c = CodepointToUTF8(codepoint);

std::string CodepointToUTF8(long codepoint)
{
    std::string out;
    if (codepoint <= 0x7f)
        out.append(1, static_cast<char>(codepoint));
    else if (codepoint <= 0x7ff)
    {
        out.append(1, static_cast<char>(0xc0 | ((codepoint >> 6) & 0x1f)));
        out.append(1, static_cast<char>(0x80 | (codepoint & 0x3f)));
    }
    else if (codepoint <= 0xffff)
    {
        out.append(1, static_cast<char>(0xe0 | ((codepoint >> 12) & 0x0f)));
        out.append(1, static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f)));
        out.append(1, static_cast<char>(0x80 | (codepoint & 0x3f)));
    }
    else
    {
        out.append(1, static_cast<char>(0xf0 | ((codepoint >> 18) & 0x07)));
        out.append(1, static_cast<char>(0x80 | ((codepoint >> 12) & 0x3f)));
        out.append(1, static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f)));
        out.append(1, static_cast<char>(0x80 | (codepoint & 0x3f)));
    }
    return out;
}

请注意，此代码不进行任何错误检查，因此如果您向它传递一个无效的代码点，您将返回一个无效的字符串。

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