如何在C ++中将Unicode字符转换为大写 [英] How to convert unicode characters to uppercase in C++

问题描述

我正在学习C ++中的unicode，并且很难使它正常工作.我尝试将单个字符视为uint64_t.如果我只需要打印出字符，它就可以工作，但是问题是我需要将它们转换为大写字母.我可以将大写字母存储在数组中，并使用与小写字母相同的索引，但是我正在寻找一种更优雅的解决方案.我发现了类似的问题，但是大多数答案使用宽字符，这是我无法使用的.这是我尝试过的:

I'm learning about unicode in C++ and I have a hard time getting it to work properly. I try to treat the individual characters as uint64_t. It works if all I need it for is to print out the characters, but the problem is that I need to convert them to uppercase. I could store the uppercase letters in an array and simply use the same index as I do for the lowercase letters, but I'm looking for a more elegant solution. I found this similar question but most of the answers used wide characters, which is not something I can use. Here is what I have attempted:

#include <iostream>
#include <locale>
#include <string>
#include <cstdint>
#include <algorithm>

// hacky solution to store a multibyte character in a uint64_t
#define E(c) ((((uint64_t) 0 | (uint32_t) c[0]) << 32) | (uint32_t) c[1])

typedef std::string::value_type char_t;
char_t upcase(char_t ch) {
    return std::use_facet<std::ctype<char_t>>(std::locale()).toupper(ch);
}

std::string toupper(const std::string &src) {
    std::string result;
    std::transform(src.begin(), src.end(), std::back_inserter(result), upcase);
    return result;
}

const uint64_t VOWS_EXTRA[]
{
E("å")  , E("ä"), E("ö"), E("ij"), E("ø"), E("æ")
};

int main(void) {
    char name[5];
    std::locale::global(std::locale("sv_SE.UTF8"));
    name[0] = (VOWS_EXTRA[3] >> 32) & ~((uint32_t)0);
    name[1] = VOWS_EXTRA[3] & ~((uint32_t)0);
    name[2] = '\0';
    std::cout << toupper(name) << std::endl;
}

我希望它可以打印出IJ字符，但实际上，它可以打印出与开头相同的字符(ij).

I expect this to print out the character IJ but in reality it prints out the same character as it was in the beginning (ij).

(编辑:好的，所以我阅读了更多有关标准C ++中的unicode支持的信息

(EDIT: OK, so I read more about the unicode support in standard C++ here. It seems like my best bet is to use something like ICU or Boost.locale for this task. C++ essentially treats std::string as a blob of binary data so doesn't seem to be an easy task to uppercase unicode letters properly. I think that my hacky solution using uint64_t isn't in any way more useful than the C++ standard library if not even worse. I'd be grateful for an example on how to achieve the behaviour stated above using ICU.)

推荐答案

看看 ICU用户指南.对于简单的(单字符)案例映射，可以使用 u_toupper .对于完整案例映射，请使用 u_strToUpper .示例代码:

Have a look at the ICU User Guide. For simple (single-character) case mapping, you can use u_toupper. For full case mapping, use u_strToUpper. Example code:

#include <unicode/uchar.h>
#include <unicode/ustdio.h>
#include <unicode/ustring.h>

int main() {
    UChar32 upper = u_toupper(U'ij');
    u_printf("%lC\n", upper);

    UChar src = u'ß';
    UChar dest[3];
    UErrorCode err = U_ZERO_ERROR;
    u_strToUpper(dest, 3, &src, 1, NULL, &err);
    u_printf("%S\n", dest);

    return 0;
}

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