Unicode字符串的跨平台迭代(使用ICU计算Graphemes)

2021-12-26 00:00:00 unicode cross-platform c++ icu

我想迭代 Unicode 字符串的每个字符，处理每个代理对并将字符序列组合为一个单元(一个字素).

I want to iterate each character of a Unicode string, treating each surrogate pair and combining character sequence as a single unit (one grapheme).

文本??????"由代码点组成:U+0928、U+092E、U+0938、U+094D、U+0924、U+0947，其中，U+0938 和 U+0947 是组合标记.

The text "??????" is comprised of the code points: U+0928, U+092E, U+0938, U+094D, U+0924, U+0947, of which, U+0938 and U+0947 are combining marks.

static void Main(string[] args)
{
    const string s = "??????";

    Console.WriteLine(s.Length); // Ouptuts "6"

    var l = 0;
    var e = System.Globalization.StringInfo.GetTextElementEnumerator(s);
    while(e.MoveNext()) l++;
    Console.WriteLine(l); // Outputs "4"
}

所以我们在 .NET 中有它.我们还有 Win32 的 CharNextW()

So there we have it in .NET. We also have Win32's CharNextW()

#include <Windows.h>
#include <iostream>
#include <string>

int main()
{
    const wchar_t * s = L"??????";

    std::cout << std::wstring(s).length() << std::endl; // Gives "6"

    int l = 0;
    while(CharNextW(s) != s)
    {
        s = CharNextW(s);
        ++l;
    }

    std::cout << l << std::endl; // Gives "4"

    return 0;
}

问题

我所知道的两种方式都特定于 Microsoft.有没有便携的方法来做到这一点?

  • 我听说过 ICU，但我无法快速找到相关内容(UnicodeString(s).length() 仍然给出 6).指向 ICU 中的相关功能/模块是可以接受的答案.
  • C++ 没有 Unicode 的概念，因此用于处理这些问题的轻量级跨平台库将是一个可以接受的答案.
  • I heard about ICU but I couldn't find something related quickly (UnicodeString(s).length() still gives 6). Would be an acceptable answer to point to the related function/module in ICU.
  • C++ doesn't have a notion of Unicode, so a lightweight cross-platform library for dealing with these issues would make an acceptable answer.

@McDowell 给出了使用 ICU 的 BreakIterator 的提示，我认为这可以看作是处理 Unicode 的事实上的跨平台标准.下面是演示其用法的示例代码(因为示例出人意料很少见):

@McDowell gave the hint to use BreakIterator from ICU, which I think can be regarded as the de-facto cross-platform standard to deal with Unicode. Here's an example code to demonstrate its use (since examples are surprisingly rare):

#include <unicode/schriter.h>
#include <unicode/brkiter.h>

#include <iostream>
#include <cassert>
#include <memory>

int main()
{
    const UnicodeString str(L"??????");

    {
        // StringCharacterIterator doesn't seem to recognize graphemes
        StringCharacterIterator iter(str);
        int count = 0;
        while(iter.hasNext())
        {
            ++count;
            iter.next();
        }
        std::cout << count << std::endl; // Gives "6"
    }

    {
        // BreakIterator works!!
        UErrorCode err = U_ZERO_ERROR;
        std::unique_ptr<BreakIterator> iter(
            BreakIterator::createCharacterInstance(Locale::getDefault(), err));
        assert(U_SUCCESS(err));
        iter->setText(str);

        int count = 0;
        while(iter->next() != BreakIterator::DONE) ++count;
        std::cout << count << std::endl; // Gives "4"
    }

    return 0;
}

推荐答案

您应该能够使用 ICU BreakIterator 用于此(假设它的特性等效于 Java 版本的字符实例).

You should be able to use the ICU BreakIterator for this (the character instance assuming it is feature-equivalent to the Java version).

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