无法从 C++ 中提取 Unicode 符号 std::string

Question

我正在阅读 C++ std::string，然后将 std::string 传递给一个函数，该函数将对其进行分析，然后从中提取 Unicode 符号和简单的 ASCII 符号。

网上搜了很多教程，都提到标准C++并不完全支持Unicode格式。他们中的许多人提到使用 ICU C++.

这是我的 C++ 程序，用于理解上述功能的最基本功能。它读取原始字符串，转换为 ICU Unicode 字符串并打印：

#include <iostream>
#include <string>
#include "unicode/unistr.h"

int main()
{
    std::string s="Hello☺";
    // at this point s contains a line of text
    // which may be ANSI or UTF-8 encoded

    // convert std::string to ICU's UnicodeString
    icu::UnicodeString ucs = icu::UnicodeString::fromUTF8(icu::StringPiece(s.c_str()));

    // convert UnicodeString to std::wstring
    std::wstring ws;
    for (int i = 0; i < ucs.length(); ++i)
      ws += static_cast<wchar_t>(ucs[i]);

    std::wcout << ws << std::endl;
}

预期输出：

Hello☺

实际输出：

Hello?

请指出我做错了什么。还建议任何 alternative/simpler 方法

谢谢

Update 1 (Older): 工作代码如下:

#include <iostream>
#include <string>
#include <locale>
#include "unicode/unistr.h"

void f(const std::string & s)
{
  std::wcout << "Inside called function" << std::endl;
  constexpr char locale_name[] = "";
  setlocale( LC_ALL, locale_name );
  std::locale::global(std::locale(locale_name));
  std::ios_base::sync_with_stdio(false);
  std::wcin.imbue(std::locale());
  std::wcout.imbue(std::locale());

  // at this point s contains a line of text which may be ANSI or UTF-8 encoded

  // convert std::string to ICU's UnicodeString
  icu::UnicodeString ucs = icu::UnicodeString::fromUTF8(icu::StringPiece(s.c_str()));

  // convert UnicodeString to std::wstring
  std::wstring ws;
  for (int i = 0; i < ucs.length(); ++i)
    ws += static_cast<wchar_t>(ucs[i]);

  std::wcout << ws << std::endl;
}

int main()
{
    constexpr char locale_name[] = "";
    setlocale( LC_ALL, locale_name );
    std::locale::global(std::locale(locale_name));
    std::ios_base::sync_with_stdio(false);
    std::wcin.imbue(std::locale());
    std::wcout.imbue(std::locale());

    std::wcout << "Inside main function" << std::endl;

    std::string s=u8"hello☺";
    // at this point s contains a line of text which may be ANSI or UTF-8 encoded

    // convert std::string to ICU's UnicodeString
    icu::UnicodeString ucs = icu::UnicodeString::fromUTF8(icu::StringPiece(s.c_str()));

    // convert UnicodeString to std::wstring
    std::wstring ws;
    for (int i = 0; i < ucs.length(); ++i)
      ws += static_cast<wchar_t>(ucs[i]);

    std::wcout << ws << std::endl;
    std::wcout << "--------------------------------" << std::endl;
    f(s);
    return 0;
}

现在，预期输出和实际输出相同，即：

Inside main function
hello☺
--------------------------------
Inside called function
hello☺

更新 2（最新）：更新 1 中提到的代码不适用于 UTF32 符号，例如 .因此，所有可能的 Unicode 符号的工作代码如下。特别感谢 @Botje 的解决方案。我希望我能给他的解决方案打上不止一个勾！！！ :)

#include <iostream>
#include <string>
#include <locale>
#include "unicode/unistr.h"
#include "unicode/ustream.h"

void f(const std::u32string & s)
{
  std::wcout << "INSIDE CALLED FUNCTION:" << std::endl;

  icu::UnicodeString ustr = icu::UnicodeString::fromUTF32(reinterpret_cast<const UChar32 *>(s.c_str()), s.size());
  std::cout << "Unicode string is: " << ustr << std::endl;

  std::cout << "Size of unicode string = " << ustr.countChar32() << std::endl;

  std::cout << "Individual characters of the string are:" << std::endl;
  for(int i=0; i < ustr.countChar32(); i++)
    std::cout << icu::UnicodeString(ustr.char32At(i)) << std::endl;

  std::cout << "--------------------------------" << std::endl;
}

int main()
{
    std::cout << "--------------------------------" << std::endl;
    constexpr char locale_name[] = "";
    setlocale( LC_ALL, locale_name );
    std::locale::global(std::locale(locale_name));
    std::ios_base::sync_with_stdio(false);
    std::wcin.imbue(std::locale());
    std::wcout.imbue(std::locale());

    std::wcout << "INSIDE MAIN FUNCTION:" << std::endl;

    std::u32string s=U"hello☺";

    icu::UnicodeString ustr = icu::UnicodeString::fromUTF32(reinterpret_cast<const UChar32 *>(s.c_str()), s.size());
    std::cout << "Unicode string is: " << ustr << std::endl;

    std::cout << "Size of unicode string = " << ustr.countChar32() << std::endl;

    std::cout << "Individual characters of the string are:" << std::endl;
    for(int i=0; i < ustr.countChar32(); i++)
      std::cout << icu::UnicodeString(ustr.char32At(i)) << std::endl;

    std::cout << "--------------------------------" << std::endl;
    f(s);
    return 0;
}

现在，预期输出和实际输出相同，即：

--------------------------------
INSIDE MAIN FUNCTION:
Unicode string is: hello☺
Size of unicode string = 7
Individual characters of the string are:
h
e
l
l
o
☺

--------------------------------
INSIDE CALLED FUNCTION:
Unicode string is: hello☺
Size of unicode string = 7
Individual characters of the string are:
h
e
l
l
o
☺

--------------------------------

Answer 1

要做到这一点，有许多障碍：

首先，您的文件（以及其中的笑脸）应编码为 UTF-8。笑脸应由文字字节 0xE2 0x98 0xBA.
您应该使用 u8 装饰器将字符串标记为包含 UTF-8 数据：u8"Hello☺"
接下来，icu::UnicodeString 的文档指出它将 Unicode 存储为 UTF-16。在这种情况下你很幸运，因为 U+263A 适合一个 UTF-16 字符。其他表情符号可能不会！您应该将其转换为 UTF-32，或者非常小心地使用 GetChar32At 函数。
最后，wcout 使用的编码应该配置为 imbue 以匹配您的环境期望的编码。查看 this question.

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