如何使用STL字符串和流读取/存储unicode

#include<iostream>
#include <fstream>
#include<string>
#include<locale>
#include <codecvt>

std::string utf16_to_utf8(const std::wstring &utf16_str) {
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> converter;
    return converter.to_bytes(utf16_str);
}

std::wstring utf8_to_utf16(const std::string &utf8_str) {
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> converter;
    return converter.from_bytes(utf8_str);
}

void write_unicode_string_to_file(const std::wstring &unicode_str, const std::string &file_path) {
    std::ofstream file(file_path, std::ios::binary);
    if (file.is_open()) {
        file.write(reinterpret_cast<const char *>(unicode_str.data()), unicode_str.size() * sizeof(wchar_t));
        file.close();
    }
}

std::wstring read_unicode_string_from_file(const std::string &file_path) {
    std::wstring unicode_str;
    std::ifstream file(file_path, std::ios::binary);
    if (file.is_open()) {
        file.seekg(0, std::ios::end);
        auto size = file.tellg();
        file.seekg(0, std::ios::beg);
        unicode_str.resize(size / sizeof(wchar_t));
        file.read(reinterpret_cast<char *>(&unicode_str[0]), size);
        file.close();
    }
    return unicode_str;
}

int main() {
    std::wstring unicode_str = L"Hello, 世界!";
    std::string utf8_str = utf16_to_utf8(unicode_str);
    std::wstring read_unicode_str = read_unicode_string_from_file("unicode_file.txt");
    std::string read_utf8_str = utf16_to_utf8(read_unicode_str);
    write_unicode_string_to_file(unicode_str, "unicode_file.txt");
    return 0;
}