C++如何检查文件字节顺序标记以获取它是否为UTF-8？

#include <fstream>
#include <iostream>

bool isUTF8(const std::string& filename) {
    std::ifstream file(filename, std::ios::binary);
    if (!file.is_open()) {
        std::cout << "Failed to open file." << std::endl;
        return false;
    }

    char bom[3];
    file.read(bom, 3);

    if (bom[0] == '\xEF' && bom[1] == '\xBB' && bom[2] == '\xBF') {
        std::cout << "The file is UTF-8 encoded with BOM." << std::endl;
        return true;
    }
    else if (bom[0] != '\xEF' && bom[1] != '\xBB' && bom[2] != '\xBF') {
        std::cout << "The file is UTF-8 encoded without BOM." << std::endl;
        return true;
    }
    else {
        std::cout << "The file is not UTF-8 encoded." << std::endl;
        return false;
    }

    file.close();
}

int main() {
    std::string filename = "example.txt";
    isUTF8(filename);

    return 0;
}