如何在C++中从文件中读取字节到十六进制字符串？

#include <fstream>
std::ifstream file("filename.txt", std::ios::binary);

char buffer[1024]; // 缓冲区大小
file.read(buffer, sizeof(buffer));

#include <sstream>
#include <iomanip>
std::stringstream hexStream;
hexStream << std::hex << std::setfill('0');
for (int i = 0; i < file.gcount(); i++) {
    hexStream << std::setw(2) << static_cast<int>(buffer[i]);
}
std::string hexString = hexStream.str();

file.close();

#include <fstream>
#include <sstream>
#include <iomanip>
#include <iostream>

std::string readFileToHexString(const std::string& filename) {
    std::ifstream file(filename, std::ios::binary);
    if (!file) {
        std::cerr << "Failed to open file: " << filename << std::endl;
        return "";
    }

    char buffer[1024]; // 缓冲区大小
    file.read(buffer, sizeof(buffer));

    std::stringstream hexStream;
    hexStream << std::hex << std::setfill('0');
    for (int i = 0; i < file.gcount(); i++) {
        hexStream << std::setw(2) << static_cast<int>(buffer[i]);
    }
    std::string hexString = hexStream.str();

    file.close();

    return hexString;
}

int main() {
    std::string filename = "example.txt";
    std::string hexString = readFileToHexString(filename);
    std::cout << "Hex string: " << hexString << std::endl;

    return 0;
}