C++ Poco计算文件的MD5值

#include <Poco/DigestEngine.h>
#include <Poco/DigestStream.h>
#include <Poco/MD5Engine.h>
#include <Poco/StreamCopier.h>

#include <fstream>
#include <string>

static constexpr const char* hex_table = "0123456789abcdef";

std::string Md5(const std::string& file_path) {
    Poco::MD5Engine md5_engine;
    Poco::DigestOutputStream output_stream(md5_engine);
    std::ifstream file_stream(file_path);
    Poco::StreamCopier::copyStream(file_stream, output_stream);
    output_stream.close();

    auto md5_val = md5_engine.digest();
    std::string res = "";
    for (int i = 0; i < 16; ++i) {
        uint8_t c = md5_val.data()[i];
        res += hex_table[c >> 4];
        res += hex_table[c & 15];
    }
    return res;
}