md.cpp

#include <iostream>
#include <iomanip>
#include <openssl/evp.h>
#include <fstream>
#include <memory>

void computeFileMD5(const std::string& filePath) {
    std::ifstream file(filePath, std::ios::binary);
    if (!file) {
        std::cerr << "Unable to open file: " << filePath << std::endl;
        return;
    }

    EVP_MD_CTX* mdctx = EVP_MD_CTX_new();
    if (!mdctx) {
        std::cerr << "Failed to create digest context." << std::endl;
        return;
    }

    if (EVP_DigestInit_ex(mdctx, EVP_md5(), nullptr) != 1) {
        std::cerr << "Failed to initialize digest context with MD5." << std::endl;
        EVP_MD_CTX_free(mdctx);
        return;
    }

    const size_t bufferSize = 32 * 1024 * 1024;
    std::unique_ptr<char[]> buffer(new char[bufferSize]);

    while (file.read(buffer.get(), bufferSize) || file.gcount() > 0) {
        if (EVP_DigestUpdate(mdctx, buffer.get(), file.gcount()) != 1) {
            std::cerr << "Failed to update hash." << std::endl;
            EVP_MD_CTX_free(mdctx);
            return;
        }
    }

    unsigned char hash[EVP_MAX_MD_SIZE];
    unsigned int hashLength = 0;
    if (EVP_DigestFinal_ex(mdctx, hash, &hashLength) != 1) {
        std::cerr << "Failed to finalize hash." << std::endl;
        EVP_MD_CTX_free(mdctx);
        return;
    }

    EVP_MD_CTX_free(mdctx);

    std::cout << "MD5 hash: ";
    for (unsigned int i = 0; i < hashLength; i++) {
        std::cout << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(hash[i]);
    }
    std::cout << std::endl;
}