engine initialization in OpenSSL

gistfile1.cpp

// http://stackoverflow.com/questions/242665/understanding-engine-initialization-in-openssl
    unsigned char* key = (unsigned char*) "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b";
    unsigned char* data = (unsigned char*) "\x48\x69\x20\x54\x68\x65\x72\x65";
    unsigned char* expected = (unsigned char*) "\x49\x2c\xe0\x20\xfe\x25\x34\xa5\x78\x9d\xc3\x84\x88\x06\xc7\x8f\x4f\x67\x11\x39\x7f\x08\xe7\xe7\xa1\x2c\xa5\xa4\x48\x3c\x8a\xa6";
    
    HMAC_CTX ctx;
    unsigned char* result;
    unsigned int result_len = 32;
    int i;
    
    result = (unsigned char*) malloc(sizeof(char) * result_len);
    ENGINE_load_builtin_engines();
    ENGINE_register_all_complete();
    HMAC_CTX_init(&ctx);
    HMAC_Init_ex(&ctx, key, 16, EVP_sha256(), NULL);
    HMAC_Update(&ctx, data, 8);
    HMAC_Final(&ctx, result, &result_len);
    for (i=0; i!=result_len; i++)
    {
        if (expected[i]!=result[i])
        {
            //("Got %02X instead of %02X at byte %d!\n", result[i], expected[i], i);
            break;
        }
    }
    
    HMAC_CTX_cleanup(&ctx);