To implement MD5 hash on a char array containg both hex and char

Question

Structure

In the source folder, there's the test.cpp

In the Header Files folder, there's the test.h

I'm trying to implement md5 hash function on a char array unsigned char dat[39] that contain both hex and char

referencing the example in How to get the MD5 hash of a file in C++?

As I cannot include <openssl/md5.h>, hence I manually add a md5.h from

www.zedwood.com/article/cpp-md5-function

to the Header Files folder

Then in the test.h file, I have added the function

oid print_md5_sum(unsigned char* md) {
    int i;
    for(i=0; i <39; i++) {
        printf("%02x",md[i]);
    }

After that, in the test.cpp file, I try to implement the md5 function

print_md5_sum(dat);

The project can compile, but the md5 function cannot work. Any insight would be greatly appreciated.