MD5 in C++ is everywhere if you search for it (except for in the standard library or in boost, which isn’t what I would have expected), but I only needed one implementation and I found this one: RSA Data Security, Inc. MD5 Message-Digest Algorithm.
I learned how to read binary files in C++ today. My function (which creates an MD5 hash of a file) ended up looking a little different to the example that I learned from:
const int BUFFER_SIZE = 1024;
int length;
char buffer[ BUFFER_SIZE ];
MD5_CTX ctx;
MD5Init( &ctx );
ifstream is( path.c_str(), ios::binary );
while ( is.good() ) {
is.read( (char *)buffer, BUFFER_SIZE );
streamsize count = is.gcount();
MD5Update( &ctx, (unsigned char *)buffer, count );
}
if ( is.eof() ) {
// it's ok, we're at the end of the file
}
else if ( is.bad() ) {
// bad bit is set
cout << "Bad bit is set while reading '" << path << "'." << endl;
cout << strerror( errno ) << endl;
exit ( 1 );
}
else if ( is.fail() ) {
cout << "Fail bit is set while reading '" << path << "'." << endl;
cout << strerror( errno ) << endl;
exit( 1 );
}
is.close();