Need some help converting C# method to C++

Question

I am a C# guy who is desperately trying to learn C++ and port some old code over. Been doing OK so far but the following method has me stumped. If anyone could give me some pointers (sorry for pun) I would be grateful.

C# method:

public static string crappyEncryption(String userKey)    
{    
    StringBuilder eStr = new StringBuilder();    
    String key1 = "somehorriblelongstring";    
    String key2 = "someotherhorriblelongstring";    
    for (int i = 0; i < userKey.Length; i++)   
    {    
        eStr.Append(key2[key1.IndexOf(userKey[i])]);    
    }    
    return encodeTo64(eStr.ToString());    
}

encodeTo64 is a local method which I have solved in C++. This weird method (if you were wondering) was a small encryption method I came up with that we could use mobile cross platform for non-essential string encryption.

Thanks very much

if your weird encodeTo64 is an algorithm from Base64 family (en.wikipedia.org/wiki/Base64) then I wouldn't call it weird, it's just a way to deal with textual communications when you need to transfer binary data. — Jack
– Jack, Commented Oct 17, 2012 at 21:18
Is there something specific that has you stumped? This doesnt look too bad. The std::string type will be what you use in place of the string builder and string. std::string has an append function, and a find function to use in place of IndexOf. — Ben313
– Ben313, Commented Oct 17, 2012 at 21:21
miscommunication - I was referring to my crappyEncryption() method as wierd. :) — user1754529
– user1754529, Commented Oct 17, 2012 at 21:22
I have got the code up to the loop going by using std:: string and std::wstring but I am getting an invalid conversion exception for the line within the loop: eStr = key2[key1.find(userKey[i])]; I have eStr defines as std::string *eStr and the key strings as std::wstring — user1754529
– user1754529, Commented Oct 17, 2012 at 21:28
If the purpose of porting the code is simply to learn C++, then sure. Generally, as a principle, porting code is a waste of productive time, when you could be wrapping the code instead. — Steztric
– Steztric, Commented Oct 17, 2012 at 21:38

Luchian Grigore · Accepted Answer · 2012-10-17 21:20:04Z

3

Not gonna give you the whole code, but some pointers:

a StringBuilder can be substituted by a std::stringstream.
a String is a std::string
it has the method length(), find() and operator[].
std::stringstream has operator << for Append.
ToString is std::stringstream::str().
you'll want to pass userKey by reference.

All concepts you don't understand can easily be found with a google search.

edited Oct 17, 2012 at 21:20

answered Oct 17, 2012 at 21:18

Luchian Grigore

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