Should identify that the key can only use AVAILABLE_CHARS characters

[ziserendexin]

I want use it to encrypt some low confidentiality string，and use the key like zise_some_thing_happen.
But the encryt_string is a bit long

It decrypt some charact worry（part of my data）.
like:
"time": "2018-12-14 17:59:16",
to
"tyme": "2018-12-14 17:59:16",

And it will not show in short string.
the reason maybe is in this if.

if(isalnum(msg[i]) or msg[i] == ' ') {
    encryptedMsg[i] = AVAILABLE_CHARS[((index(msg[i]) + index(newKey[i])) % AVAILABLE_CHARS.size())];
} else {
    encryptedMsg[i] = msg[i];
}

After base64, some string will change to '_', and it will get worry index in newKey.

But I can't recurrent it in short string, and my error string have a little confidentiality needs. if you need it. Please give me a email, and i will send it to you.

On the other hand，
in

easy-encryption/vigenere.h

Line 50 in 2bf5753

encryptedMsg[i] = AVAILABLE_CHARS[((index(msg[i]) + index(newKey[i])) % AVAILABLE_CHARS.size())];

AVAILABLE_CHARS.size() is a determine value, and .size() will caculate this value every time in your for loop.

It will better in this way:

AVAILABLE_CHARS_SIZE = AVAILABLE_CHARS.size()
for(i = 0; i < msgLen; ++i) {
    encryptedMsg[i] = AVAILABLE_CHARS[((index(msg[i]) + index(newKey[i])) % AVAILABLE_CHARS_SIZE)];
}

At last, in windows, call exe in cmd have max limit,32768. so if your encrypted string is too long, you can`t decrypt or encrypt it in python.