将字符串拆分为字符然后返回字符串

Question

I was doing a simple c++ chat and i wanted to encrypt the messages with a simple made code. So i thought it would be like chars ax and then it would replace them for example a -11. So it would need to

1. Split the message into chars
2. Change the chars into number
3. Put them back in the right order.

So does anyone knows how to do it? Thanks :)

Answer 1

A simple way of doing is to run a loop and process the characters at every iteration.

#include <iostream>
#include <string.h>

using namespace std;    

int main() {    

int num = 3;    //your choice for encryption
int len = 30;   //length of string
char * str = new char[len];
cin>>str;

//encrypt
for (int i = 0; i < strlen(str);i++)
{
    str[i] += num;
}

cout<<str<<endl;
return 0;
}

Answer 2

std::string will store arbitrary values of char , and let you access individual characters quite easily. For encryption, however, you might prefer to work with unsigned char , which is pretty easy too -- std::string is just a typedef for std::basic_string<char> , but std::basic_string<unsigned char> is pretty easy to manage.

It sounds like what you want is on the order of a Ceaser cipher, though it's easiest if you just "encrypt" everything, rather than just letters.

std::basic_string<unsigned char> s;

for (int i=0; i<s.length(); i++)
    s[i] += 5;

Then to "decrypt" you'd just do the opposite:

for (int i=0; i<s.length; i++)
    s[i] -= 5;

Answer 3

A string in C++ is already an array of chars, unless your chat program uses Unicode or another character set encoding. In that case, things become much more complicated because the string might be a byte array fresh off the network (not characters) or it might be an array of decoded wide characters (a wstring).

But assuming that you have either an ASCII string of 8-bit characters or a decoded wide string of 32-bit characters, steps 1 and 2 are quite easy. Step 1 is done for you. You should be able to access each character using an array index, like mystring[1] , mystring[2] . Step 2 is easy because characters are numbers. Simply do your math on the character value. You can add, subtract or multiply: whatever you like. Be aware that an 8-bit char probably has a value range from -128 to +127.

The order of the characters doesn't change in the string. So just leave them in place.

If your encoding method changes the length of the string, then you will need to create a new copy of the string. The best way to do it would be while you are doing the math. In C++, use the push_back method to add a new character to the "back" of the new string.