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Concatenate strings/chars in a loop.

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Join Date: Jul 2009

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Anon17

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Concatenate strings/chars in a loop.

Jul 27th, 2009

Hi there.

I have an encryption method which handles a string char by char and converts it to base 32, then adds it onto the result string. However, it seems to completely replace the result string instead of adding onto the end of it. My code:

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char *encrypt(std::string input, std::string key) {
	char* result;
	int lenIn = input.length();
	int lenKey = key.length();
	int i = 0;
	int numKey;
	while (i < lenIn) {
		numKey = charCodeAt(key, i % lenKey);
		long n = long(charCodeAt(input, i) + numKey);
		ltostr(n, base32, 32);
		if (i = 0) {
                        //Cannot concatenate a blank char* it seems
			result = base32;
		} else {
			char* tempresult = result;
			sprintf(result,"%s%s",tempresult,base32);
		}
		i++;
	}
	return result;
}
char *encrypt(std::string input, std::string key) {
	char* result;
	int lenIn = input.length();
	int lenKey = key.length();
	int i = 0;
	int numKey;
	while (i < lenIn) {
		numKey = charCodeAt(key, i % lenKey);
		long n = long(charCodeAt(input, i) + numKey);
		ltostr(n, base32, 32);
		if (i = 0) {
                        //Cannot concatenate a blank char* it seems
			result = base32;
		} else {
			char* tempresult = result;
			sprintf(result,"%s%s",tempresult,base32);
		}
		i++;
	}
	return result;
}

charCodeAt simply gets the unicode number in int format of the character entered. Can anyone help out?

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Join Date: Dec 2005

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Salem

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Void main'ers are DOOMed

Re: Concatenate strings/chars in a loop.

Jul 27th, 2009

> char* result;
This is an uninitialised pointer!
Result - you're scribbling characters all over someone else's memory - and they're not going to be happy about it.

You're already using std::string, so carry on using std::string for everything else in your program.