Re: comparing char to other known char's

[James Colannino <james@colannino.org>]

Eric Bambach wrote:

> Generally speaking (in terms of input validation), its better practice to 
> check against a LEGAL set of characters rather than an illegal set. That way 
> you can get all the characters you need, but everything else is blocked. If 
> you block illegal ones you're bound to miss a few or even ones from extended 
> charsets and input methods that you might not have thought of that could 
> wreck havoc in your program.

Here's what I've whipped up based on your suggestion that I should look
for legal characters instead of the other way around:

<CODE>

/* This function returns 1 if the character being checked is legal and 0
if it isn't. */

int legal_characters(char character_to_check) {

	int index;
	legal_characters[] =
"abcdefghijklmnopqrstuvwxyzAVCDEFGHIJKLMNOPQRSTUVWXYZ1234567890_-";

	int number_of_legal_chars = sizeof(legal_characters) / sizeof(char);

	for (index = 0; index < number_of_legal_chars; ++index) {
		if (character_to_check == legal_characters[index])
			return 1;
	}

	return 0;

</CODE>

How does this function look?

James
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