Thanks guys! I didn't know that about split operations.
Jonny, do you have benchmarks handy on your django port? If not, I'll hack something together and get them myself. If it is faster, I'd just rather it be brought into node itself then me stumble around in the dark anymore.
This past day I've done some more thinking on how regex might be done differently so as to not use splits and less lines. The result is the code below. The additions to the regex currently found in node fix the :: prefix issue as well as a::b::c and a:b:c situations. The trade off is that in some cases the tests can 3-5 times slower than the old net.isIP. I still think that's okay if better results are given. Still though, I want to believe this could be faster. I do have some code laying around for converting an IPv6 string to Buffer object.
It's also ran though the test-net-isip.js unit without issue, which is more than I could have said for my last set of code.
Beyond these, perhaps delving into some C and sending data straight to inet_pton and letting it success or fail would bring the speed up.
isIP = function(input) {
if (!input) {
return 0;
} else if (/^(\d?\d?\d)\.(\d?\d?\d)\.(\d?\d?\d)\.(\d?\d?\d)$/.test(input)) {
var parts = input.split('.');
for (var i = 0; i < parts.length; i++) {
var part = parseInt(parts[i]);
if (part < 0 || 255 < part) {
return 0;
}
}
return 4;
} else if (/^::$|^::1$|^([a-fA-F0-9]{0,4}::?){1,7}([a-fA-F0-9]{0,4})$/.test(input) && !(/::.+::/.test(input))) {
if (input.match(/:/g).length < 7 && !(/::/.test(input))) {
return 0;
}
return 6;
} else {
return 0;
}
};