crc32

crc32.js

// from https://github.com/gildas-lormeau/zip.js/blob/master/WebContent/zip.js

function Crc32() {
	this.crc = -1;
}
Crc32.prototype.append = function append(data) {
	var crc = this.crc | 0, table = this.table;
	for (var offset = 0, len = data.length | 0; offset < len; offset++)
		crc = (crc >>> 8) ^ table[(crc ^ data[offset]) & 0xFF];
	this.crc = crc;
};
Crc32.prototype.get = function get() {
	return ~this.crc;
};
Crc32.prototype.table = (function() {
	var i, j, t, table = []; // Uint32Array is actually slower than []
	for (i = 0; i < 256; i++) {
		t = i;
		for (j = 0; j < 8; j++)
			if (t & 1)
				t = (t >>> 1) ^ 0xEDB88320;
			else
				t = t >>> 1;
		table[i] = t;
	}
	return table;
})();