first commit

assets/scripts/libs/gzip/crc32.ts

@@ -0,0 +1,83 @@
+var table = [];
+var poly = 0xEDB88320; // reverse polynomial
+
+function makeTable() {
+	var c, n, k;
+
+	for (n = 0; n < 256; n += 1) {
+		c = n;
+		for (k = 0; k < 8; k += 1) {
+			if (c & 1) {
+				c = poly ^ (c >>> 1);
+			} else {
+				c = c >>> 1;
+			}
+		}
+		table[n] = c >>> 0;
+	}
+}
+
+function strToArr(str) {
+	// sweet hack to turn string into a 'byte' array
+	return Array.prototype.map.call(str, function (c) {
+		return c.charCodeAt(0);
+	});
+}
+
+function crcDirect(arr) {
+	var crc = -1, // initial contents of LFBSR
+		i, j, l, temp;
+
+	for (i = 0, l = arr.length; i < l; i += 1) {
+		temp = (crc ^ arr[i]) & 0xff;
+
+		// read 8 bits one at a time
+		for (j = 0; j < 8; j += 1) {
+			if ((temp & 1) === 1) {
+				temp = (temp >>> 1) ^ poly;
+			} else {
+				temp = (temp >>> 1);
+			}
+		}
+		crc = (crc >>> 8) ^ temp;
+	}
+
+	// flip bits
+	return crc ^ -1;
+}
+
+
+function crcTable(arr, append) {
+	var crc, i, l;
+
+	// if we're in append mode, don't reset crc
+	// if arr is null or undefined, reset table and return
+	if (typeof crcTable.crc === 'undefined' || !append || !arr) {
+		crcTable.crc = 0 ^ -1;
+
+		if (!arr) {
+			return;
+		}
+	}
+
+	// store in temp variable for minor speed gain
+	crc = crcTable.crc;
+
+	for (i = 0, l = arr.length; i < l; i += 1) {
+		crc = (crc >>> 8) ^ table[(crc ^ arr[i]) & 0xff];
+	}
+
+	crcTable.crc = crc;
+
+	return crc ^ -1;
+}
+
+makeTable();
+
+export function crc32(val, direct) {
+	var val = (typeof val === 'string') ? strToArr(val) : val,
+		ret = direct ? crcDirect(val) : crcTable(val);
+
+	// convert to 2's complement hex
+	return (ret >>> 0).toString(16);
+};