js-crc32/crc32.js

/* crc32.js (C) 2014 SheetJS -- http://sheetjs.com */
/* vim: set ts=2: */
var CRC32 = {};
(function(CRC32) {
CRC32.version = '0.2.1';
/* see perf/crc32table.js */
function signed_crc_table() {
	var c, table = new Array(256);

	for(var n =0; n != 256; ++n){
		c = n;
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
		table[n] = c;
	}

	return typeof Int32Array !== 'undefined' ? new Int32Array(table) : table;
}

var table = signed_crc_table();
/* charCodeAt is the best approach for binary strings */
var use_buffer = typeof Buffer !== 'undefined';
function crc32_bstr(bstr) {
	if(bstr.length > 32768) if(use_buffer) return crc32_buf_8(Buffer(bstr));
	var crc = -1, L = bstr.length - 1;
	for(var i = 0; i < L;) {
		crc =  table[(crc ^ bstr.charCodeAt(i++)) & 0xFF] ^ (crc >>> 8);
		crc =  table[(crc ^ bstr.charCodeAt(i++)) & 0xFF] ^ (crc >>> 8);
	}
	if(i === L) crc = (crc >>> 8) ^ table[(crc ^ bstr.charCodeAt(i)) & 0xFF];
	return crc ^ -1;
}

function crc32_buf(buf) {
	if(buf.length > 10000) return crc32_buf_8(buf);
	for(var crc = -1, i = 0, L=buf.length-3; i < L;) {
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
	}
	while(i < L+3) crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
	return crc ^ -1;
}

function crc32_buf_8(buf) {
	for(var crc = -1, i = 0, L=buf.length-7; i < L;) {
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
		crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
	}
	while(i < L+7) crc = (crc >>> 8) ^ table[(crc^buf[i++])&0xFF];
	return crc ^ -1;
}

/* much much faster to intertwine utf8 and crc */
function crc32_str(str) {
	for(var crc = -1, i = 0, L=str.length, c, d; i < L;) {
		c = str.charCodeAt(i++);
		if(c < 0x80) {
			crc = (crc >>> 8) ^ table[(crc ^ c) & 0xFF];
		} else if(c < 0x800) {
			crc = (crc >>> 8) ^ table[(crc ^ (192|((c>>6)&31))) & 0xFF];
			crc = (crc >>> 8) ^ table[(crc ^ (128|(c&63))) & 0xFF];
		} else if(c >= 0xD800 && c < 0xE000) {
			c = (c&1023)+64; d = str.charCodeAt(i++) & 1023;
			crc = (crc >>> 8) ^ table[(crc ^ (240|((c>>8)&7))) & 0xFF];
			crc = (crc >>> 8) ^ table[(crc ^ (128|((c>>2)&63))) & 0xFF];
			crc = (crc >>> 8) ^ table[(crc ^ (128|((d>>6)&15)|(c&3))) & 0xFF];
			crc = (crc >>> 8) ^ table[(crc ^ (128|(d&63))) & 0xFF];
		} else {
			crc = (crc >>> 8) ^ table[(crc ^ (224|((c>>12)&15))) & 0xFF];
			crc = (crc >>> 8) ^ table[(crc ^ (128|((c>>6)&63))) & 0xFF];
			crc = (crc >>> 8) ^ table[(crc ^ (128|(c&63))) & 0xFF];
		}
	}
	return crc ^ -1;
}
CRC32.table = table;
CRC32.bstr = crc32_bstr;
CRC32.buf = crc32_buf;
CRC32.str = crc32_str;
})(typeof exports !== "undefined" && typeof DO_NOT_EXPORT_CRC === 'undefined' ? exports : CRC32);