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var util = require('./util');
/*** polynomials
*/
exports.polynomials = {
'ieee802_3': 0xEDB88320,
'castagnoli': 0x82F63B78,
'kooperman': 0xEB31D82E
};
/*** Table
*/
exports.Table = function (polynomial) {
var term, table = [];
for (var i = 0; i < 256; i++) {
term = i;
for (var j = 0; j < 8; j++) {
if (term & 1)
term = (term >>> 1) ^ polynomial;
else
term = term >>> 1;
}
table[i] = term;
}
return table;
};
/*** table
*/
exports.table = exports.Table(exports.polynomials.ieee802_3);
/*** hash
returns the crc32 hash for a string as an integer.
*/
exports.hash = function (bin, table) {
if (util.no(table))
table = exports.table;
var crc = 0xFFFFFFFF;
for (var i = 0; i < bin.length; i ++) {
var x = bin.charCodeAt(i);
if (x & ~0xFF)
throw new Error(
"crc32 can only encode strings of bytes. " +
"Consider using utf8.js#encode."
);
crc = (crc >>> 8) ^ table[x ^ (crc & 0xFF)];
}
return ~crc;
};
/*
References
==========
http://www.webtoolkit.info/
Javascript crc32
*/
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