UUID v5 calculator for email addresses

uuidv5-email.js

var crypto = require('crypto');

var nsURL = new Buffer([0x6b,0xa7,0xb8,0x11,0x9d,0xad,0x11,0xd1,0x80,0xb4,0x00,0xc0,0x4f,0xd4,0x30,0xc8]);

var emailUUID = function(email) {
    var shasum = crypto.createHash('sha1');
    shasum.update(Buffer.concat([nsURL, new Buffer('mailto:'+email)]));
    shasum=shasum.digest();
    var result = new Buffer(16);
    shasum.copy(result, 0, 0, 16);
    result.writeUInt16LE((result.readUInt16LE(6) & 0x0FFF) | (5 << 12), 6);
    result.writeUInt8((result.readUInt8(8) & 0x3F) | 0x80, 6);
    return result.slice(0,4).toString('hex') +
        '-' + result.slice(4,6).toString('hex') +
        '-' + result.slice(6,8).toString('hex') +
        '-' + result.slice(8,10).toString('hex') +
        '-' + result.slice(10).toString('hex')
}