get time from uuid.v1 string

getTimeFromUuidv1.js

/**
 * extract time from uuid.v1 string
 *
 * originally from
 * node-uuid/uuid.js at master · krassif/node-uuid
 * https://github.com/krassif/node-uuid/blob/master/uuid.js
 *
 * @param    buf     buffer
 * @param    offset  offset
 * @returns {number} msec
 */
	// extracts time (msecs) from v1 type uuid
function v1time(buf, offset) {

	var msec = 0, nsec = 0;
	var i = buf && offset || 0;
	var b = buf||[];

	// inspect version at offset 6
	if ((b[i+6]&0x10)!=0x10) {
		throw new Error("uuid version 1 expected"); }

	// 'time_low'
	var tl = 0;
	tl |= ( b[i++] & 0xff ) << 24;
	tl |= ( b[i++] & 0xff ) << 16;
	tl |= ( b[i++] & 0xff ) << 8;
	tl |=   b[i++] & 0xff ;

	// `time_mid`
	var tmh = 0;
	tmh |= ( b[i++] & 0xff ) << 8;
	tmh |=   b[i++] & 0xff;

	// `time_high_minus_version`
	tmh |= ( b[i++] & 0xf ) << 24;
	tmh |= ( b[i++] & 0xff ) << 16;

	// account for the sign bit
	msec = 1.0 * ( ( tl >>> 1 ) * 2 + ( ( tl & 0x7fffffff ) % 2 ) ) / 10000.0;
	msec += 1.0 * ( ( tmh >>> 1 ) * 2 + ( ( tmh & 0x7fffffff ) % 2 ) ) * 0x100000000 / 10000.0;

	// Per 4.1.4 - Convert from Gregorian epoch to unix epoch
	msec -= 12219292800000;

	// getting the nsec. they are not needed now though
	// nsec = ( tl & 0xfffffff ) % 10000;

	return msec;
}