novnc/lib/util/int.js

An HTML5 VNC client

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.hashUInt8Array = hashUInt8Array;
exports.toSigned32bit = toSigned32bit;
exports.toSignedRelative16bit = toSignedRelative16bit;
exports.toUnsigned32bit = toUnsigned32bit;
/*
 * noVNC: HTML5 VNC client
 * Copyright (C) 2020 The noVNC Authors
 * Licensed under MPL 2.0 (see LICENSE.txt)
 *
 * See README.md for usage and integration instructions.
 */

function toUnsigned32bit(toConvert) {
  return toConvert >>> 0;
}
function toSigned32bit(toConvert) {
  return toConvert | 0;
}

/*
* Converts a signed 32bit integer to a signed 16bit int
* Uses second most significant bit to represent it is relative
*/
function toSignedRelative16bit(toConvert) {
  // TODO: move these so they are not computed with every func call
  var negmask16 = 1 << 15;
  var negmask32 = 1 << 31;
  var relmask16 = 1 << 14;
  var converted16 = toConvert | 0;

  // number is negative
  if ((toConvert & negmask32) != 0) {
    // clear the 32bit negative bit
    // not neccessary because the last 16bits will get dropped anyway
    converted16 *= -1;

    // set the 16bit negative bit
    converted16 |= negmask16;
    // set the relative bit
    converted16 |= relmask16;
  } else {
    // set the relative bit
    converted16 |= relmask16;
  }
  return converted16;
}

/* Fast hashing function with low entropy  */
function hashUInt8Array(data) {
  var h;
  for (var i = 0; i < data.length; i++) {
    h = Math.imul(31, h) + data[i] | 0;
  }
  return h;
}