@graffy/common/cjs/encode/number.js

Common libraries that used by various Graffy modules.

"use strict";

exports.__esModule = true;
exports.encode = encode;
exports.decode = decode;

/*
  Order-preserving encoding of 64-bit floating point numbers.
*/
function encode(number) {
  var buffer = new ArrayBuffer(8);
  var view = new DataView(buffer);
  view.setFloat64(0, number);
  /* if first bit is set */

  if (number < 0) {
    view.setUint32(0, ~view.getUint32(0) >>> 0);
    view.setUint32(4, ~view.getUint32(4) >>> 0);
  } else {
    /* non-negative number, just set the leading bit. */
    view.setUint8(0, view.getUint8(0) | 0x80);
  }

  return new Uint8Array(buffer);
}

function decode(u8Arr) {
  var buffer = u8Arr.buffer,
      byteOffset = u8Arr.byteOffset,
      byteLength = u8Arr.byteLength;
  var view = new DataView(buffer, byteOffset, byteLength);
  var high = view.getUint8(0);

  if (high & 0x80) {
    // originally a non-negative number. Just set the sign bit back to 0.
    view.setUint8(0, high & 0x7f);
  } else {
    view.setUint32(0, ~view.getUint32(0) >>> 0);
    view.setUint32(4, ~view.getUint32(4) >>> 0);
  }

  return view.getFloat64(0);
}