cordova-plugin-googlemaps/www/encoding.js

Google Maps native SDK for Android and iOS, and Google Maps JavaScript API v3 for browser.

var LatLng = require('./LatLng');
var common = require('./Common');

/*****************************************************************************
 * geometry Encode / decode points
 * http://jsfiddle.net/8nzg7tta/
 *****************************************************************************/
//decode function
function decodePath(encoded, precision) {
  precision = precision || 5;
  precision = Math.pow(10, -precision);
  var len = encoded.length,
    index = 0,
    lat = 0,
    lng = 0,
    array = [];
  while (index < len) {
    var b, shift = 0,
      result = 0;
    do {
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);
    var dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lat += dlat;
    shift = 0;
    result = 0;
    do {
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);
    var dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lng += dlng;
    array.push(new LatLng(lat * precision, lng * precision));
  }
  return array;
}

//encode functions
function encodePath(points) {
  var plat = 0;
  var plng = 0;
  var encoded_points = '';

  points = common.convertToPositionArray(points);

  for (var i = 0; i < points.length; ++i) {
    encoded_points += encodePoint(plat, plng, points[i].lat, points[i].lng);
    plat = points[i].lat;
    plng = points[i].lng;
  }

  return encoded_points;
}

function encodePoint(plat, plng, lat, lng) {
  var late5 = Math.round(lat * 1e5);
  var plate5 = Math.round(plat * 1e5);

  var lnge5 = Math.round(lng * 1e5);
  var plnge5 = Math.round(plng * 1e5);

  var dlng = lnge5 - plnge5;
  var dlat = late5 - plate5;

  return encodeSignedNumber(dlat) + encodeSignedNumber(dlng);
}

function encodeSignedNumber(num) {
  var sgn_num = num << 1;

  if (num < 0) {
    sgn_num = ~(sgn_num);
  }

  return (encodeNumber(sgn_num));
}

function encodeNumber(num) {
  var encodeString = '';

  while (num >= 0x20) {
    encodeString += (String.fromCharCode((0x20 | (num & 0x1f)) + 63));
    num >>= 5;
  }

  encodeString += (String.fromCharCode(num + 63));
  return encodeString;
}

module.exports = {
  decodePath: decodePath,
  encodePath: encodePath
};