vector-tile-esm/src/vectortilefeature.js

Parses vector tiles

import { types, toGeoJSON } from "./geojson.js";

export function VectorTileFeature(pbf, end, extent, keys, values) {
  // Public
  this.properties = {};
  this.extent = extent;
  this.type = 0;

  // Private
  this._pbf = pbf;
  this._geometry = -1;
  this._keys = keys;
  this._values = values;

  pbf.readFields(readFeature, this, end);
}

function readFeature(tag, feature, pbf) {
  if (tag == 1) feature.id = pbf.readVarint();
  else if (tag == 2) readTag(pbf, feature);
  else if (tag == 3) feature.type = pbf.readVarint();
  else if (tag == 4) feature._geometry = pbf.pos;
}

function readTag(pbf, feature) {
  const end = pbf.readVarint() + pbf.pos;
  const { _keys, _values } = feature;

  while (pbf.pos < end) {
    const key = _keys[pbf.readVarint()];
    const value = _values[pbf.readVarint()];
    feature.properties[key] = value;
  }
}

VectorTileFeature.prototype.loadGeometry = function() {
  const pbf = this._pbf;
  pbf.pos = this._geometry;

  const end = pbf.readVarint() + pbf.pos;
  let cmd = 1;
  let length = 0;
  let x = 0;
  let y = 0;
  const lines = [];
  let line;

  while (pbf.pos < end) {
    if (length <= 0) {
      const cmdLen = pbf.readVarint();
      cmd = cmdLen & 0x7;
      length = cmdLen >> 3;
    }

    length--;

    if (cmd === 1 || cmd === 2) {
      x += pbf.readSVarint();
      y += pbf.readSVarint();

      if (cmd === 1) { // moveTo
        if (line) lines.push(line);
        line = [];
      }

      line.push({ x, y });

    } else if (cmd === 7) {
      // Workaround for https://github.com/mapbox/mapnik-vector-tile/issues/90
      if (line) line.push({ // closePolygon
        x: line[0].x,
        y: line[0].y
      });

    } else {
      throw Error("unknown command " + cmd);
    }
  }

  if (line) lines.push(line);

  return lines;
};

VectorTileFeature.prototype.bbox = function() {
  const pbf = this._pbf;
  pbf.pos = this._geometry;

  const end = pbf.readVarint() + pbf.pos;
  let cmd = 1;
  let length = 0;
  let x = 0;
  let y = 0;
  let x1 = Infinity;
  let x2 = -Infinity;
  let y1 = Infinity;
  let y2 = -Infinity;

  while (pbf.pos < end) {
    if (length <= 0) {
      const cmdLen = pbf.readVarint();
      cmd = cmdLen & 0x7;
      length = cmdLen >> 3;
    }

    length--;

    if (cmd === 1 || cmd === 2) {
      x += pbf.readSVarint();
      y += pbf.readSVarint();
      if (x < x1) x1 = x;
      if (x > x2) x2 = x;
      if (y < y1) y1 = y;
      if (y > y2) y2 = y;

    } else if (cmd !== 7) {
      throw Error("unknown command " + cmd);
    }
  }

  return [x1, y1, x2, y2];
};

VectorTileFeature.types = types;
VectorTileFeature.prototype.toGeoJSON = toGeoJSON;