@kibeo/loaders.gl-mvt/dist/esm/lib/mapbox-vector-tile/vector-tile-layer.js

Loader for Mapbox Vector Tiles

import VectorTileFeature from './vector-tile-feature.js';
export default class VectorTileLayer {
  constructor(pbf, end) {
    this.version = 1;
    this.name = null;
    this.extent = 4096;
    this.length = 0;
    this._pbf = pbf;
    this._keys = [];
    this._values = [];
    this._features = [];
    pbf.readFields(readLayer, this, end);
    this.length = this._features.length;
  }

  feature(i) {
    if (i < 0 || i >= this._features.length) {
      throw new Error('feature index out of bounds');
    }

    this._pbf.pos = this._features[i];

    const end = this._pbf.readVarint() + this._pbf.pos;

    return new VectorTileFeature(this._pbf, end, this.extent, this._keys, this._values);
  }

}

function readLayer(tag, layer, pbf) {
  if (tag === 15) layer.version = pbf.readVarint();else if (tag === 1) layer.name = pbf.readString();else if (tag === 5) layer.extent = pbf.readVarint();else if (tag === 2) layer._features.push(pbf.pos);else if (tag === 3) layer._keys.push(pbf.readString());else if (tag === 4) layer._values.push(readValueMessage(pbf));
}

function readValueMessage(pbf) {
  let value = null;
  const end = pbf.readVarint() + pbf.pos;

  while (pbf.pos < end) {
    const tag = pbf.readVarint() >> 3;
    value = tag === 1 ? pbf.readString() : tag === 2 ? pbf.readFloat() : tag === 3 ? pbf.readDouble() : tag === 4 ? pbf.readVarint64() : tag === 5 ? pbf.readVarint() : tag === 6 ? pbf.readSVarint() : tag === 7 ? pbf.readBoolean() : null;
  }

  return value;
}
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