gis-tools-ts/dist/readers/gtfs/realtime/index.js

A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.

import { GTFSRealtimeEntity } from './entity.js';
import { GTFSRealtimeHeader } from './header.js';
import { PbfReader } from 'pbf-ts';
export * from './stop/index.js';
export * from './trip/index.js';
export * from './alert.js';
export * from './entity.js';
export * from './header.js';
export * from './position.js';
export * from './shape.js';
export * from './util.js';
export * from './vehiclePosition.js';
/**
 * # GTFS Realtime message.
 *
 * ## Description
 * The input is a Uint8Array that has encoded protobuffer messages.
 * See {@link https://open-s2.github.io/pbf/classes/PbfReader.html}.
 *
 * The contents of a feed message.
 * A feed is a continuous stream of feed messages. Each message in the stream is
 * obtained as a response to an appropriate HTTP GET request.
 * A realtime feed is always defined with relation to an existing GTFS feed.
 * All the entity ids are resolved with respect to the GTFS feed.
 * Note that "required" and "optional" as stated in this file refer to Protocol
 * Buffer cardinality, not semantic cardinality.  See reference.md at
 * https://github.com/google/transit/tree/master/gtfs-realtime for field
 * semantic cardinality.
 *
 * ## Usage
 *
 * ```ts
 * import { GTFSRealtimeReader } from 'gis-tools-ts';
 *
 * const gtfsRealtimeReader = new GTFSRealtimeReader(data);
 * const { header, entities } = gtfsRealtimeReader;
 * for (const entity of entities) {
 *   console.log(entity);
 * }
 * ```
 *
 * ## Links
 * - https://mobilitydatabase.org
 * - https://developers.google.com/transit/gtfs/examples/overview
 * - https://mobilitydata.github.io/
 * - https://www.transit.land
 */
export class GTFSRealtimeReader {
    header;
    entities = [];
    /**
     * @param data - the input data to parse
     * @param end - the size of the data, leave blank to parse the entire data
     */
    constructor(data, end = 0) {
        const pbf = new PbfReader(data);
        pbf.readFields(this.#readMessage, this, end);
    }
    /**
     * Read in the message
     * @param tag - the tag to read
     * @param message - the GTFSRealtime object to modify
     * @param pbf - the Protobuf to pull the appropriate data from
     */
    #readMessage(tag, message, pbf) {
        if (tag === 1) {
            message.header = new GTFSRealtimeHeader(pbf, pbf.readVarint() + pbf.pos);
        }
        else if (tag === 2) {
            message.entities.push(new GTFSRealtimeEntity(pbf, pbf.readVarint() + pbf.pos));
        }
        else
            throw new Error('GTFSRealtime: unknown tag ' + tag);
    }
}
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