Function init

src/gridfs/download.ts:305–413

(stream: GridFSBucketReadStream)

}

function init(stream: GridFSBucketReadStream): void {
  const findOneOptions: FindOptions = {};
  if (stream.s.readPreference) {
    findOneOptions.readPreference = stream.s.readPreference;
  }
  if (stream.s.options && stream.s.options.sort) {
    findOneOptions.sort = stream.s.options.sort;
  }
  if (stream.s.options && stream.s.options.skip) {
    findOneOptions.skip = stream.s.options.skip;
  }

  const handleReadResult = (doc: Document | null) => {
    if (stream.destroyed) return;

    if (!doc) {
      const identifier = stream.s.filter._id
        ? stream.s.filter._id.toString()
        : stream.s.filter.filename;
      const errmsg = `FileNotFound: file ${identifier} was not found`;
      // TODO(NODE-3483)
      const err = new MongoRuntimeError(errmsg);
      err.code = 'ENOENT'; // TODO: NODE-3338 set property as part of constructor
      return stream.destroy(err);
    }

    // If document is empty, kill the stream immediately and don't
    // execute any reads
    if (doc.length <= 0) {
      stream.push(null);
      return;
    }

    if (stream.destroyed) {
      // If user destroys the stream before we have a cursor, wait
      // until the query is done to say we're 'closed' because we can't
      // cancel a query.
      stream.destroy();
      return;
    }

    try {
      stream.s.bytesToSkip = handleStartOption(stream, doc, stream.s.options);
    } catch (error) {
      return stream.destroy(error);
    }

    const filter: Document = { files_id: doc._id };

    // Currently (MongoDB 3.4.4) skip function does not support the index,
    // it needs to retrieve all the documents first and then skip them. (CS-25811)
    // As work around we use $gte on the "n" field.
    if (stream.s.options && stream.s.options.start != null) {
      const skip = Math.floor(stream.s.options.start / doc.chunkSize);
      if (skip > 0) {
        filter['n'] = { $gte: skip };
      }
    }