tedious/lib/incoming-message-stream.js

A TDS driver, for connecting to MS SQLServer databases.

"use strict";

const BufferList = require('bl');

const _require = require('readable-stream'),
      Transform = _require.Transform;

const Message = require('./message');

const _require2 = require('./packet'),
      Packet = _require2.Packet,
      HEADER_LENGTH = _require2.HEADER_LENGTH;

/**
  IncomingMessageStream
  Transform received TDS data into individual IncomingMessage streams.
*/
class IncomingMessageStream extends Transform {
  constructor(debug) {
    super({
      readableObjectMode: true
    });
    this.debug = debug;
    this.currentMessage = undefined;
    this.bl = new BufferList();
  }

  pause() {
    super.pause();

    if (this.currentMessage) {
      this.currentMessage.pause();
    }
  }

  resume() {
    super.resume();

    if (this.currentMessage) {
      this.currentMessage.resume();
    }
  }

  processBufferedData(callback) {
    // The packet header is always 8 bytes of length.
    while (this.bl.length >= HEADER_LENGTH) {
      // Get the full packet length
      const length = this.bl.readUInt16BE(2);

      if (this.bl.length >= length) {
        const data = this.bl.slice(0, length);
        this.bl.consume(length); // TODO: Get rid of creating `Packet` instances here.

        const packet = new Packet(data);
        this.debug.packet('Received', packet);
        this.debug.data(packet);
        let message = this.currentMessage;

        if (message === undefined) {
          message = new Message({
            type: packet.type(),
            resetConnection: false
          });
          this.push(message);
        }

        if (packet.isLast()) {
          this.currentMessage = undefined; // Wait until the current message was fully processed before we
          // continue processing any remaining messages.

          message.once('end', () => {
            this.processBufferedData(callback);
          });
          message.end(packet.data());
          return;
        } else {
          this.currentMessage = message; // If too much data is buffering up in the
          // current message, wait for it to drain.

          if (!message.write(packet.data())) {
            message.once('drain', () => {
              this.processBufferedData(callback);
            });
            return;
          }
        }
      } else {
        break;
      }
    } // Not enough data to read the next packet. Stop here and wait for
    // the next call to `_transform`.


    callback();
  }

  _transform(chunk, encoding, callback) {
    this.bl.append(chunk);
    this.processBufferedData(callback);
  }

}

module.exports = IncomingMessageStream;