ttyplay.js

'use strict';

var events = require('events');
var util = require('util');

var Transform = require('stream').Transform;

/**
 * @constructor
 * @name TtyPlayStream
 * @param {Hash} options
 */
var TtyPlayStream = function(options) {

  var self = this;

  if (options === undefined) {
    self.settings = {};
  } else {
    // Copy the options
    self.settings = JSON.parse(JSON.stringify(options));
  }

  // PlaceHolder for unparsed chunk parts
  self.prevChunk = null;

  // Run parent constructor
  Transform.call(this, self.settings);

};

util.inherits(TtyPlayStream, Transform);

module.exports = TtyPlayStream;

TtyPlayStream.prototype._transform = function(chunk, encoding, callback) {

  var self = this;

  var combinedChunk ;

  if (self.prevChunk === null) {
    combinedChunk = chunk.slice(0);
  } else {
    combinedChunk = Buffer.concat([self.prevChunk, chunk]);
  }

  var action = function(header, packet, cb) {
    //console.log(header);
    self.push(packet.payload);
    cb(null);
  };

  // This is called when there is no more to parse
  // buffer contains the chunk that can not be parsed into a record
  var done = function(err, buffer) {
    self.prevChunk = buffer;
    callback(null);
  };

  parseBuffer(combinedChunk, action , done);

};

TtyPlayStream.prototype._flush = function(callback) {
  console.log('before end');
  callback(null);
};

function parseBuffer(chunk, action, callback) {

  var buffer = chunk.slice(0);

  var record = parseRecord(buffer);

  if ( record === null) {
    callback(null, buffer);
  } else {
    var header = record.header;
    var packet = record.packet;

    action(header, packet, function() {
      var rest = record.packet.rest;
      parseBuffer(rest, action, callback);
    });

  }
}

function parseHeader(chunk) {
  var result = {};

  if (chunk.length >= 12) {
      // 32Bit  (= 4 Bytes) Little Endian
      var sec = chunk.readUInt32LE(0);
      var usec = chunk.readUInt32LE(4);
      var payloadLength = chunk.readUInt32LE(8);

      result.sec = sec;
      result.usec = usec;
      result.length = payloadLength;
      result.header = chunk.slice(0, 11);
      result.rest = chunk.slice(12);
      //console.log(result);
      return result;

  } else {
    return null;
  }
}

function parsePacket(chunk, length) {
  var result = {};

  if (chunk.length >= length) {
      result.payload = chunk.slice(0,length -1);
      result.rest = chunk.slice(length);
      //console.log(result);
      return result;
  } else {
    return null;
  }
}

function parseRecord(chunk) {
  var result = {};

  var header = parseHeader(chunk);

  if ( header === null) {
    return null;
  } else {
    var chunkLeft = header.rest;
    var packet = parsePacket(chunkLeft, header.length);

    if (packet === null) {
      return null;
    } else {
      return {
        header: header,
        packet: packet
      }
    }
  }

}