Source: encoding/element-reader.js

  1. /**
  2.  * Copyright (C) 2013-2016 Regents of the University of California.
  3.  * @author: Jeff Thompson <jefft0@remap.ucla.edu>
  4.  *
  5.  * This program is free software: you can redistribute it and/or modify
  6.  * it under the terms of the GNU Lesser General Public License as published by
  7.  * the Free Software Foundation, either version 3 of the License, or
  8.  * (at your option) any later version.
  9.  *
  10.  * This program is distributed in the hope that it will be useful,
  11.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13.  * GNU Lesser General Public License for more details.
  14.  *
  15.  * You should have received a copy of the GNU Lesser General Public License
  16.  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17.  * A copy of the GNU Lesser General Public License is in the file COPYING.
  18.  */
  20. /** @ignore */
  21. var DataUtils = require('./data-utils.js').DataUtils; /** @ignore */
  22. var Tlv = require('./tlv/tlv.js').Tlv; /** @ignore */
  23. var TlvStructureDecoder = require('./tlv/tlv-structure-decoder.js').TlvStructureDecoder; /** @ignore */
  24. var DecodingException = require('./decoding-exception.js').DecodingException; /** @ignore */
  25. var NdnCommon = require('../util/ndn-common.js').NdnCommon; /** @ignore */
  26. var LOG = require('../log.js').Log.LOG;
  28. /**
  29.  * A ElementReader lets you call onReceivedData multiple times which uses a
  30.  * TlvStructureDecoder to detect the end of a TLV element and calls
  31.  * elementListener.onReceivedElement(element) with the element.  This handles
  32.  * the case where a single call to onReceivedData may contain multiple elements.
  33.  * @constructor
  34.  * @param {{onReceivedElement:function}} elementListener
  35.  */
  36. var ElementReader = function ElementReader(elementListener)
  37. {
  38.   this.elementListener = elementListener;
  39.   this.dataParts = [];
  40.   this.tlvStructureDecoder = new TlvStructureDecoder();
  41. };
  43. exports.ElementReader = ElementReader;
  45. ElementReader.prototype.onReceivedData = function(/* Buffer */ data)
  46. {
  47.   // Process multiple objects in the data.
  48.   while (true) {
  49.     var gotElementEnd;
  50.     var offset;
  52.     try {
  53.       if (this.dataParts.length == 0) {
  54.         // This is the beginning of an element.
  55.         if (data.length <= 0)
  56.           // Wait for more data.
  57.           return;
  58.       }
  60.       // Scan the input to check if a whole TLV object has been read.
  61.       this.tlvStructureDecoder.seek(0);
  62.       gotElementEnd = this.tlvStructureDecoder.findElementEnd(data);
  63.       offset = this.tlvStructureDecoder.getOffset();
  64.     } catch (ex) {
  65.       // Reset to read a new element on the next call.
  66.       this.dataParts = [];
  67.       this.tlvStructureDecoder = new TlvStructureDecoder();
  69.       throw ex;
  70.     }
  72.     if (gotElementEnd) {
  73.       // Got the remainder of an object.  Report to the caller.
  74.       this.dataParts.push(data.slice(0, offset));
  75.       var element = DataUtils.concatArrays(this.dataParts);
  76.       this.dataParts = [];
  78.       // Reset to read a new object. Do this before calling onReceivedElement
  79.       // in case it throws an exception.
  80.       data = data.slice(offset, data.length);
  81.       this.tlvStructureDecoder = new TlvStructureDecoder();
  83.       this.elementListener.onReceivedElement(element);
  84.       if (data.length == 0)
  85.         // No more data in the packet.
  86.         return;
  88.       // else loop back to decode.
  89.     }
  90.     else {
  91.       // Save a copy. We will call concatArrays later.
  92.       var totalLength = data.length;
  93.       for (var i = 0; i < this.dataParts.length; ++i)
  94.         totalLength += this.dataParts[i].length;
  95.       if (totalLength > NdnCommon.MAX_NDN_PACKET_SIZE) {
  96.         // Reset to read a new element on the next call.
  97.         this.dataParts = [];
  98.         this.tlvStructureDecoder = new TlvStructureDecoder();
  100.         throw new DecodingException(new Error
  101.           ("The incoming packet exceeds the maximum limit Face.getMaxNdnPacketSize()"));
  102.       }
  104.       this.dataParts.push(new Buffer(data));
  105.       if (LOG > 3) console.log('Incomplete packet received. Length ' + data.length + '. Wait for more input.');
  106.         return;
  107.     }
  108.   }
  109. };