XMPP implementation in JavaScript.

remoting/webapp/xmpp_stream_parser.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+/**
+ * XmppStreamParser is used to split data received over XMPP connection into
+ * individual stanzas. Data is fed to the parser using appendData() method.
+ * onStartCallback is called once for the stream header and after that
+ * onStanzaCallback is called for each complete stanza.
+ *
+ * @param {function(Element):void} onStanzaCallback
+ * @param {function(string):void} onErrorCallback
+ * @constructor
+ */
+remoting.XmppStreamParser = function(onStanzaCallback, onErrorCallback) {
+  this.onStanzaCallback_ = onStanzaCallback;
+  this.onErrorCallback_ = onErrorCallback;
+
+
+  /** @type {Array.<ArrayBuffer>} */
+  this.data_ = [];
+  this.depth_ = 0;
+  this.error_ = false;
+  this.startTag_ = '';
+  this.startTagEnd_ = '';
+  this.currentStanza_ = '';
+}
+
+/** @param {ArrayBuffer} data */
+remoting.XmppStreamParser.prototype.appendData = function(data) {
+  base.debug.assert(!this.error_);
+
+  this.data_.push(data);
+
+  // Check if the newly appended data completes XML tag or a piece of text by
+  // looking for '<' and '>' char codes. This has to be done before converting
+  // data to string because the input may not contain complete UTF-8 sequence.
+  var tagStartCode = '<'.charCodeAt(0);
+  var tagEndCode = '>'.charCodeAt(0);
+  var spaceCode = ' '.charCodeAt(0);
+  var tryAgain = true;
+  while (this.data_.length > 0 && tryAgain && !this.error_) {
+    tryAgain = false;
+
+    // If we are not currently in a middle of a stanza then skip spaces (server
+    // may send spaces periodically as heartbeats) and make sure that the first
+    // character starts XML tag.
+    if (this.depth_ <= 1) {
+      var view = new DataView(this.data_[0]);
+      var firstChar = view.getUint8(0);
+      if (firstChar == spaceCode) {
+        tryAgain = true;
+        this.extractToken_(1);
+        continue;
+      } else if (firstChar != tagStartCode) {
+        this.processError_('Received unexpected text data: ' +
+                           base.decodeUtf8(this.data_[0]));
+        return;
+      }
+    }
+
+    var view = new DataView(this.data_[this.data_.length - 1]);
+    for (var i = 0; i < view.byteLength; ++i) {
+      var currentChar = view.getUint8(i);
+      if (currentChar == tagStartCode) {
+        if (this.data_.length > 1 || i > 0) {
+          this.processText_(this.extractToken_(i));
+          tryAgain = true;
+          break;
+        }
+      } else if (currentChar == tagEndCode) {
+        var tag = this.extractToken_(i + 1);
+        if (tag.charAt(0) != '<') {
+          this.processError_('Received \'>\' without \'<\': ' + tag);
+          return;
+        }
+        this.processTag_(tag);
+        tryAgain = true;
+        break;
+      }
+    }
+  }
+}
+
+/** @param {string} text */
+remoting.XmppStreamParser.prototype.processText_ = function(text) {
+  // Tokenization code in appendData() shouldn't allow text tokens in between
+  // stanzas.
+  base.debug.assert(this.depth_ > 1);
+  this.currentStanza_ += text;
+}
+
+/** @param {string} tag */
+remoting.XmppStreamParser.prototype.processTag_ = function(tag) {
+  base.debug.assert(tag.charAt(0) == '<');
+  base.debug.assert(tag.charAt(tag.length - 1) == '>');
+
+  this.currentStanza_ += tag;
+
+  var openTag = tag.charAt(1) != '/';
+  if (openTag) {
+    ++this.depth_;
+    if (this.depth_ == 1) {
+      this.startTag_ = this.currentStanza_;
+      this.currentStanza_ = '';
+
+      // Create end tag matching the start.
+      var tagName =
+          this.startTag_.substr(1, this.startTag_.length - 2).split(' ', 1)[0];
+      this.startTagEnd_ = '</' + tagName + '>';
+
+      // Try parsing start together with the end
+      var parsed = this.parseTag_(this.startTag_ + this.startTagEnd_);
+      if (!parsed) {
+        this.processError_('Failed to parse start tag: ' + this.startTag_);
+        return;
+      }
+    }
+  }
+
+  var closingTag =
+      (tag.charAt(1) == '/') || (tag.charAt(tag.length - 2) == '/');
+  if (closingTag) {
+    // The first start tag is not expected to be closed.
+    if (this.depth_ <= 1) {
+      this.processError_('Unexpected closing tag: ' + tag)
+      return;
+    }
+    --this.depth_;
+    if (this.depth_ == 1) {
+      this.processCompleteStanza_();
+      this.currentStanza_ = '';
+    }
+  }
+}
+
+remoting.XmppStreamParser.prototype.processCompleteStanza_ = function() {
+  var stanza = this.startTag_ + this.currentStanza_ + this.startTagEnd_;
+  var parsed = this.parseTag_(stanza);
+  if (!parsed) {
+    this.processError_('Failed to parse stanza: ' + this.currentStanza_);
+    return;
+  }
+  this.onStanzaCallback_(parsed.childNodes[0]);
+}
+
+/** @param {string} text */
+remoting.XmppStreamParser.prototype.processError_ = function(text) {
+  this.onErrorCallback_(text);
+  this.error_ = true;
+}
+
+/**
+ * Helper that assembles block of data from pieces in this.data_ up to specified
+ * position in the last buffer and then removes that data from this.data_ .
+ *
+ * @param {number} endPos Specifies how many bytes should be taken from the last
+ *   buffer in this.data_ .
+ * @returns {string}
+ */
+remoting.XmppStreamParser.prototype.extractToken_ = function(endPos) {
+  var size = endPos;
+  for (var i = 0; i < this.data_.length - 1; ++i) {
+    size += this.data_[i].byteLength;
+  }
+
+  var buffer = new Uint8Array(size);
+  var pos = 0;
+  for (var i = 0; i < this.data_.length - 1; ++i) {
+    buffer.set(new Uint8Array(this.data_[i]), pos);
+    pos += this.data_[i].byteLength;
+  }
+  if (endPos > 0) {
+    buffer.set(new Uint8Array(this.data_[this.data_.length - 1], 0, endPos),
+               pos);
+    pos += endPos;
+  }
+  base.debug.assert(pos == size);
+
+  // Remove copied data from |data_|.
+  var dataLeft = this.data_[this.data_.length - 1].slice(endPos);
+  if (dataLeft.byteLength == 0) {
+    this.data_ = []
+  } else {
+    this.data_ = [dataLeft];
+  }
+
+  return base.decodeUtf8(buffer.buffer);
+}
+
+/**
+ * @param {string} text
+ * @return {Element}
+ */
+remoting.XmppStreamParser.prototype.parseTag_ = function(text) {
+  /** @type {Document} */
+  var result = new DOMParser().parseFromString(text, 'text/xml');
+  if (result.querySelector('parsererror') != null)
+    return null;
+  return result.firstChild;
+}