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 parse XMPP stream. Data is fed to the parser
+ * using appendData() method and it calls |onStanzaCallback| and
+ * |onErrorCallback| specified using setCallbacks().
+ *
+ * @constructor
+ */
+remoting.XmppStreamParser = function() {
+  /** @type {function(Element):void} @private */
+  this.onStanzaCallback_ = function(stanza) {};
+  /** @type {function(string):void} @private */
+  this.onErrorCallback_ = function(error) {};
+
+  /**
+   * Buffer containing the data that has been received but haven't been parsed.
+   * @private
+   */
+  this.data_ = new ArrayBuffer(0);
+
+  /**
+   * Current depth in the XML stream.
+   * @private
+   */
+  this.depth_ = 0;
+
+  /**
+   * Set to true after error.
+   * @private
+   */
+  this.error_ = false;
+
+  /**
+   * The <stream> opening tag received at the beginning of the stream.
+   * @private
+   */
+  this.startTag_ = '';
+
+  /**
+   * Closing tag matching |startTag_|.
+   * @private
+   */
+  this.startTagEnd_ = '';
+
+  /**
+   * String containing current incomplete stanza.
+   * @private
+   */
+  this.currentStanza_ = '';
+}
+
+/**
+ * Sets callbacks to be called on incoming stanzas and on error.
+ *
+ * @param {function(Element):void} onStanzaCallback
+ * @param {function(string):void} onErrorCallback
+ */
+remoting.XmppStreamParser.prototype.setCallbacks =
+    function(onStanzaCallback, onErrorCallback) {
+  this.onStanzaCallback_ = onStanzaCallback;
+  this.onErrorCallback_ = onErrorCallback;
+}
+
+/** @param {ArrayBuffer} data */
+remoting.XmppStreamParser.prototype.appendData = function(data) {
+  base.debug.assert(!this.error_);
+
+  if (this.data_.byteLength > 0) {
+    // Concatenate two buffers.
+    var newData = new Uint8Array(this.data_.byteLength + data.byteLength);
+    newData.set(new Uint8Array(this.data_), 0);
+    newData.set(new Uint8Array(data), this.data_.byteLength);
+    this.data_ = newData.buffer;
+  } else {
+    this.data_ = 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_.byteLength > 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_);
+      var firstChar = view.getUint8(0);
+      if (firstChar == spaceCode) {
+        tryAgain = true;
+        this.data_ = this.data_.slice(1);
+        continue;
+      } else if (firstChar != tagStartCode) {
+        var dataAsText = '';
+        try {
+          dataAsText = base.decodeUtf8(this.data_);
+        } catch (exception) {
+          dataAsText = 'charCode = ' + firstChar;
+        }
+        this.processError_('Received unexpected text data: ' + dataAsText);
+        return;
+      }
+    }
+
+    // Iterate over characters in the buffer to find complete tags.
+    var view = new DataView(this.data_);
+    for (var i = 0; i < view.byteLength; ++i) {
+      var currentChar = view.getUint8(i);
+      if (currentChar == tagStartCode) {
+        if (i > 0) {
+          var text = this.extractStringFromBuffer_(i);
+          if (text == null)
+            return;
+          this.processText_(text);
+          tryAgain = true;
+          break;
+        }
+      } else if (currentChar == tagEndCode) {
+        var tag = this.extractStringFromBuffer_(i + 1);
+        if (tag == null)
+          return;
+        if (tag.charAt(0) != '<') {
+          this.processError_('Received \'>\' without \'<\': ' + tag);
+          return;
+        }
+        this.processTag_(tag);
+        tryAgain = true;
+        break;
+      }
+    }
+  }
+}
+
+/**
+ * @param {string} text
+ * @private
+ */
+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
+ * @private
+ */
+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_ = '';
+    }
+  }
+}
+
+/**
+ * @private
+ */
+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.firstElementChild);
+}
+
+/**
+ * @param {string} text
+ * @private
+ */
+remoting.XmppStreamParser.prototype.processError_ = function(text) {
+  this.onErrorCallback_(text);
+  this.error_ = true;
+}
+
+/**
+ * Helper to extract and decode |bytes| bytes from |data_|. Returns NULL in case
+ * the buffer contains invalidUTF-8.
+ *
+ * @param {number} bytes Specifies how many bytes should be extracted.
+ * @returns {string?}
+ * @private
+ */
+remoting.XmppStreamParser.prototype.extractStringFromBuffer_ = function(bytes) {
+  var result = '';
+  try {
+    result = base.decodeUtf8(this.data_.slice(0, bytes));
+  } catch (exception) {
+    this.processError_('Received invalid UTF-8 data.');
+    result = null;
+  }
+  this.data_ = this.data_.slice(bytes);
+  return result;
+}
+
+/**
+ * @param {string} text
+ * @return {Element}
+ * @private
+ */
+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.firstElementChild;
+}