Add sessions to HttpServer.

runtime/bin/http_session.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+const String _DART_SESSION_ID = "DARTSESSID";
+
+// A _HttpSession is a node in a double-linked list, with _next and _prev being
+// the previous and next pointers.
+class _HttpSession implements HttpSession {
+  _HttpSession(_HttpSessionManager this._sessionManager, String this.id)
+    : _lastSeen = new Date.now();
+
+  void destroy() {
+    _destroyed = true;
+    _sessionManager._removeFromTimeoutQueue(this);
+    _sessionManager._sessions.remove(id);
+  }
+
+  // Mark the session as seen. This will reset the timeout and move the node to
+  // the end of the timeout queue.
+  void _markSeen() {
+    _lastSeen = new Date.now();
+    _sessionManager._bumpToEnd(this);
+  }
+
+  Dynamic data;
+
+  Date get lastSeen => _lastSeen;
+
+  final String id;
+
+  void set onTimeout(void callback()) {
+    _timeoutCallback = callback;
+  }
+
+  // Destroyed marked. Used by the http connection to see if a session is valid.
+  bool _destroyed = false;
+  Date _lastSeen;
+  Function _timeoutCallback;
+  _HttpSessionManager _sessionManager;
+  // Pointers in timeout queue.
+  _HttpSession _prev;
+  _HttpSession _next;
+}
+
+// Private class used to manage all the active sessions. The sessions are stored
+// in two ways:
+//
+//  * In a map, mapping from ID to HttpSession.
+//  * In a linked list, used as a timeout queue.
+class _HttpSessionManager {
+  _HttpSessionManager() : _sessions = {};
+
+  String createSessionId() {
+    const int _KEY_LENGTH = 16;  // 128 bits.
+    var data = _getRandomBytes(_KEY_LENGTH);
+    return CryptoUtils.bytesToHex(data);
+  }
+
+  _HttpSession getSession(String id) {
+    return _sessions[id];
+  }
+
+  _HttpSession createSession(init(HttpSession session)) {
+    var id = createSessionId();
+    // TODO(ajohnsen): Consider adding a limit and throwing an exception.
+    // Should be very unlikely however.
+    while (_sessions.containsKey(id)) {
+      id = createSessionId();
+    }
+    var session = _sessions[id] = new _HttpSession(this, id);
+    if (init != null) init(session);
+    _addToTimeoutQueue(session);
+    return session;
+  }
+
+  void set sessionTimeout(int timeout) {
+    _sessionTimeout = timeout;
+    _stopTimer();
+    _startTimer();
+  }
+
+  void close() {
+    _stopTimer();
+  }
+
+  void _bumpToEnd(_HttpSession session) {
+    _removeFromTimeoutQueue(session);
+    _addToTimeoutQueue(session);
+  }
+
+  void _addToTimeoutQueue(_HttpSession session) {
+    if (_head == null) {
+      assert(_tail == null);
+      _tail = _head = session;
+      _startTimer();
+    } else {
+      assert(_timer != null);
+      assert(_tail != null);
+      // Add to end.
+      _tail._next = session;
+      session._prev = _tail;
+      _tail = session;
+    }
+  }
+
+  void _removeFromTimeoutQueue(_HttpSession session) {
+    if (session._next != null) {
+      session._next._prev = session._prev;
+    }
+    if (session._prev != null) {
+      session._prev._next = session._next;
+    }
+    if (_head == session) {
+      // We removed the head element, start new timer.
+      _head = session._next;
+      _stopTimer();
+      _startTimer();
+    }
+    if (_tail == session) {
+      _tail = session._prev;
+    }
+    session._next = session._prev = null;
+  }
+
+  void _timerTimeout(_) {
+    _stopTimer();  // Clear timer.
+    assert(_head != null);
+    var session = _head;
+    session.destroy();  // Will remove the session from timeout queue and map.
+    if (session._timeoutCallback != null) {
+      session._timeoutCallback();
+    }
+  }
+
+  void _startTimer() {
+    assert(_timer == null);
+    if (_head != null) {
+      int seconds = new Date.now().difference(_head.lastSeen).inSeconds;
+      _timer = new Timer((_sessionTimeout - seconds) * 1000, _timerTimeout);
+    }
+  }
+
+  void _stopTimer() {
+    if (_timer != null) {
+      _timer.cancel();
+      _timer = null;
+    }
+  }
+
+  Map<String, _HttpSession> _sessions;
+  int _sessionTimeout = 20 * 60;  // 20 mins.
+  _HttpSession _head;
+  _HttpSession _tail;
+  Timer _timer;
+
+  static Uint8List _getRandomBytes(int count)
+      native "Crypto_GetRandomBytes";
+}
+