Add base to the repository.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 170 insertions, 0 deletions

diff --git a/base/observer_list.h b/base/observer_list.h
new file mode 100644
index 0000000..a64808d
--- /dev/null
+++ b/base/observer_list.h
@@ -0,0 +1,170 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef BASE_OBSERVER_LIST_H__
+#define BASE_OBSERVER_LIST_H__
+
+#include <vector>
+#include <algorithm>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// OVERVIEW:
+//
+//   A container for a list of observers.  Unlike a normal STL vector or list,
+//   this container can be modified during iteration without invalidating the
+//   iterator.  So, it safely handles the case of an observer removing itself
+//   or other observers from the list while observers are being notified.
+//
+// TYPICAL USAGE:
+//
+//   class MyWidget {
+//    public:
+//     ...
+//
+//     class Observer {
+//      public:
+//       virtual void OnFoo(MyWidget* w) = 0;
+//       virtual void OnBar(MyWidget* w, int x, int y) = 0;
+//     };
+//
+//     void AddObserver(Observer* obs) {
+//       observer_list_.AddObserver(obs);
+//     }
+//
+//     void RemoveObserver(Observer* obs) {
+//       observer_list_.RemoveObserver(obs);
+//     }
+//
+//     void NotifyFoo() {
+//       FOR_EACH_OBSERVER(Observer, observer_list_, OnFoo(this));
+//     }
+//
+//     void NotifyBar(int x, int y) {
+//       FOR_EACH_OBSERVER(Observer, observer_list_, OnBar(this, x, y));
+//     }
+//
+//    private:
+//     ObserverList<Observer> observer_list_;
+//   };
+//
+///////////////////////////////////////////////////////////////////////////////
+
+template <class ObserverType, bool check_empty = false>
+class ObserverList {
+ public:
+  ObserverList() : notify_depth_(0) {}
+  ~ObserverList() {
+    // When check_empty is true, assert that the list is empty on destruction.
+    if (check_empty) {
+      Compact();
+      DCHECK_EQ(observers_.size(), 0);
+    }
+  }
+
+  // Add an observer to the list.
+  void AddObserver(ObserverType* obs) {
+    DCHECK(find(observers_.begin(), observers_.end(), obs) == observers_.end())
+        << "Observers can only be added once!";
+    observers_.push_back(obs);
+  }
+
+  // Remove an observer from the list.
+  void RemoveObserver(ObserverType* obs) {
+    ListType::iterator it = find(observers_.begin(), observers_.end(), obs);
+    if (it != observers_.end()) {
+      if (notify_depth_) {
+        *it = 0;
+      } else {
+        observers_.erase(it);
+      }
+    }
+  }
+
+  // An iterator class that can be used to access the list of observers.  See
+  // also the FOREACH_OBSERVER macro defined below.
+  class Iterator {
+   public:
+    Iterator(const ObserverList<ObserverType>& list) : list_(list), index_(0) {
+      ++list_.notify_depth_;
+    }
+
+    ~Iterator() {
+      if (--list_.notify_depth_ == 0)
+        list_.Compact();
+    }
+
+    ObserverType* GetNext() {
+      ListType& observers = list_.observers_;
+      // Advance if the current element is null
+      while (index_ < observers.size() && !observers[index_])
+        ++index_;
+      return index_ < observers.size() ? observers[index_++] : NULL;
+    }
+
+   private:
+    const ObserverList<ObserverType>& list_;
+    size_t index_;
+  };
+
+ private:
+  typedef std::vector<ObserverType*> ListType;
+
+  void Compact() const {
+    ListType::iterator it = observers_.begin();
+    while (it != observers_.end()) {
+      if (*it) {
+        ++it;
+      } else {
+        it = observers_.erase(it);
+      }
+    }
+  }
+
+  // These are marked mutable to facilitate having NotifyAll be const.
+  mutable ListType observers_;
+  mutable int notify_depth_;
+
+  friend class ObserverList::Iterator;
+
+  DISALLOW_EVIL_CONSTRUCTORS(ObserverList);
+};
+
+#define FOR_EACH_OBSERVER(ObserverType, observer_list, func)  \
+  do {                                                        \
+    ObserverList<ObserverType>::Iterator it(observer_list);   \
+    ObserverType* obs;                                        \
+    while (obs = it.GetNext())                                \
+      obs->func;                                              \
+  } while (0)
+
+#endif  // BASE_OBSERVER_LIST_H__