kc3-lang/angle/src/libANGLE/Observer.h

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• Hash : 3418fe80
  Author :
  Date : 2018-04-09T14:08:19
  

  Optimize Subject's binding method.
  
  Using FixedVector, we can remove the need for dynamic allocation in
  most of the use cases. Only when we exceed a certain amount of fixed
  storage do we need to spill into the heap.
  
  Bug: angleproject:2389
  Bug: chromium:829906
  Change-Id: Ib5f7073b58876bfd2400bd87b743bddcee5e5dc8
  Reviewed-on: https://chromium-review.googlesource.com/1002884
  Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
  Reviewed-by: Luc Ferron <lucferron@chromium.org>
  Commit-Queue: Jamie Madill <jmadill@chromium.org>
  

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• src/libANGLE/Observer.h

• //
  // Copyright 2016 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  // Observer:
  //   Implements the Observer pattern for sending state change notifications
  //   from Subject objects to dependent Observer objects.
  //
  //   See design document:
  //   https://docs.google.com/document/d/15Edfotqg6_l1skTEL8ADQudF_oIdNa7i8Po43k6jMd4/
  
  #ifndef LIBANGLE_OBSERVER_H_
  #define LIBANGLE_OBSERVER_H_
  
  #include "common/FixedVector.h"
  #include "common/angleutils.h"
  
  namespace gl
  {
  class Context;
  }  // namespace gl
  
  namespace angle
  {
  
  using SubjectIndex = size_t;
  
  enum class SubjectMessage
  {
      CONTENTS_CHANGED,
      STORAGE_CHANGED,
      DEPENDENT_DIRTY_BITS,
  };
  
  // The observing class inherits from this interface class.
  class ObserverInterface
  {
    public:
      virtual ~ObserverInterface();
      virtual void onSubjectStateChange(const gl::Context *context,
                                        SubjectIndex index,
                                        SubjectMessage message) = 0;
  };
  
  class ObserverBinding;
  
  // Maintains a list of observer bindings. Sends update messages to the observer.
  class Subject : NonCopyable
  {
    public:
      Subject();
      virtual ~Subject();
  
      void onStateChange(const gl::Context *context, SubjectMessage message) const;
      bool hasObservers() const;
      void resetObservers();
  
    private:
      // Only the ObserverBinding class should add or remove observers.
      friend class ObserverBinding;
      void addObserver(ObserverBinding *observer);
      void removeObserver(ObserverBinding *observer);
  
      // Keep a short list of observers so we can allocate/free them quickly. But since we support
      // unlimited bindings, have a spill-over list of that uses dynamic allocation.
      static constexpr size_t kMaxFixedObservers = 8;
      angle::FixedVector<ObserverBinding *, kMaxFixedObservers> mFastObservers;
      std::vector<ObserverBinding *> mSlowObservers;
  };
  
  // Keeps a binding between a Subject and Observer, with a specific subject index.
  class ObserverBinding final
  {
    public:
      ObserverBinding(ObserverInterface *observer, SubjectIndex index);
      ~ObserverBinding();
      ObserverBinding(const ObserverBinding &other);
      ObserverBinding &operator=(const ObserverBinding &other);
  
      void bind(Subject *subject);
      void reset();
      void onStateChange(const gl::Context *context, SubjectMessage message) const;
      void onSubjectReset();
  
      const Subject *getSubject() const;
  
    private:
      Subject *mSubject;
      ObserverInterface *mObserver;
      SubjectIndex mIndex;
  };
  
  }  // namespace angle
  
  #endif  // LIBANGLE_OBSERVER_H_
  

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