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 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /**

  * MODULE NOTES:

  *

  * The Deque is a very small, very efficient container object

  * than can hold elements of type void*, offering the following features:

  *    Its interface supports pushing and popping of elements.

  *    It can iterate (via an interator class) its elements.

  *    When full, it can efficiently resize dynamically.

  *

  *

  * NOTE: The only bit of trickery here is that this deque is

  * built upon a ring-buffer. Like all ring buffers, the first

  * element may not be at index[0]. The mOrigin member determines

  * where the first child is. This point is quietly hidden from

  * customers of this class.

  *

  */

 #ifndef _NSDEQUE

 #define _NSDEQUE

 #include "nscore.h"

 #include "nsDebug.h"

 #include "mozilla/Attributes.h"

 #include "mozilla/fallible.h"

 #include "mozilla/MemoryReporting.h"

 /**

  * The nsDequeFunctor class is used when you want to create

  * callbacks between the deque and your generic code.

  * Use these objects in a call to ForEach();

  *

  */

 class nsDequeFunctor{

 public:

   virtual void* operator()(void* anObject)=0;

   virtual ~nsDequeFunctor() {}

 };

 /******************************************************

  * Here comes the nsDeque class itself...

  ******************************************************/

 /**

  * The deque (double-ended queue) class is a common container type,

  * whose behavior mimics a line in your favorite checkout stand.

  * Classic CS describes the common behavior of a queue as FIFO.

  * A deque allows insertion and removal at both ends of

  * the container.

  *

  * The deque stores pointers to items.

  */

 class nsDequeIterator;

 class NS_COM_GLUE nsDeque {

   friend class nsDequeIterator;

   typedef mozilla::fallible_t fallible_t;

   public:

    nsDeque(nsDequeFunctor* aDeallocator = nullptr);

   ~nsDeque();

   /**

    * Returns the number of elements currently stored in

    * this deque.

    *

    * @return  number of elements currently in the deque

    */

   inline int32_t GetSize() const {return mSize;}

   /**

    * Appends new member at the end of the deque.

    *

    * @param   item to store in deque

    */

   void Push(void* aItem) {

     if (!Push(aItem, fallible_t())) {

       NS_ABORT_OOM(mSize);

     }

   }

   bool Push(void* aItem, const fallible_t&) NS_WARN_UNUSED_RESULT;

   /**

    * Inserts new member at the front of the deque.

    *

    * @param   item to store in deque

    */

   void PushFront(void* aItem) {

     if (!PushFront(aItem, fallible_t())) {

       NS_ABORT_OOM(mSize);

     }

   }

   bool PushFront(void* aItem, const fallible_t&) NS_WARN_UNUSED_RESULT;

   /**

    * Remove and return the last item in the container.

    *

    * @return  the item that was the last item in container

    */

   void* Pop();

   /**

    * Remove and return the first item in the container.

    *

    * @return  the item that was first item in container

    */

   void* PopFront();

   /**

    * Retrieve the bottom item without removing it.

    *

    * @return  the first item in container

    */

   void* Peek();

   /**

    * Return topmost item without removing it.

    *

    * @return  the first item in container

    */

   void* PeekFront();

   /**

    * Retrieve the i'th member from the deque without removing it.

    *

    * @param   index of desired item

    * @return  i'th element in list

    */

   void* ObjectAt(int aIndex) const;

   /**

    * Removes and returns the i'th member from the deque.

    *

    * @param   index of desired item

    * @return  the element which was removed

    */

   void* RemoveObjectAt(int aIndex);

   /**

    * Remove all items from container without destroying them.

    */

   void Empty();

   /**

    * Remove and delete all items from container.

    * Deletes are handled by the deallocator nsDequeFunctor

    * which is specified at deque construction.

    */

   void Erase();

   /**

    * Creates a new iterator, pointing to the first

    * item in the deque.

    *

    * @return  new dequeIterator

    */

   nsDequeIterator Begin() const;

   /**

    * Creates a new iterator, pointing to the last

    * item in the deque.

    *

    * @return  new dequeIterator

    */

   nsDequeIterator End() const;

   void* Last() const;

   /**

    * Call this method when you want to iterate all the

    * members of the container, passing a functor along

    * to call your code.

    *

    * @param   aFunctor object to call for each member

    */

   void ForEach(nsDequeFunctor& aFunctor) const;

   /**

    * Call this method when you want to iterate all the

    * members of the container, calling the functor you 

    * passed with each member. This process will interrupt

    * if your function returns non 0 to this method.

    *

    * @param   aFunctor object to call for each member

    * @return  first nonzero result of aFunctor or 0.

    */

   const void* FirstThat(nsDequeFunctor& aFunctor) const;

   void SetDeallocator(nsDequeFunctor* aDeallocator);

   size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

 protected:

   int32_t         mSize;

   int32_t         mCapacity;

   int32_t         mOrigin;

   nsDequeFunctor* mDeallocator;

   void*           mBuffer[8];

   void**          mData;

 private:

   /**

    * Copy constructor (PRIVATE)

    *

    * @param another deque

    */

   nsDeque(const nsDeque& other);

   /**

    * Deque assignment operator (PRIVATE)

    *

    * @param   another deque

    * @return  *this

    */

   nsDeque& operator=(const nsDeque& anOther);

   bool GrowCapacity();

 };

 /******************************************************

  * Here comes the nsDequeIterator class...

  ******************************************************/

 class NS_COM_GLUE nsDequeIterator {

 public:

   /**

    * DequeIterator is an object that knows how to iterate

    * (forward and backward) through a Deque. Normally,

    * you don't need to do this, but there are some special

    * cases where it is pretty handy.

    *

    * One warning: the iterator is not bound to an item,

    * it is bound to an index, so if you insert or remove

    * from the beginning while using an iterator

    * (which is not recommended) then the iterator will

    * point to a different item.  @see GetCurrent()

    *

    * Here you go.

    *

    * @param   aQueue is the deque object to be iterated

    * @param   aIndex is the starting position for your iteration

    */

   nsDequeIterator(const nsDeque& aQueue, int aIndex=0);

   /**

    * Create a copy of a DequeIterator

    *

    * @param   aCopy is another iterator to copy from

    */

   nsDequeIterator(const nsDequeIterator& aCopy);

   /**

    * Moves iterator to first element in the deque

    * @return  *this

    */

   nsDequeIterator& First();

   /**

    * Standard assignment operator for dequeiterator

    * @param   aCopy is another iterator to copy from

    * @return  *this

    */

   nsDequeIterator& operator=(const nsDequeIterator& aCopy);

   /**

    * preform ! operation against two iterators to test for equivalence

    * (or lack thereof)!

    *

    * @param   aIter is the object to be compared to

    * @return  TRUE if NOT equal.

    */

   bool operator!=(nsDequeIterator& aIter);

   /**

    * Compare two iterators for increasing order.

    *

    * @param   aIter is the other iterator to be compared to

    * @return  TRUE if this object points to an element before

    *          the element pointed to by aIter.

    *          FALSE if this and aIter are not iterating over

    *          the same deque.

    */

   bool operator<(nsDequeIterator& aIter);

   /**

    * Compare two iterators for equivalence.

    *

    * @param   aIter is the other iterator to be compared to

    * @return  TRUE if EQUAL

    */

   bool operator==(nsDequeIterator& aIter);

   /**

    * Compare two iterators for non strict decreasing order.

    *

    * @param   aIter is the other iterator to be compared to

    * @return  TRUE if this object points to the same element, or

    *          an element after the element pointed to by aIter.

    *          FALSE if this and aIter are not iterating over

    *          the same deque.

    */

   bool operator>=(nsDequeIterator& aIter);

   /**

    * Pre-increment operator

    * Iterator will advance one index towards the end.

    *

    * @return  object_at(++index)

    */

   void* operator++();

   /**

    * Post-increment operator

    * Iterator will advance one index towards the end.

    *

    * @param   param is ignored

    * @return  object_at(mIndex++)

    */

   void* operator++(int);

   /**

    * Pre-decrement operator

    * Iterator will advance one index towards the beginning.

    *

    * @return  object_at(--index)

    */

   void* operator--();

   /**

    * Post-decrement operator

    * Iterator will advance one index towards the beginning.

    *

    * @param   param is ignored

    * @return  object_at(index--)

    */

   void* operator--(int);

   /**

    * Retrieve the the iterator's notion of current node.

    *

    * Note that the iterator floats, so you don't need to do:

    * <code>++iter; aDeque.PopFront();</code>

    * Unless you actually want your iterator to jump 2 positions

    * relative to its origin.

    *

    * Picture: [1 2i 3 4]

    * PopFront()

    * Picture: [2 3i 4]

    * Note that I still happily points to object at the second index.

    *

    * @return  object at i'th index

    */

   void* GetCurrent();

   /**

    * Call this method when you want to iterate all the

    * members of the container, passing a functor along

    * to call your code.

    *

    * @param   aFunctor object to call for each member

    * @return  *this

    */

   void ForEach(nsDequeFunctor& aFunctor) const;

   /**

    * Call this method when you want to iterate all the

    * members of the container, calling the functor you 

    * passed with each member. This process will interrupt

    * if your function returns non 0 to this method.

    *

    * @param   aFunctor object to call for each member

    * @return  first nonzero result of aFunctor or 0.

    */

   const void* FirstThat(nsDequeFunctor& aFunctor) const;

   protected:

   int32_t         mIndex;

   const nsDeque&  mDeque;

 };

 #endif