/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 items of type void*, offering the following features:
* - Its interface supports pushing, popping, and peeking of items at the back
* or front, and retrieval from any position.
* - It can iterate over items via a ForEach method, range-for, or an iterator
* class.
* - 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
* item 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(), and as custom deallocators.
*/
class nsDequeFunctor {
public:
virtual void operator()(void* aObject) = 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 nsDeque {
typedef mozilla::fallible_t fallible_t;
public:
/**
* Constructs an empty deque.
*
* @param aDeallocator Optional deallocator functor that will be called from
* Erase() and the destructor on any remaining item.
* The deallocator is owned by the deque and will be
* deleted at destruction time.
*/
explicit nsDeque(nsDequeFunctor* aDeallocator = nullptr);
/**
* Deque destructor. Erases all items, deletes the deallocator.
*/
~nsDeque();
/**
* Returns the number of items currently stored in
* this deque.
*
* @return number of items currently in the deque
*/
inline size_t GetSize() const { return mSize; }
/**
* Appends new member at the end of the deque.
*
* @param aItem item to store in deque
*/
void Push(void* aItem) {
if (!Push(aItem, mozilla::fallible)) {
NS_ABORT_OOM(mSize * sizeof(void*));
}
}
/**
* Appends new member at the end of the deque.
*
* @param aItem item to store in deque
* @return true if succeeded, false if failed to resize deque as needed
*/
MOZ_MUST_USE bool Push(void* aItem, const fallible_t&);
/**
* Inserts new member at the front of the deque.
*
* @param aItem item to store in deque
*/
void PushFront(void* aItem) {
if (!PushFront(aItem, mozilla::fallible)) {
NS_ABORT_OOM(mSize * sizeof(void*));
}
}
/**
* Inserts new member at the front of the deque.
*
* @param aItem item to store in deque
* @return true if succeeded, false if failed to resize deque as needed
*/
MOZ_MUST_USE bool PushFront(void* aItem, const fallible_t&);
/**
* 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 last item without removing it.
*
* @return the last item in container
*/
void* Peek() const;
/**
* Retrieve the first item without removing it.
*
* @return the first item in container
*/
void* PeekFront() const;
/**
* Retrieve a member from the deque without removing it.
*
* @param index of desired item
* @return item in list, or nullptr if index is outside the deque
*/
void* ObjectAt(size_t aIndex) const;
/**
* Remove and delete all items from container.
* Deletes are handled by the deallocator nsDequeFunctor
* which is specified at deque construction.
*/
void Erase();
/**
* Call this method when you want to iterate through all
* items in the container, passing a functor along
* to call your code.
* If the deque is modified during ForEach, iteration will continue based on
* item indices; meaning that front operations may effectively skip over
* items or visit some items multiple times.
*
* @param aFunctor object to call for each member
*/
void ForEach(nsDequeFunctor& aFunctor) const;
// This iterator assumes that the deque itself is const, i.e., it cannot be
// modified while the iterator is used.
// Also it is a 'const' iterator in that it provides copies of the deque's
// elements, and therefore it is not possible to modify the deque's contents
// by assigning to a dereference of this iterator.
class ConstDequeIterator {
public:
ConstDequeIterator(const nsDeque& aDeque, size_t aIndex)
: mDeque(aDeque), mIndex(aIndex) {}
ConstDequeIterator& operator++() {
++mIndex;
return *this;
}
bool operator==(const ConstDequeIterator& aOther) const {
return mIndex == aOther.mIndex;
}
bool operator!=(const ConstDequeIterator& aOther) const {
return mIndex != aOther.mIndex;
}
void* operator*() const {
// Don't allow out-of-deque dereferences.
MOZ_RELEASE_ASSERT(mIndex < mDeque.GetSize());
return mDeque.ObjectAt(mIndex);
}
private:
const nsDeque& mDeque;
size_t mIndex;
};
// If this deque is const, we can provide ConstDequeIterator's.
ConstDequeIterator begin() const { return ConstDequeIterator(*this, 0); }
ConstDequeIterator end() const { return ConstDequeIterator(*this, mSize); }
// It is a 'const' iterator in that it provides copies of the deque's
// elements, and therefore it is not possible to modify the deque's contents
// by assigning to a dereference of this iterator.
// If the deque is modified in other ways, this iterator will stay at the same
// index, and will handle past-the-end comparisons, but not dereferencing.
class ConstIterator {
public:
// Special index for the end iterator, to track the possibly-shifting
// deque size.
static const size_t EndIteratorIndex = size_t(-1);
ConstIterator(const nsDeque& aDeque, size_t aIndex)
: mDeque(aDeque), mIndex(aIndex) {}
ConstIterator& operator++() {
// End-iterator shouldn't be modified.
MOZ_ASSERT(mIndex != EndIteratorIndex);
++mIndex;
return *this;
}
bool operator==(const ConstIterator& aOther) const {
return EffectiveIndex() == aOther.EffectiveIndex();
}
bool operator!=(const ConstIterator& aOther) const {
return EffectiveIndex() != aOther.EffectiveIndex();
}
void* operator*() const {
// Don't allow out-of-deque dereferences.
MOZ_RELEASE_ASSERT(mIndex < mDeque.GetSize());
return mDeque.ObjectAt(mIndex);
}
private:
// 0 <= index < deque.GetSize() inside the deque, deque.GetSize() otherwise.
// Only used when comparing indices, not to actually access items.
size_t EffectiveIndex() const {
return (mIndex < mDeque.GetSize()) ? mIndex : mDeque.GetSize();
}
const nsDeque& mDeque;
size_t mIndex; // May point outside the deque!
};
// If this deque is *not* const, we provide ConstIterator's that can handle
// deque size changes.
ConstIterator begin() { return ConstIterator(*this, 0); }
ConstIterator end() {
return ConstIterator(*this, ConstIterator::EndIteratorIndex);
}
size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
protected:
size_t mSize;
size_t mCapacity;
size_t mOrigin;
nsDequeFunctor* mDeallocator;
void* mBuffer[8];
void** mData;
private:
/**
* Copy constructor (deleted)
*
* @param aOther another deque
*/
nsDeque(const nsDeque& aOther) = delete;
/**
* Deque assignment operator (deleted)
*
* @param aOther another deque
* @return *this
*/
nsDeque& operator=(const nsDeque& aOther) = delete;
bool GrowCapacity();
void SetDeallocator(nsDequeFunctor* aDeallocator);
/**
* Remove all items from container without destroying them.
*/
void Empty();
};
#endif