/* -*- 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 T*, 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 <cstddef>
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Assertions.h"
#include "mozilla/fallible.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/RefPtr.h"
#include "nsCOMPtr.h"
#include "nsDebug.h"
#include "nsISupports.h"
namespace mozilla {
namespace detail {
/**
* 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.
*
* nsDequeBase implements the untyped deque data structure while
* nsDeque provides the typed implementation and iterators.
*/
class nsDequeBase {
public:
/**
* 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; }
protected:
size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
const;
/**
* 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 nsDequeBase();
/**
* Deque destructor. Erases all items, deletes the deallocator.
*/
~nsDequeBase();
/**
* 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
*/
[[nodiscard]]
bool Push(
void* aItem,
const fallible_t&);
/**
* 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
*/
[[nodiscard]]
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;
bool GrowCapacity();
/**
* Remove all items from container without destroying them.
*/
void Empty();
size_t mSize;
size_t mCapacity;
size_t mOrigin;
void* mBuffer[8];
void** mData;
nsDequeBase&
operator=(
const nsDequeBase& aOther) =
delete;
nsDequeBase(
const nsDequeBase& aOther) =
delete;
};
// 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.
template <
typename Deque>
class ConstDequeIterator {
public:
ConstDequeIterator(
const Deque& 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;
}
typename Deque::PointerType
operator*()
const {
// Don't allow out-of-deque dereferences.
MOZ_RELEASE_ASSERT(mIndex < mDeque.GetSize());
return mDeque.ObjectAt(mIndex);
}
private:
const Deque& mDeque;
size_t mIndex;
};
// 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.
template <
typename Deque>
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 Deque& 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();
}
typename Deque::PointerType
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 Deque& mDeque;
size_t mIndex;
// May point outside the deque!
};
}
// namespace detail
}
// namespace mozilla
/**
* 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.
*/
template <
typename T>
class nsDequeFunctor {
public:
virtual void operator()(T* aObject) = 0;
virtual ~nsDequeFunctor() =
default;
};
/******************************************************
* 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.
*/
template <
typename T>
class nsDeque :
public mozilla::detail::nsDequeBase {
typedef mozilla::fallible_t fallible_t;
public:
using PointerType = T*;
using ConstDequeIterator = mozilla::detail::ConstDequeIterator<nsDeque<T>>;
using ConstIterator = mozilla::detail::ConstIterator<nsDeque<T>>;
/**
* 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<T>* aDeallocator = nullptr) {
MOZ_COUNT_CTOR(nsDeque);
mDeallocator = aDeallocator;
}
/**
* Deque destructor. Erases all items, deletes the deallocator.
*/
~nsDeque() {
MOZ_COUNT_DTOR(nsDeque);
Erase();
SetDeallocator(nullptr);
}
/**
* Appends new member at the end of the deque.
*
* @param aItem item to store in deque
*/
inline void Push(T* aItem) {
if (!nsDequeBase::Push(aItem, mozilla::fallible)) {
NS_ABORT_OOM(mSize *
sizeof(T*));
}
}
/**
* 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
*/
[[nodiscard]]
inline bool Push(T* aItem,
const fallible_t& aFaillible) {
return nsDequeBase::Push(aItem, aFaillible);
}
/**
* Inserts new member at the front of the deque.
*
* @param aItem item to store in deque
*/
inline void PushFront(T* aItem) {
if (!nsDequeBase::PushFront(aItem, mozilla::fallible)) {
NS_ABORT_OOM(mSize *
sizeof(T*));
}
}
/**
* 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
*/
[[nodiscard]]
bool PushFront(T* aItem,
const fallible_t& aFallible) {
return nsDequeBase::PushFront(aItem, aFallible);
}
/**
* Remove and return the last item in the container.
*
* @return the item that was the last item in container
*/
inline T* Pop() {
return static_cast<T*>(nsDequeBase::Pop()); }
/**
* Remove and return the first item in the container.
*
* @return the item that was first item in container
*/
inline T* PopFront() {
return static_cast<T*>(nsDequeBase::PopFront()); }
/**
* Retrieve the last item without removing it.
*
* @return the last item in container
*/
inline T* Peek()
const {
return static_cast<T*>(nsDequeBase::Peek()); }
/**
* Retrieve the first item without removing it.
*
* @return the first item in container
*/
inline T* PeekFront()
const {
return static_cast<T*>(nsDequeBase::PeekFront());
}
/**
* 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
*/
inline T* ObjectAt(size_t aIndex)
const {
if (NS_WARN_IF(aIndex >= GetSize())) {
return nullptr;
}
return static_cast<T*>(nsDequeBase::ObjectAt(aIndex));
}
/**
* Remove and delete all items from container.
* Deletes are handled by the deallocator nsDequeFunctor
* which is specified at deque construction.
*/
void Erase() {
if (mDeallocator && mSize) {
ForEach(*mDeallocator);
}
Empty();
}
/**
* 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<T>& aFunctor)
const {
for (size_t i = 0; i < mSize; ++i) {
aFunctor(ObjectAt(i));
}
}
// If this deque is const, we can provide ConstDequeIterator's.
ConstDequeIterator begin()
const {
return ConstDequeIterator(*
this, 0); }
ConstDequeIterator end()
const {
return ConstDequeIterator(*
this, mSize); }
// 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 size = nsDequeBase::SizeOfExcludingThis(aMallocSizeOf);
if (mDeallocator) {
size += aMallocSizeOf(mDeallocator);
}
return size;
}
size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)
const {
return aMallocSizeOf(
this) + SizeOfExcludingThis(aMallocSizeOf);
}
protected:
nsDequeFunctor<T>* mDeallocator;
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;
void SetDeallocator(nsDequeFunctor<T>* aDeallocator) {
delete mDeallocator;
mDeallocator = aDeallocator;
}
};
/**
* Specialization of nsDeque for reference counted pointers.
*
* Provides builtin reference handling as part of Push/Peek/Pop
*/
template <
typename T>
class nsRefPtrDeque :
private nsDeque<T> {
typedef mozilla::fallible_t fallible_t;
class RefPtrDeallocator :
public nsDequeFunctor<T> {
public:
virtual void operator()(T* aObject) override {
RefPtr<T> releaseMe = dont_AddRef(aObject);
}
};
public:
using PointerType = RefPtr<T>;
using ConstDequeIterator =
mozilla::detail::ConstDequeIterator<nsRefPtrDeque<T>>;
using ConstIterator = mozilla::detail::ConstIterator<nsRefPtrDeque<T>>;
explicit nsRefPtrDeque() : nsDeque<T>(
new RefPtrDeallocator()) {}
inline void PushFront(already_AddRefed<T> aItem) {
T* item = aItem.take();
nsDeque<T>::PushFront(item);
}
inline void PushFront(T* aItem) { PushFront(do_AddRef(aItem)); }
inline void Push(T* aItem) { Push(do_AddRef(aItem)); }
inline void Push(already_AddRefed<T> aItem) {
T* item = aItem.take();
nsDeque<T>::Push(item);
}
inline already_AddRefed<T> PopFront() {
return dont_AddRef(nsDeque<T>::PopFront());
}
inline already_AddRefed<T> Pop() {
return dont_AddRef(nsDeque<T>::Pop()); }
inline T* PeekFront()
const {
return nsDeque<T>::PeekFront(); }
inline T* Peek()
const {
return nsDeque<T>::Peek(); }
inline T* ObjectAt(size_t aIndex)
const {
return nsDeque<T>::ObjectAt(aIndex);
}
inline void Erase() { nsDeque<T>::Erase(); }
// If this deque is const, we can provide ConstDequeIterator's.
ConstDequeIterator begin()
const {
return ConstDequeIterator(*
this, 0); }
ConstDequeIterator end()
const {
return ConstDequeIterator(*
this, GetSize());
}
// 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);
}
inline size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
const {
return nsDeque<T>::SizeOfExcludingThis(aMallocSizeOf);
}
inline size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)
const {
return nsDeque<T>::SizeOfIncludingThis(aMallocSizeOf);
}
inline size_t GetSize()
const {
return nsDeque<T>::GetSize(); }
/**
* 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<T>& aFunctor)
const {
size_t size = GetSize();
for (size_t i = 0; i < size; ++i) {
aFunctor(ObjectAt(i));
}
}
};
#endif
