Source code

Revision control

Other Tools

/* -*- 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 */
#ifndef nsCOMArray_h__
#define nsCOMArray_h__
#include "mozilla/Attributes.h"
#include "mozilla/ArrayIterator.h"
#include "mozilla/MemoryReporting.h"
#include "nsCycleCollectionNoteChild.h"
#include "nsTArray.h"
#include "nsISupports.h"
#include <iterator>
// See below for the definition of nsCOMArray<T>
// a class that's nsISupports-specific, so that we can contain the
// work of this class in the XPCOM dll
class nsCOMArray_base {
friend class nsArrayBase;
nsCOMArray_base() = default;
explicit nsCOMArray_base(int32_t aCount) : mArray(aCount) {}
nsCOMArray_base(const nsCOMArray_base& aOther);
nsCOMArray_base(nsCOMArray_base&& aOther) = default;
nsCOMArray_base& operator=(nsCOMArray_base&& aOther) = default;
int32_t IndexOf(nsISupports* aObject, uint32_t aStartIndex = 0) const;
bool Contains(nsISupports* aObject) const { return IndexOf(aObject) != -1; }
int32_t IndexOfObject(nsISupports* aObject) const;
bool ContainsObject(nsISupports* aObject) const {
return IndexOfObject(aObject) != -1;
typedef bool (*nsBaseArrayEnumFunc)(void* aElement, void* aData);
// enumerate through the array with a callback.
bool EnumerateForwards(nsBaseArrayEnumFunc aFunc, void* aData) const;
bool EnumerateBackwards(nsBaseArrayEnumFunc aFunc, void* aData) const;
typedef int (*nsISupportsComparatorFunc)(nsISupports* aElement1,
nsISupports* aElement2, void* aData);
struct nsISupportsComparatorContext {
nsISupportsComparatorFunc mComparatorFunc;
void* mData;
static int VoidStarComparator(const void* aElement1, const void* aElement2,
void* aData);
void Sort(nsISupportsComparatorFunc aFunc, void* aData);
bool InsertObjectAt(nsISupports* aObject, int32_t aIndex);
void InsertElementAt(uint32_t aIndex, nsISupports* aElement);
void InsertElementAt(uint32_t aIndex, already_AddRefed<nsISupports> aElement);
bool InsertObjectsAt(const nsCOMArray_base& aObjects, int32_t aIndex);
void InsertElementsAt(uint32_t aIndex, const nsCOMArray_base& aElements);
void InsertElementsAt(uint32_t aIndex, nsISupports* const* aElements,
uint32_t aCount);
void ReplaceObjectAt(nsISupports* aObject, int32_t aIndex);
void ReplaceElementAt(uint32_t aIndex, nsISupports* aElement) {
nsISupports* oldElement = mArray[aIndex];
NS_IF_ADDREF(mArray[aIndex] = aElement);
bool AppendObject(nsISupports* aObject) {
return InsertObjectAt(aObject, Count());
void AppendElement(nsISupports* aElement) {
InsertElementAt(Length(), aElement);
void AppendElement(already_AddRefed<nsISupports> aElement) {
InsertElementAt(Length(), std::move(aElement));
bool AppendObjects(const nsCOMArray_base& aObjects) {
return InsertObjectsAt(aObjects, Count());
void AppendElements(const nsCOMArray_base& aElements) {
return InsertElementsAt(Length(), aElements);
void AppendElements(nsISupports* const* aElements, uint32_t aCount) {
return InsertElementsAt(Length(), aElements, aCount);
bool RemoveObject(nsISupports* aObject);
nsISupports** Elements() { return mArray.Elements(); }
void SwapElements(nsCOMArray_base& aOther) {
// elements in the array (including null elements!)
int32_t Count() const { return mArray.Length(); }
// nsTArray-compatible version
uint32_t Length() const { return mArray.Length(); }
bool IsEmpty() const { return mArray.IsEmpty(); }
// If the array grows, the newly created entries will all be null;
// if the array shrinks, the excess entries will all be released.
bool SetCount(int32_t aNewCount);
// nsTArray-compatible version
void TruncateLength(uint32_t aNewLength) {
if (mArray.Length() > aNewLength) {
RemoveElementsAt(aNewLength, mArray.Length() - aNewLength);
// remove all elements in the array, and call NS_RELEASE on each one
void Clear();
nsISupports* ObjectAt(int32_t aIndex) const { return mArray[aIndex]; }
// nsTArray-compatible version
nsISupports* ElementAt(uint32_t aIndex) const { return mArray[aIndex]; }
nsISupports* SafeObjectAt(int32_t aIndex) const {
return mArray.SafeElementAt(aIndex, nullptr);
// nsTArray-compatible version
nsISupports* SafeElementAt(uint32_t aIndex) const {
return mArray.SafeElementAt(aIndex, nullptr);
nsISupports* operator[](int32_t aIndex) const { return mArray[aIndex]; }
// remove an element at a specific position, shrinking the array
// as necessary
bool RemoveObjectAt(int32_t aIndex);
// nsTArray-compatible version
void RemoveElementAt(uint32_t aIndex);
// remove a range of elements at a specific position, shrinking the array
// as necessary
bool RemoveObjectsAt(int32_t aIndex, int32_t aCount);
// nsTArray-compatible version
void RemoveElementsAt(uint32_t aIndex, uint32_t aCount);
void SwapElementsAt(uint32_t aIndex1, uint32_t aIndex2) {
nsISupports* tmp = mArray[aIndex1];
mArray[aIndex1] = mArray[aIndex2];
mArray[aIndex2] = tmp;
// Ensures there is enough space to store a total of aCapacity objects.
// This method never deletes any objects.
void SetCapacity(uint32_t aCapacity) { mArray.SetCapacity(aCapacity); }
uint32_t Capacity() { return mArray.Capacity(); }
// Measures the size of the array's element storage. If you want to measure
// anything hanging off the array, you must iterate over the elements and
// measure them individually; hence the "Shallow" prefix. Note that because
// each element in an nsCOMArray<T> is actually a T* any such iteration
// should use a SizeOfIncludingThis() function on each element rather than a
// SizeOfExcludingThis() function, so that the memory taken by the T itself
// is included as well as anything it points to.
size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const {
return mArray.ShallowSizeOfExcludingThis(aMallocSizeOf);
// the actual storage
nsTArray<nsISupports*> mArray;
// don't implement these, defaults will muck with refcounts!
nsCOMArray_base& operator=(const nsCOMArray_base& aOther) = delete;
inline void ImplCycleCollectionUnlink(nsCOMArray_base& aField) {
inline void ImplCycleCollectionTraverse(
nsCycleCollectionTraversalCallback& aCallback, nsCOMArray_base& aField,
const char* aName, uint32_t aFlags = 0) {
aFlags |= CycleCollectionEdgeNameArrayFlag;
int32_t length = aField.Count();
for (int32_t i = 0; i < length; ++i) {
CycleCollectionNoteChild(aCallback, aField[i], aName, aFlags);
// a non-XPCOM, refcounting array of XPCOM objects
// used as a member variable or stack variable - this object is NOT
// refcounted, but the objects that it holds are
// most of the read-only accessors like ObjectAt()/etc do NOT refcount
// on the way out. This means that you can do one of two things:
// * does an addref, but holds onto a reference
// nsCOMPtr<T> foo = array[i];
// * avoids the refcount, but foo might go stale if array[i] is ever
// * modified/removed. Be careful not to NS_RELEASE(foo)!
// T* foo = array[i];
// This array will accept null as an argument for any object, and will store
// null in the array. But that also means that methods like ObjectAt() may
// return null when referring to an existing, but null entry in the array.
template <class T>
class nsCOMArray : public nsCOMArray_base {
typedef int32_t index_type;
typedef mozilla::ArrayIterator<T*, nsCOMArray> iterator;
typedef mozilla::ArrayIterator<const T*, nsCOMArray> const_iterator;
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
nsCOMArray() = default;
explicit nsCOMArray(int32_t aCount) : nsCOMArray_base(aCount) {}
explicit nsCOMArray(const nsCOMArray<T>& aOther) : nsCOMArray_base(aOther) {}
nsCOMArray(nsCOMArray<T>&& aOther) = default;
~nsCOMArray() = default;
// We have a move assignment operator, but no copy assignment operator.
nsCOMArray<T>& operator=(nsCOMArray<T>&& aOther) = default;
// these do NOT refcount on the way out, for speed
T* ObjectAt(int32_t aIndex) const {
return static_cast<T*>(nsCOMArray_base::ObjectAt(aIndex));
// nsTArray-compatible version
T* ElementAt(uint32_t aIndex) const {
return static_cast<T*>(nsCOMArray_base::ElementAt(aIndex));
// these do NOT refcount on the way out, for speed
T* SafeObjectAt(int32_t aIndex) const {
return static_cast<T*>(nsCOMArray_base::SafeObjectAt(aIndex));
// nsTArray-compatible version
T* SafeElementAt(uint32_t aIndex) const {
return static_cast<T*>(nsCOMArray_base::SafeElementAt(aIndex));
// indexing operator for syntactic sugar
T* operator[](int32_t aIndex) const { return ObjectAt(aIndex); }
// index of the element in question.. does NOT refcount
// note: this does not check COM object identity. Use
// IndexOfObject() for that purpose
int32_t IndexOf(T* aObject, uint32_t aStartIndex = 0) const {
return nsCOMArray_base::IndexOf(aObject, aStartIndex);
bool Contains(T* aObject) const { return nsCOMArray_base::Contains(aObject); }
// index of the element in question.. be careful!
// this is much slower than IndexOf() because it uses
// QueryInterface to determine actual COM identity of the object
// if you need to do this frequently then consider enforcing
// COM object identity before adding/comparing elements
int32_t IndexOfObject(T* aObject) const {
return nsCOMArray_base::IndexOfObject(aObject);
bool ContainsObject(nsISupports* aObject) const {
return nsCOMArray_base::ContainsObject(aObject);
// inserts aObject at aIndex, shifting the objects at aIndex and
// later to make space
bool InsertObjectAt(T* aObject, int32_t aIndex) {
return nsCOMArray_base::InsertObjectAt(aObject, aIndex);
// nsTArray-compatible version
void InsertElementAt(uint32_t aIndex, T* aElement) {
nsCOMArray_base::InsertElementAt(aIndex, aElement);
// inserts the objects from aObject at aIndex, shifting the
// objects at aIndex and later to make space
bool InsertObjectsAt(const nsCOMArray<T>& aObjects, int32_t aIndex) {
return nsCOMArray_base::InsertObjectsAt(aObjects, aIndex);
// nsTArray-compatible version
void InsertElementsAt(uint32_t aIndex, const nsCOMArray<T>& aElements) {
nsCOMArray_base::InsertElementsAt(aIndex, aElements);
void InsertElementsAt(uint32_t aIndex, T* const* aElements, uint32_t aCount) {
aIndex, reinterpret_cast<nsISupports* const*>(aElements), aCount);
// replaces an existing element. Warning: if the array grows,
// the newly created entries will all be null
void ReplaceObjectAt(T* aObject, int32_t aIndex) {
nsCOMArray_base::ReplaceObjectAt(aObject, aIndex);
// nsTArray-compatible version
void ReplaceElementAt(uint32_t aIndex, T* aElement) {
nsCOMArray_base::ReplaceElementAt(aIndex, aElement);
typedef int (*TComparatorFunc)(T* aElement1, T* aElement2, void* aData);
struct TComparatorContext {
TComparatorFunc mComparatorFunc;
void* mData;
static int nsISupportsComparator(nsISupports* aElement1,
nsISupports* aElement2, void* aData) {
auto ctx = static_cast<TComparatorContext*>(aData);
return (*ctx->mComparatorFunc)(static_cast<T*>(aElement1),
static_cast<T*>(aElement2), ctx->mData);
void Sort(TComparatorFunc aFunc, void* aData) {
TComparatorContext ctx = {aFunc, aData};
nsCOMArray_base::Sort(nsISupportsComparator, &ctx);
// append an object, growing the array as necessary
bool AppendObject(T* aObject) {
return nsCOMArray_base::AppendObject(aObject);
// nsTArray-compatible version
void AppendElement(T* aElement) { nsCOMArray_base::AppendElement(aElement); }
void AppendElement(already_AddRefed<T> aElement) {
// append objects, growing the array as necessary
bool AppendObjects(const nsCOMArray<T>& aObjects) {
return nsCOMArray_base::AppendObjects(aObjects);
// nsTArray-compatible version
void AppendElements(const nsCOMArray<T>& aElements) {
return nsCOMArray_base::AppendElements(aElements);
void AppendElements(T* const* aElements, uint32_t aCount) {
InsertElementsAt(Length(), aElements, aCount);
// remove the first instance of the given object and shrink the
// array as necessary
// Warning: if you pass null here, it will remove the first null element
bool RemoveObject(T* aObject) {
return nsCOMArray_base::RemoveObject(aObject);
// nsTArray-compatible version
bool RemoveElement(T* aElement) {
return nsCOMArray_base::RemoveObject(aElement);
T** Elements() { return reinterpret_cast<T**>(nsCOMArray_base::Elements()); }
void SwapElements(nsCOMArray<T>& aOther) {
// Methods for range-based for loops.
iterator begin() { return iterator(*this, 0); }
const_iterator begin() const { return const_iterator(*this, 0); }
const_iterator cbegin() const { return begin(); }
iterator end() { return iterator(*this, Length()); }
const_iterator end() const { return const_iterator(*this, Length()); }
const_iterator cend() const { return end(); }
// Methods for reverse iterating.
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(end());
const_reverse_iterator crbegin() const { return rbegin(); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const {
return const_reverse_iterator(begin());
const_reverse_iterator crend() const { return rend(); }
// don't implement these!
nsCOMArray<T>& operator=(const nsCOMArray<T>& aOther) = delete;
template <typename T>
inline void ImplCycleCollectionUnlink(nsCOMArray<T>& aField) {
template <typename E>
inline void ImplCycleCollectionTraverse(
nsCycleCollectionTraversalCallback& aCallback, nsCOMArray<E>& aField,
const char* aName, uint32_t aFlags = 0) {
aFlags |= CycleCollectionEdgeNameArrayFlag;
int32_t length = aField.Count();
for (int32_t i = 0; i < length; ++i) {
CycleCollectionNoteChild(aCallback, aField[i], aName, aFlags);