mirror of
https://github.com/mozilla/gecko-dev.git
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419 lines
14 KiB
C++
419 lines
14 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsTObserverArray_h___
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#define nsTObserverArray_h___
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#include "mozilla/MemoryReporting.h"
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#include "nsTArray.h"
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#include "nsCycleCollectionNoteChild.h"
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/**
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* An array of observers. Like a normal array, but supports iterators that are
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* stable even if the array is modified during iteration.
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* The template parameter T is the observer type the array will hold;
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* N is the number of built-in storage slots that come with the array.
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* NOTE: You probably want to use nsTObserverArray, unless you specifically
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* want built-in storage. See below.
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* @see nsTObserverArray, nsTArray
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*/
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class NS_COM_GLUE nsTObserverArray_base {
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public:
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typedef uint32_t index_type;
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typedef uint32_t size_type;
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typedef int32_t diff_type;
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protected:
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class Iterator_base {
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protected:
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friend class nsTObserverArray_base;
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Iterator_base(index_type aPosition, Iterator_base* aNext)
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: mPosition(aPosition),
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mNext(aNext) {
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}
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// The current position of the iterator. Its exact meaning differs
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// depending on iterator. See nsTObserverArray<T>::ForwardIterator.
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index_type mPosition;
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// The next iterator currently iterating the same array
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Iterator_base* mNext;
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};
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nsTObserverArray_base()
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: mIterators(nullptr) {
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}
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~nsTObserverArray_base() {
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NS_ASSERTION(mIterators == nullptr, "iterators outlasting array");
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}
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/**
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* Adjusts iterators after an element has been inserted or removed
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* from the array.
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* @param modPos Position where elements were added or removed.
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* @param adjustment -1 if an element was removed, 1 if an element was
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* added.
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*/
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void AdjustIterators(index_type aModPos, diff_type aAdjustment);
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/**
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* Clears iterators when the array is destroyed.
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*/
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void ClearIterators();
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mutable Iterator_base* mIterators;
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};
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template<class T, uint32_t N>
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class nsAutoTObserverArray : protected nsTObserverArray_base {
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public:
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typedef T elem_type;
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typedef nsTArray<T> array_type;
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nsAutoTObserverArray() {
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}
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//
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// Accessor methods
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//
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// @return The number of elements in the array.
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size_type Length() const {
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return mArray.Length();
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}
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// @return True if the array is empty or false otherwise.
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bool IsEmpty() const {
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return mArray.IsEmpty();
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}
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// This method provides direct access to the i'th element of the array.
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// The given index must be within the array bounds. If the underlying array
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// may change during iteration, use an iterator instead of this function.
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// @param i The index of an element in the array.
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// @return A reference to the i'th element of the array.
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elem_type& ElementAt(index_type i) {
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return mArray.ElementAt(i);
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}
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// Same as above, but readonly.
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const elem_type& ElementAt(index_type i) const {
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return mArray.ElementAt(i);
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}
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// This method provides direct access to the i'th element of the array in
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// a bounds safe manner. If the requested index is out of bounds the
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// provided default value is returned.
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// @param i The index of an element in the array.
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// @param def The value to return if the index is out of bounds.
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elem_type& SafeElementAt(index_type i, elem_type& def) {
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return mArray.SafeElementAt(i, def);
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}
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// Same as above, but readonly.
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const elem_type& SafeElementAt(index_type i, const elem_type& def) const {
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return mArray.SafeElementAt(i, def);
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}
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// No operator[] is provided because the point of this class is to support
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// allow modifying the array during iteration, and ElementAt() is not safe
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// in those conditions.
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//
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// Search methods
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//
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// This method searches, starting from the beginning of the array,
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// for the first element in this array that is equal to the given element.
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// 'operator==' must be defined for elem_type.
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// @param item The item to search for.
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// @return true if the element was found.
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template<class Item>
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bool Contains(const Item& item) const {
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return IndexOf(item) != array_type::NoIndex;
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}
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// This method searches for the offset of the first element in this
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// array that is equal to the given element.
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// 'operator==' must be defined for elem_type.
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// @param item The item to search for.
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// @param start The index to start from.
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// @return The index of the found element or NoIndex if not found.
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template<class Item>
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index_type IndexOf(const Item& item, index_type start = 0) const {
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return mArray.IndexOf(item, start);
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}
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//
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// Mutation methods
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//
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// Insert a given element at the given index.
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// @param index The index at which to insert item.
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// @param item The item to insert,
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// @return A pointer to the newly inserted element, or a null on DOM
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template<class Item>
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elem_type *InsertElementAt(index_type aIndex, const Item& aItem) {
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elem_type* item = mArray.InsertElementAt(aIndex, aItem);
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AdjustIterators(aIndex, 1);
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return item;
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}
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// Same as above but without copy constructing.
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// This is useful to avoid temporaries.
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elem_type* InsertElementAt(index_type aIndex) {
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elem_type* item = mArray.InsertElementAt(aIndex);
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AdjustIterators(aIndex, 1);
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return item;
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}
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// Prepend an element to the array unless it already exists in the array.
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// 'operator==' must be defined for elem_type.
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// @param item The item to prepend.
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// @return true if the element was found, or inserted successfully.
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template<class Item>
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bool PrependElementUnlessExists(const Item& item) {
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if (Contains(item)) {
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return true;
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}
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bool inserted = mArray.InsertElementAt(0, item) != nullptr;
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AdjustIterators(0, 1);
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return inserted;
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}
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// Append an element to the array.
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// @param item The item to append.
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// @return A pointer to the newly appended element, or null on OOM.
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template<class Item>
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elem_type* AppendElement(const Item& item) {
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return mArray.AppendElement(item);
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}
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// Same as above, but without copy-constructing. This is useful to avoid
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// temporaries.
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elem_type* AppendElement() {
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return mArray.AppendElement();
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}
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// Append an element to the array unless it already exists in the array.
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// 'operator==' must be defined for elem_type.
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// @param item The item to append.
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// @return true if the element was found, or inserted successfully.
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template<class Item>
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bool AppendElementUnlessExists(const Item& item) {
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return Contains(item) || AppendElement(item) != nullptr;
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}
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// Remove an element from the array.
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// @param index The index of the item to remove.
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void RemoveElementAt(index_type index) {
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NS_ASSERTION(index < mArray.Length(), "invalid index");
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mArray.RemoveElementAt(index);
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AdjustIterators(index, -1);
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}
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// This helper function combines IndexOf with RemoveElementAt to "search
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// and destroy" the first element that is equal to the given element.
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// 'operator==' must be defined for elem_type.
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// @param item The item to search for.
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// @return true if the element was found and removed.
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template<class Item>
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bool RemoveElement(const Item& item) {
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index_type index = mArray.IndexOf(item, 0);
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if (index == array_type::NoIndex)
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return false;
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mArray.RemoveElementAt(index);
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AdjustIterators(index, -1);
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return true;
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}
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// Removes all observers and collapses all iterators to the beginning of
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// the array. The result is that forward iterators will see all elements
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// in the array.
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void Clear() {
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mArray.Clear();
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ClearIterators();
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}
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// Returns the number of bytes on the heap taken up by this object, not
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// including sizeof(*this).
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size_t SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
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return mArray.SizeOfExcludingThis(mallocSizeOf);
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}
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//
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// Iterators
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//
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// Base class for iterators. Do not use this directly.
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class Iterator : public Iterator_base {
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protected:
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friend class nsAutoTObserverArray;
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typedef nsAutoTObserverArray<T, N> array_type;
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Iterator(index_type aPosition, const array_type& aArray)
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: Iterator_base(aPosition, aArray.mIterators),
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mArray(const_cast<array_type&>(aArray)) {
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aArray.mIterators = this;
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}
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~Iterator() {
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NS_ASSERTION(mArray.mIterators == this,
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"Iterators must currently be destroyed in opposite order "
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"from the construction order. It is suggested that you "
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"simply put them on the stack");
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mArray.mIterators = mNext;
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}
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// The array we're iterating
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array_type& mArray;
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};
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// Iterates the array forward from beginning to end. mPosition points
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// to the element that will be returned on next call to GetNext.
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// Elements:
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// - prepended to the array during iteration *will not* be traversed
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// - appended during iteration *will* be traversed
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// - removed during iteration *will not* be traversed.
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// @see EndLimitedIterator
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class ForwardIterator : protected Iterator {
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public:
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typedef nsAutoTObserverArray<T, N> array_type;
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typedef Iterator base_type;
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ForwardIterator(const array_type& aArray)
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: Iterator(0, aArray) {
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}
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ForwardIterator(const array_type& aArray, index_type aPos)
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: Iterator(aPos, aArray) {
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}
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bool operator <(const ForwardIterator& aOther) const {
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NS_ASSERTION(&this->mArray == &aOther.mArray,
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"not iterating the same array");
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return base_type::mPosition < aOther.mPosition;
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}
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// Returns true if there are more elements to iterate.
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// This must precede a call to GetNext(). If false is
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// returned, GetNext() must not be called.
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bool HasMore() const {
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return base_type::mPosition < base_type::mArray.Length();
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}
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// Returns the next element and steps one step. This must
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// be preceded by a call to HasMore().
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// @return The next observer.
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elem_type& GetNext() {
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NS_ASSERTION(HasMore(), "iterating beyond end of array");
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return base_type::mArray.ElementAt(base_type::mPosition++);
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}
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};
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// EndLimitedIterator works like ForwardIterator, but will not iterate new
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// observers appended to the array after the iterator was created.
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class EndLimitedIterator : protected ForwardIterator {
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public:
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typedef nsAutoTObserverArray<T, N> array_type;
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typedef Iterator base_type;
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EndLimitedIterator(const array_type& aArray)
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: ForwardIterator(aArray),
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mEnd(aArray, aArray.Length()) {
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}
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// Returns true if there are more elements to iterate.
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// This must precede a call to GetNext(). If false is
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// returned, GetNext() must not be called.
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bool HasMore() const {
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return *this < mEnd;
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}
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// Returns the next element and steps one step. This must
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// be preceded by a call to HasMore().
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// @return The next observer.
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elem_type& GetNext() {
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NS_ASSERTION(HasMore(), "iterating beyond end of array");
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return base_type::mArray.ElementAt(base_type::mPosition++);
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}
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private:
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ForwardIterator mEnd;
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};
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protected:
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nsAutoTArray<T, N> mArray;
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};
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template<class T>
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class nsTObserverArray : public nsAutoTObserverArray<T, 0> {
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public:
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typedef nsAutoTObserverArray<T, 0> base_type;
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typedef nsTObserverArray_base::size_type size_type;
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//
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// Initialization methods
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//
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nsTObserverArray() {}
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// Initialize this array and pre-allocate some number of elements.
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explicit nsTObserverArray(size_type capacity) {
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base_type::mArray.SetCapacity(capacity);
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}
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};
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template <typename T, uint32_t N>
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inline void
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ImplCycleCollectionUnlink(nsAutoTObserverArray<T, N>& aField)
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{
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aField.Clear();
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}
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template <typename T, uint32_t N>
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inline void
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ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
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nsAutoTObserverArray<T, N>& aField,
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const char* aName,
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uint32_t aFlags = 0)
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{
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aFlags |= CycleCollectionEdgeNameArrayFlag;
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size_t length = aField.Length();
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for (size_t i = 0; i < length; ++i) {
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ImplCycleCollectionTraverse(aCallback, aField.ElementAt(i), aName, aFlags);
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}
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}
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// XXXbz I wish I didn't have to pass in the observer type, but I
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// don't see a way to get it out of array_.
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// Note that this macro only works if the array holds pointers to XPCOM objects.
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#define NS_OBSERVER_ARRAY_NOTIFY_XPCOM_OBSERVERS(array_, obstype_, func_, params_) \
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PR_BEGIN_MACRO \
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nsTObserverArray<obstype_ *>::ForwardIterator iter_(array_); \
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nsRefPtr<obstype_> obs_; \
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while (iter_.HasMore()) { \
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obs_ = iter_.GetNext(); \
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obs_ -> func_ params_ ; \
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} \
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PR_END_MACRO
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// Note that this macro only works if the array holds pointers to XPCOM objects.
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#define NS_OBSERVER_ARRAY_NOTIFY_OBSERVERS(array_, obstype_, func_, params_) \
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PR_BEGIN_MACRO \
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nsTObserverArray<obstype_ *>::ForwardIterator iter_(array_); \
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obstype_* obs_; \
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while (iter_.HasMore()) { \
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obs_ = iter_.GetNext(); \
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obs_ -> func_ params_ ; \
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} \
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PR_END_MACRO
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#endif // nsTObserverArray_h___
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