xpcom/ds/nsCOMArray.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsCOMArray_h__
   8 #define nsCOMArray_h__
   9
  10 #include "mozilla/Attributes.h"
  11 #include "mozilla/ArrayIterator.h"
  12 #include "mozilla/MemoryReporting.h"
  13
  14 #include "nsCycleCollectionNoteChild.h"
  15 #include "nsTArray.h"
  16 #include "nsISupports.h"
  17
  18 #include <iterator>
  19
  20 // See below for the definition of nsCOMArray<T>
  21
  22 // a class that's nsISupports-specific, so that we can contain the
  23 // work of this class in the XPCOM dll
  24 class nsCOMArray_base {
  25   friend class nsArrayBase;
  26
  27  protected:
  28   nsCOMArray_base() = default;
  29   explicit nsCOMArray_base(int32_t aCount) : mArray(aCount) {}
  30   nsCOMArray_base(const nsCOMArray_base& aOther);
  31   nsCOMArray_base(nsCOMArray_base&& aOther) = default;
  32   nsCOMArray_base& operator=(nsCOMArray_base&& aOther) = default;
  33   ~nsCOMArray_base();
  34
  35   int32_t IndexOf(nsISupports* aObject, uint32_t aStartIndex = 0) const;
  36   bool Contains(nsISupports* aObject) const { return IndexOf(aObject) != -1; }
  37
  38   int32_t IndexOfObject(nsISupports* aObject) const;
  39   bool ContainsObject(nsISupports* aObject) const {
  40     return IndexOfObject(aObject) != -1;
  41   }
  42
  43   typedef bool (*nsBaseArrayEnumFunc)(void* aElement, void* aData);
  44
  45   // enumerate through the array with a callback.
  46   bool EnumerateForwards(nsBaseArrayEnumFunc aFunc, void* aData) const;
  47
  48   bool EnumerateBackwards(nsBaseArrayEnumFunc aFunc, void* aData) const;
  49
  50   bool InsertObjectAt(nsISupports* aObject, int32_t aIndex);
  51   void InsertElementAt(uint32_t aIndex, nsISupports* aElement);
  52   void InsertElementAt(uint32_t aIndex, already_AddRefed<nsISupports> aElement);
  53   bool InsertObjectsAt(const nsCOMArray_base& aObjects, int32_t aIndex);
  54   void InsertElementsAt(uint32_t aIndex, const nsCOMArray_base& aElements);
  55   void InsertElementsAt(uint32_t aIndex, nsISupports* const* aElements,
  56                         uint32_t aCount);
  57   void ReplaceObjectAt(nsISupports* aObject, int32_t aIndex);
  58   void ReplaceElementAt(uint32_t aIndex, nsISupports* aElement) {
  59     nsISupports* oldElement = mArray[aIndex];
  60     NS_IF_ADDREF(mArray[aIndex] = aElement);
  61     NS_IF_RELEASE(oldElement);
  62   }
  63   bool AppendObject(nsISupports* aObject) {
  64     return InsertObjectAt(aObject, Count());
  65   }
  66   void AppendElement(nsISupports* aElement) {
  67     InsertElementAt(Length(), aElement);
  68   }
  69   void AppendElement(already_AddRefed<nsISupports> aElement) {
  70     InsertElementAt(Length(), std::move(aElement));
  71   }
  72
  73   bool AppendObjects(const nsCOMArray_base& aObjects) {
  74     return InsertObjectsAt(aObjects, Count());
  75   }
  76   void AppendElements(const nsCOMArray_base& aElements) {
  77     return InsertElementsAt(Length(), aElements);
  78   }
  79   void AppendElements(nsISupports* const* aElements, uint32_t aCount) {
  80     return InsertElementsAt(Length(), aElements, aCount);
  81   }
  82   bool RemoveObject(nsISupports* aObject);
  83   nsISupports** Elements() { return mArray.Elements(); }
  84   void SwapElements(nsCOMArray_base& aOther) {
  85     mArray.SwapElements(aOther.mArray);
  86   }
  87
  88  public:
  89   // elements in the array (including null elements!)
  90   int32_t Count() const { return mArray.Length(); }
  91   // nsTArray-compatible version
  92   uint32_t Length() const { return mArray.Length(); }
  93   bool IsEmpty() const { return mArray.IsEmpty(); }
  94
  95   // If the array grows, the newly created entries will all be null;
  96   // if the array shrinks, the excess entries will all be released.
  97   bool SetCount(int32_t aNewCount);
  98   // nsTArray-compatible version
  99   void TruncateLength(uint32_t aNewLength) {
 100     if (mArray.Length() > aNewLength) {
 101       RemoveElementsAt(aNewLength, mArray.Length() - aNewLength);
 102     }
 103   }
 104
 105   // remove all elements in the array, and call NS_RELEASE on each one
 106   void Clear();
 107
 108   nsISupports* ObjectAt(int32_t aIndex) const { return mArray[aIndex]; }
 109   // nsTArray-compatible version
 110   nsISupports* ElementAt(uint32_t aIndex) const { return mArray[aIndex]; }
 111
 112   nsISupports* SafeObjectAt(int32_t aIndex) const {
 113     return mArray.SafeElementAt(aIndex, nullptr);
 114   }
 115   // nsTArray-compatible version
 116   nsISupports* SafeElementAt(uint32_t aIndex) const {
 117     return mArray.SafeElementAt(aIndex, nullptr);
 118   }
 119
 120   nsISupports* operator[](int32_t aIndex) const { return mArray[aIndex]; }
 121
 122   // remove an element at a specific position, shrinking the array
 123   // as necessary
 124   bool RemoveObjectAt(int32_t aIndex);
 125   // nsTArray-compatible version
 126   void RemoveElementAt(uint32_t aIndex);
 127
 128   // remove a range of elements at a specific position, shrinking the array
 129   // as necessary
 130   bool RemoveObjectsAt(int32_t aIndex, int32_t aCount);
 131   // nsTArray-compatible version
 132   void RemoveElementsAt(uint32_t aIndex, uint32_t aCount);
 133
 134   void SwapElementsAt(uint32_t aIndex1, uint32_t aIndex2) {
 135     nsISupports* tmp = mArray[aIndex1];
 136     mArray[aIndex1] = mArray[aIndex2];
 137     mArray[aIndex2] = tmp;
 138   }
 139
 140   // Ensures there is enough space to store a total of aCapacity objects.
 141   // This method never deletes any objects.
 142   void SetCapacity(uint32_t aCapacity) { mArray.SetCapacity(aCapacity); }
 143   uint32_t Capacity() { return mArray.Capacity(); }
 144
 145   // Measures the size of the array's element storage. If you want to measure
 146   // anything hanging off the array, you must iterate over the elements and
 147   // measure them individually; hence the "Shallow" prefix. Note that because
 148   // each element in an nsCOMArray<T> is actually a T* any such iteration
 149   // should use a SizeOfIncludingThis() function on each element rather than a
 150   // SizeOfExcludingThis() function, so that the memory taken by the T itself
 151   // is included as well as anything it points to.
 152   size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const {
 153     return mArray.ShallowSizeOfExcludingThis(aMallocSizeOf);
 154   }
 155
 156  protected:
 157   // the actual storage
 158   nsTArray<nsISupports*> mArray;
 159
 160  private:
 161   // don't implement these, defaults will muck with refcounts!
 162   nsCOMArray_base& operator=(const nsCOMArray_base& aOther) = delete;
 163 };
 164
 165 inline void ImplCycleCollectionUnlink(nsCOMArray_base& aField) {
 166   aField.Clear();
 167 }
 168
 169 inline void ImplCycleCollectionTraverse(
 170     nsCycleCollectionTraversalCallback& aCallback, nsCOMArray_base& aField,
 171     const char* aName, uint32_t aFlags = 0) {
 172   aFlags |= CycleCollectionEdgeNameArrayFlag;
 173   int32_t length = aField.Count();
 174   for (int32_t i = 0; i < length; ++i) {
 175     CycleCollectionNoteChild(aCallback, aField[i], aName, aFlags);
 176   }
 177 }
 178
 179 // a non-XPCOM, refcounting array of XPCOM objects
 180 // used as a member variable or stack variable - this object is NOT
 181 // refcounted, but the objects that it holds are
 182 //
 183 // most of the read-only accessors like ObjectAt()/etc do NOT refcount
 184 // on the way out. This means that you can do one of two things:
 185 //
 186 // * does an addref, but holds onto a reference
 187 // nsCOMPtr<T> foo = array[i];
 188 //
 189 // * avoids the refcount, but foo might go stale if array[i] is ever
 190 // * modified/removed. Be careful not to NS_RELEASE(foo)!
 191 // T* foo = array[i];
 192 //
 193 // This array will accept null as an argument for any object, and will store
 194 // null in the array. But that also means that methods like ObjectAt() may
 195 // return null when referring to an existing, but null entry in the array.
 196 template <class T>
 197 class nsCOMArray : public nsCOMArray_base {
 198  public:
 199   typedef int32_t index_type;
 200   typedef mozilla::ArrayIterator<T*, nsCOMArray> iterator;
 201   typedef mozilla::ArrayIterator<const T*, nsCOMArray> const_iterator;
 202   typedef std::reverse_iterator<iterator> reverse_iterator;
 203   typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
 204
 205   nsCOMArray() = default;
 206   explicit nsCOMArray(int32_t aCount) : nsCOMArray_base(aCount) {}
 207   explicit nsCOMArray(const nsCOMArray<T>& aOther) : nsCOMArray_base(aOther) {}
 208   nsCOMArray(nsCOMArray<T>&& aOther) = default;
 209   ~nsCOMArray() = default;
 210
 211   // We have a move assignment operator, but no copy assignment operator.
 212   nsCOMArray<T>& operator=(nsCOMArray<T>&& aOther) = default;
 213
 214   // these do NOT refcount on the way out, for speed
 215   T* ObjectAt(int32_t aIndex) const {
 216     return static_cast<T*>(nsCOMArray_base::ObjectAt(aIndex));
 217   }
 218   // nsTArray-compatible version
 219   T* ElementAt(uint32_t aIndex) const {
 220     return static_cast<T*>(nsCOMArray_base::ElementAt(aIndex));
 221   }
 222
 223   // these do NOT refcount on the way out, for speed
 224   T* SafeObjectAt(int32_t aIndex) const {
 225     return static_cast<T*>(nsCOMArray_base::SafeObjectAt(aIndex));
 226   }
 227   // nsTArray-compatible version
 228   T* SafeElementAt(uint32_t aIndex) const {
 229     return static_cast<T*>(nsCOMArray_base::SafeElementAt(aIndex));
 230   }
 231
 232   // indexing operator for syntactic sugar
 233   T* operator[](int32_t aIndex) const { return ObjectAt(aIndex); }
 234
 235   // index of the element in question.. does NOT refcount
 236   // note: this does not check COM object identity. Use
 237   // IndexOfObject() for that purpose
 238   int32_t IndexOf(T* aObject, uint32_t aStartIndex = 0) const {
 239     return nsCOMArray_base::IndexOf(aObject, aStartIndex);
 240   }
 241   bool Contains(T* aObject) const { return nsCOMArray_base::Contains(aObject); }
 242
 243   // index of the element in question.. be careful!
 244   // this is much slower than IndexOf() because it uses
 245   // QueryInterface to determine actual COM identity of the object
 246   // if you need to do this frequently then consider enforcing
 247   // COM object identity before adding/comparing elements
 248   int32_t IndexOfObject(T* aObject) const {
 249     return nsCOMArray_base::IndexOfObject(aObject);
 250   }
 251   bool ContainsObject(nsISupports* aObject) const {
 252     return nsCOMArray_base::ContainsObject(aObject);
 253   }
 254
 255   // inserts aObject at aIndex, shifting the objects at aIndex and
 256   // later to make space
 257   bool InsertObjectAt(T* aObject, int32_t aIndex) {
 258     return nsCOMArray_base::InsertObjectAt(aObject, aIndex);
 259   }
 260   // nsTArray-compatible version
 261   void InsertElementAt(uint32_t aIndex, T* aElement) {
 262     nsCOMArray_base::InsertElementAt(aIndex, aElement);
 263   }
 264
 265   // inserts the objects from aObject at aIndex, shifting the
 266   // objects at aIndex and later to make space
 267   bool InsertObjectsAt(const nsCOMArray<T>& aObjects, int32_t aIndex) {
 268     return nsCOMArray_base::InsertObjectsAt(aObjects, aIndex);
 269   }
 270   // nsTArray-compatible version
 271   void InsertElementsAt(uint32_t aIndex, const nsCOMArray<T>& aElements) {
 272     nsCOMArray_base::InsertElementsAt(aIndex, aElements);
 273   }
 274   void InsertElementsAt(uint32_t aIndex, T* const* aElements, uint32_t aCount) {
 275     nsCOMArray_base::InsertElementsAt(
 276         aIndex, reinterpret_cast<nsISupports* const*>(aElements), aCount);
 277   }
 278
 279   // replaces an existing element. Warning: if the array grows,
 280   // the newly created entries will all be null
 281   void ReplaceObjectAt(T* aObject, int32_t aIndex) {
 282     nsCOMArray_base::ReplaceObjectAt(aObject, aIndex);
 283   }
 284   // nsTArray-compatible version
 285   void ReplaceElementAt(uint32_t aIndex, T* aElement) {
 286     nsCOMArray_base::ReplaceElementAt(aIndex, aElement);
 287   }
 288
 289   using TComparatorFunc = int (*)(T*, T*);
 290
 291   // The default sort function uses nsTArray::Sort.
 292   // Note that the order of equal items is unstable with this.
 293   void Sort(TComparatorFunc aFunc) {
 294     mArray.Sort(
 295         [aFunc](nsISupports* const& aLeft, nsISupports* const& aRight) -> int {
 296           return aFunc(static_cast<T*>(aLeft), static_cast<T*>(aRight));
 297         });
 298   }
 299
 300   // Sort with a stable algorithm, uses nsTArray::StableSort.
 301   void StableSort(TComparatorFunc aFunc) {
 302     mArray.StableSort(
 303         [aFunc](nsISupports* const& aLeft, nsISupports* const& aRight) -> int {
 304           return aFunc(static_cast<T*>(aLeft), static_cast<T*>(aRight));
 305         });
 306   }
 307
 308   // append an object, growing the array as necessary
 309   bool AppendObject(T* aObject) {
 310     return nsCOMArray_base::AppendObject(aObject);
 311   }
 312   // nsTArray-compatible version
 313   void AppendElement(T* aElement) { nsCOMArray_base::AppendElement(aElement); }
 314   void AppendElement(already_AddRefed<T> aElement) {
 315     nsCOMArray_base::AppendElement(std::move(aElement));
 316   }
 317
 318   // append objects, growing the array as necessary
 319   bool AppendObjects(const nsCOMArray<T>& aObjects) {
 320     return nsCOMArray_base::AppendObjects(aObjects);
 321   }
 322   // nsTArray-compatible version
 323   void AppendElements(const nsCOMArray<T>& aElements) {
 324     return nsCOMArray_base::AppendElements(aElements);
 325   }
 326   void AppendElements(T* const* aElements, uint32_t aCount) {
 327     InsertElementsAt(Length(), aElements, aCount);
 328   }
 329
 330   // remove the first instance of the given object and shrink the
 331   // array as necessary
 332   // Warning: if you pass null here, it will remove the first null element
 333   bool RemoveObject(T* aObject) {
 334     return nsCOMArray_base::RemoveObject(aObject);
 335   }
 336   // nsTArray-compatible version
 337   bool RemoveElement(T* aElement) {
 338     return nsCOMArray_base::RemoveObject(aElement);
 339   }
 340
 341   T** Elements() { return reinterpret_cast<T**>(nsCOMArray_base::Elements()); }
 342   void SwapElements(nsCOMArray<T>& aOther) {
 343     nsCOMArray_base::SwapElements(aOther);
 344   }
 345
 346   // Methods for range-based for loops.
 347   iterator begin() { return iterator(*this, 0); }
 348   const_iterator begin() const { return const_iterator(*this, 0); }
 349   const_iterator cbegin() const { return begin(); }
 350   iterator end() { return iterator(*this, Length()); }
 351   const_iterator end() const { return const_iterator(*this, Length()); }
 352   const_iterator cend() const { return end(); }
 353
 354   // Methods for reverse iterating.
 355   reverse_iterator rbegin() { return reverse_iterator(end()); }
 356   const_reverse_iterator rbegin() const {
 357     return const_reverse_iterator(end());
 358   }
 359   const_reverse_iterator crbegin() const { return rbegin(); }
 360   reverse_iterator rend() { return reverse_iterator(begin()); }
 361   const_reverse_iterator rend() const {
 362     return const_reverse_iterator(begin());
 363   }
 364   const_reverse_iterator crend() const { return rend(); }
 365
 366  private:
 367   // don't implement these!
 368   nsCOMArray<T>& operator=(const nsCOMArray<T>& aOther) = delete;
 369 };
 370
 371 template <typename T>
 372 inline void ImplCycleCollectionUnlink(nsCOMArray<T>& aField) {
 373   aField.Clear();
 374 }
 375
 376 template <typename E>
 377 inline void ImplCycleCollectionTraverse(
 378     nsCycleCollectionTraversalCallback& aCallback, nsCOMArray<E>& aField,
 379     const char* aName, uint32_t aFlags = 0) {
 380   aFlags |= CycleCollectionEdgeNameArrayFlag;
 381   int32_t length = aField.Count();
 382   for (int32_t i = 0; i < length; ++i) {
 383     CycleCollectionNoteChild(aCallback, aField[i], aName, aFlags);
 384   }
 385 }
 386
 387 #endif