xpcom/ds/nsTObserverArray.h
author Petru Lingurar <petru.lingurar@softvision.ro>
Fri, 13 Jul 2018 17:16:37 +0300
changeset 426733 c2b1f1b52866d2c58f5e23fe2df97c9127ebcacf
parent 372149 559f7f92c891782597759947b89be636c2d4767b
child 441177 2b7fce8c4f926662732fae0deaf857121810f1ab
permissions -rw-r--r--
Bug 1385464 - Start using support library v. 26; r=nalexander This patch also: Resolves missing resources and api changes - LeanplumActionBarActivity was removed because Support Library 26 deprecated ActionBarActivity. Class was already not in use. - CustomTabsService added two new methods which we need to override. Tested to make sure that previous functionality was maintained but with the addition of the two new methods maybe that feature could be improved. - For checking layout direction we'll use our own new method from ViewUtil which mimics what the now restricted method from the support library would do. - Upgraded to use AppCompatResources#getDrawable(..) in place of the now restricted AppCompatDrawableManager.get().getDrawable(..). Resolves obscure leaks and crashes after the upgrade - LoaderManager.destroyLoader(..) was added before the existing call to LoaderManager.restartLoader(..) to prevent potential Cursor leaks - Disable website suggestions depending on the address bar inputs when running in automation to avoid Robocop tests failing (they were entering serially maybe 100 characters in <5 ms which created around that many new Threads, operation that could cause the Executor to throw a RejectedExecutionException) At the moment this functionality is not covered by tests anyway and it was the only fix I could find that would not involve changing the whole implemenation for address bar suggestions, implementation which in the real world works ok. MozReview-Commit-ID: 2fX1SBHiSh0

/* -*- 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/. */

#ifndef nsTObserverArray_h___
#define nsTObserverArray_h___

#include "mozilla/MemoryReporting.h"
#include "nsTArray.h"
#include "nsCycleCollectionNoteChild.h"

#include <functional>

/**
 * An array of observers. Like a normal array, but supports iterators that are
 * stable even if the array is modified during iteration.
 * The template parameter T is the observer type the array will hold;
 * N is the number of built-in storage slots that come with the array.
 * NOTE: You probably want to use nsTObserverArray, unless you specifically
 * want built-in storage. See below.
 * @see nsTObserverArray, nsTArray
 */

class nsTObserverArray_base
{
public:
  typedef size_t index_type;
  typedef size_t size_type;
  typedef ptrdiff_t diff_type;

protected:
  class Iterator_base
  {
  protected:
    friend class nsTObserverArray_base;

    Iterator_base(index_type aPosition, Iterator_base* aNext)
      : mPosition(aPosition)
      , mNext(aNext)
    {
    }

    // The current position of the iterator. Its exact meaning differs
    // depending on iterator. See nsTObserverArray<T>::ForwardIterator.
    index_type mPosition;

    // The next iterator currently iterating the same array
    Iterator_base* mNext;
  };

  nsTObserverArray_base() : mIterators(nullptr) {}

  ~nsTObserverArray_base()
  {
    NS_ASSERTION(mIterators == nullptr, "iterators outlasting array");
  }

  /**
   * Adjusts iterators after an element has been inserted or removed
   * from the array.
   * @param aModPos     Position where elements were added or removed.
   * @param aAdjustment -1 if an element was removed, 1 if an element was
   *                    added.
   */
  void AdjustIterators(index_type aModPos, diff_type aAdjustment);

  /**
   * Clears iterators when the array is destroyed.
   */
  void ClearIterators();

  mutable Iterator_base* mIterators;
};

template<class T, size_t N>
class nsAutoTObserverArray : protected nsTObserverArray_base
{
public:
  typedef T           elem_type;
  typedef nsTArray<T> array_type;

  nsAutoTObserverArray() {}

  //
  // Accessor methods
  //

  // @return The number of elements in the array.
  size_type Length() const { return mArray.Length(); }

  // @return True if the array is empty or false otherwise.
  bool IsEmpty() const { return mArray.IsEmpty(); }

  // This method provides direct, readonly access to the array elements.
  // @return A pointer to the first element of the array.  If the array is
  // empty, then this pointer must not be dereferenced.
  const elem_type* Elements() const
  {
    return mArray.Elements();
  }
  elem_type* Elements()
  {
    return mArray.Elements();
  }

  // This method provides direct access to an element of the array. The given
  // index must be within the array bounds. If the underlying array may change
  // during iteration, use an iterator instead of this function.
  // @param aIndex The index of an element in the array.
  // @return A reference to the i'th element of the array.
  elem_type& ElementAt(index_type aIndex)
  {
    return mArray.ElementAt(aIndex);
  }

  // Same as above, but readonly.
  const elem_type& ElementAt(index_type aIndex) const
  {
    return mArray.ElementAt(aIndex);
  }

  // This method provides direct access to an element of the array in a bounds
  // safe manner. If the requested index is out of bounds the provided default
  // value is returned.
  // @param aIndex The index of an element in the array.
  // @param aDef   The value to return if the index is out of bounds.
  elem_type& SafeElementAt(index_type aIndex, elem_type& aDef)
  {
    return mArray.SafeElementAt(aIndex, aDef);
  }

  // Same as above, but readonly.
  const elem_type& SafeElementAt(index_type aIndex, const elem_type& aDef) const
  {
    return mArray.SafeElementAt(aIndex, aDef);
  }

  // No operator[] is provided because the point of this class is to support
  // allow modifying the array during iteration, and ElementAt() is not safe
  // in those conditions.

  //
  // Search methods
  //

  // This method searches, starting from the beginning of the array,
  // for the first element in this array that is equal to the given element.
  // 'operator==' must be defined for elem_type.
  // @param aItem The item to search for.
  // @return      true if the element was found.
  template<class Item>
  bool Contains(const Item& aItem) const
  {
    return IndexOf(aItem) != array_type::NoIndex;
  }

  // This method searches for the offset of the first element in this
  // array that is equal to the given element.
  // 'operator==' must be defined for elem_type.
  // @param aItem  The item to search for.
  // @param aStart The index to start from.
  // @return The index of the found element or NoIndex if not found.
  template<class Item>
  index_type IndexOf(const Item& aItem, index_type aStart = 0) const
  {
    return mArray.IndexOf(aItem, aStart);
  }

  //
  // Mutation methods
  //

  // Insert a given element at the given index.
  // @param aIndex The index at which to insert item.
  // @param aItem  The item to insert,
  // @return A pointer to the newly inserted element, or a null on DOM
  template<class Item>
  elem_type* InsertElementAt(index_type aIndex, const Item& aItem)
  {
    elem_type* item = mArray.InsertElementAt(aIndex, aItem);
    AdjustIterators(aIndex, 1);
    return item;
  }

  // Same as above but without copy constructing.
  // This is useful to avoid temporaries.
  elem_type* InsertElementAt(index_type aIndex)
  {
    elem_type* item = mArray.InsertElementAt(aIndex);
    AdjustIterators(aIndex, 1);
    return item;
  }

  // Prepend an element to the array unless it already exists in the array.
  // 'operator==' must be defined for elem_type.
  // @param aItem The item to prepend.
  // @return true if the element was found, or inserted successfully.
  template<class Item>
  bool PrependElementUnlessExists(const Item& aItem)
  {
    if (Contains(aItem)) {
      return true;
    }

    bool inserted = mArray.InsertElementAt(0, aItem) != nullptr;
    AdjustIterators(0, 1);
    return inserted;
  }

  // Append an element to the array.
  // @param aItem The item to append.
  // @return A pointer to the newly appended element, or null on OOM.
  template<class Item>
  elem_type* AppendElement(const Item& aItem)
  {
    return mArray.AppendElement(aItem);
  }

  // Same as above, but without copy-constructing. This is useful to avoid
  // temporaries.
  elem_type* AppendElement()
  {
    return mArray.AppendElement();
  }

  // Append an element to the array unless it already exists in the array.
  // 'operator==' must be defined for elem_type.
  // @param aItem The item to append.
  // @return true if the element was found, or inserted successfully.
  template<class Item>
  bool AppendElementUnlessExists(const Item& aItem)
  {
    return Contains(aItem) || AppendElement(aItem) != nullptr;
  }

  // Remove an element from the array.
  // @param aIndex The index of the item to remove.
  void RemoveElementAt(index_type aIndex)
  {
    NS_ASSERTION(aIndex < mArray.Length(), "invalid index");
    mArray.RemoveElementAt(aIndex);
    AdjustIterators(aIndex, -1);
  }

  // This helper function combines IndexOf with RemoveElementAt to "search
  // and destroy" the first element that is equal to the given element.
  // 'operator==' must be defined for elem_type.
  // @param aItem The item to search for.
  // @return true if the element was found and removed.
  template<class Item>
  bool RemoveElement(const Item& aItem)
  {
    index_type index = mArray.IndexOf(aItem, 0);
    if (index == array_type::NoIndex) {
      return false;
    }

    mArray.RemoveElementAt(index);
    AdjustIterators(index, -1);
    return true;
  }

  // See nsTArray::RemoveElementsBy.
  template <typename Predicate>
  void RemoveElementsBy(Predicate aPredicate)
  {
    index_type i = 0;
    mArray.RemoveElementsBy([&](const elem_type& aItem) {
      if (aPredicate(aItem)) {
        // This element is going to be removed.
        AdjustIterators(i, -1);
        return true;
      }
      ++i;
      return false;
    });
  }

  // Removes all observers and collapses all iterators to the beginning of
  // the array. The result is that forward iterators will see all elements
  // in the array.
  void Clear()
  {
    mArray.Clear();
    ClearIterators();
  }

  // Compact the array to minimize the memory it uses
  void Compact() { mArray.Compact(); }

  // Returns the number of bytes on the heap taken up by this object, not
  // including sizeof(*this). If you want to measure anything hanging off the
  // array, you must iterate over the elements and measure them individually;
  // hence the "Shallow" prefix.
  size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
  {
    return mArray.ShallowSizeOfExcludingThis(aMallocSizeOf);
  }

  //
  // Iterators
  //

  // Base class for iterators. Do not use this directly.
  class Iterator : public Iterator_base
  {
  protected:
    friend class nsAutoTObserverArray;
    typedef nsAutoTObserverArray<T, N> array_type;

    Iterator(index_type aPosition, const array_type& aArray)
      : Iterator_base(aPosition, aArray.mIterators)
      , mArray(const_cast<array_type&>(aArray))
    {
      aArray.mIterators = this;
    }

    ~Iterator()
    {
      NS_ASSERTION(mArray.mIterators == this,
                   "Iterators must currently be destroyed in opposite order "
                   "from the construction order. It is suggested that you "
                   "simply put them on the stack");
      mArray.mIterators = mNext;
    }

    // The array we're iterating
    array_type& mArray;
  };

  // Iterates the array forward from beginning to end. mPosition points
  // to the element that will be returned on next call to GetNext.
  // Elements:
  // - prepended to the array during iteration *will not* be traversed
  // - appended during iteration *will* be traversed
  // - removed during iteration *will not* be traversed.
  // @see EndLimitedIterator
  class ForwardIterator : protected Iterator
  {
  public:
    typedef nsAutoTObserverArray<T, N> array_type;
    typedef Iterator                   base_type;

    explicit ForwardIterator(const array_type& aArray)
      : Iterator(0, aArray)
    {
    }

    ForwardIterator(const array_type& aArray, index_type aPos)
      : Iterator(aPos, aArray)
    {
    }

    bool operator<(const ForwardIterator& aOther) const
    {
      NS_ASSERTION(&this->mArray == &aOther.mArray,
                   "not iterating the same array");
      return base_type::mPosition < aOther.mPosition;
    }

    // Returns true if there are more elements to iterate.
    // This must precede a call to GetNext(). If false is
    // returned, GetNext() must not be called.
    bool HasMore() const
    {
      return base_type::mPosition < base_type::mArray.Length();
    }

    // Returns the next element and steps one step. This must
    // be preceded by a call to HasMore().
    // @return The next observer.
    elem_type& GetNext()
    {
      NS_ASSERTION(HasMore(), "iterating beyond end of array");
      return base_type::mArray.Elements()[base_type::mPosition++];
    }
  };

  // EndLimitedIterator works like ForwardIterator, but will not iterate new
  // observers appended to the array after the iterator was created.
  class EndLimitedIterator : protected ForwardIterator
  {
  public:
    typedef nsAutoTObserverArray<T, N> array_type;
    typedef Iterator                   base_type;

    explicit EndLimitedIterator(const array_type& aArray)
      : ForwardIterator(aArray)
      , mEnd(aArray, aArray.Length())
    {
    }

    // Returns true if there are more elements to iterate.
    // This must precede a call to GetNext(). If false is
    // returned, GetNext() must not be called.
    bool HasMore() const { return *this < mEnd; }

    // Returns the next element and steps one step. This must
    // be preceded by a call to HasMore().
    // @return The next observer.
    elem_type& GetNext()
    {
      NS_ASSERTION(HasMore(), "iterating beyond end of array");
      return base_type::mArray.Elements()[base_type::mPosition++];
    }

  private:
    ForwardIterator mEnd;
  };

  // Iterates the array backward from end to start. mPosition points
  // to the element that was returned last.
  // Elements:
  // - prepended to the array during iteration *will* be traversed,
  //   unless the iteration already arrived at the first element
  // - appended during iteration *will not* be traversed
  // - removed during iteration *will not* be traversed.
  class BackwardIterator : protected Iterator
  {
  public:
    typedef nsAutoTObserverArray<T, N> array_type;
    typedef Iterator                   base_type;

    explicit BackwardIterator(const array_type& aArray)
      : Iterator(aArray.Length(), aArray)
    {
    }

    // Returns true if there are more elements to iterate.
    // This must precede a call to GetNext(). If false is
    // returned, GetNext() must not be called.
    bool HasMore() const { return base_type::mPosition > 0; }

    // Returns the next element and steps one step. This must
    // be preceded by a call to HasMore().
    // @return The next observer.
    elem_type& GetNext()
    {
      NS_ASSERTION(HasMore(), "iterating beyond start of array");
      return base_type::mArray.Elements()[--base_type::mPosition];
    }

    // Removes the element at the current iterator position.
    // (the last element returned from |GetNext()|)
    // This will not affect the next call to |GetNext()|
    void Remove()
    {
      return base_type::mArray.RemoveElementAt(base_type::mPosition);
    }
  };

protected:
  AutoTArray<T, N> mArray;
};

template<class T>
class nsTObserverArray : public nsAutoTObserverArray<T, 0>
{
public:
  typedef nsAutoTObserverArray<T, 0>       base_type;
  typedef nsTObserverArray_base::size_type size_type;

  //
  // Initialization methods
  //

  nsTObserverArray() {}

  // Initialize this array and pre-allocate some number of elements.
  explicit nsTObserverArray(size_type aCapacity)
  {
    base_type::mArray.SetCapacity(aCapacity);
  }
};

template<typename T, size_t N>
inline void
ImplCycleCollectionUnlink(nsAutoTObserverArray<T, N>& aField)
{
  aField.Clear();
}

template<typename T, size_t N>
inline void
ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
                            nsAutoTObserverArray<T, N>& aField,
                            const char* aName,
                            uint32_t aFlags = 0)
{
  aFlags |= CycleCollectionEdgeNameArrayFlag;
  size_t length = aField.Length();
  for (size_t i = 0; i < length; ++i) {
    ImplCycleCollectionTraverse(aCallback, aField.ElementAt(i), aName, aFlags);
  }
}

// XXXbz I wish I didn't have to pass in the observer type, but I
// don't see a way to get it out of array_.
// Note that this macro only works if the array holds pointers to XPCOM objects.
#define NS_OBSERVER_ARRAY_NOTIFY_XPCOM_OBSERVERS(array_, obstype_, func_, params_) \
  do {                                                                       \
    nsTObserverArray<obstype_ *>::ForwardIterator iter_(array_);             \
    RefPtr<obstype_> obs_;                                                 \
    while (iter_.HasMore()) {                                                 \
      obs_ = iter_.GetNext();                                                \
      obs_ -> func_ params_ ;                                                \
    }                                                                        \
  } while(0)

// Note that this macro only works if the array holds pointers to XPCOM objects.
#define NS_OBSERVER_ARRAY_NOTIFY_OBSERVERS(array_, obstype_, func_, params_) \
  do {                                                                       \
    nsTObserverArray<obstype_ *>::ForwardIterator iter_(array_);             \
    obstype_* obs_;                                                          \
    while (iter_.HasMore()) {                                                \
      obs_ = iter_.GetNext();                                                \
      obs_ -> func_ params_ ;                                                \
    }                                                                        \
  } while(0)

// Note that this macro only works if the array holds pointers to XPCOM objects.
#define NS_OBSERVER_AUTO_ARRAY_NOTIFY_OBSERVERS(array_, obstype_, num_, func_, params_) \
  do {                                                                       \
    nsAutoTObserverArray<obstype_ *, num_>::ForwardIterator iter_(array_);   \
    obstype_* obs_;                                                          \
    while (iter_.HasMore()) {                                                \
      obs_ = iter_.GetNext();                                                \
      obs_ -> func_ params_ ;                                                \
    }                                                                        \
  } while(0)

#define NS_OBSERVER_ARRAY_NOTIFY_OBSERVERS_WITH_QI(array_, basetype_, obstype_, func_, params_) \
  do {                                                                       \
    nsTObserverArray<basetype_ *>::ForwardIterator iter_(array_);            \
    basetype_* obsbase_;                                                     \
    while (iter_.HasMore()) {                                                \
      obsbase_ = iter_.GetNext();                                            \
      nsCOMPtr<obstype_> obs_ = do_QueryInterface(obsbase_);                 \
      if (obs_) {                                                            \
        obs_ -> func_ params_ ;                                              \
      }                                                                      \
    }                                                                        \
  } while(0)

#define NS_OBSERVER_AUTO_ARRAY_NOTIFY_OBSERVERS_WITH_QI(array_, basetype_, num_, obstype_, func_, params_) \
  do {                                                                       \
    nsAutoTObserverArray<basetype_ *, num_>::ForwardIterator iter_(array_);  \
    basetype_* obsbase_;                                                     \
    while (iter_.HasMore()) {                                                \
      obsbase_ = iter_.GetNext();                                            \
      nsCOMPtr<obstype_> obs_ = do_QueryInterface(obsbase_);                 \
      if (obs_) {                                                            \
        obs_ -> func_ params_ ;                                              \
      }                                                                      \
    }                                                                        \
  } while(0)
#endif // nsTObserverArray_h___