diff -r 000000000000 -r 6474c204b198 xpcom/glue/nsTArray.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/glue/nsTArray.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,1830 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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 nsTArray_h__
+#define nsTArray_h__
+
+#include "nsTArrayForwardDeclare.h"
+#include "mozilla/Alignment.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/TypeTraits.h"
+
+#include <string.h>
+
+#include "nsCycleCollectionNoteChild.h"
+#include "nsAlgorithm.h"
+#include "nscore.h"
+#include "nsQuickSort.h"
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"
+#include <new>
+
+namespace JS {
+template <class T>
+class Heap;
+} /* namespace JS */
+
+class nsRegion;
+class nsIntRegion;
+
+//
+// nsTArray is a resizable array class, like std::vector.
+//
+// Unlike std::vector, which follows C++'s construction/destruction rules,
+// nsTArray assumes that your "T" can be memmoved()'ed safely.
+//
+// The public classes defined in this header are
+//
+//   nsTArray<T>,
+//   FallibleTArray<T>,
+//   nsAutoTArray<T, N>, and
+//   AutoFallibleTArray<T, N>.
+//
+// nsTArray and nsAutoTArray are infallible; if one tries to make an allocation
+// which fails, it crashes the program.  In contrast, FallibleTArray and
+// AutoFallibleTArray are fallible; if you use one of these classes, you must
+// check the return values of methods such as Append() which may allocate.  If
+// in doubt, choose an infallible type.
+//
+// InfallibleTArray and AutoInfallibleTArray are aliases for nsTArray and
+// nsAutoTArray.
+//
+// If you just want to declare the nsTArray types (e.g., if you're in a header
+// file and don't need the full nsTArray definitions) consider including
+// nsTArrayForwardDeclare.h instead of nsTArray.h.
+//
+// The template parameter (i.e., T in nsTArray<T>) specifies the type of the
+// elements and has the following requirements:
+//
+//   T MUST be safely memmove()'able.
+//   T MUST define a copy-constructor.
+//   T MAY define operator< for sorting.
+//   T MAY define operator== for searching.
+//
+// (Note that the memmove requirement may be relaxed for certain types - see
+// nsTArray_CopyChooser below.)
+//
+// For methods taking a Comparator instance, the Comparator must be a class
+// defining the following methods:
+//
+//   class Comparator {
+//     public:
+//       /** @return True if the elements are equals; false otherwise. */
+//       bool Equals(const elem_type& a, const Item& b) const;
+//
+//       /** @return True if (a < b); false otherwise. */
+//       bool LessThan(const elem_type& a, const Item& b) const;
+//   };
+//
+// The Equals method is used for searching, and the LessThan method is used for
+// searching and sorting.  The |Item| type above can be arbitrary, but must
+// match the Item type passed to the sort or search function.
+//
+
+
+//
+// nsTArrayFallibleResult and nsTArrayInfallibleResult types are proxy types
+// which are used because you cannot use a templated type which is bound to
+// void as an argument to a void function.  In order to work around that, we
+// encode either a void or a boolean inside these proxy objects, and pass them
+// to the aforementioned function instead, and then use the type information to
+// decide what to do in the function.
+//
+// Note that public nsTArray methods should never return a proxy type.  Such
+// types are only meant to be used in the internal nsTArray helper methods.
+// Public methods returning non-proxy types cannot be called from other
+// nsTArray members.
+//
+struct nsTArrayFallibleResult
+{
+  // Note: allows implicit conversions from and to bool
+  nsTArrayFallibleResult(bool result)
+    : mResult(result)
+  {}
+
+  operator bool() {
+    return mResult;
+  }
+
+private:
+  bool mResult;
+};
+
+struct nsTArrayInfallibleResult
+{
+};
+
+//
+// nsTArray*Allocators must all use the same |free()|, to allow swap()'ing
+// between fallible and infallible variants.
+//
+
+struct nsTArrayFallibleAllocatorBase
+{
+  typedef bool ResultType;
+  typedef nsTArrayFallibleResult ResultTypeProxy;
+
+  static ResultType Result(ResultTypeProxy result) {
+    return result;
+  }
+
+  static bool Successful(ResultTypeProxy result) {
+    return result;
+  }
+
+  static ResultTypeProxy SuccessResult() {
+    return true;
+  }
+
+  static ResultTypeProxy FailureResult() {
+    return false;
+  }
+
+  static ResultType ConvertBoolToResultType(bool aValue) {
+    return aValue;
+  }
+};
+
+struct nsTArrayInfallibleAllocatorBase
+{
+  typedef void ResultType;
+  typedef nsTArrayInfallibleResult ResultTypeProxy;
+
+  static ResultType Result(ResultTypeProxy result) {
+  }
+
+  static bool Successful(ResultTypeProxy) {
+    return true;
+  }
+
+  static ResultTypeProxy SuccessResult() {
+    return ResultTypeProxy();
+  }
+
+  static ResultTypeProxy FailureResult() {
+    NS_RUNTIMEABORT("Infallible nsTArray should never fail");
+    return ResultTypeProxy();
+  }
+
+  static ResultType ConvertBoolToResultType(bool aValue) {
+    if (!aValue) {
+      NS_RUNTIMEABORT("infallible nsTArray should never convert false to ResultType");
+    }
+  }
+};
+
+#if defined(MOZALLOC_HAVE_XMALLOC)
+#include "mozilla/mozalloc_abort.h"
+
+struct nsTArrayFallibleAllocator : nsTArrayFallibleAllocatorBase
+{
+  static void* Malloc(size_t size) {
+    return moz_malloc(size);
+  }
+
+  static void* Realloc(void* ptr, size_t size) {
+    return moz_realloc(ptr, size);
+  }
+
+  static void Free(void* ptr) {
+    moz_free(ptr);
+  }
+
+  static void SizeTooBig(size_t) {
+  }
+};
+
+struct nsTArrayInfallibleAllocator : nsTArrayInfallibleAllocatorBase
+{
+  static void* Malloc(size_t size) {
+    return moz_xmalloc(size);
+  }
+
+  static void* Realloc(void* ptr, size_t size) {
+    return moz_xrealloc(ptr, size);
+  }
+
+  static void Free(void* ptr) {
+    moz_free(ptr);
+  }
+
+  static void SizeTooBig(size_t size) {
+    NS_ABORT_OOM(size);
+  }
+};
+
+#else
+#include <stdlib.h>
+
+struct nsTArrayFallibleAllocator : nsTArrayFallibleAllocatorBase
+{
+  static void* Malloc(size_t size) {
+    return malloc(size);
+  }
+
+  static void* Realloc(void* ptr, size_t size) {
+    return realloc(ptr, size);
+  }
+
+  static void Free(void* ptr) {
+    free(ptr);
+  }
+
+  static void SizeTooBig(size_t) {
+  }
+};
+
+struct nsTArrayInfallibleAllocator : nsTArrayInfallibleAllocatorBase
+{
+  static void* Malloc(size_t size) {
+    void* ptr = malloc(size);
+    if (MOZ_UNLIKELY(!ptr)) {
+      NS_ABORT_OOM(size);
+    }
+    return ptr;
+  }
+
+  static void* Realloc(void* ptr, size_t size) {
+    void* newptr = realloc(ptr, size);
+    if (MOZ_UNLIKELY(!ptr && size)) {
+      NS_ABORT_OOM(size);
+    }
+    return newptr;
+  }
+
+  static void Free(void* ptr) {
+    free(ptr);
+  }
+
+  static void SizeTooBig(size_t size) {
+    NS_ABORT_OOM(size);
+  }
+};
+
+#endif
+
+// nsTArray_base stores elements into the space allocated beyond
+// sizeof(*this).  This is done to minimize the size of the nsTArray
+// object when it is empty.
+struct NS_COM_GLUE nsTArrayHeader
+{
+  static nsTArrayHeader sEmptyHdr;
+
+  uint32_t mLength;
+  uint32_t mCapacity : 31;
+  uint32_t mIsAutoArray : 1;
+};
+
+// This class provides a SafeElementAt method to nsTArray<T*> which does
+// not take a second default value parameter.
+template <class E, class Derived>
+struct nsTArray_SafeElementAtHelper
+{
+  typedef E*       elem_type;
+  typedef uint32_t index_type;
+
+  // No implementation is provided for these two methods, and that is on
+  // purpose, since we don't support these functions on non-pointer type
+  // instantiations.
+  elem_type& SafeElementAt(index_type i);
+  const elem_type& SafeElementAt(index_type i) const;
+};
+
+template <class E, class Derived>
+struct nsTArray_SafeElementAtHelper<E*, Derived>
+{
+  typedef E*       elem_type;
+  typedef uint32_t index_type;
+
+  elem_type SafeElementAt(index_type i) {
+    return static_cast<Derived*> (this)->SafeElementAt(i, nullptr);
+  }
+
+  const elem_type SafeElementAt(index_type i) const {
+    return static_cast<const Derived*> (this)->SafeElementAt(i, nullptr);
+  }
+};
+
+// E is the base type that the smart pointer is templated over; the
+// smart pointer can act as E*.
+template <class E, class Derived>
+struct nsTArray_SafeElementAtSmartPtrHelper
+{
+  typedef E*       elem_type;
+  typedef uint32_t index_type;
+
+  elem_type SafeElementAt(index_type i) {
+    return static_cast<Derived*> (this)->SafeElementAt(i, nullptr);
+  }
+
+  const elem_type SafeElementAt(index_type i) const {
+    return static_cast<const Derived*> (this)->SafeElementAt(i, nullptr);
+  }
+};
+
+template <class T> class nsCOMPtr;
+
+template <class E, class Derived>
+struct nsTArray_SafeElementAtHelper<nsCOMPtr<E>, Derived> :
+  public nsTArray_SafeElementAtSmartPtrHelper<E, Derived>
+{
+};
+
+template <class T> class nsRefPtr;
+
+template <class E, class Derived>
+struct nsTArray_SafeElementAtHelper<nsRefPtr<E>, Derived> :
+  public nsTArray_SafeElementAtSmartPtrHelper<E, Derived>
+{
+};
+
+//
+// This class serves as a base class for nsTArray.  It shouldn't be used
+// directly.  It holds common implementation code that does not depend on the
+// element type of the nsTArray.
+//
+template<class Alloc, class Copy>
+class nsTArray_base
+{
+  // Allow swapping elements with |nsTArray_base|s created using a
+  // different allocator.  This is kosher because all allocators use
+  // the same free().
+  template<class Allocator, class Copier>
+  friend class nsTArray_base;
+
+protected:
+  typedef nsTArrayHeader Header;
+
+public:
+  typedef uint32_t size_type;
+  typedef uint32_t index_type;
+
+  // @return The number of elements in the array.
+  size_type Length() const {
+    return mHdr->mLength;
+  }
+
+  // @return True if the array is empty or false otherwise.
+  bool IsEmpty() const {
+    return Length() == 0;
+  }
+
+  // @return The number of elements that can fit in the array without forcing
+  // the array to be re-allocated.  The length of an array is always less
+  // than or equal to its capacity.
+  size_type Capacity() const {
+    return mHdr->mCapacity;
+  }
+
+#ifdef DEBUG
+  void* DebugGetHeader() const {
+    return mHdr;
+  }
+#endif
+
+protected:
+  nsTArray_base();
+
+  ~nsTArray_base();
+
+  // Resize the storage if necessary to achieve the requested capacity.
+  // @param capacity     The requested number of array elements.
+  // @param elemSize     The size of an array element.
+  // @return False if insufficient memory is available; true otherwise.
+  typename Alloc::ResultTypeProxy EnsureCapacity(size_type capacity, size_type elemSize);
+
+  // Resize the storage to the minimum required amount.
+  // @param elemSize     The size of an array element.
+  // @param elemAlign    The alignment in bytes of an array element.
+  void ShrinkCapacity(size_type elemSize, size_t elemAlign);
+
+  // This method may be called to resize a "gap" in the array by shifting
+  // elements around.  It updates mLength appropriately.  If the resulting
+  // array has zero elements, then the array's memory is free'd.
+  // @param start        The starting index of the gap.
+  // @param oldLen       The current length of the gap.
+  // @param newLen       The desired length of the gap.
+  // @param elemSize     The size of an array element.
+  // @param elemAlign    The alignment in bytes of an array element.
+  void ShiftData(index_type start, size_type oldLen, size_type newLen,
+                 size_type elemSize, size_t elemAlign);
+
+  // This method increments the length member of the array's header.
+  // Note that mHdr may actually be sEmptyHdr in the case where a
+  // zero-length array is inserted into our array. But then n should
+  // always be 0.
+  void IncrementLength(uint32_t n) {
+    if (mHdr == EmptyHdr()) {
+      if (MOZ_UNLIKELY(n != 0)) {
+        // Writing a non-zero length to the empty header would be extremely bad.
+        MOZ_CRASH();
+      }
+    } else {
+      mHdr->mLength += n;
+    }
+  }
+
+  // This method inserts blank slots into the array.
+  // @param index the place to insert the new elements. This must be no
+  //              greater than the current length of the array.
+  // @param count the number of slots to insert
+  // @param elementSize the size of an array element.
+  // @param elemAlign the alignment in bytes of an array element.
+  bool InsertSlotsAt(index_type index, size_type count,
+                       size_type elementSize, size_t elemAlign);
+
+protected:
+  template<class Allocator>
+  typename Alloc::ResultTypeProxy
+  SwapArrayElements(nsTArray_base<Allocator, Copy>& other,
+                    size_type elemSize,
+                    size_t elemAlign);
+
+  // This is an RAII class used in SwapArrayElements.
+  class IsAutoArrayRestorer {
+    public:
+      IsAutoArrayRestorer(nsTArray_base<Alloc, Copy> &array, size_t elemAlign);
+      ~IsAutoArrayRestorer();
+
+    private:
+      nsTArray_base<Alloc, Copy> &mArray;
+      size_t mElemAlign;
+      bool mIsAuto;
+  };
+
+  // Helper function for SwapArrayElements. Ensures that if the array
+  // is an nsAutoTArray that it doesn't use the built-in buffer.
+  bool EnsureNotUsingAutoArrayBuffer(size_type elemSize);
+
+  // Returns true if this nsTArray is an nsAutoTArray with a built-in buffer.
+  bool IsAutoArray() const {
+    return mHdr->mIsAutoArray;
+  }
+
+  // Returns a Header for the built-in buffer of this nsAutoTArray.
+  Header* GetAutoArrayBuffer(size_t elemAlign) {
+    MOZ_ASSERT(IsAutoArray(), "Should be an auto array to call this");
+    return GetAutoArrayBufferUnsafe(elemAlign);
+  }
+  const Header* GetAutoArrayBuffer(size_t elemAlign) const {
+    MOZ_ASSERT(IsAutoArray(), "Should be an auto array to call this");
+    return GetAutoArrayBufferUnsafe(elemAlign);
+  }
+
+  // Returns a Header for the built-in buffer of this nsAutoTArray, but doesn't
+  // assert that we are an nsAutoTArray.
+  Header* GetAutoArrayBufferUnsafe(size_t elemAlign) {
+    return const_cast<Header*>(static_cast<const nsTArray_base<Alloc, Copy>*>(this)->
+                               GetAutoArrayBufferUnsafe(elemAlign));
+  }
+  const Header* GetAutoArrayBufferUnsafe(size_t elemAlign) const;
+
+  // Returns true if this is an nsAutoTArray and it currently uses the
+  // built-in buffer to store its elements.
+  bool UsesAutoArrayBuffer() const;
+
+  // The array's elements (prefixed with a Header).  This pointer is never
+  // null.  If the array is empty, then this will point to sEmptyHdr.
+  Header *mHdr;
+
+  Header* Hdr() const {
+    return mHdr;
+  }
+
+  Header** PtrToHdr() {
+    return &mHdr;
+  }
+
+  static Header* EmptyHdr() {
+    return &Header::sEmptyHdr;
+  }
+};
+
+//
+// This class defines convenience functions for element specific operations.
+// Specialize this template if necessary.
+//
+template<class E>
+class nsTArrayElementTraits
+{
+public:
+  // Invoke the default constructor in place.
+  static inline void Construct(E *e) {
+    // Do NOT call "E()"! That triggers C++ "default initialization"
+    // which zeroes out POD ("plain old data") types such as regular
+    // ints.  We don't want that because it can be a performance issue
+    // and people don't expect it; nsTArray should work like a regular
+    // C/C++ array in this respect.
+    new (static_cast<void *>(e)) E;
+  }
+  // Invoke the copy-constructor in place.
+  template<class A>
+  static inline void Construct(E *e, const A &arg) {
+    typedef typename mozilla::RemoveCV<E>::Type E_NoCV;
+    typedef typename mozilla::RemoveCV<A>::Type A_NoCV;
+    static_assert(!mozilla::IsSame<E_NoCV*, A_NoCV>::value,
+                  "For safety, we disallow constructing nsTArray<E> elements "
+                  "from E* pointers. See bug 960591.");
+    new (static_cast<void *>(e)) E(arg);
+  }
+  // Invoke the destructor in place.
+  static inline void Destruct(E *e) {
+    e->~E();
+  }
+};
+
+// The default comparator used by nsTArray
+template<class A, class B>
+class nsDefaultComparator
+{
+public:
+  bool Equals(const A& a, const B& b) const {
+    return a == b;
+  }
+  bool LessThan(const A& a, const B& b) const {
+    return a < b;
+  }
+};
+
+template <class E> class InfallibleTArray;
+template <class E> class FallibleTArray;
+
+template<bool IsPod, bool IsSameType>
+struct AssignRangeAlgorithm {
+  template<class Item, class ElemType, class IndexType, class SizeType>
+  static void implementation(ElemType* elements, IndexType start,
+                             SizeType count, const Item *values) {
+    ElemType *iter = elements + start, *end = iter + count;
+    for (; iter != end; ++iter, ++values)
+      nsTArrayElementTraits<ElemType>::Construct(iter, *values);
+  }
+};
+
+template<>
+struct AssignRangeAlgorithm<true, true> {
+  template<class Item, class ElemType, class IndexType, class SizeType>
+  static void implementation(ElemType* elements, IndexType start,
+                             SizeType count, const Item *values) {
+    memcpy(elements + start, values, count * sizeof(ElemType));
+  }
+};
+
+//
+// Normally elements are copied with memcpy and memmove, but for some element
+// types that is problematic.  The nsTArray_CopyChooser template class can be
+// specialized to ensure that copying calls constructors and destructors
+// instead, as is done below for JS::Heap<E> elements.
+//
+
+//
+// A class that defines how to copy elements using memcpy/memmove.
+//
+struct nsTArray_CopyWithMemutils
+{
+  const static bool allowRealloc = true;
+
+  static void CopyElements(void* dest, const void* src, size_t count, size_t elemSize) {
+    memcpy(dest, src, count * elemSize);
+  }
+
+  static void CopyHeaderAndElements(void* dest, const void* src, size_t count, size_t elemSize) {
+    memcpy(dest, src, sizeof(nsTArrayHeader) + count * elemSize);
+  }
+
+  static void MoveElements(void* dest, const void* src, size_t count, size_t elemSize) {
+    memmove(dest, src, count * elemSize);
+  }
+};
+
+//
+// A template class that defines how to copy elements calling their constructors
+// and destructors appropriately.
+//
+template <class ElemType>
+struct nsTArray_CopyWithConstructors
+{
+  typedef nsTArrayElementTraits<ElemType> traits;
+
+  const static bool allowRealloc = false;
+
+  static void CopyElements(void* dest, void* src, size_t count, size_t elemSize) {
+    ElemType* destElem = static_cast<ElemType*>(dest);
+    ElemType* srcElem = static_cast<ElemType*>(src);
+    ElemType* destElemEnd = destElem + count;
+#ifdef DEBUG
+    ElemType* srcElemEnd = srcElem + count;
+    MOZ_ASSERT(srcElemEnd <= destElem || srcElemEnd > destElemEnd);
+#endif
+    while (destElem != destElemEnd) {
+      traits::Construct(destElem, *srcElem);
+      traits::Destruct(srcElem);
+      ++destElem;
+      ++srcElem;
+    }
+  }
+
+  static void CopyHeaderAndElements(void* dest, void* src, size_t count, size_t elemSize) {
+    nsTArrayHeader* destHeader = static_cast<nsTArrayHeader*>(dest);
+    nsTArrayHeader* srcHeader = static_cast<nsTArrayHeader*>(src);
+    *destHeader = *srcHeader;
+    CopyElements(static_cast<uint8_t*>(dest) + sizeof(nsTArrayHeader),
+                 static_cast<uint8_t*>(src) + sizeof(nsTArrayHeader),
+                 count, elemSize);
+  }
+
+  static void MoveElements(void* dest, void* src, size_t count, size_t elemSize) {
+    ElemType* destElem = static_cast<ElemType*>(dest);
+    ElemType* srcElem = static_cast<ElemType*>(src);
+    ElemType* destElemEnd = destElem + count;
+    ElemType* srcElemEnd = srcElem + count;
+    if (destElem == srcElem) {
+      return;  // In practice, we don't do this.
+    } else if (srcElemEnd > destElem && srcElemEnd < destElemEnd) {
+      while (destElemEnd != destElem) {
+        --destElemEnd;
+        --srcElemEnd;
+        traits::Construct(destElemEnd, *srcElemEnd);
+        traits::Destruct(srcElem);
+      }
+    } else {
+      CopyElements(dest, src, count, elemSize);
+    }
+  }
+};
+
+//
+// The default behaviour is to use memcpy/memmove for everything.
+//
+template <class E>
+struct nsTArray_CopyChooser {
+  typedef nsTArray_CopyWithMemutils Type;
+};
+
+//
+// Some classes require constructors/destructors to be called, so they are
+// specialized here.
+//
+template <class E>
+struct nsTArray_CopyChooser<JS::Heap<E> > {
+  typedef nsTArray_CopyWithConstructors<JS::Heap<E> > Type;
+};
+
+template<>
+struct nsTArray_CopyChooser<nsRegion> {
+  typedef nsTArray_CopyWithConstructors<nsRegion> Type;
+};
+
+template<>
+struct nsTArray_CopyChooser<nsIntRegion> {
+  typedef nsTArray_CopyWithConstructors<nsIntRegion> Type;
+};
+
+//
+// Base class for nsTArray_Impl that is templated on element type and derived
+// nsTArray_Impl class, to allow extra conversions to be added for specific
+// types.
+//
+template <class E, class Derived>
+struct nsTArray_TypedBase : public nsTArray_SafeElementAtHelper<E, Derived> {};
+
+//
+// Specialization of nsTArray_TypedBase for arrays containing JS::Heap<E>
+// elements.
+//
+// These conversions are safe because JS::Heap<E> and E share the same
+// representation, and since the result of the conversions are const references
+// we won't miss any barriers.
+//
+// The static_cast is necessary to obtain the correct address for the derived
+// class since we are a base class used in multiple inheritance.
+//
+template <class E, class Derived>
+struct nsTArray_TypedBase<JS::Heap<E>, Derived>
+ : public nsTArray_SafeElementAtHelper<JS::Heap<E>, Derived>
+{
+  operator const nsTArray<E>& () {
+    static_assert(sizeof(E) == sizeof(JS::Heap<E>),
+                  "JS::Heap<E> must be binary compatible with E.");
+    Derived* self = static_cast<Derived*>(this);
+    return *reinterpret_cast<nsTArray<E> *>(self);
+  }
+
+  operator const FallibleTArray<E>& () {
+    Derived* self = static_cast<Derived*>(this);
+    return *reinterpret_cast<FallibleTArray<E> *>(self);
+  }
+};
+
+
+//
+// nsTArray_Impl contains most of the guts supporting nsTArray, FallibleTArray,
+// nsAutoTArray, and AutoFallibleTArray.
+//
+// The only situation in which you might need to use nsTArray_Impl in your code
+// is if you're writing code which mutates a TArray which may or may not be
+// infallible.
+//
+// Code which merely reads from a TArray which may or may not be infallible can
+// simply cast the TArray to |const nsTArray&|; both fallible and infallible
+// TArrays can be cast to |const nsTArray&|.
+//
+template<class E, class Alloc>
+class nsTArray_Impl : public nsTArray_base<Alloc, typename nsTArray_CopyChooser<E>::Type>,
+                      public nsTArray_TypedBase<E, nsTArray_Impl<E, Alloc> >
+{
+public:
+  typedef typename nsTArray_CopyChooser<E>::Type     copy_type;
+  typedef nsTArray_base<Alloc, copy_type>            base_type;
+  typedef typename base_type::size_type              size_type;
+  typedef typename base_type::index_type             index_type;
+  typedef E                                          elem_type;
+  typedef nsTArray_Impl<E, Alloc>                    self_type;
+  typedef nsTArrayElementTraits<E>                   elem_traits;
+  typedef nsTArray_SafeElementAtHelper<E, self_type> safeelementat_helper_type;
+
+  using safeelementat_helper_type::SafeElementAt;
+  using base_type::EmptyHdr;
+
+  // A special value that is used to indicate an invalid or unknown index
+  // into the array.
+  enum {
+    NoIndex = index_type(-1)
+  };
+
+  using base_type::Length;
+
+  //
+  // Finalization method
+  //
+
+  ~nsTArray_Impl() { Clear(); }
+
+  //
+  // Initialization methods
+  //
+
+  nsTArray_Impl() {}
+
+  // Initialize this array and pre-allocate some number of elements.
+  explicit nsTArray_Impl(size_type capacity) {
+    SetCapacity(capacity);
+  }
+
+  // The array's copy-constructor performs a 'deep' copy of the given array.
+  // @param other  The array object to copy.
+  //
+  // It's very important that we declare this method as taking |const
+  // self_type&| as opposed to taking |const nsTArray_Impl<E, OtherAlloc>| for
+  // an arbitrary OtherAlloc.
+  //
+  // If we don't declare a constructor taking |const self_type&|, C++ generates
+  // a copy-constructor for this class which merely copies the object's
+  // members, which is obviously wrong.
+  //
+  // You can pass an nsTArray_Impl<E, OtherAlloc> to this method because
+  // nsTArray_Impl<E, X> can be cast to const nsTArray_Impl<E, Y>&.  So the
+  // effect on the API is the same as if we'd declared this method as taking
+  // |const nsTArray_Impl<E, OtherAlloc>&|.
+  explicit nsTArray_Impl(const self_type& other) {
+    AppendElements(other);
+  }
+
+  // Allow converting to a const array with a different kind of allocator,
+  // Since the allocator doesn't matter for const arrays
+  template<typename Allocator>
+  operator const nsTArray_Impl<E, Allocator>&() const {
+    return *reinterpret_cast<const nsTArray_Impl<E, Allocator>*>(this);
+  }
+  // And we have to do this for our subclasses too
+  operator const nsTArray<E>&() const {
+    return *reinterpret_cast<const InfallibleTArray<E>*>(this);
+  }
+  operator const FallibleTArray<E>&() const {
+    return *reinterpret_cast<const FallibleTArray<E>*>(this);
+  }
+
+  // The array's assignment operator performs a 'deep' copy of the given
+  // array.  It is optimized to reuse existing storage if possible.
+  // @param other  The array object to copy.
+  self_type& operator=(const self_type& other) {
+    ReplaceElementsAt(0, Length(), other.Elements(), other.Length());
+    return *this;
+  }
+
+  // Return true if this array has the same length and the same
+  // elements as |other|.
+  template<typename Allocator>
+  bool operator==(const nsTArray_Impl<E, Allocator>& other) const {
+    size_type len = Length();
+    if (len != other.Length())
+      return false;
+
+    // XXX std::equal would be as fast or faster here
+    for (index_type i = 0; i < len; ++i)
+      if (!(operator[](i) == other[i]))
+        return false;
+
+    return true;
+  }
+
+  // Return true if this array does not have the same length and the same
+  // elements as |other|.
+  bool operator!=(const self_type& other) const {
+    return !operator==(other);
+  }
+
+  template<typename Allocator>
+  self_type& operator=(const nsTArray_Impl<E, Allocator>& other) {
+    ReplaceElementsAt(0, Length(), other.Elements(), other.Length());
+    return *this;
+  }
+
+  // @return The amount of memory used by this nsTArray_Impl, excluding
+  // sizeof(*this).
+  size_t SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
+    if (this->UsesAutoArrayBuffer() || Hdr() == EmptyHdr())
+      return 0;
+    return mallocSizeOf(this->Hdr());
+  }
+
+  // @return The amount of memory used by this nsTArray_Impl, including
+  // sizeof(*this).
+  size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
+    return mallocSizeOf(this) + SizeOfExcludingThis(mallocSizeOf);
+  }
+
+  //
+  // Accessor methods
+  //
+
+  // This method provides direct 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.
+  elem_type* Elements() {
+    return reinterpret_cast<elem_type *>(Hdr() + 1);
+  }
+
+  // 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 reinterpret_cast<const elem_type *>(Hdr() + 1);
+  }
+
+  // This method provides direct access to the i'th element of the array.
+  // The given index must be within the array bounds.
+  // @param i  The index of an element in the array.
+  // @return   A reference to the i'th element of the array.
+  elem_type& ElementAt(index_type i) {
+    MOZ_ASSERT(i < Length(), "invalid array index");
+    return Elements()[i];
+  }
+
+  // This method provides direct, readonly access to the i'th element of the
+  // array.  The given index must be within the array bounds.
+  // @param i  The index of an element in the array.
+  // @return   A const reference to the i'th element of the array.
+  const elem_type& ElementAt(index_type i) const {
+    MOZ_ASSERT(i < Length(), "invalid array index");
+    return Elements()[i];
+  }
+
+  // This method provides direct access to the i'th element of the array in
+  // a bounds safe manner. If the requested index is out of bounds the
+  // provided default value is returned.
+  // @param i  The index of an element in the array.
+  // @param def The value to return if the index is out of bounds.
+  elem_type& SafeElementAt(index_type i, elem_type& def) {
+    return i < Length() ? Elements()[i] : def;
+  }
+
+  // This method provides direct access to the i'th element of the array in
+  // a bounds safe manner. If the requested index is out of bounds the
+  // provided default value is returned.
+  // @param i  The index of an element in the array.
+  // @param def The value to return if the index is out of bounds.
+  const elem_type& SafeElementAt(index_type i, const elem_type& def) const {
+    return i < Length() ? Elements()[i] : def;
+  }
+
+  // Shorthand for ElementAt(i)
+  elem_type& operator[](index_type i) {
+    return ElementAt(i);
+  }
+
+  // Shorthand for ElementAt(i)
+  const elem_type& operator[](index_type i) const {
+    return ElementAt(i);
+  }
+
+  // Shorthand for ElementAt(length - 1)
+  elem_type& LastElement() {
+    return ElementAt(Length() - 1);
+  }
+
+  // Shorthand for ElementAt(length - 1)
+  const elem_type& LastElement() const {
+    return ElementAt(Length() - 1);
+  }
+
+  // Shorthand for SafeElementAt(length - 1, def)
+  elem_type& SafeLastElement(elem_type& def) {
+    return SafeElementAt(Length() - 1, def);
+  }
+
+  // Shorthand for SafeElementAt(length - 1, def)
+  const elem_type& SafeLastElement(const elem_type& def) const {
+    return SafeElementAt(Length() - 1, def);
+  }
+
+  //
+  // Search methods
+  //
+
+  // This method searches for the first element in this array that is equal
+  // to the given element.
+  // @param item   The item to search for.
+  // @param comp   The Comparator used to determine element equality.
+  // @return       true if the element was found.
+  template<class Item, class Comparator>
+  bool Contains(const Item& item, const Comparator& comp) const {
+    return IndexOf(item, 0, comp) != NoIndex;
+  }
+
+  // This method searches for the first element in this array that is equal
+  // to the given element.  This method assumes that 'operator==' is defined
+  // for elem_type.
+  // @param item   The item to search for.
+  // @return       true if the element was found.
+  template<class Item>
+  bool Contains(const Item& item) const {
+    return IndexOf(item) != NoIndex;
+  }
+
+  // This method searches for the offset of the first element in this
+  // array that is equal to the given element.
+  // @param item   The item to search for.
+  // @param start  The index to start from.
+  // @param comp   The Comparator used to determine element equality.
+  // @return       The index of the found element or NoIndex if not found.
+  template<class Item, class Comparator>
+  index_type IndexOf(const Item& item, index_type start,
+                     const Comparator& comp) const {
+    const elem_type* iter = Elements() + start, *end = Elements() + Length();
+    for (; iter != end; ++iter) {
+      if (comp.Equals(*iter, item))
+        return index_type(iter - Elements());
+    }
+    return NoIndex;
+  }
+
+  // This method searches for the offset of the first element in this
+  // array that is equal to the given element.  This method assumes
+  // that 'operator==' is defined for elem_type.
+  // @param item   The item to search for.
+  // @param start  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& item, index_type start = 0) const {
+    return IndexOf(item, start, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // This method searches for the offset of the last element in this
+  // array that is equal to the given element.
+  // @param item   The item to search for.
+  // @param start  The index to start from.  If greater than or equal to the
+  //               length of the array, then the entire array is searched.
+  // @param comp   The Comparator used to determine element equality.
+  // @return       The index of the found element or NoIndex if not found.
+  template<class Item, class Comparator>
+  index_type LastIndexOf(const Item& item, index_type start,
+                         const Comparator& comp) const {
+    size_type endOffset = start >= Length() ? Length() : start + 1;
+    const elem_type* end = Elements() - 1, *iter = end + endOffset;
+    for (; iter != end; --iter) {
+      if (comp.Equals(*iter, item))
+        return index_type(iter - Elements());
+    }
+    return NoIndex;
+  }
+
+  // This method searches for the offset of the last element in this
+  // array that is equal to the given element.  This method assumes
+  // that 'operator==' is defined for elem_type.
+  // @param item   The item to search for.
+  // @param start  The index to start from.  If greater than or equal to the
+  //               length of the array, then the entire array is searched.
+  // @return       The index of the found element or NoIndex if not found.
+  template<class Item>
+  index_type LastIndexOf(const Item& item,
+                         index_type start = NoIndex) const {
+    return LastIndexOf(item, start, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // This method searches for the offset for the element in this array
+  // that is equal to the given element. The array is assumed to be sorted.
+  // @param item   The item to search for.
+  // @param comp   The Comparator used.
+  // @return       The index of the found element or NoIndex if not found.
+  template<class Item, class Comparator>
+  index_type BinaryIndexOf(const Item& item, const Comparator& comp) const {
+    index_type low = 0, high = Length();
+    while (high > low) {
+      index_type mid = (high + low) >> 1;
+      if (comp.Equals(ElementAt(mid), item))
+        return mid;
+      if (comp.LessThan(ElementAt(mid), item))
+        low = mid + 1;
+      else
+        high = mid;
+    }
+    return NoIndex;
+  }
+
+  // This method searches for the offset for the element in this array
+  // that is equal to the given element. The array is assumed to be sorted.
+  // This method assumes that 'operator==' and 'operator<' are defined.
+  // @param item   The item to search for.
+  // @return       The index of the found element or NoIndex if not found.
+  template<class Item>
+  index_type BinaryIndexOf(const Item& item) const {
+    return BinaryIndexOf(item, nsDefaultComparator<elem_type, Item>());
+  }
+
+  //
+  // Mutation methods
+  //
+  // This method call the destructor on each element of the array, empties it,
+  // but does not shrink the array's capacity.
+  // See also SetLengthAndRetainStorage.
+  // Make sure to call Compact() if needed to avoid keeping a huge array
+  // around.
+  void ClearAndRetainStorage() {
+    if (base_type::mHdr == EmptyHdr()) {
+      return;
+    }
+
+    DestructRange(0, Length());
+    base_type::mHdr->mLength = 0;
+  }
+
+  // This method modifies the length of the array, but unlike SetLength
+  // it doesn't deallocate/reallocate the current internal storage.
+  // The new length MUST be shorter than or equal to the current capacity.
+  // If the new length is larger than the existing length of the array,
+  // then new elements will be constructed using elem_type's default
+  // constructor.  If shorter, elements will be destructed and removed.
+  // See also ClearAndRetainStorage.
+  // @param newLen  The desired length of this array.
+  void SetLengthAndRetainStorage(size_type newLen) {
+    MOZ_ASSERT(newLen <= base_type::Capacity());
+    size_type oldLen = Length();
+    if (newLen > oldLen) {
+      InsertElementsAt(oldLen, newLen - oldLen);
+      return;
+    }
+    if (newLen < oldLen) {
+      DestructRange(newLen, oldLen - newLen);
+      base_type::mHdr->mLength = newLen;
+    }
+  }
+
+  // This method replaces a range of elements in this array.
+  // @param start     The starting index of the elements to replace.
+  // @param count     The number of elements to replace.  This may be zero to
+  //                  insert elements without removing any existing elements.
+  // @param array     The values to copy into this array.  Must be non-null,
+  //                  and these elements must not already exist in the array
+  //                  being modified.
+  // @param arrayLen  The number of values to copy into this array.
+  // @return          A pointer to the new elements in the array, or null if
+  //                  the operation failed due to insufficient memory.
+  template<class Item>
+  elem_type *ReplaceElementsAt(index_type start, size_type count,
+                               const Item* array, size_type arrayLen) {
+    // Adjust memory allocation up-front to catch errors.
+    if (!Alloc::Successful(this->EnsureCapacity(Length() + arrayLen - count, sizeof(elem_type))))
+      return nullptr;
+    DestructRange(start, count);
+    this->ShiftData(start, count, arrayLen, sizeof(elem_type), MOZ_ALIGNOF(elem_type));
+    AssignRange(start, arrayLen, array);
+    return Elements() + start;
+  }
+
+  // A variation on the ReplaceElementsAt method defined above.
+  template<class Item>
+  elem_type *ReplaceElementsAt(index_type start, size_type count,
+                               const nsTArray<Item>& array) {
+    return ReplaceElementsAt(start, count, array.Elements(), array.Length());
+  }
+
+  // A variation on the ReplaceElementsAt method defined above.
+  template<class Item>
+  elem_type *ReplaceElementsAt(index_type start, size_type count,
+                               const Item& item) {
+    return ReplaceElementsAt(start, count, &item, 1);
+  }
+
+  // A variation on the ReplaceElementsAt method defined above.
+  template<class Item>
+  elem_type *ReplaceElementAt(index_type index, const Item& item) {
+    return ReplaceElementsAt(index, 1, &item, 1);
+  }
+
+  // A variation on the ReplaceElementsAt method defined above.
+  template<class Item>
+  elem_type *InsertElementsAt(index_type index, const Item* array,
+                              size_type arrayLen) {
+    return ReplaceElementsAt(index, 0, array, arrayLen);
+  }
+
+  // A variation on the ReplaceElementsAt method defined above.
+  template<class Item, class Allocator>
+  elem_type *InsertElementsAt(index_type index, const nsTArray_Impl<Item, Allocator>& array) {
+    return ReplaceElementsAt(index, 0, array.Elements(), array.Length());
+  }
+
+  // A variation on the ReplaceElementsAt method defined above.
+  template<class Item>
+  elem_type *InsertElementAt(index_type index, const Item& item) {
+    return ReplaceElementsAt(index, 0, &item, 1);
+  }
+
+  // Insert a new element without copy-constructing. This is useful to avoid
+  // temporaries.
+  // @return A pointer to the newly inserted element, or null on OOM.
+  elem_type* InsertElementAt(index_type index) {
+    if (!Alloc::Successful(this->EnsureCapacity(Length() + 1, sizeof(elem_type))))
+      return nullptr;
+    this->ShiftData(index, 0, 1, sizeof(elem_type), MOZ_ALIGNOF(elem_type));
+    elem_type *elem = Elements() + index;
+    elem_traits::Construct(elem);
+    return elem;
+  }
+
+  // This method searches for the smallest index of an element that is strictly
+  // greater than |item|.  If |item| is inserted at this index, the array will
+  // remain sorted and |item| would come after all elements that are equal to
+  // it.  If |item| is greater than or equal to all elements in the array, the
+  // array length is returned.
+  //
+  // Note that consumers who want to know whether there are existing items equal
+  // to |item| in the array can just check that the return value here is > 0 and
+  // indexing into the previous slot gives something equal to |item|.
+  //
+  //
+  // @param item   The item to search for.
+  // @param comp   The Comparator used.
+  // @return        The index of greatest element <= to |item|
+  // @precondition The array is sorted
+  template<class Item, class Comparator>
+  index_type
+  IndexOfFirstElementGt(const Item& item,
+                        const Comparator& comp) const {
+    // invariant: low <= [idx] <= high
+    index_type low = 0, high = Length();
+    while (high > low) {
+      index_type mid = (high + low) >> 1;
+      // Comparators are not required to provide a LessThan(Item&, elem_type),
+      // so we can't do comp.LessThan(item, ElementAt(mid)).
+      if (comp.LessThan(ElementAt(mid), item) ||
+          comp.Equals(ElementAt(mid), item)) {
+        // item >= ElementAt(mid), so our desired index is at least mid+1.
+        low = mid + 1;
+      } else {
+        // item < ElementAt(mid).  Our desired index is therefore at most mid.
+        high = mid;
+      }
+    }
+    MOZ_ASSERT(high == low);
+    return low;
+  }
+
+  // A variation on the IndexOfFirstElementGt method defined above.
+  template<class Item>
+  index_type
+  IndexOfFirstElementGt(const Item& item) const {
+    return IndexOfFirstElementGt(item, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // Inserts |item| at such an index to guarantee that if the array
+  // was previously sorted, it will remain sorted after this
+  // insertion.
+  template<class Item, class Comparator>
+  elem_type *InsertElementSorted(const Item& item, const Comparator& comp) {
+    index_type index = IndexOfFirstElementGt(item, comp);
+    return InsertElementAt(index, item);
+  }
+
+  // A variation on the InsertElementSorted method defined above.
+  template<class Item>
+  elem_type *InsertElementSorted(const Item& item) {
+    return InsertElementSorted(item, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // This method appends elements to the end of this array.
+  // @param array     The elements to append to this array.
+  // @param arrayLen  The number of elements to append to this array.
+  // @return          A pointer to the new elements in the array, or null if
+  //                  the operation failed due to insufficient memory.
+  template<class Item>
+  elem_type *AppendElements(const Item* array, size_type arrayLen) {
+    if (!Alloc::Successful(this->EnsureCapacity(Length() + arrayLen, sizeof(elem_type))))
+      return nullptr;
+    index_type len = Length();
+    AssignRange(len, arrayLen, array);
+    this->IncrementLength(arrayLen);
+    return Elements() + len;
+  }
+
+  // A variation on the AppendElements method defined above.
+  template<class Item, class Allocator>
+  elem_type *AppendElements(const nsTArray_Impl<Item, Allocator>& array) {
+    return AppendElements(array.Elements(), array.Length());
+  }
+
+  // A variation on the AppendElements method defined above.
+  template<class Item>
+  elem_type *AppendElement(const Item& item) {
+    return AppendElements(&item, 1);
+  }
+
+  // Append new elements without copy-constructing. This is useful to avoid
+  // temporaries.
+  // @return A pointer to the newly appended elements, or null on OOM.
+  elem_type *AppendElements(size_type count) {
+    if (!Alloc::Successful(this->EnsureCapacity(Length() + count, sizeof(elem_type))))
+      return nullptr;
+    elem_type *elems = Elements() + Length();
+    size_type i;
+    for (i = 0; i < count; ++i) {
+      elem_traits::Construct(elems + i);
+    }
+    this->IncrementLength(count);
+    return elems;
+  }
+
+  // Append a new element without copy-constructing. This is useful to avoid
+  // temporaries.
+  // @return A pointer to the newly appended element, or null on OOM.
+  elem_type *AppendElement() {
+    return AppendElements(1);
+  }
+
+  // Move all elements from another array to the end of this array without
+  // calling copy constructors or destructors.
+  // @return A pointer to the newly appended elements, or null on OOM.
+  template<class Item, class Allocator>
+  elem_type *MoveElementsFrom(nsTArray_Impl<Item, Allocator>& array) {
+    MOZ_ASSERT(&array != this, "argument must be different array");
+    index_type len = Length();
+    index_type otherLen = array.Length();
+    if (!Alloc::Successful(this->EnsureCapacity(len + otherLen, sizeof(elem_type))))
+      return nullptr;
+    copy_type::CopyElements(Elements() + len, array.Elements(), otherLen, sizeof(elem_type));
+    this->IncrementLength(otherLen);
+    array.ShiftData(0, otherLen, 0, sizeof(elem_type), MOZ_ALIGNOF(elem_type));
+    return Elements() + len;
+  }
+
+  // This method removes a range of elements from this array.
+  // @param start  The starting index of the elements to remove.
+  // @param count  The number of elements to remove.
+  void RemoveElementsAt(index_type start, size_type count) {
+    MOZ_ASSERT(count == 0 || start < Length(), "Invalid start index");
+    MOZ_ASSERT(start + count <= Length(), "Invalid length");
+    // Check that the previous assert didn't overflow
+    MOZ_ASSERT(start <= start + count, "Start index plus length overflows");
+    DestructRange(start, count);
+    this->ShiftData(start, count, 0, sizeof(elem_type), MOZ_ALIGNOF(elem_type));
+  }
+
+  // A variation on the RemoveElementsAt method defined above.
+  void RemoveElementAt(index_type index) {
+    RemoveElementsAt(index, 1);
+  }
+
+  // A variation on the RemoveElementsAt method defined above.
+  void Clear() {
+    RemoveElementsAt(0, Length());
+  }
+
+  // This helper function combines IndexOf with RemoveElementAt to "search
+  // and destroy" the first element that is equal to the given element.
+  // @param item  The item to search for.
+  // @param comp  The Comparator used to determine element equality.
+  // @return true if the element was found
+  template<class Item, class Comparator>
+  bool RemoveElement(const Item& item, const Comparator& comp) {
+    index_type i = IndexOf(item, 0, comp);
+    if (i == NoIndex)
+      return false;
+
+    RemoveElementAt(i);
+    return true;
+  }
+
+  // A variation on the RemoveElement method defined above that assumes
+  // that 'operator==' is defined for elem_type.
+  template<class Item>
+  bool RemoveElement(const Item& item) {
+    return RemoveElement(item, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // This helper function combines IndexOfFirstElementGt with
+  // RemoveElementAt to "search and destroy" the last element that
+  // is equal to the given element.
+  // @param item  The item to search for.
+  // @param comp  The Comparator used to determine element equality.
+  // @return true if the element was found
+  template<class Item, class Comparator>
+  bool RemoveElementSorted(const Item& item, const Comparator& comp) {
+    index_type index = IndexOfFirstElementGt(item, comp);
+    if (index > 0 && comp.Equals(ElementAt(index - 1), item)) {
+      RemoveElementAt(index - 1);
+      return true;
+    }
+    return false;
+  }
+
+  // A variation on the RemoveElementSorted method defined above.
+  template<class Item>
+  bool RemoveElementSorted(const Item& item) {
+    return RemoveElementSorted(item, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // This method causes the elements contained in this array and the given
+  // array to be swapped.
+  template<class Allocator>
+  typename Alloc::ResultType
+  SwapElements(nsTArray_Impl<E, Allocator>& other) {
+    return Alloc::Result(this->SwapArrayElements(other, sizeof(elem_type),
+                                                 MOZ_ALIGNOF(elem_type)));
+  }
+
+  //
+  // Allocation
+  //
+
+  // This method may increase the capacity of this array object by the
+  // specified amount.  This method may be called in advance of several
+  // AppendElement operations to minimize heap re-allocations.  This method
+  // will not reduce the number of elements in this array.
+  // @param capacity  The desired capacity of this array.
+  // @return True if the operation succeeded; false if we ran out of memory
+  typename Alloc::ResultType SetCapacity(size_type capacity) {
+    return Alloc::Result(this->EnsureCapacity(capacity, sizeof(elem_type)));
+  }
+
+  // This method modifies the length of the array.  If the new length is
+  // larger than the existing length of the array, then new elements will be
+  // constructed using elem_type's default constructor.  Otherwise, this call
+  // removes elements from the array (see also RemoveElementsAt).
+  // @param newLen  The desired length of this array.
+  // @return        True if the operation succeeded; false otherwise.
+  // See also TruncateLength if the new length is guaranteed to be
+  // smaller than the old.
+  typename Alloc::ResultType SetLength(size_type newLen) {
+    size_type oldLen = Length();
+    if (newLen > oldLen) {
+      return Alloc::ConvertBoolToResultType(InsertElementsAt(oldLen, newLen - oldLen) != nullptr);
+    }
+
+    TruncateLength(newLen);
+    return Alloc::ConvertBoolToResultType(true);
+  }
+
+  // This method modifies the length of the array, but may only be
+  // called when the new length is shorter than the old.  It can
+  // therefore be called when elem_type has no default constructor,
+  // unlike SetLength.  It removes elements from the array (see also
+  // RemoveElementsAt).
+  // @param newLen  The desired length of this array.
+  void TruncateLength(size_type newLen) {
+    size_type oldLen = Length();
+    NS_ABORT_IF_FALSE(newLen <= oldLen,
+                      "caller should use SetLength instead");
+    RemoveElementsAt(newLen, oldLen - newLen);
+  }
+
+  // This method ensures that the array has length at least the given
+  // length.  If the current length is shorter than the given length,
+  // then new elements will be constructed using elem_type's default
+  // constructor.
+  // @param minLen  The desired minimum length of this array.
+  // @return        True if the operation succeeded; false otherwise.
+typename Alloc::ResultType EnsureLengthAtLeast(size_type minLen) {
+    size_type oldLen = Length();
+    if (minLen > oldLen) {
+      return Alloc::ConvertBoolToResultType(!!InsertElementsAt(oldLen, minLen - oldLen));
+    }
+    return Alloc::ConvertBoolToResultType(true);
+  }
+
+  // This method inserts elements into the array, constructing
+  // them using elem_type's default constructor.
+  // @param index the place to insert the new elements. This must be no
+  //              greater than the current length of the array.
+  // @param count the number of elements to insert
+  elem_type *InsertElementsAt(index_type index, size_type count) {
+    if (!base_type::InsertSlotsAt(index, count, sizeof(elem_type), MOZ_ALIGNOF(elem_type))) {
+      return nullptr;
+    }
+
+    // Initialize the extra array elements
+    elem_type *iter = Elements() + index, *end = iter + count;
+    for (; iter != end; ++iter) {
+      elem_traits::Construct(iter);
+    }
+
+    return Elements() + index;
+  }
+
+  // This method inserts elements into the array, constructing them
+  // elem_type's copy constructor (or whatever one-arg constructor
+  // happens to match the Item type).
+  // @param index the place to insert the new elements. This must be no
+  //              greater than the current length of the array.
+  // @param count the number of elements to insert.
+  // @param item the value to use when constructing the new elements.
+  template<class Item>
+  elem_type *InsertElementsAt(index_type index, size_type count,
+                              const Item& item) {
+    if (!base_type::InsertSlotsAt(index, count, sizeof(elem_type), MOZ_ALIGNOF(elem_type))) {
+      return nullptr;
+    }
+
+    // Initialize the extra array elements
+    elem_type *iter = Elements() + index, *end = iter + count;
+    for (; iter != end; ++iter) {
+      elem_traits::Construct(iter, item);
+    }
+
+    return Elements() + index;
+  }
+
+  // This method may be called to minimize the memory used by this array.
+  void Compact() {
+    ShrinkCapacity(sizeof(elem_type), MOZ_ALIGNOF(elem_type));
+  }
+
+  //
+  // Sorting
+  //
+
+  // This function is meant to be used with the NS_QuickSort function.  It
+  // maps the callback API expected by NS_QuickSort to the Comparator API
+  // used by nsTArray_Impl.  See nsTArray_Impl::Sort.
+  template<class Comparator>
+  static int Compare(const void* e1, const void* e2, void *data) {
+    const Comparator* c = reinterpret_cast<const Comparator*>(data);
+    const elem_type* a = static_cast<const elem_type*>(e1);
+    const elem_type* b = static_cast<const elem_type*>(e2);
+    return c->LessThan(*a, *b) ? -1 : (c->Equals(*a, *b) ? 0 : 1);
+  }
+
+  // This method sorts the elements of the array.  It uses the LessThan
+  // method defined on the given Comparator object to collate elements.
+  // @param comp The Comparator used to collate elements.
+  template<class Comparator>
+  void Sort(const Comparator& comp) {
+    NS_QuickSort(Elements(), Length(), sizeof(elem_type),
+                 Compare<Comparator>, const_cast<Comparator*>(&comp));
+  }
+
+  // A variation on the Sort method defined above that assumes that
+  // 'operator<' is defined for elem_type.
+  void Sort() {
+    Sort(nsDefaultComparator<elem_type, elem_type>());
+  }
+
+  //
+  // Binary Heap
+  //
+
+  // Sorts the array into a binary heap.
+  // @param comp The Comparator used to create the heap
+  template<class Comparator>
+  void MakeHeap(const Comparator& comp) {
+    if (!Length()) {
+      return;
+    }
+    index_type index = (Length() - 1) / 2;
+    do {
+      SiftDown(index, comp);
+    } while (index--);
+  }
+
+  // A variation on the MakeHeap method defined above.
+  void MakeHeap() {
+    MakeHeap(nsDefaultComparator<elem_type, elem_type>());
+  }
+
+  // Adds an element to the heap
+  // @param item The item to add
+  // @param comp The Comparator used to sift-up the item
+  template<class Item, class Comparator>
+  elem_type *PushHeap(const Item& item, const Comparator& comp) {
+    if (!base_type::InsertSlotsAt(Length(), 1, sizeof(elem_type), MOZ_ALIGNOF(elem_type))) {
+      return nullptr;
+    }
+    // Sift up the new node
+    elem_type *elem = Elements();
+    index_type index = Length() - 1;
+    index_type parent_index = (index - 1) / 2;
+    while (index && comp.LessThan(elem[parent_index], item)) {
+      elem[index] = elem[parent_index];
+      index = parent_index;
+      parent_index = (index - 1) / 2;
+    }
+    elem[index] = item;
+    return &elem[index];
+  }
+
+  // A variation on the PushHeap method defined above.
+  template<class Item>
+  elem_type *PushHeap(const Item& item) {
+    return PushHeap(item, nsDefaultComparator<elem_type, Item>());
+  }
+
+  // Delete the root of the heap and restore the heap
+  // @param comp The Comparator used to restore the heap
+  template<class Comparator>
+  void PopHeap(const Comparator& comp) {
+    if (!Length()) {
+      return;
+    }
+    index_type last_index = Length() - 1;
+    elem_type *elem = Elements();
+    elem[0] = elem[last_index];
+    TruncateLength(last_index);
+    if (Length()) {
+      SiftDown(0, comp);
+    }
+  }
+
+  // A variation on the PopHeap method defined above.
+  void PopHeap() {
+    PopHeap(nsDefaultComparator<elem_type, elem_type>());
+  }
+
+protected:
+  using base_type::Hdr;
+  using base_type::ShrinkCapacity;
+
+  // This method invokes elem_type's destructor on a range of elements.
+  // @param start  The index of the first element to destroy.
+  // @param count  The number of elements to destroy.
+  void DestructRange(index_type start, size_type count) {
+    elem_type *iter = Elements() + start, *end = iter + count;
+    for (; iter != end; ++iter) {
+      elem_traits::Destruct(iter);
+    }
+  }
+
+  // This method invokes elem_type's copy-constructor on a range of elements.
+  // @param start   The index of the first element to construct.
+  // @param count   The number of elements to construct.
+  // @param values  The array of elements to copy.
+  template<class Item>
+  void AssignRange(index_type start, size_type count,
+                   const Item *values) {
+    AssignRangeAlgorithm<mozilla::IsPod<Item>::value,
+                         mozilla::IsSame<Item, elem_type>::value>
+      ::implementation(Elements(), start, count, values);
+  }
+
+  // This method sifts an item down to its proper place in a binary heap
+  // @param index The index of the node to start sifting down from
+  // @param comp  The Comparator used to sift down
+  template<class Comparator>
+  void SiftDown(index_type index, const Comparator& comp) {
+    elem_type *elem = Elements();
+    elem_type item = elem[index];
+    index_type end = Length() - 1;
+    while ((index * 2) < end) {
+      const index_type left = (index * 2) + 1;
+      const index_type right = (index * 2) + 2;
+      const index_type parent_index = index;
+      if (comp.LessThan(item, elem[left])) {
+        if (left < end &&
+            comp.LessThan(elem[left], elem[right])) {
+          index = right;
+        } else {
+          index = left;
+        }
+      } else if (left < end &&
+                 comp.LessThan(item, elem[right])) {
+        index = right;
+      } else {
+        break;
+      }
+      elem[parent_index] = elem[index];
+    }
+    elem[index] = item;
+  }
+};
+
+template <typename E, typename Alloc>
+inline void
+ImplCycleCollectionUnlink(nsTArray_Impl<E, Alloc>& aField)
+{
+  aField.Clear();
+}
+
+template <typename E, typename Alloc>
+inline void
+ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
+                            nsTArray_Impl<E, Alloc>& aField,
+                            const char* aName,
+                            uint32_t aFlags = 0)
+{
+  aFlags |= CycleCollectionEdgeNameArrayFlag;
+  uint32_t length = aField.Length();
+  for (uint32_t i = 0; i < length; ++i) {
+    ImplCycleCollectionTraverse(aCallback, aField[i], aName, aFlags);
+  }
+}
+
+//
+// nsTArray is an infallible vector class.  See the comment at the top of this
+// file for more details.
+//
+template <class E>
+class nsTArray : public nsTArray_Impl<E, nsTArrayInfallibleAllocator>
+{
+public:
+  typedef nsTArray_Impl<E, nsTArrayInfallibleAllocator> base_type;
+  typedef nsTArray<E>                                   self_type;
+  typedef typename base_type::size_type                 size_type;
+
+  nsTArray() {}
+  explicit nsTArray(size_type capacity) : base_type(capacity) {}
+  explicit nsTArray(const nsTArray& other) : base_type(other) {}
+
+  template<class Allocator>
+  explicit nsTArray(const nsTArray_Impl<E, Allocator>& other) : base_type(other) {}
+};
+
+//
+// FallibleTArray is a fallible vector class.
+//
+template <class E>
+class FallibleTArray : public nsTArray_Impl<E, nsTArrayFallibleAllocator>
+{
+public:
+  typedef nsTArray_Impl<E, nsTArrayFallibleAllocator>   base_type;
+  typedef FallibleTArray<E>                             self_type;
+  typedef typename base_type::size_type                 size_type;
+
+  FallibleTArray() {}
+  explicit FallibleTArray(size_type capacity) : base_type(capacity) {}
+  explicit FallibleTArray(const FallibleTArray<E>& other) : base_type(other) {}
+
+  template<class Allocator>
+  explicit FallibleTArray(const nsTArray_Impl<E, Allocator>& other) : base_type(other) {}
+};
+
+//
+// nsAutoArrayBase is a base class for AutoFallibleTArray and nsAutoTArray.
+// You shouldn't use this class directly.
+//
+template <class TArrayBase, uint32_t N>
+class nsAutoArrayBase : public TArrayBase
+{
+public:
+  typedef nsAutoArrayBase<TArrayBase, N> self_type;
+  typedef TArrayBase base_type;
+  typedef typename base_type::Header Header;
+  typedef typename base_type::elem_type elem_type;
+
+  template<typename Allocator>
+  self_type& operator=(const nsTArray_Impl<elem_type, Allocator>& other) {
+    base_type::operator=(other);
+    return *this;
+  }
+
+protected:
+  nsAutoArrayBase() {
+    Init();
+  }
+
+  // We need this constructor because nsAutoTArray and friends all have
+  // implicit copy-constructors.  If we don't have this method, those
+  // copy-constructors will call nsAutoArrayBase's implicit copy-constructor,
+  // which won't call Init() and set up the auto buffer!
+  nsAutoArrayBase(const self_type &aOther) {
+    Init();
+    this->AppendElements(aOther);
+  }
+
+private:
+  // nsTArray_base casts itself as an nsAutoArrayBase in order to get a pointer
+  // to mAutoBuf.
+  template<class Allocator, class Copier>
+  friend class nsTArray_base;
+
+  void Init() {
+    static_assert(MOZ_ALIGNOF(elem_type) <= 8,
+                  "can't handle alignments greater than 8, "
+                  "see nsTArray_base::UsesAutoArrayBuffer()");
+    // Temporary work around for VS2012 RC compiler crash
+    Header** phdr = base_type::PtrToHdr();
+    *phdr = reinterpret_cast<Header*>(&mAutoBuf);
+    (*phdr)->mLength = 0;
+    (*phdr)->mCapacity = N;
+    (*phdr)->mIsAutoArray = 1;
+
+    MOZ_ASSERT(base_type::GetAutoArrayBuffer(MOZ_ALIGNOF(elem_type)) ==
+               reinterpret_cast<Header*>(&mAutoBuf),
+               "GetAutoArrayBuffer needs to be fixed");
+  }
+
+  // Declare mAutoBuf aligned to the maximum of the header's alignment and
+  // elem_type's alignment.  We need to use a union rather than
+  // MOZ_ALIGNED_DECL because GCC is picky about what goes into
+  // __attribute__((aligned(foo))).
+  union {
+    char mAutoBuf[sizeof(nsTArrayHeader) + N * sizeof(elem_type)];
+    // Do the max operation inline to ensure that it is a compile-time constant.
+    mozilla::AlignedElem<(MOZ_ALIGNOF(Header) > MOZ_ALIGNOF(elem_type))
+                         ? MOZ_ALIGNOF(Header) : MOZ_ALIGNOF(elem_type)> mAlign;
+  };
+};
+
+//
+// nsAutoTArray<E, N> is an infallible vector class with N elements of inline
+// storage.  If you try to store more than N elements inside an
+// nsAutoTArray<E, N>, we'll call malloc() and store them all on the heap.
+//
+// Note that you can cast an nsAutoTArray<E, N> to
+// |const AutoFallibleTArray<E, N>&|.
+//
+template<class E, uint32_t N>
+class nsAutoTArray : public nsAutoArrayBase<nsTArray<E>, N>
+{
+  typedef nsAutoTArray<E, N> self_type;
+  typedef nsAutoArrayBase<nsTArray<E>, N> Base;
+
+public:
+  nsAutoTArray() {}
+
+  template<typename Allocator>
+  explicit nsAutoTArray(const nsTArray_Impl<E, Allocator>& other) {
+    Base::AppendElements(other);
+  }
+
+  operator const AutoFallibleTArray<E, N>&() const {
+    return *reinterpret_cast<const AutoFallibleTArray<E, N>*>(this);
+  }
+};
+
+//
+// AutoFallibleTArray<E, N> is a fallible vector class with N elements of
+// inline storage.
+//
+template<class E, uint32_t N>
+class AutoFallibleTArray : public nsAutoArrayBase<FallibleTArray<E>, N>
+{
+  typedef AutoFallibleTArray<E, N> self_type;
+  typedef nsAutoArrayBase<FallibleTArray<E>, N> Base;
+
+public:
+  AutoFallibleTArray() {}
+
+  template<typename Allocator>
+  explicit AutoFallibleTArray(const nsTArray_Impl<E, Allocator>& other) {
+    Base::AppendElements(other);
+  }
+
+  operator const nsAutoTArray<E, N>&() const {
+    return *reinterpret_cast<const nsAutoTArray<E, N>*>(this);
+  }
+};
+
+// Assert that nsAutoTArray doesn't have any extra padding inside.
+//
+// It's important that the data stored in this auto array takes up a multiple of
+// 8 bytes; e.g. nsAutoTArray<uint32_t, 1> wouldn't work.  Since nsAutoTArray
+// contains a pointer, its size must be a multiple of alignof(void*).  (This is
+// because any type may be placed into an array, and there's no padding between
+// elements of an array.)  The compiler pads the end of the structure to
+// enforce this rule.
+//
+// If we used nsAutoTArray<uint32_t, 1> below, this assertion would fail on a
+// 64-bit system, where the compiler inserts 4 bytes of padding at the end of
+// the auto array to make its size a multiple of alignof(void*) == 8 bytes.
+
+static_assert(sizeof(nsAutoTArray<uint32_t, 2>) ==
+              sizeof(void*) + sizeof(nsTArrayHeader) + sizeof(uint32_t) * 2,
+              "nsAutoTArray shouldn't contain any extra padding, "
+              "see the comment");
+
+// Definitions of nsTArray_Impl methods
+#include "nsTArray-inl.h"
+
+#endif  // nsTArray_h__