diff -r 000000000000 -r 6474c204b198 xpcom/glue/nsTArray-inl.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/glue/nsTArray-inl.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,420 @@
+/* -*- 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__
+#  error "Don't include this file directly"
+#endif
+
+template<class Alloc, class Copy>
+nsTArray_base<Alloc, Copy>::nsTArray_base()
+  : mHdr(EmptyHdr()) {
+  MOZ_COUNT_CTOR(nsTArray_base);
+}
+
+template<class Alloc, class Copy>
+nsTArray_base<Alloc, Copy>::~nsTArray_base() {
+  if (mHdr != EmptyHdr() && !UsesAutoArrayBuffer()) {
+    Alloc::Free(mHdr);
+  }
+  MOZ_COUNT_DTOR(nsTArray_base);
+}
+
+template<class Alloc, class Copy>
+const nsTArrayHeader* nsTArray_base<Alloc, Copy>::GetAutoArrayBufferUnsafe(size_t elemAlign) const {
+  // Assuming |this| points to an nsAutoArray, we want to get a pointer to
+  // mAutoBuf.  So just cast |this| to nsAutoArray* and read &mAutoBuf!
+
+  const void* autoBuf = &reinterpret_cast<const nsAutoArrayBase<nsTArray<uint32_t>, 1>*>(this)->mAutoBuf;
+
+  // If we're on a 32-bit system and elemAlign is 8, we need to adjust our
+  // pointer to take into account the extra alignment in the auto array.
+
+  static_assert(sizeof(void*) != 4 ||
+                (MOZ_ALIGNOF(mozilla::AlignedElem<8>) == 8 &&
+                 sizeof(nsAutoTArray<mozilla::AlignedElem<8>, 1>) ==
+                   sizeof(void*) + sizeof(nsTArrayHeader) +
+                   4 + sizeof(mozilla::AlignedElem<8>)),
+                "auto array padding wasn't what we expected");
+
+  // We don't support alignments greater than 8 bytes.
+  NS_ABORT_IF_FALSE(elemAlign <= 4 || elemAlign == 8, "unsupported alignment.");
+  if (sizeof(void*) == 4 && elemAlign == 8) {
+    autoBuf = reinterpret_cast<const char*>(autoBuf) + 4;
+  }
+
+  return reinterpret_cast<const Header*>(autoBuf);
+}
+
+template<class Alloc, class Copy>
+bool nsTArray_base<Alloc, Copy>::UsesAutoArrayBuffer() const {
+  if (!mHdr->mIsAutoArray) {
+    return false;
+  }
+
+  // This is nuts.  If we were sane, we'd pass elemAlign as a parameter to
+  // this function.  Unfortunately this function is called in nsTArray_base's
+  // destructor, at which point we don't know elem_type's alignment.
+  //
+  // We'll fall on our face and return true when we should say false if
+  //
+  //   * we're not using our auto buffer,
+  //   * elemAlign == 4, and
+  //   * mHdr == GetAutoArrayBuffer(8).
+  //
+  // This could happen if |*this| lives on the heap and malloc allocated our
+  // buffer on the heap adjacent to |*this|.
+  //
+  // However, we can show that this can't happen.  If |this| is an auto array
+  // (as we ensured at the beginning of the method), GetAutoArrayBuffer(8)
+  // always points to memory owned by |*this|, because (as we assert below)
+  //
+  //   * GetAutoArrayBuffer(8) is at most 4 bytes past GetAutoArrayBuffer(4), and 
+  //   * sizeof(nsTArrayHeader) > 4.
+  //
+  // Since nsAutoTArray always contains an nsTArrayHeader,
+  // GetAutoArrayBuffer(8) will always point inside the auto array object,
+  // even if it doesn't point at the beginning of the header.
+  //
+  // Note that this means that we can't store elements with alignment 16 in an
+  // nsTArray, because GetAutoArrayBuffer(16) could lie outside the memory
+  // owned by this nsAutoTArray.  We statically assert that elem_type's
+  // alignment is 8 bytes or less in nsAutoArrayBase.
+
+  static_assert(sizeof(nsTArrayHeader) > 4,
+                "see comment above");
+
+#ifdef DEBUG
+  ptrdiff_t diff = reinterpret_cast<const char*>(GetAutoArrayBuffer(8)) -
+                   reinterpret_cast<const char*>(GetAutoArrayBuffer(4));
+  NS_ABORT_IF_FALSE(diff >= 0 && diff <= 4, "GetAutoArrayBuffer doesn't do what we expect.");
+#endif
+
+  return mHdr == GetAutoArrayBuffer(4) || mHdr == GetAutoArrayBuffer(8);
+}
+
+
+template<class Alloc, class Copy>
+typename Alloc::ResultTypeProxy
+nsTArray_base<Alloc, Copy>::EnsureCapacity(size_type capacity, size_type elemSize) {
+  // This should be the most common case so test this first
+  if (capacity <= mHdr->mCapacity)
+    return Alloc::SuccessResult();
+
+  // If the requested memory allocation exceeds size_type(-1)/2, then
+  // our doubling algorithm may not be able to allocate it.
+  // Additionally we couldn't fit in the Header::mCapacity
+  // member. Just bail out in cases like that.  We don't want to be
+  // allocating 2 GB+ arrays anyway.
+  if ((uint64_t)capacity * elemSize > size_type(-1)/2) {
+    Alloc::SizeTooBig((size_t)capacity * elemSize);
+    return Alloc::FailureResult();
+  }
+
+  if (mHdr == EmptyHdr()) {
+    // Malloc() new data
+    Header *header = static_cast<Header*>
+                     (Alloc::Malloc(sizeof(Header) + capacity * elemSize));
+    if (!header)
+      return Alloc::FailureResult();
+    header->mLength = 0;
+    header->mCapacity = capacity;
+    header->mIsAutoArray = 0;
+    mHdr = header;
+
+    return Alloc::SuccessResult();
+  }
+
+  // We increase our capacity so |capacity * elemSize + sizeof(Header)| is the
+  // next power of two, if this value is less than pageSize bytes, or otherwise
+  // so it's the next multiple of pageSize.
+  const uint32_t pageSizeBytes = 12;
+  const uint32_t pageSize = 1 << pageSizeBytes;
+
+  uint32_t minBytes = capacity * elemSize + sizeof(Header);
+  uint32_t bytesToAlloc;
+  if (minBytes >= pageSize) {
+    // Round up to the next multiple of pageSize.
+    bytesToAlloc = pageSize * ((minBytes + pageSize - 1) / pageSize);
+  }
+  else {
+    // Round up to the next power of two.  See
+    // http://graphics.stanford.edu/~seander/bithacks.html
+    bytesToAlloc = minBytes - 1;
+    bytesToAlloc |= bytesToAlloc >> 1;
+    bytesToAlloc |= bytesToAlloc >> 2;
+    bytesToAlloc |= bytesToAlloc >> 4;
+    bytesToAlloc |= bytesToAlloc >> 8;
+    bytesToAlloc |= bytesToAlloc >> 16;
+    bytesToAlloc++;
+
+    MOZ_ASSERT((bytesToAlloc & (bytesToAlloc - 1)) == 0,
+               "nsTArray's allocation size should be a power of two!");
+  }
+
+  Header *header;
+  if (UsesAutoArrayBuffer() || !Copy::allowRealloc) {
+    // Malloc() and copy
+    header = static_cast<Header*>(Alloc::Malloc(bytesToAlloc));
+    if (!header)
+      return Alloc::FailureResult();
+
+    Copy::CopyHeaderAndElements(header, mHdr, Length(), elemSize);
+
+    if (!UsesAutoArrayBuffer())
+      Alloc::Free(mHdr);
+  } else {
+    // Realloc() existing data
+    header = static_cast<Header*>(Alloc::Realloc(mHdr, bytesToAlloc));
+    if (!header)
+      return Alloc::FailureResult();
+  }
+
+  // How many elements can we fit in bytesToAlloc?
+  uint32_t newCapacity = (bytesToAlloc - sizeof(Header)) / elemSize;
+  MOZ_ASSERT(newCapacity >= capacity, "Didn't enlarge the array enough!");
+  header->mCapacity = newCapacity;
+
+  mHdr = header;
+
+  return Alloc::SuccessResult();
+}
+
+template<class Alloc, class Copy>
+void
+nsTArray_base<Alloc, Copy>::ShrinkCapacity(size_type elemSize, size_t elemAlign) {
+  if (mHdr == EmptyHdr() || UsesAutoArrayBuffer())
+    return;
+
+  if (mHdr->mLength >= mHdr->mCapacity)  // should never be greater than...
+    return;
+
+  size_type length = Length();
+
+  if (IsAutoArray() && GetAutoArrayBuffer(elemAlign)->mCapacity >= length) {
+    Header* header = GetAutoArrayBuffer(elemAlign);
+
+    // Copy data, but don't copy the header to avoid overwriting mCapacity
+    header->mLength = length;
+    Copy::CopyElements(header + 1, mHdr + 1, length, elemSize);
+
+    Alloc::Free(mHdr);
+    mHdr = header;
+    return;
+  }
+
+  if (length == 0) {
+    MOZ_ASSERT(!IsAutoArray(), "autoarray should have fit 0 elements");
+    Alloc::Free(mHdr);
+    mHdr = EmptyHdr();
+    return;
+  }
+
+  size_type size = sizeof(Header) + length * elemSize;
+  void *ptr = Alloc::Realloc(mHdr, size);
+  if (!ptr)
+    return;
+  mHdr = static_cast<Header*>(ptr);
+  mHdr->mCapacity = length;
+}
+
+template<class Alloc, class Copy>
+void
+nsTArray_base<Alloc, Copy>::ShiftData(index_type start,
+                                size_type oldLen, size_type newLen,
+                                size_type elemSize, size_t elemAlign) {
+  if (oldLen == newLen)
+    return;
+
+  // Determine how many elements need to be shifted
+  size_type num = mHdr->mLength - (start + oldLen);
+
+  // Compute the resulting length of the array
+  mHdr->mLength += newLen - oldLen;
+  if (mHdr->mLength == 0) {
+    ShrinkCapacity(elemSize, elemAlign);
+  } else {
+    // Maybe nothing needs to be shifted
+    if (num == 0)
+      return;
+    // Perform shift (change units to bytes first)
+    start *= elemSize;
+    newLen *= elemSize;
+    oldLen *= elemSize;
+    char *base = reinterpret_cast<char*>(mHdr + 1) + start;
+    Copy::MoveElements(base + newLen, base + oldLen, num, elemSize);
+  }
+}
+
+template<class Alloc, class Copy>
+bool
+nsTArray_base<Alloc, Copy>::InsertSlotsAt(index_type index, size_type count,
+                                    size_type elementSize, size_t elemAlign)  {
+  MOZ_ASSERT(index <= Length(), "Bogus insertion index");
+  size_type newLen = Length() + count;
+
+  EnsureCapacity(newLen, elementSize);
+
+  // Check for out of memory conditions
+  if (Capacity() < newLen)
+    return false;
+
+  // Move the existing elements as needed.  Note that this will
+  // change our mLength, so no need to call IncrementLength.
+  ShiftData(index, 0, count, elementSize, elemAlign);
+
+  return true;
+}
+
+// nsTArray_base::IsAutoArrayRestorer is an RAII class which takes
+// |nsTArray_base &array| in its constructor.  When it's destructed, it ensures
+// that
+//
+//   * array.mIsAutoArray has the same value as it did when we started, and
+//   * if array has an auto buffer and mHdr would otherwise point to sEmptyHdr,
+//     array.mHdr points to array's auto buffer.
+
+template<class Alloc, class Copy>
+nsTArray_base<Alloc, Copy>::IsAutoArrayRestorer::IsAutoArrayRestorer(
+  nsTArray_base<Alloc, Copy> &array,
+  size_t elemAlign)
+  : mArray(array),
+    mElemAlign(elemAlign),
+    mIsAuto(array.IsAutoArray())
+{
+}
+
+template<class Alloc, class Copy>
+nsTArray_base<Alloc, Copy>::IsAutoArrayRestorer::~IsAutoArrayRestorer() {
+  // Careful: We don't want to set mIsAutoArray = 1 on sEmptyHdr.
+  if (mIsAuto && mArray.mHdr == mArray.EmptyHdr()) {
+    // Call GetAutoArrayBufferUnsafe() because GetAutoArrayBuffer() asserts
+    // that mHdr->mIsAutoArray is true, which surely isn't the case here.
+    mArray.mHdr = mArray.GetAutoArrayBufferUnsafe(mElemAlign);
+    mArray.mHdr->mLength = 0;
+  }
+  else if (mArray.mHdr != mArray.EmptyHdr()) {
+    mArray.mHdr->mIsAutoArray = mIsAuto;
+  }
+}
+
+template<class Alloc, class Copy>
+template<class Allocator>
+typename Alloc::ResultTypeProxy
+nsTArray_base<Alloc, Copy>::SwapArrayElements(nsTArray_base<Allocator, Copy>& other,
+                                              size_type elemSize, size_t elemAlign) {
+
+  // EnsureNotUsingAutoArrayBuffer will set mHdr = sEmptyHdr even if we have an
+  // auto buffer.  We need to point mHdr back to our auto buffer before we
+  // return, otherwise we'll forget that we have an auto buffer at all!
+  // IsAutoArrayRestorer takes care of this for us.
+
+  IsAutoArrayRestorer ourAutoRestorer(*this, elemAlign);
+  typename nsTArray_base<Allocator, Copy>::IsAutoArrayRestorer otherAutoRestorer(other, elemAlign);
+
+  // If neither array uses an auto buffer which is big enough to store the
+  // other array's elements, then ensure that both arrays use malloc'ed storage
+  // and swap their mHdr pointers.
+  if ((!UsesAutoArrayBuffer() || Capacity() < other.Length()) &&
+      (!other.UsesAutoArrayBuffer() || other.Capacity() < Length())) {
+
+    if (!EnsureNotUsingAutoArrayBuffer(elemSize) ||
+        !other.EnsureNotUsingAutoArrayBuffer(elemSize)) {
+      return Alloc::FailureResult();
+    }
+
+    Header *temp = mHdr;
+    mHdr = other.mHdr;
+    other.mHdr = temp;
+
+    return Alloc::SuccessResult();
+  }
+
+  // Swap the two arrays by copying, since at least one is using an auto
+  // buffer which is large enough to hold all of the other's elements.  We'll
+  // copy the shorter array into temporary storage.
+  //
+  // (We could do better than this in some circumstances.  Suppose we're
+  // swapping arrays X and Y.  X has space for 2 elements in its auto buffer,
+  // but currently has length 4, so it's using malloc'ed storage.  Y has length
+  // 2.  When we swap X and Y, we don't need to use a temporary buffer; we can
+  // write Y straight into X's auto buffer, write X's malloc'ed buffer on top
+  // of Y, and then switch X to using its auto buffer.)
+
+  if (!Alloc::Successful(EnsureCapacity(other.Length(), elemSize)) ||
+      !Allocator::Successful(other.EnsureCapacity(Length(), elemSize))) {
+    return Alloc::FailureResult();
+  }
+
+  // The EnsureCapacity calls above shouldn't have caused *both* arrays to
+  // switch from their auto buffers to malloc'ed space.
+  NS_ABORT_IF_FALSE(UsesAutoArrayBuffer() ||
+                    other.UsesAutoArrayBuffer(),
+                    "One of the arrays should be using its auto buffer.");
+
+  size_type smallerLength = XPCOM_MIN(Length(), other.Length());
+  size_type largerLength = XPCOM_MAX(Length(), other.Length());
+  void *smallerElements, *largerElements;
+  if (Length() <= other.Length()) {
+    smallerElements = Hdr() + 1;
+    largerElements = other.Hdr() + 1;
+  }
+  else {
+    smallerElements = other.Hdr() + 1;
+    largerElements = Hdr() + 1;
+  }
+
+  // Allocate temporary storage for the smaller of the two arrays.  We want to
+  // allocate this space on the stack, if it's not too large.  Sounds like a
+  // job for AutoTArray!  (One of the two arrays we're swapping is using an
+  // auto buffer, so we're likely not allocating a lot of space here.  But one
+  // could, in theory, allocate a huge AutoTArray on the heap.)
+  nsAutoArrayBase<nsTArray_Impl<uint8_t, Alloc>, 64> temp;
+  if (!Alloc::Successful(temp.EnsureCapacity(smallerLength, elemSize))) {
+    return Alloc::FailureResult();
+  }
+
+  Copy::CopyElements(temp.Elements(), smallerElements, smallerLength, elemSize);
+  Copy::CopyElements(smallerElements, largerElements, largerLength, elemSize);
+  Copy::CopyElements(largerElements, temp.Elements(), smallerLength, elemSize);
+
+  // Swap the arrays' lengths.
+  NS_ABORT_IF_FALSE((other.Length() == 0 || mHdr != EmptyHdr()) &&
+                    (Length() == 0 || other.mHdr != EmptyHdr()),
+                    "Don't set sEmptyHdr's length.");
+  size_type tempLength = Length();
+  mHdr->mLength = other.Length();
+  other.mHdr->mLength = tempLength;
+
+  return Alloc::SuccessResult();
+}
+
+template<class Alloc, class Copy>
+bool
+nsTArray_base<Alloc, Copy>::EnsureNotUsingAutoArrayBuffer(size_type elemSize) {
+  if (UsesAutoArrayBuffer()) {
+
+    // If you call this on a 0-length array, we'll set that array's mHdr to
+    // sEmptyHdr, in flagrant violation of the nsAutoTArray invariants.  It's
+    // up to you to set it back!  (If you don't, the nsAutoTArray will forget
+    // that it has an auto buffer.)
+    if (Length() == 0) {
+      mHdr = EmptyHdr();
+      return true;
+    }
+
+    size_type size = sizeof(Header) + Length() * elemSize;
+
+    Header* header = static_cast<Header*>(Alloc::Malloc(size));
+    if (!header)
+      return false;
+
+    Copy::CopyHeaderAndElements(header, mHdr, Length(), elemSize);
+    header->mCapacity = Length();
+    mHdr = header;
+  }
+
+  return true;
+}