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gecko-dev/xpcom/ds/nsTArray-inl.h

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/* -*- 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 nsTArray_h__
# error "Don't include this file directly"
#endif
template <class Alloc, class RelocationStrategy>
nsTArray_base<Alloc, RelocationStrategy>::nsTArray_base() : mHdr(EmptyHdr()) {
MOZ_COUNT_CTOR(nsTArray_base);
}
template <class Alloc, class RelocationStrategy>
nsTArray_base<Alloc, RelocationStrategy>::~nsTArray_base() {
if (mHdr != EmptyHdr() && !UsesAutoArrayBuffer()) {
Alloc::Free(mHdr);
}
MOZ_COUNT_DTOR(nsTArray_base);
}
template <class Alloc, class RelocationStrategy>
nsTArray_base<Alloc, RelocationStrategy>::nsTArray_base(const nsTArray_base&)
: mHdr(EmptyHdr()) {
// Actual copying happens through nsTArray_CopyEnabler, we just need to do the
// initialization of mHdr.
MOZ_COUNT_CTOR(nsTArray_base);
}
template <class Alloc, class RelocationStrategy>
nsTArray_base<Alloc, RelocationStrategy>&
nsTArray_base<Alloc, RelocationStrategy>::operator=(const nsTArray_base&) {
// Actual copying happens through nsTArray_CopyEnabler, so do nothing here (do
// not copy mHdr).
return *this;
}
template <class Alloc, class RelocationStrategy>
const nsTArrayHeader*
nsTArray_base<Alloc, RelocationStrategy>::GetAutoArrayBufferUnsafe(
size_t aElemAlign) 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 AutoTArray<nsTArray<uint32_t>, 1>*>(this)
->mAutoBuf;
// If we're on a 32-bit system and aElemAlign 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(AutoTArray<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.
MOZ_ASSERT(aElemAlign <= 4 || aElemAlign == 8, "unsupported alignment.");
if (sizeof(void*) == 4 && aElemAlign == 8) {
autoBuf = reinterpret_cast<const char*>(autoBuf) + 4;
}
return reinterpret_cast<const Header*>(autoBuf);
}
template <class Alloc, class RelocationStrategy>
bool nsTArray_base<Alloc, RelocationStrategy>::UsesAutoArrayBuffer() const {
if (!mHdr->mIsAutoArray) {
return false;
}
// This is nuts. If we were sane, we'd pass aElemAlign 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,
// * aElemAlign == 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 AutoTArray 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 AutoTArray. We statically assert that elem_type's
// alignment is 8 bytes or less in AutoTArray.
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));
MOZ_ASSERT(diff >= 0 && diff <= 4,
"GetAutoArrayBuffer doesn't do what we expect.");
#endif
return mHdr == GetAutoArrayBuffer(4) || mHdr == GetAutoArrayBuffer(8);
}
// defined in nsTArray.cpp
bool IsTwiceTheRequiredBytesRepresentableAsUint32(size_t aCapacity,
size_t aElemSize);
template <class Alloc, class RelocationStrategy>
template <typename ActualAlloc>
typename ActualAlloc::ResultTypeProxy
nsTArray_base<Alloc, RelocationStrategy>::ExtendCapacity(size_type aLength,
size_type aCount,
size_type aElemSize) {
mozilla::CheckedInt<size_type> newLength = aLength;
newLength += aCount;
if (!newLength.isValid()) {
return ActualAlloc::FailureResult();
}
return this->EnsureCapacity<ActualAlloc>(newLength.value(), aElemSize);
}
template <class Alloc, class RelocationStrategy>
template <typename ActualAlloc>
typename ActualAlloc::ResultTypeProxy
nsTArray_base<Alloc, RelocationStrategy>::EnsureCapacity(size_type aCapacity,
size_type aElemSize) {
// This should be the most common case so test this first
if (aCapacity <= mHdr->mCapacity) {
return ActualAlloc::SuccessResult();
}
// If the requested memory allocation exceeds size_type(-1)/2, then
// our doubling algorithm may not be able to allocate it.
// Additionally, if it exceeds uint32_t(-1) then 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 (!IsTwiceTheRequiredBytesRepresentableAsUint32(aCapacity, aElemSize)) {
ActualAlloc::SizeTooBig((size_t)aCapacity * aElemSize);
return ActualAlloc::FailureResult();
}
size_t reqSize = sizeof(Header) + aCapacity * aElemSize;
if (mHdr == EmptyHdr()) {
// Malloc() new data
Header* header = static_cast<Header*>(ActualAlloc::Malloc(reqSize));
if (!header) {
return ActualAlloc::FailureResult();
}
header->mLength = 0;
header->mCapacity = aCapacity;
header->mIsAutoArray = 0;
mHdr = header;
return ActualAlloc::SuccessResult();
}
// We increase our capacity so that the allocated buffer grows exponentially,
// which gives us amortized O(1) appending. Below the threshold, we use
// powers-of-two. Above the threshold, we grow by at least 1.125, rounding up
// to the nearest MiB.
const size_t slowGrowthThreshold = 8 * 1024 * 1024;
size_t bytesToAlloc;
if (reqSize >= slowGrowthThreshold) {
size_t currSize = sizeof(Header) + Capacity() * aElemSize;
size_t minNewSize = currSize + (currSize >> 3); // multiply by 1.125
bytesToAlloc = reqSize > minNewSize ? reqSize : minNewSize;
// Round up to the next multiple of MiB.
const size_t MiB = 1 << 20;
bytesToAlloc = MiB * ((bytesToAlloc + MiB - 1) / MiB);
} else {
// Round up to the next power of two.
bytesToAlloc = mozilla::RoundUpPow2(reqSize);
}
Header* header;
if (UsesAutoArrayBuffer() || !RelocationStrategy::allowRealloc) {
// Malloc() and copy
header = static_cast<Header*>(ActualAlloc::Malloc(bytesToAlloc));
if (!header) {
return ActualAlloc::FailureResult();
}
RelocationStrategy::RelocateNonOverlappingRegionWithHeader(
header, mHdr, Length(), aElemSize);
if (!UsesAutoArrayBuffer()) {
ActualAlloc::Free(mHdr);
}
} else {
// Realloc() existing data
header = static_cast<Header*>(ActualAlloc::Realloc(mHdr, bytesToAlloc));
if (!header) {
return ActualAlloc::FailureResult();
}
}
// How many elements can we fit in bytesToAlloc?
size_t newCapacity = (bytesToAlloc - sizeof(Header)) / aElemSize;
MOZ_ASSERT(newCapacity >= aCapacity, "Didn't enlarge the array enough!");
header->mCapacity = newCapacity;
mHdr = header;
return ActualAlloc::SuccessResult();
}
// We don't need use Alloc template parameter specified here because failure to
// shrink the capacity will leave the array unchanged.
template <class Alloc, class RelocationStrategy>
void nsTArray_base<Alloc, RelocationStrategy>::ShrinkCapacity(
size_type aElemSize, size_t aElemAlign) {
if (mHdr == EmptyHdr() || UsesAutoArrayBuffer()) {
return;
}
if (mHdr->mLength >= mHdr->mCapacity) { // should never be greater than...
return;
}
size_type length = Length();
if (IsAutoArray() && GetAutoArrayBuffer(aElemAlign)->mCapacity >= length) {
Header* header = GetAutoArrayBuffer(aElemAlign);
// Move the data, but don't copy the header to avoid overwriting mCapacity.
header->mLength = length;
RelocationStrategy::RelocateNonOverlappingRegion(header + 1, mHdr + 1,
length, aElemSize);
nsTArrayFallibleAllocator::Free(mHdr);
mHdr = header;
return;
}
if (length == 0) {
MOZ_ASSERT(!IsAutoArray(), "autoarray should have fit 0 elements");
nsTArrayFallibleAllocator::Free(mHdr);
mHdr = EmptyHdr();
return;
}
size_type size = sizeof(Header) + length * aElemSize;
void* ptr = nsTArrayFallibleAllocator::Realloc(mHdr, size);
if (!ptr) {
return;
}
mHdr = static_cast<Header*>(ptr);
mHdr->mCapacity = length;
}
template <class Alloc, class RelocationStrategy>
void nsTArray_base<Alloc, RelocationStrategy>::ShrinkCapacityToZero(
size_type aElemSize, size_t aElemAlign) {
MOZ_ASSERT(mHdr->mLength == 0);
if (mHdr == EmptyHdr() || UsesAutoArrayBuffer()) {
return;
}
const bool isAutoArray = IsAutoArray();
nsTArrayFallibleAllocator::Free(mHdr);
if (isAutoArray) {
mHdr = GetAutoArrayBufferUnsafe(aElemAlign);
mHdr->mLength = 0;
} else {
mHdr = EmptyHdr();
}
}
template <class Alloc, class RelocationStrategy>
template <typename ActualAlloc>
void nsTArray_base<Alloc, RelocationStrategy>::ShiftData(index_type aStart,
size_type aOldLen,
size_type aNewLen,
size_type aElemSize,
size_t aElemAlign) {
if (aOldLen == aNewLen) {
return;
}
// Determine how many elements need to be shifted
size_type num = mHdr->mLength - (aStart + aOldLen);
// Compute the resulting length of the array
mHdr->mLength += aNewLen - aOldLen;
if (mHdr->mLength == 0) {
ShrinkCapacityToZero(aElemSize, aElemAlign);
} else {
// Maybe nothing needs to be shifted
if (num == 0) {
return;
}
// Perform shift (change units to bytes first)
aStart *= aElemSize;
aNewLen *= aElemSize;
aOldLen *= aElemSize;
char* baseAddr = reinterpret_cast<char*>(mHdr + 1) + aStart;
RelocationStrategy::RelocateOverlappingRegion(
baseAddr + aNewLen, baseAddr + aOldLen, num, aElemSize);
}
}
template <class Alloc, class RelocationStrategy>
template <typename ActualAlloc>
void nsTArray_base<Alloc, RelocationStrategy>::SwapFromEnd(index_type aStart,
size_type aCount,
size_type aElemSize,
size_t aElemAlign) {
// This method is part of the implementation of
// nsTArray::SwapRemoveElement{s,}At. For more information, read the
// documentation on that method.
if (aCount == 0) {
return;
}
// We are going to be removing aCount elements. Update our length to point to
// the new end of the array.
size_type oldLength = mHdr->mLength;
mHdr->mLength -= aCount;
if (mHdr->mLength == 0) {
// If we have no elements remaining in the array, we can free our buffer.
ShrinkCapacityToZero(aElemSize, aElemAlign);
return;
}
// Determine how many elements we need to move from the end of the array into
// the now-removed section. This will either be the number of elements which
// were removed (if there are more elements in the tail of the array), or the
// entire tail of the array, whichever is smaller.
size_type relocCount = std::min(aCount, mHdr->mLength - aStart);
if (relocCount == 0) {
return;
}
// Move the elements which are now stranded after the end of the array back
// into the now-vacated memory.
index_type sourceBytes = (oldLength - relocCount) * aElemSize;
index_type destBytes = aStart * aElemSize;
// Perform the final copy. This is guaranteed to be a non-overlapping copy
// as our source contains only still-valid entries, and the destination
// contains only invalid entries which need to be overwritten.
MOZ_ASSERT(sourceBytes >= destBytes,
"The source should be after the destination.");
MOZ_ASSERT(sourceBytes - destBytes >= relocCount * aElemSize,
"The range should be nonoverlapping");
char* baseAddr = reinterpret_cast<char*>(mHdr + 1);
RelocationStrategy::RelocateNonOverlappingRegion(
baseAddr + destBytes, baseAddr + sourceBytes, relocCount, aElemSize);
}
template <class Alloc, class RelocationStrategy>
template <typename ActualAlloc>
typename ActualAlloc::ResultTypeProxy
nsTArray_base<Alloc, RelocationStrategy>::InsertSlotsAt(index_type aIndex,
size_type aCount,
size_type aElemSize,
size_t aElemAlign) {
if (MOZ_UNLIKELY(aIndex > Length())) {
InvalidArrayIndex_CRASH(aIndex, Length());
}
if (!ActualAlloc::Successful(
this->ExtendCapacity<ActualAlloc>(Length(), aCount, aElemSize))) {
return ActualAlloc::FailureResult();
}
// Move the existing elements as needed. Note that this will
// change our mLength, so no need to call IncrementLength.
ShiftData<ActualAlloc>(aIndex, 0, aCount, aElemSize, aElemAlign);
return ActualAlloc::SuccessResult();
}
// 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
// sEmptyTArrayHeader, array.mHdr points to array's auto buffer.
template <class Alloc, class RelocationStrategy>
nsTArray_base<Alloc, RelocationStrategy>::IsAutoArrayRestorer::
IsAutoArrayRestorer(nsTArray_base<Alloc, RelocationStrategy>& aArray,
size_t aElemAlign)
: mArray(aArray), mElemAlign(aElemAlign), mIsAuto(aArray.IsAutoArray()) {}
template <class Alloc, class RelocationStrategy>
nsTArray_base<Alloc,
RelocationStrategy>::IsAutoArrayRestorer::~IsAutoArrayRestorer() {
// Careful: We don't want to set mIsAutoArray = 1 on sEmptyTArrayHeader.
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 RelocationStrategy>
template <typename ActualAlloc, class Allocator>
typename ActualAlloc::ResultTypeProxy
nsTArray_base<Alloc, RelocationStrategy>::SwapArrayElements(
nsTArray_base<Allocator, RelocationStrategy>& aOther, size_type aElemSize,
size_t aElemAlign) {
// EnsureNotUsingAutoArrayBuffer will set mHdr = sEmptyTArrayHeader 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, aElemAlign);
typename nsTArray_base<Allocator, RelocationStrategy>::IsAutoArrayRestorer
otherAutoRestorer(aOther, aElemAlign);
// 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() < aOther.Length()) &&
(!aOther.UsesAutoArrayBuffer() || aOther.Capacity() < Length())) {
if (!EnsureNotUsingAutoArrayBuffer<ActualAlloc>(aElemSize) ||
!aOther.template EnsureNotUsingAutoArrayBuffer<ActualAlloc>(
aElemSize)) {
return ActualAlloc::FailureResult();
}
Header* temp = mHdr;
mHdr = aOther.mHdr;
aOther.mHdr = temp;
return ActualAlloc::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 aOther'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 (!ActualAlloc::Successful(
EnsureCapacity<ActualAlloc>(aOther.Length(), aElemSize)) ||
!Allocator::Successful(
aOther.template EnsureCapacity<Allocator>(Length(), aElemSize))) {
return ActualAlloc::FailureResult();
}
// The EnsureCapacity calls above shouldn't have caused *both* arrays to
// switch from their auto buffers to malloc'ed space.
MOZ_ASSERT(UsesAutoArrayBuffer() || aOther.UsesAutoArrayBuffer(),
"One of the arrays should be using its auto buffer.");
size_type smallerLength = XPCOM_MIN(Length(), aOther.Length());
size_type largerLength = XPCOM_MAX(Length(), aOther.Length());
void* smallerElements;
void* largerElements;
if (Length() <= aOther.Length()) {
smallerElements = Hdr() + 1;
largerElements = aOther.Hdr() + 1;
} else {
smallerElements = aOther.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.)
AutoTArray<uint8_t, 64 * sizeof(void*)> temp;
if (!ActualAlloc::Successful(temp.template EnsureCapacity<ActualAlloc>(
smallerLength * aElemSize, sizeof(uint8_t)))) {
return ActualAlloc::FailureResult();
}
RelocationStrategy::RelocateNonOverlappingRegion(
temp.Elements(), smallerElements, smallerLength, aElemSize);
RelocationStrategy::RelocateNonOverlappingRegion(
smallerElements, largerElements, largerLength, aElemSize);
RelocationStrategy::RelocateNonOverlappingRegion(
largerElements, temp.Elements(), smallerLength, aElemSize);
// Swap the arrays' lengths.
MOZ_ASSERT((aOther.Length() == 0 || mHdr != EmptyHdr()) &&
(Length() == 0 || aOther.mHdr != EmptyHdr()),
"Don't set sEmptyTArrayHeader's length.");
size_type tempLength = Length();
// Avoid writing to EmptyHdr, since it can trigger false
// positives with TSan.
if (mHdr != EmptyHdr()) {
mHdr->mLength = aOther.Length();
}
if (aOther.mHdr != EmptyHdr()) {
aOther.mHdr->mLength = tempLength;
}
return ActualAlloc::SuccessResult();
}
template <class Alloc, class RelocationStrategy>
template <class Allocator>
void nsTArray_base<Alloc, RelocationStrategy>::MoveInit(
nsTArray_base<Allocator, RelocationStrategy>& aOther, size_type aElemSize,
size_t aElemAlign) {
// This method is similar to SwapArrayElements, but specialized for the case
// where the target array is empty with no allocated heap storage. It is
// provided and used to simplify template instantiation and enable better code
// generation.
MOZ_ASSERT(Length() == 0);
MOZ_ASSERT(Capacity() == 0 || (IsAutoArray() && UsesAutoArrayBuffer()));
// EnsureNotUsingAutoArrayBuffer will set mHdr = sEmptyTArrayHeader 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, aElemAlign);
typename nsTArray_base<Allocator, RelocationStrategy>::IsAutoArrayRestorer
otherAutoRestorer(aOther, aElemAlign);
// 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 ((!IsAutoArray() || Capacity() < aOther.Length()) &&
!aOther.UsesAutoArrayBuffer()) {
mHdr = aOther.mHdr;
aOther.mHdr = EmptyHdr();
return;
}
// Move the data by copying, since at least one has an auto
// buffer which is large enough to hold all of the aOther's elements.
EnsureCapacity<nsTArrayInfallibleAllocator>(aOther.Length(), aElemSize);
// The EnsureCapacity calls above shouldn't have caused *both* arrays to
// switch from their auto buffers to malloc'ed space.
MOZ_ASSERT(UsesAutoArrayBuffer() || aOther.UsesAutoArrayBuffer(),
"One of the arrays should be using its auto buffer.");
RelocationStrategy::RelocateNonOverlappingRegion(Hdr() + 1, aOther.Hdr() + 1,
aOther.Length(), aElemSize);
// Swap the arrays' lengths.
MOZ_ASSERT((aOther.Length() == 0 || mHdr != EmptyHdr()) &&
(Length() == 0 || aOther.mHdr != EmptyHdr()),
"Don't set sEmptyTArrayHeader's length.");
// Avoid writing to EmptyHdr, since it can trigger false
// positives with TSan.
if (mHdr != EmptyHdr()) {
mHdr->mLength = aOther.Length();
}
if (aOther.mHdr != EmptyHdr()) {
aOther.mHdr->mLength = 0;
}
}
template <class Alloc, class RelocationStrategy>
template <class Allocator>
void nsTArray_base<Alloc, RelocationStrategy>::MoveConstructNonAutoArray(
nsTArray_base<Allocator, RelocationStrategy>& aOther, size_type aElemSize,
size_t aElemAlign) {
// We know that we are not an (Copyable)AutoTArray and we know that we are
// empty, so don't use SwapArrayElements which doesn't know either of these
// facts and is very complex.
// aOther might be an (Copyable)AutoTArray though, and it might use its inline
// buffer.
const bool otherUsesAutoArrayBuffer = aOther.UsesAutoArrayBuffer();
if (otherUsesAutoArrayBuffer) {
// Use nsTArrayInfallibleAllocator regardless of Alloc because this is
// called from a move constructor, which cannot report an error to the
// caller.
aOther.template EnsureNotUsingAutoArrayBuffer<nsTArrayInfallibleAllocator>(
aElemSize);
}
const bool otherIsAuto = otherUsesAutoArrayBuffer || aOther.IsAutoArray();
mHdr = aOther.mHdr;
if (otherIsAuto) {
mHdr->mIsAutoArray = false;
aOther.mHdr = aOther.GetAutoArrayBufferUnsafe(aElemAlign);
aOther.mHdr->mLength = 0;
} else {
aOther.mHdr = aOther.EmptyHdr();
}
}
template <class Alloc, class RelocationStrategy>
template <typename ActualAlloc>
bool nsTArray_base<Alloc, RelocationStrategy>::EnsureNotUsingAutoArrayBuffer(
size_type aElemSize) {
if (UsesAutoArrayBuffer()) {
// If you call this on a 0-length array, we'll set that array's mHdr to
// sEmptyTArrayHeader, in flagrant violation of the AutoTArray invariants.
// It's up to you to set it back! (If you don't, the AutoTArray will
// forget that it has an auto buffer.)
if (Length() == 0) {
mHdr = EmptyHdr();
return true;
}
size_type size = sizeof(Header) + Length() * aElemSize;
Header* header = static_cast<Header*>(ActualAlloc::Malloc(size));
if (!header) {
return false;
}
RelocationStrategy::RelocateNonOverlappingRegionWithHeader(
header, mHdr, Length(), aElemSize);
header->mCapacity = Length();
mHdr = header;
}
return true;
}
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