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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
+
+// NOTE: We don't use MOZ_COUNT_CTOR/MOZ_COUNT_DTOR to perform leak checking of
+// nsTArray_base objects intentionally for the following reasons:
+// * The leak logging isn't as useful as other types of logging, as
+// nsTArray_base is frequently relocated without invoking a constructor, such
+// as when stored within another nsTArray. This means that
+// XPCOM_MEM_LOG_CLASSES cannot be used to identify specific leaks of nsTArray
+// objects.
+// * The nsTArray type is layout compatible with the ThinVec crate with the
+// correct flags, and ThinVec does not currently perform leak logging.
+// This means that if a large number of arrays are transferred between Rust
+// and C++ code using ThinVec, for example within another ThinVec, they
+// will not be logged correctly and might appear as e.g. negative leaks.
+// * Leaks which have been found thanks to the leak logging added by this
+// type have often not been significant, and/or have needed to be
+// circumvented using some other mechanism. Most leaks found with this type
+// in them also include other types which will continue to be tracked.
+
+template <class Alloc, class RelocationStrategy>
+nsTArray_base<Alloc, RelocationStrategy>::nsTArray_base() : mHdr(EmptyHdr()) {}
+
+template <class Alloc, class RelocationStrategy>
+nsTArray_base<Alloc, RelocationStrategy>::~nsTArray_base() {
+ if (!HasEmptyHeader() && !UsesAutoArrayBuffer()) {
+ Alloc::Free(mHdr);
+ }
+}
+
+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.
+}
+
+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 value_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 value_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 (HasEmptyHeader()) {
+ // 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 (HasEmptyHeader() || 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 newSize = sizeof(Header) + length * aElemSize;
+
+ Header* newHeader;
+ if (!RelocationStrategy::allowRealloc) {
+ // Malloc() and copy.
+ newHeader =
+ static_cast<Header*>(nsTArrayFallibleAllocator::Malloc(newSize));
+ if (!newHeader) {
+ return;
+ }
+
+ RelocationStrategy::RelocateNonOverlappingRegionWithHeader(
+ newHeader, mHdr, Length(), aElemSize);
+
+ nsTArrayFallibleAllocator::Free(mHdr);
+ } else {
+ // Realloc() existing data.
+ newHeader =
+ static_cast<Header*>(nsTArrayFallibleAllocator::Realloc(mHdr, newSize));
+ if (!newHeader) {
+ return;
+ }
+ }
+
+ mHdr = newHeader;
+ 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 (HasEmptyHeader() || 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())) {
+ mozilla::detail::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.HasEmptyHeader()) {
+ // 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.HasEmptyHeader()) {
+ 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 || !HasEmptyHeader()) &&
+ (Length() == 0 || !aOther.HasEmptyHeader()),
+ "Don't set sEmptyTArrayHeader's length.");
+ size_type tempLength = Length();
+
+ // Avoid writing to EmptyHdr, since it can trigger false
+ // positives with TSan.
+ if (!HasEmptyHeader()) {
+ mHdr->mLength = aOther.Length();
+ }
+ if (!aOther.HasEmptyHeader()) {
+ 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 || !HasEmptyHeader()) &&
+ (Length() == 0 || !aOther.HasEmptyHeader()),
+ "Don't set sEmptyTArrayHeader's length.");
+
+ // Avoid writing to EmptyHdr, since it can trigger false
+ // positives with TSan.
+ if (!HasEmptyHeader()) {
+ mHdr->mLength = aOther.Length();
+ }
+ if (!aOther.HasEmptyHeader()) {
+ 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.
+
+ if (aOther.IsEmpty()) {
+ return;
+ }
+
+ // 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;
+ // We might write to mHdr, so ensure it's not the static empty header. aOther
+ // shouldn't have been empty if we get here anyway.
+ MOZ_ASSERT(!HasEmptyHeader());
+
+ 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-20 14:38:30 +0000