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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 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 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 Copy>
+bool
+nsTArray_base<Alloc, Copy>::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 Copy>
+template<typename ActualAlloc>
+typename ActualAlloc::ResultTypeProxy
+nsTArray_base<Alloc, Copy>::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() || !Copy::allowRealloc) {
+ // Malloc() and copy
+ header = static_cast<Header*>(ActualAlloc::Malloc(bytesToAlloc));
+ if (!header) {
+ return ActualAlloc::FailureResult();
+ }
+
+ Copy::MoveNonOverlappingRegionWithHeader(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 Copy>
+void
+nsTArray_base<Alloc, Copy>::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;
+ Copy::MoveNonOverlappingRegion(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 Copy>
+template<typename ActualAlloc>
+void
+nsTArray_base<Alloc, Copy>::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) {
+ ShrinkCapacity(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;
+ Copy::MoveOverlappingRegion(baseAddr + aNewLen, baseAddr + aOldLen, num, aElemSize);
+ }
+}
+
+template<class Alloc, class Copy>
+template<typename ActualAlloc>
+bool
+nsTArray_base<Alloc, Copy>::InsertSlotsAt(index_type aIndex, size_type aCount,
+ size_type aElemSize,
+ size_t aElemAlign)
+{
+ MOZ_ASSERT(aIndex <= Length(), "Bogus insertion index");
+ size_type newLen = Length() + aCount;
+
+ EnsureCapacity<ActualAlloc>(newLen, aElemSize);
+
+ // 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<ActualAlloc>(aIndex, 0, aCount, aElemSize, aElemAlign);
+
+ 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>& aArray,
+ size_t aElemAlign)
+ : mArray(aArray)
+ , mElemAlign(aElemAlign)
+ , mIsAuto(aArray.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<typename ActualAlloc, class Allocator>
+typename ActualAlloc::ResultTypeProxy
+nsTArray_base<Alloc, Copy>::SwapArrayElements(nsTArray_base<Allocator,
+ Copy>& aOther,
+ size_type aElemSize,
+ size_t aElemAlign)
+{
+
+ // 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, aElemAlign);
+ typename nsTArray_base<Allocator, Copy>::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<nsTArray_Impl<uint8_t, ActualAlloc>, 64> temp;
+ if (!ActualAlloc::Successful(temp.template EnsureCapacity<ActualAlloc>(smallerLength,
+ aElemSize))) {
+ return ActualAlloc::FailureResult();
+ }
+
+ Copy::MoveNonOverlappingRegion(temp.Elements(), smallerElements, smallerLength, aElemSize);
+ Copy::MoveNonOverlappingRegion(smallerElements, largerElements, largerLength, aElemSize);
+ Copy::MoveNonOverlappingRegion(largerElements, temp.Elements(), smallerLength, aElemSize);
+
+ // Swap the arrays' lengths.
+ MOZ_ASSERT((aOther.Length() == 0 || mHdr != EmptyHdr()) &&
+ (Length() == 0 || aOther.mHdr != EmptyHdr()),
+ "Don't set sEmptyHdr'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 Copy>
+template<typename ActualAlloc>
+bool
+nsTArray_base<Alloc, Copy>::EnsureNotUsingAutoArrayBuffer(size_type aElemSize)
+{
+ 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 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;
+ }
+
+ Copy::MoveNonOverlappingRegionWithHeader(header, mHdr, Length(), aElemSize);
+ header->mCapacity = Length();
+ mHdr = header;
+ }
+
+ return true;
+}
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