michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef nsTArray_h__
michael@0: #  error "Don't include this file directly"
michael@0: #endif
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: nsTArray_base<Alloc, Copy>::nsTArray_base()
michael@0:   : mHdr(EmptyHdr()) {
michael@0:   MOZ_COUNT_CTOR(nsTArray_base);
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: nsTArray_base<Alloc, Copy>::~nsTArray_base() {
michael@0:   if (mHdr != EmptyHdr() && !UsesAutoArrayBuffer()) {
michael@0:     Alloc::Free(mHdr);
michael@0:   }
michael@0:   MOZ_COUNT_DTOR(nsTArray_base);
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: const nsTArrayHeader* nsTArray_base<Alloc, Copy>::GetAutoArrayBufferUnsafe(size_t elemAlign) const {
michael@0:   // Assuming |this| points to an nsAutoArray, we want to get a pointer to
michael@0:   // mAutoBuf.  So just cast |this| to nsAutoArray* and read &mAutoBuf!
michael@0: 
michael@0:   const void* autoBuf = &reinterpret_cast<const nsAutoArrayBase<nsTArray<uint32_t>, 1>*>(this)->mAutoBuf;
michael@0: 
michael@0:   // If we're on a 32-bit system and elemAlign is 8, we need to adjust our
michael@0:   // pointer to take into account the extra alignment in the auto array.
michael@0: 
michael@0:   static_assert(sizeof(void*) != 4 ||
michael@0:                 (MOZ_ALIGNOF(mozilla::AlignedElem<8>) == 8 &&
michael@0:                  sizeof(nsAutoTArray<mozilla::AlignedElem<8>, 1>) ==
michael@0:                    sizeof(void*) + sizeof(nsTArrayHeader) +
michael@0:                    4 + sizeof(mozilla::AlignedElem<8>)),
michael@0:                 "auto array padding wasn't what we expected");
michael@0: 
michael@0:   // We don't support alignments greater than 8 bytes.
michael@0:   NS_ABORT_IF_FALSE(elemAlign <= 4 || elemAlign == 8, "unsupported alignment.");
michael@0:   if (sizeof(void*) == 4 && elemAlign == 8) {
michael@0:     autoBuf = reinterpret_cast<const char*>(autoBuf) + 4;
michael@0:   }
michael@0: 
michael@0:   return reinterpret_cast<const Header*>(autoBuf);
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: bool nsTArray_base<Alloc, Copy>::UsesAutoArrayBuffer() const {
michael@0:   if (!mHdr->mIsAutoArray) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   // This is nuts.  If we were sane, we'd pass elemAlign as a parameter to
michael@0:   // this function.  Unfortunately this function is called in nsTArray_base's
michael@0:   // destructor, at which point we don't know elem_type's alignment.
michael@0:   //
michael@0:   // We'll fall on our face and return true when we should say false if
michael@0:   //
michael@0:   //   * we're not using our auto buffer,
michael@0:   //   * elemAlign == 4, and
michael@0:   //   * mHdr == GetAutoArrayBuffer(8).
michael@0:   //
michael@0:   // This could happen if |*this| lives on the heap and malloc allocated our
michael@0:   // buffer on the heap adjacent to |*this|.
michael@0:   //
michael@0:   // However, we can show that this can't happen.  If |this| is an auto array
michael@0:   // (as we ensured at the beginning of the method), GetAutoArrayBuffer(8)
michael@0:   // always points to memory owned by |*this|, because (as we assert below)
michael@0:   //
michael@0:   //   * GetAutoArrayBuffer(8) is at most 4 bytes past GetAutoArrayBuffer(4), and 
michael@0:   //   * sizeof(nsTArrayHeader) > 4.
michael@0:   //
michael@0:   // Since nsAutoTArray always contains an nsTArrayHeader,
michael@0:   // GetAutoArrayBuffer(8) will always point inside the auto array object,
michael@0:   // even if it doesn't point at the beginning of the header.
michael@0:   //
michael@0:   // Note that this means that we can't store elements with alignment 16 in an
michael@0:   // nsTArray, because GetAutoArrayBuffer(16) could lie outside the memory
michael@0:   // owned by this nsAutoTArray.  We statically assert that elem_type's
michael@0:   // alignment is 8 bytes or less in nsAutoArrayBase.
michael@0: 
michael@0:   static_assert(sizeof(nsTArrayHeader) > 4,
michael@0:                 "see comment above");
michael@0: 
michael@0: #ifdef DEBUG
michael@0:   ptrdiff_t diff = reinterpret_cast<const char*>(GetAutoArrayBuffer(8)) -
michael@0:                    reinterpret_cast<const char*>(GetAutoArrayBuffer(4));
michael@0:   NS_ABORT_IF_FALSE(diff >= 0 && diff <= 4, "GetAutoArrayBuffer doesn't do what we expect.");
michael@0: #endif
michael@0: 
michael@0:   return mHdr == GetAutoArrayBuffer(4) || mHdr == GetAutoArrayBuffer(8);
michael@0: }
michael@0: 
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: typename Alloc::ResultTypeProxy
michael@0: nsTArray_base<Alloc, Copy>::EnsureCapacity(size_type capacity, size_type elemSize) {
michael@0:   // This should be the most common case so test this first
michael@0:   if (capacity <= mHdr->mCapacity)
michael@0:     return Alloc::SuccessResult();
michael@0: 
michael@0:   // If the requested memory allocation exceeds size_type(-1)/2, then
michael@0:   // our doubling algorithm may not be able to allocate it.
michael@0:   // Additionally we couldn't fit in the Header::mCapacity
michael@0:   // member. Just bail out in cases like that.  We don't want to be
michael@0:   // allocating 2 GB+ arrays anyway.
michael@0:   if ((uint64_t)capacity * elemSize > size_type(-1)/2) {
michael@0:     Alloc::SizeTooBig((size_t)capacity * elemSize);
michael@0:     return Alloc::FailureResult();
michael@0:   }
michael@0: 
michael@0:   if (mHdr == EmptyHdr()) {
michael@0:     // Malloc() new data
michael@0:     Header *header = static_cast<Header*>
michael@0:                      (Alloc::Malloc(sizeof(Header) + capacity * elemSize));
michael@0:     if (!header)
michael@0:       return Alloc::FailureResult();
michael@0:     header->mLength = 0;
michael@0:     header->mCapacity = capacity;
michael@0:     header->mIsAutoArray = 0;
michael@0:     mHdr = header;
michael@0: 
michael@0:     return Alloc::SuccessResult();
michael@0:   }
michael@0: 
michael@0:   // We increase our capacity so |capacity * elemSize + sizeof(Header)| is the
michael@0:   // next power of two, if this value is less than pageSize bytes, or otherwise
michael@0:   // so it's the next multiple of pageSize.
michael@0:   const uint32_t pageSizeBytes = 12;
michael@0:   const uint32_t pageSize = 1 << pageSizeBytes;
michael@0: 
michael@0:   uint32_t minBytes = capacity * elemSize + sizeof(Header);
michael@0:   uint32_t bytesToAlloc;
michael@0:   if (minBytes >= pageSize) {
michael@0:     // Round up to the next multiple of pageSize.
michael@0:     bytesToAlloc = pageSize * ((minBytes + pageSize - 1) / pageSize);
michael@0:   }
michael@0:   else {
michael@0:     // Round up to the next power of two.  See
michael@0:     // http://graphics.stanford.edu/~seander/bithacks.html
michael@0:     bytesToAlloc = minBytes - 1;
michael@0:     bytesToAlloc |= bytesToAlloc >> 1;
michael@0:     bytesToAlloc |= bytesToAlloc >> 2;
michael@0:     bytesToAlloc |= bytesToAlloc >> 4;
michael@0:     bytesToAlloc |= bytesToAlloc >> 8;
michael@0:     bytesToAlloc |= bytesToAlloc >> 16;
michael@0:     bytesToAlloc++;
michael@0: 
michael@0:     MOZ_ASSERT((bytesToAlloc & (bytesToAlloc - 1)) == 0,
michael@0:                "nsTArray's allocation size should be a power of two!");
michael@0:   }
michael@0: 
michael@0:   Header *header;
michael@0:   if (UsesAutoArrayBuffer() || !Copy::allowRealloc) {
michael@0:     // Malloc() and copy
michael@0:     header = static_cast<Header*>(Alloc::Malloc(bytesToAlloc));
michael@0:     if (!header)
michael@0:       return Alloc::FailureResult();
michael@0: 
michael@0:     Copy::CopyHeaderAndElements(header, mHdr, Length(), elemSize);
michael@0: 
michael@0:     if (!UsesAutoArrayBuffer())
michael@0:       Alloc::Free(mHdr);
michael@0:   } else {
michael@0:     // Realloc() existing data
michael@0:     header = static_cast<Header*>(Alloc::Realloc(mHdr, bytesToAlloc));
michael@0:     if (!header)
michael@0:       return Alloc::FailureResult();
michael@0:   }
michael@0: 
michael@0:   // How many elements can we fit in bytesToAlloc?
michael@0:   uint32_t newCapacity = (bytesToAlloc - sizeof(Header)) / elemSize;
michael@0:   MOZ_ASSERT(newCapacity >= capacity, "Didn't enlarge the array enough!");
michael@0:   header->mCapacity = newCapacity;
michael@0: 
michael@0:   mHdr = header;
michael@0: 
michael@0:   return Alloc::SuccessResult();
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: void
michael@0: nsTArray_base<Alloc, Copy>::ShrinkCapacity(size_type elemSize, size_t elemAlign) {
michael@0:   if (mHdr == EmptyHdr() || UsesAutoArrayBuffer())
michael@0:     return;
michael@0: 
michael@0:   if (mHdr->mLength >= mHdr->mCapacity)  // should never be greater than...
michael@0:     return;
michael@0: 
michael@0:   size_type length = Length();
michael@0: 
michael@0:   if (IsAutoArray() && GetAutoArrayBuffer(elemAlign)->mCapacity >= length) {
michael@0:     Header* header = GetAutoArrayBuffer(elemAlign);
michael@0: 
michael@0:     // Copy data, but don't copy the header to avoid overwriting mCapacity
michael@0:     header->mLength = length;
michael@0:     Copy::CopyElements(header + 1, mHdr + 1, length, elemSize);
michael@0: 
michael@0:     Alloc::Free(mHdr);
michael@0:     mHdr = header;
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   if (length == 0) {
michael@0:     MOZ_ASSERT(!IsAutoArray(), "autoarray should have fit 0 elements");
michael@0:     Alloc::Free(mHdr);
michael@0:     mHdr = EmptyHdr();
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   size_type size = sizeof(Header) + length * elemSize;
michael@0:   void *ptr = Alloc::Realloc(mHdr, size);
michael@0:   if (!ptr)
michael@0:     return;
michael@0:   mHdr = static_cast<Header*>(ptr);
michael@0:   mHdr->mCapacity = length;
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: void
michael@0: nsTArray_base<Alloc, Copy>::ShiftData(index_type start,
michael@0:                                 size_type oldLen, size_type newLen,
michael@0:                                 size_type elemSize, size_t elemAlign) {
michael@0:   if (oldLen == newLen)
michael@0:     return;
michael@0: 
michael@0:   // Determine how many elements need to be shifted
michael@0:   size_type num = mHdr->mLength - (start + oldLen);
michael@0: 
michael@0:   // Compute the resulting length of the array
michael@0:   mHdr->mLength += newLen - oldLen;
michael@0:   if (mHdr->mLength == 0) {
michael@0:     ShrinkCapacity(elemSize, elemAlign);
michael@0:   } else {
michael@0:     // Maybe nothing needs to be shifted
michael@0:     if (num == 0)
michael@0:       return;
michael@0:     // Perform shift (change units to bytes first)
michael@0:     start *= elemSize;
michael@0:     newLen *= elemSize;
michael@0:     oldLen *= elemSize;
michael@0:     char *base = reinterpret_cast<char*>(mHdr + 1) + start;
michael@0:     Copy::MoveElements(base + newLen, base + oldLen, num, elemSize);
michael@0:   }
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: bool
michael@0: nsTArray_base<Alloc, Copy>::InsertSlotsAt(index_type index, size_type count,
michael@0:                                     size_type elementSize, size_t elemAlign)  {
michael@0:   MOZ_ASSERT(index <= Length(), "Bogus insertion index");
michael@0:   size_type newLen = Length() + count;
michael@0: 
michael@0:   EnsureCapacity(newLen, elementSize);
michael@0: 
michael@0:   // Check for out of memory conditions
michael@0:   if (Capacity() < newLen)
michael@0:     return false;
michael@0: 
michael@0:   // Move the existing elements as needed.  Note that this will
michael@0:   // change our mLength, so no need to call IncrementLength.
michael@0:   ShiftData(index, 0, count, elementSize, elemAlign);
michael@0: 
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // nsTArray_base::IsAutoArrayRestorer is an RAII class which takes
michael@0: // |nsTArray_base &array| in its constructor.  When it's destructed, it ensures
michael@0: // that
michael@0: //
michael@0: //   * array.mIsAutoArray has the same value as it did when we started, and
michael@0: //   * if array has an auto buffer and mHdr would otherwise point to sEmptyHdr,
michael@0: //     array.mHdr points to array's auto buffer.
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: nsTArray_base<Alloc, Copy>::IsAutoArrayRestorer::IsAutoArrayRestorer(
michael@0:   nsTArray_base<Alloc, Copy> &array,
michael@0:   size_t elemAlign)
michael@0:   : mArray(array),
michael@0:     mElemAlign(elemAlign),
michael@0:     mIsAuto(array.IsAutoArray())
michael@0: {
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: nsTArray_base<Alloc, Copy>::IsAutoArrayRestorer::~IsAutoArrayRestorer() {
michael@0:   // Careful: We don't want to set mIsAutoArray = 1 on sEmptyHdr.
michael@0:   if (mIsAuto && mArray.mHdr == mArray.EmptyHdr()) {
michael@0:     // Call GetAutoArrayBufferUnsafe() because GetAutoArrayBuffer() asserts
michael@0:     // that mHdr->mIsAutoArray is true, which surely isn't the case here.
michael@0:     mArray.mHdr = mArray.GetAutoArrayBufferUnsafe(mElemAlign);
michael@0:     mArray.mHdr->mLength = 0;
michael@0:   }
michael@0:   else if (mArray.mHdr != mArray.EmptyHdr()) {
michael@0:     mArray.mHdr->mIsAutoArray = mIsAuto;
michael@0:   }
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: template<class Allocator>
michael@0: typename Alloc::ResultTypeProxy
michael@0: nsTArray_base<Alloc, Copy>::SwapArrayElements(nsTArray_base<Allocator, Copy>& other,
michael@0:                                               size_type elemSize, size_t elemAlign) {
michael@0: 
michael@0:   // EnsureNotUsingAutoArrayBuffer will set mHdr = sEmptyHdr even if we have an
michael@0:   // auto buffer.  We need to point mHdr back to our auto buffer before we
michael@0:   // return, otherwise we'll forget that we have an auto buffer at all!
michael@0:   // IsAutoArrayRestorer takes care of this for us.
michael@0: 
michael@0:   IsAutoArrayRestorer ourAutoRestorer(*this, elemAlign);
michael@0:   typename nsTArray_base<Allocator, Copy>::IsAutoArrayRestorer otherAutoRestorer(other, elemAlign);
michael@0: 
michael@0:   // If neither array uses an auto buffer which is big enough to store the
michael@0:   // other array's elements, then ensure that both arrays use malloc'ed storage
michael@0:   // and swap their mHdr pointers.
michael@0:   if ((!UsesAutoArrayBuffer() || Capacity() < other.Length()) &&
michael@0:       (!other.UsesAutoArrayBuffer() || other.Capacity() < Length())) {
michael@0: 
michael@0:     if (!EnsureNotUsingAutoArrayBuffer(elemSize) ||
michael@0:         !other.EnsureNotUsingAutoArrayBuffer(elemSize)) {
michael@0:       return Alloc::FailureResult();
michael@0:     }
michael@0: 
michael@0:     Header *temp = mHdr;
michael@0:     mHdr = other.mHdr;
michael@0:     other.mHdr = temp;
michael@0: 
michael@0:     return Alloc::SuccessResult();
michael@0:   }
michael@0: 
michael@0:   // Swap the two arrays by copying, since at least one is using an auto
michael@0:   // buffer which is large enough to hold all of the other's elements.  We'll
michael@0:   // copy the shorter array into temporary storage.
michael@0:   //
michael@0:   // (We could do better than this in some circumstances.  Suppose we're
michael@0:   // swapping arrays X and Y.  X has space for 2 elements in its auto buffer,
michael@0:   // but currently has length 4, so it's using malloc'ed storage.  Y has length
michael@0:   // 2.  When we swap X and Y, we don't need to use a temporary buffer; we can
michael@0:   // write Y straight into X's auto buffer, write X's malloc'ed buffer on top
michael@0:   // of Y, and then switch X to using its auto buffer.)
michael@0: 
michael@0:   if (!Alloc::Successful(EnsureCapacity(other.Length(), elemSize)) ||
michael@0:       !Allocator::Successful(other.EnsureCapacity(Length(), elemSize))) {
michael@0:     return Alloc::FailureResult();
michael@0:   }
michael@0: 
michael@0:   // The EnsureCapacity calls above shouldn't have caused *both* arrays to
michael@0:   // switch from their auto buffers to malloc'ed space.
michael@0:   NS_ABORT_IF_FALSE(UsesAutoArrayBuffer() ||
michael@0:                     other.UsesAutoArrayBuffer(),
michael@0:                     "One of the arrays should be using its auto buffer.");
michael@0: 
michael@0:   size_type smallerLength = XPCOM_MIN(Length(), other.Length());
michael@0:   size_type largerLength = XPCOM_MAX(Length(), other.Length());
michael@0:   void *smallerElements, *largerElements;
michael@0:   if (Length() <= other.Length()) {
michael@0:     smallerElements = Hdr() + 1;
michael@0:     largerElements = other.Hdr() + 1;
michael@0:   }
michael@0:   else {
michael@0:     smallerElements = other.Hdr() + 1;
michael@0:     largerElements = Hdr() + 1;
michael@0:   }
michael@0: 
michael@0:   // Allocate temporary storage for the smaller of the two arrays.  We want to
michael@0:   // allocate this space on the stack, if it's not too large.  Sounds like a
michael@0:   // job for AutoTArray!  (One of the two arrays we're swapping is using an
michael@0:   // auto buffer, so we're likely not allocating a lot of space here.  But one
michael@0:   // could, in theory, allocate a huge AutoTArray on the heap.)
michael@0:   nsAutoArrayBase<nsTArray_Impl<uint8_t, Alloc>, 64> temp;
michael@0:   if (!Alloc::Successful(temp.EnsureCapacity(smallerLength, elemSize))) {
michael@0:     return Alloc::FailureResult();
michael@0:   }
michael@0: 
michael@0:   Copy::CopyElements(temp.Elements(), smallerElements, smallerLength, elemSize);
michael@0:   Copy::CopyElements(smallerElements, largerElements, largerLength, elemSize);
michael@0:   Copy::CopyElements(largerElements, temp.Elements(), smallerLength, elemSize);
michael@0: 
michael@0:   // Swap the arrays' lengths.
michael@0:   NS_ABORT_IF_FALSE((other.Length() == 0 || mHdr != EmptyHdr()) &&
michael@0:                     (Length() == 0 || other.mHdr != EmptyHdr()),
michael@0:                     "Don't set sEmptyHdr's length.");
michael@0:   size_type tempLength = Length();
michael@0:   mHdr->mLength = other.Length();
michael@0:   other.mHdr->mLength = tempLength;
michael@0: 
michael@0:   return Alloc::SuccessResult();
michael@0: }
michael@0: 
michael@0: template<class Alloc, class Copy>
michael@0: bool
michael@0: nsTArray_base<Alloc, Copy>::EnsureNotUsingAutoArrayBuffer(size_type elemSize) {
michael@0:   if (UsesAutoArrayBuffer()) {
michael@0: 
michael@0:     // If you call this on a 0-length array, we'll set that array's mHdr to
michael@0:     // sEmptyHdr, in flagrant violation of the nsAutoTArray invariants.  It's
michael@0:     // up to you to set it back!  (If you don't, the nsAutoTArray will forget
michael@0:     // that it has an auto buffer.)
michael@0:     if (Length() == 0) {
michael@0:       mHdr = EmptyHdr();
michael@0:       return true;
michael@0:     }
michael@0: 
michael@0:     size_type size = sizeof(Header) + Length() * elemSize;
michael@0: 
michael@0:     Header* header = static_cast<Header*>(Alloc::Malloc(size));
michael@0:     if (!header)
michael@0:       return false;
michael@0: 
michael@0:     Copy::CopyHeaderAndElements(header, mHdr, Length(), elemSize);
michael@0:     header->mCapacity = Length();
michael@0:     mHdr = header;
michael@0:   }
michael@0: 
michael@0:   return true;
michael@0: }