gecko-dev/xpcom/ds/nsSupportsArray.cpp

/* -*- 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/. */

#include <stdint.h>
#include <string.h>
#include "mozilla/CheckedInt.h"
#include "mozilla/MathAlgorithms.h"
#include "nsSupportsArray.h"
#include "nsSupportsArrayEnumerator.h"
#include "nsIObjectInputStream.h"
#include "nsIObjectOutputStream.h"

nsresult
nsQueryElementAt::operator()(const nsIID& aIID, void** aResult) const
{
  nsresult status =
    mCollection ? mCollection->QueryElementAt(mIndex, aIID, aResult) :
                  NS_ERROR_NULL_POINTER;

  if (mErrorPtr) {
    *mErrorPtr = status;
  }

  return status;
}

nsSupportsArray::nsSupportsArray()
{
  mArray = mAutoArray;
  mArraySize = kAutoArraySize;
  mCount = 0;
}

nsSupportsArray::~nsSupportsArray()
{
  DeleteArray();
}

bool
nsSupportsArray::GrowArrayBy(uint32_t aGrowBy)
{
  const uint32_t kGrowArrayBy = 8;
  const uint32_t kLinearThreshold = 16 * sizeof(nsISupports*);

  // We have to grow the array. Grow by kGrowArrayBy slots if we're smaller
  // than kLinearThreshold bytes, or a power of two if we're larger.
  // This is much more efficient with most memory allocators, especially
  // if it's very large, or of the allocator is binned.
  if (aGrowBy < kGrowArrayBy) {
    aGrowBy = kGrowArrayBy;
  }

  CheckedUint32 newCount(mArraySize);
  newCount += aGrowBy;  // Minimum increase
  CheckedUint32 newSize(sizeof(mArray[0]));
  newSize *= newCount;

  if (!newSize.isValid()) {
    return false;
  }

  if (newSize.value() >= kLinearThreshold) {
    // newCount includes enough space for at least kGrowArrayBy new slots.
    // Select the next power-of-two size in bytes above that if newSize is
    // not a power of two.
    if (newSize.value() & (newSize.value() - 1)) {
      newSize = UINT64_C(1) << mozilla::CeilingLog2(newSize.value());
      if (!newSize.isValid()) {
        return false;
      }
    }

    newCount = newSize / sizeof(mArray[0]);
  }
  // XXX This would be far more efficient in many allocators if we used
  // XXX PR_Realloc(), etc
  nsISupports** oldArray = mArray;

  mArray = new nsISupports*[newCount.value()];
  mArraySize = newCount.value();

  if (oldArray) {                   // need to move old data
    if (0 < mCount) {
      ::memcpy(mArray, oldArray, mCount * sizeof(nsISupports*));
    }
    if (oldArray != &(mAutoArray[0])) {
      delete[] oldArray;
    }
  }

  return true;
}

nsresult
nsSupportsArray::Create(nsISupports* aOuter, REFNSIID aIID, void** aResult)
{
  if (aOuter) {
    return NS_ERROR_NO_AGGREGATION;
  }

  nsCOMPtr<nsISupportsArray> it = new nsSupportsArray();

  return it->QueryInterface(aIID, aResult);
}

NS_IMPL_ISUPPORTS(nsSupportsArray, nsISupportsArray, nsICollection,
                  nsISerializable)

NS_IMETHODIMP
nsSupportsArray::Read(nsIObjectInputStream* aStream)
{
  nsresult rv;

  uint32_t newArraySize;
  rv = aStream->Read32(&newArraySize);
  if (NS_FAILED(rv)) {
    return rv;
  }

  if (newArraySize <= kAutoArraySize) {
    if (mArray != mAutoArray) {
      delete[] mArray;
      mArray = mAutoArray;
    }
    newArraySize = kAutoArraySize;
  } else {
    if (newArraySize <= mArraySize) {
      // Keep non-default-size mArray, it's more than big enough.
      newArraySize = mArraySize;
    } else {
      nsISupports** array = new nsISupports*[newArraySize];
      if (mArray != mAutoArray) {
        delete[] mArray;
      }
      mArray = array;
    }
  }
  mArraySize = newArraySize;

  rv = aStream->Read32(&mCount);
  if (NS_FAILED(rv)) {
    return rv;
  }

  NS_ASSERTION(mCount <= mArraySize, "overlarge mCount!");
  if (mCount > mArraySize) {
    mCount = mArraySize;
  }

  for (uint32_t i = 0; i < mCount; i++) {
    rv = aStream->ReadObject(true, &mArray[i]);
    if (NS_FAILED(rv)) {
      return rv;
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
nsSupportsArray::Write(nsIObjectOutputStream* aStream)
{
  nsresult rv;

  rv = aStream->Write32(mArraySize);
  if (NS_FAILED(rv)) {
    return rv;
  }

  rv = aStream->Write32(mCount);
  if (NS_FAILED(rv)) {
    return rv;
  }

  for (uint32_t i = 0; i < mCount; i++) {
    rv = aStream->WriteObject(mArray[i], true);
    if (NS_FAILED(rv)) {
      return rv;
    }
  }

  return NS_OK;
}

void
nsSupportsArray::DeleteArray(void)
{
  Clear();
  if (mArray != &(mAutoArray[0])) {
    delete[] mArray;
    mArray = mAutoArray;
    mArraySize = kAutoArraySize;
  }
}

NS_IMETHODIMP
nsSupportsArray::GetElementAt(uint32_t aIndex, nsISupports** aOutPtr)
{
  *aOutPtr = nullptr;
  if (aIndex < mCount) {
    NS_IF_ADDREF(*aOutPtr = mArray[aIndex]);
  }
  return NS_OK;
}

NS_IMETHODIMP_(int32_t)
nsSupportsArray::IndexOf(const nsISupports* aPossibleElement)
{
  const nsISupports** start = (const nsISupports**)mArray;  // work around goofy compiler behavior
  const nsISupports** ep = start;
  const nsISupports** end = (start + mCount);
  while (ep < end) {
    if (aPossibleElement == *ep) {
      return (ep - start);
    }
    ep++;
  }
  return -1;
}

NS_IMETHODIMP_(int32_t)
nsSupportsArray::LastIndexOf(const nsISupports* aPossibleElement)
{
  if (0 < mCount) {
    const nsISupports** start = (const nsISupports**)mArray;  // work around goofy compiler behavior
    const nsISupports** ep = (start + mCount);
    while (start <= --ep) {
      if (aPossibleElement == *ep) {
        return (ep - start);
      }
    }
  }
  return -1;
}

NS_IMETHODIMP_(bool)
nsSupportsArray::InsertElementAt(nsISupports* aElement, uint32_t aIndex)
{
  if (aIndex <= mCount) {
    CheckedUint32 newCount(mCount);
    newCount += 1;
    if (!newCount.isValid()) {
      return false;
    }

    if (mArraySize < newCount.value()) {
      // need to grow the array
      if (!GrowArrayBy(1)) {
        return false;
      }
    }

    // Could be slightly more efficient if GrowArrayBy knew about the
    // split, but the difference is trivial.
    uint32_t slide = (mCount - aIndex);
    if (0 < slide) {
      ::memmove(mArray + aIndex + 1, mArray + aIndex,
                slide * sizeof(nsISupports*));
    }

    mArray[aIndex] = aElement;
    NS_IF_ADDREF(aElement);
    mCount++;

    return true;
  }
  return false;
}

NS_IMETHODIMP_(bool)
nsSupportsArray::ReplaceElementAt(nsISupports* aElement, uint32_t aIndex)
{
  if (aIndex < mCount) {
    NS_IF_ADDREF(aElement);  // addref first in case it's the same object!
    NS_IF_RELEASE(mArray[aIndex]);
    mArray[aIndex] = aElement;
    return true;
  }
  return false;
}

NS_IMETHODIMP_(bool)
nsSupportsArray::RemoveElementsAt(uint32_t aIndex, uint32_t aCount)
{
  if (aIndex + aCount <= mCount) {
    for (uint32_t i = 0; i < aCount; i++) {
      NS_IF_RELEASE(mArray[aIndex + i]);
    }
    mCount -= aCount;
    int32_t slide = (mCount - aIndex);
    if (0 < slide) {
      ::memmove(mArray + aIndex, mArray + aIndex + aCount,
                slide * sizeof(nsISupports*));
    }
    return true;
  }
  return false;
}

NS_IMETHODIMP
nsSupportsArray::RemoveElement(nsISupports* aElement)
{
  int32_t theIndex = IndexOf(aElement);
  if (theIndex >= 0) {
    return RemoveElementAt(theIndex) ? NS_OK : NS_ERROR_FAILURE;
  }

  return NS_ERROR_FAILURE;
}

NS_IMETHODIMP
nsSupportsArray::Clear(void)
{
  if (0 < mCount) {
    do {
      --mCount;
      NS_IF_RELEASE(mArray[mCount]);
    } while (0 != mCount);
  }
  return NS_OK;
}

NS_IMETHODIMP
nsSupportsArray::Compact(void)
{
  if ((mArraySize != mCount) && (kAutoArraySize < mArraySize)) {
    nsISupports** oldArray = mArray;
    if (mCount <= kAutoArraySize) {
      mArray = mAutoArray;
      mArraySize = kAutoArraySize;
    } else {
      mArray = new nsISupports*[mCount];
      if (!mArray) {
        mArray = oldArray;
        return NS_OK;
      }
      mArraySize = mCount;
    }

    ::memcpy(mArray, oldArray, mCount * sizeof(nsISupports*));
    delete[] oldArray;
  }
  return NS_OK;
}

NS_IMETHODIMP
nsSupportsArray::Enumerate(nsIEnumerator** aResult)
{
  nsSupportsArrayEnumerator* e = new nsSupportsArrayEnumerator(this);
  *aResult = e;
  NS_ADDREF(e);
  return NS_OK;
}

NS_IMETHODIMP
nsSupportsArray::Clone(nsISupportsArray** aResult)
{
  nsCOMPtr<nsISupportsArray> newArray;
  nsresult rv = NS_NewISupportsArray(getter_AddRefs(newArray));
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  uint32_t count = 0;
  Count(&count);
  for (uint32_t i = 0; i < count; i++) {
    if (!newArray->InsertElementAt(mArray[i], i)) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
  }

  newArray.forget(aResult);
  return NS_OK;
}

nsresult
NS_NewISupportsArray(nsISupportsArray** aInstancePtrResult)
{
  nsresult rv;
  rv = nsSupportsArray::Create(nullptr, NS_GET_IID(nsISupportsArray),
                               (void**)aInstancePtrResult);
  return rv;
}