xslt/xpath/txNodeSet.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "txNodeSet.h"
#include "txLog.h"
#include "nsMemory.h"
#include "txXPathTreeWalker.h"
#include <algorithm>

/**
 * Implementation of an XPath nodeset
 */

#ifdef NS_BUILD_REFCNT_LOGGING
#  define LOG_CHUNK_MOVE(_start, _new_start, _count)         \
    {                                                        \
      txXPathNode* start = const_cast<txXPathNode*>(_start); \
      while (start < _start + _count) {                      \
        NS_LogDtor(start, "txXPathNode", sizeof(*start));    \
        ++start;                                             \
      }                                                      \
      start = const_cast<txXPathNode*>(_new_start);          \
      while (start < _new_start + _count) {                  \
        NS_LogCtor(start, "txXPathNode", sizeof(*start));    \
        ++start;                                             \
      }                                                      \
    }
#else
#  define LOG_CHUNK_MOVE(_start, _new_start, _count)
#endif

static const int32_t kTxNodeSetMinSize = 4;
static const int32_t kTxNodeSetGrowFactor = 2;

#define kForward 1
#define kReversed -1

txNodeSet::txNodeSet(txResultRecycler* aRecycler)
    : txAExprResult(aRecycler),
      mStart(nullptr),
      mEnd(nullptr),
      mStartBuffer(nullptr),
      mEndBuffer(nullptr),
      mDirection(kForward),
      mMarks(nullptr) {}

txNodeSet::txNodeSet(const txXPathNode& aNode, txResultRecycler* aRecycler)
    : txAExprResult(aRecycler),
      mStart(nullptr),
      mEnd(nullptr),
      mStartBuffer(nullptr),
      mEndBuffer(nullptr),
      mDirection(kForward),
      mMarks(nullptr) {
  if (!ensureGrowSize(1)) {
    return;
  }

  new (mStart) txXPathNode(aNode);
  ++mEnd;
}

txNodeSet::txNodeSet(const txNodeSet& aSource, txResultRecycler* aRecycler)
    : txAExprResult(aRecycler),
      mStart(nullptr),
      mEnd(nullptr),
      mStartBuffer(nullptr),
      mEndBuffer(nullptr),
      mDirection(kForward),
      mMarks(nullptr) {
  append(aSource);
}

txNodeSet::~txNodeSet() {
  delete[] mMarks;

  if (mStartBuffer) {
    destroyElements(mStart, mEnd);

    free(mStartBuffer);
  }
}

nsresult txNodeSet::add(const txXPathNode& aNode) {
  NS_ASSERTION(mDirection == kForward,
               "only append(aNode) is supported on reversed nodesets");

  if (isEmpty()) {
    return append(aNode);
  }

  bool dupe;
  txXPathNode* pos = findPosition(aNode, mStart, mEnd, dupe);

  if (dupe) {
    return NS_OK;
  }

  // save pos, ensureGrowSize messes with the pointers
  int32_t moveSize = mEnd - pos;
  int32_t offset = pos - mStart;
  if (!ensureGrowSize(1)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  // set pos to where it was
  pos = mStart + offset;

  if (moveSize > 0) {
    LOG_CHUNK_MOVE(pos, pos + 1, moveSize);
    memmove(pos + 1, pos, moveSize * sizeof(txXPathNode));
  }

  new (pos) txXPathNode(aNode);
  ++mEnd;

  return NS_OK;
}

nsresult txNodeSet::add(const txNodeSet& aNodes) {
  return add(aNodes, copyElements, nullptr);
}

nsresult txNodeSet::addAndTransfer(txNodeSet* aNodes) {
  // failure is out-of-memory, transfer didn't happen
  nsresult rv = add(*aNodes, transferElements, destroyElements);
  NS_ENSURE_SUCCESS(rv, rv);

#ifdef TX_DONT_RECYCLE_BUFFER
  if (aNodes->mStartBuffer) {
    free(aNodes->mStartBuffer);
    aNodes->mStartBuffer = aNodes->mEndBuffer = nullptr;
  }
#endif
  aNodes->mStart = aNodes->mEnd = aNodes->mStartBuffer;

  return NS_OK;
}

/**
 * add(aNodeSet, aTransferOp)
 *
 * The code is optimized to make a minimum number of calls to
 * Node::compareDocumentPosition. The idea is this:
 * We have the two nodesets (number indicate "document position")
 *
 * 1 3 7             <- source 1
 * 2 3 6 8 9         <- source 2
 * _ _ _ _ _ _ _ _   <- result
 *
 *
 * When merging these nodesets into the result, the nodes are transfered
 * in chunks to the end of the buffer so that each chunk does not contain
 * a node from the other nodeset, in document order.
 *
 * We select the last non-transfered node in the first nodeset and find
 * where in the other nodeset it would be inserted. In this case we would
 * take the 7 from the first nodeset and find the position between the
 * 6 and 8 in the second. We then take the nodes after the insert-position
 * and transfer them to the end of the resulting nodeset. Which in this case
 * means that we first transfered the 8 and 9 nodes, giving us the following:
 *
 * 1 3 7             <- source 1
 * 2 3 6             <- source 2
 * _ _ _ _ _ _ 8 9   <- result
 *
 * The corresponding procedure is done for the second nodeset, that is
 * the insertion position of the 6 in the first nodeset is found, which
 * is between the 3 and the 7. The 7 is memmoved (as it stays within
 * the same nodeset) to the result buffer.
 *
 * As the result buffer is filled from the end, it is safe to share the
 * buffer between this nodeset and the result.
 *
 * This is repeated until both of the nodesets are empty.
 *
 * If we find a duplicate node when searching for where insertposition we
 * check for sequences of duplicate nodes, which can be optimized.
 *
 */
nsresult txNodeSet::add(const txNodeSet& aNodes, transferOp aTransfer,
                        destroyOp aDestroy) {
  NS_ASSERTION(mDirection == kForward,
               "only append(aNode) is supported on reversed nodesets");

  if (aNodes.isEmpty()) {
    return NS_OK;
  }

  if (!ensureGrowSize(aNodes.size())) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  // This is probably a rather common case, so lets try to shortcut.
  if (mStart == mEnd ||
      txXPathNodeUtils::comparePosition(mEnd[-1], *aNodes.mStart) < 0) {
    aTransfer(mEnd, aNodes.mStart, aNodes.mEnd);
    mEnd += aNodes.size();

    return NS_OK;
  }

  // Last element in this nodeset
  txXPathNode* thisPos = mEnd;

  // Last element of the other nodeset
  txXPathNode* otherPos = aNodes.mEnd;

  // Pointer to the insertion point in this nodeset
  txXPathNode* insertPos = mEndBuffer;

  bool dupe;
  txXPathNode* pos;
  int32_t count;
  while (thisPos > mStart || otherPos > aNodes.mStart) {
    // Find where the last remaining node of this nodeset would
    // be inserted in the other nodeset.
    if (thisPos > mStart) {
      pos = findPosition(thisPos[-1], aNodes.mStart, otherPos, dupe);

      if (dupe) {
        const txXPathNode* deletePos = thisPos;
        --thisPos;  // this is already added
        // check dupe sequence
        while (thisPos > mStart && pos > aNodes.mStart &&
               thisPos[-1] == pos[-1]) {
          --thisPos;
          --pos;
        }

        if (aDestroy) {
          aDestroy(thisPos, deletePos);
        }
      }
    } else {
      pos = aNodes.mStart;
    }

    // Transfer the otherNodes after the insertion point to the result
    count = otherPos - pos;
    if (count > 0) {
      insertPos -= count;
      aTransfer(insertPos, pos, otherPos);
      otherPos -= count;
    }

    // Find where the last remaining node of the otherNodeset would
    // be inserted in this nodeset.
    if (otherPos > aNodes.mStart) {
      pos = findPosition(otherPos[-1], mStart, thisPos, dupe);

      if (dupe) {
        const txXPathNode* deletePos = otherPos;
        --otherPos;  // this is already added
        // check dupe sequence
        while (otherPos > aNodes.mStart && pos > mStart &&
               otherPos[-1] == pos[-1]) {
          --otherPos;
          --pos;
        }

        if (aDestroy) {
          aDestroy(otherPos, deletePos);
        }
      }
    } else {
      pos = mStart;
    }

    // Move the nodes from this nodeset after the insertion point
    // to the result
    count = thisPos - pos;
    if (count > 0) {
      insertPos -= count;
      LOG_CHUNK_MOVE(pos, insertPos, count);
      memmove(insertPos, pos, count * sizeof(txXPathNode));
      thisPos -= count;
    }
  }
  mStart = insertPos;
  mEnd = mEndBuffer;

  return NS_OK;
}

/**
 * Append API
 * These functions should be used with care.
 * They are intended to be used when the caller assures that the resulting
 * nodeset remains in document order.
 * Abuse will break document order, and cause errors in the result.
 * These functions are significantly faster than the add API, as no
 * order info operations will be performed.
 */

nsresult txNodeSet::append(const txXPathNode& aNode) {
  if (!ensureGrowSize(1)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  if (mDirection == kForward) {
    new (mEnd) txXPathNode(aNode);
    ++mEnd;

    return NS_OK;
  }

  new (--mStart) txXPathNode(aNode);

  return NS_OK;
}

nsresult txNodeSet::append(const txNodeSet& aNodes) {
  NS_ASSERTION(mDirection == kForward,
               "only append(aNode) is supported on reversed nodesets");

  if (aNodes.isEmpty()) {
    return NS_OK;
  }

  int32_t appended = aNodes.size();
  if (!ensureGrowSize(appended)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  copyElements(mEnd, aNodes.mStart, aNodes.mEnd);
  mEnd += appended;

  return NS_OK;
}

nsresult txNodeSet::mark(int32_t aIndex) {
  NS_ASSERTION(aIndex >= 0 && mStart && mEnd - mStart > aIndex,
               "index out of bounds");
  if (!mMarks) {
    int32_t length = size();
    mMarks = new bool[length];
    memset(mMarks, 0, length * sizeof(bool));
  }
  if (mDirection == kForward) {
    mMarks[aIndex] = true;
  } else {
    mMarks[size() - aIndex - 1] = true;
  }

  return NS_OK;
}

nsresult txNodeSet::sweep() {
  if (!mMarks) {
    // sweep everything
    clear();
  }

  int32_t chunk, pos = 0;
  int32_t length = size();
  txXPathNode* insertion = mStartBuffer;

  while (pos < length) {
    while (pos < length && !mMarks[pos]) {
      // delete unmarked
      mStart[pos].~txXPathNode();
      ++pos;
    }
    // find chunk to move
    chunk = 0;
    while (pos < length && mMarks[pos]) {
      ++pos;
      ++chunk;
    }
    // move chunk
    if (chunk > 0) {
      LOG_CHUNK_MOVE(mStart + pos - chunk, insertion, chunk);
      memmove(insertion, mStart + pos - chunk, chunk * sizeof(txXPathNode));
      insertion += chunk;
    }
  }
  mStart = mStartBuffer;
  mEnd = insertion;
  delete[] mMarks;
  mMarks = nullptr;

  return NS_OK;
}

void txNodeSet::clear() {
  destroyElements(mStart, mEnd);
#ifdef TX_DONT_RECYCLE_BUFFER
  if (mStartBuffer) {
    free(mStartBuffer);
    mStartBuffer = mEndBuffer = nullptr;
  }
#endif
  mStart = mEnd = mStartBuffer;
  delete[] mMarks;
  mMarks = nullptr;
  mDirection = kForward;
}

int32_t txNodeSet::indexOf(const txXPathNode& aNode, uint32_t aStart) const {
  NS_ASSERTION(mDirection == kForward,
               "only append(aNode) is supported on reversed nodesets");

  if (!mStart || mStart == mEnd) {
    return -1;
  }

  txXPathNode* pos = mStart + aStart;
  for (; pos < mEnd; ++pos) {
    if (*pos == aNode) {
      return pos - mStart;
    }
  }

  return -1;
}

const txXPathNode& txNodeSet::get(int32_t aIndex) const {
  if (mDirection == kForward) {
    return mStart[aIndex];
  }

  return mEnd[-aIndex - 1];
}

short txNodeSet::getResultType() { return txAExprResult::NODESET; }

bool txNodeSet::booleanValue() { return !isEmpty(); }
double txNodeSet::numberValue() {
  nsAutoString str;
  stringValue(str);

  return txDouble::toDouble(str);
}

void txNodeSet::stringValue(nsString& aStr) {
  NS_ASSERTION(mDirection == kForward,
               "only append(aNode) is supported on reversed nodesets");
  if (isEmpty()) {
    return;
  }
  txXPathNodeUtils::appendNodeValue(get(0), aStr);
}

const nsString* txNodeSet::stringValuePointer() { return nullptr; }

bool txNodeSet::ensureGrowSize(int32_t aSize) {
  // check if there is enough place in the buffer as is
  if (mDirection == kForward && aSize <= mEndBuffer - mEnd) {
    return true;
  }

  if (mDirection == kReversed && aSize <= mStart - mStartBuffer) {
    return true;
  }

  // check if we just have to align mStart to have enough space
  int32_t oldSize = mEnd - mStart;
  int32_t oldLength = mEndBuffer - mStartBuffer;
  int32_t ensureSize = oldSize + aSize;
  if (ensureSize <= oldLength) {
    // just move the buffer
    txXPathNode* dest = mStartBuffer;
    if (mDirection == kReversed) {
      dest = mEndBuffer - oldSize;
    }
    LOG_CHUNK_MOVE(mStart, dest, oldSize);
    memmove(dest, mStart, oldSize * sizeof(txXPathNode));
    mStart = dest;
    mEnd = dest + oldSize;

    return true;
  }

  // This isn't 100% safe. But until someone manages to make a 1gig nodeset
  // it should be ok.
  int32_t newLength = std::max(oldLength, kTxNodeSetMinSize);

  while (newLength < ensureSize) {
    newLength *= kTxNodeSetGrowFactor;
  }

  txXPathNode* newArr =
      static_cast<txXPathNode*>(moz_xmalloc(newLength * sizeof(txXPathNode)));

  txXPathNode* dest = newArr;
  if (mDirection == kReversed) {
    dest += newLength - oldSize;
  }

  if (oldSize > 0) {
    LOG_CHUNK_MOVE(mStart, dest, oldSize);
    memcpy(dest, mStart, oldSize * sizeof(txXPathNode));
  }

  if (mStartBuffer) {
#ifdef DEBUG
    memset(mStartBuffer, 0, (mEndBuffer - mStartBuffer) * sizeof(txXPathNode));
#endif
    free(mStartBuffer);
  }

  mStartBuffer = newArr;
  mEndBuffer = mStartBuffer + newLength;
  mStart = dest;
  mEnd = dest + oldSize;

  return true;
}

txXPathNode* txNodeSet::findPosition(const txXPathNode& aNode,
                                     txXPathNode* aFirst, txXPathNode* aLast,
                                     bool& aDupe) const {
  aDupe = false;
  if (aLast - aFirst <= 2) {
    // If we search 2 nodes or less there is no point in further divides
    txXPathNode* pos = aFirst;
    for (; pos < aLast; ++pos) {
      int cmp = txXPathNodeUtils::comparePosition(aNode, *pos);
      if (cmp < 0) {
        return pos;
      }

      if (cmp == 0) {
        aDupe = true;

        return pos;
      }
    }
    return pos;
  }

  // (cannot add two pointers)
  txXPathNode* midpos = aFirst + (aLast - aFirst) / 2;
  int cmp = txXPathNodeUtils::comparePosition(aNode, *midpos);
  if (cmp == 0) {
    aDupe = true;

    return midpos;
  }

  if (cmp > 0) {
    return findPosition(aNode, midpos + 1, aLast, aDupe);
  }

  // midpos excluded as end of range

  return findPosition(aNode, aFirst, midpos, aDupe);
}

/* static */
void txNodeSet::copyElements(txXPathNode* aDest, const txXPathNode* aStart,
                             const txXPathNode* aEnd) {
  const txXPathNode* pos = aStart;
  while (pos < aEnd) {
    new (aDest) txXPathNode(*pos);
    ++aDest;
    ++pos;
  }
}

/* static */
void txNodeSet::transferElements(txXPathNode* aDest, const txXPathNode* aStart,
                                 const txXPathNode* aEnd) {
  LOG_CHUNK_MOVE(aStart, aDest, (aEnd - aStart));
  memcpy(aDest, aStart, (aEnd - aStart) * sizeof(txXPathNode));
}