Source/WebCore/contentextensions/DFAMinimizer.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2015 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  * THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "DFAMinimizer.h"

 #if ENABLE(CONTENT_EXTENSIONS)

 #include "DFA.h"
 #include "DFANode.h"
 #include "MutableRangeList.h"
 #include <wtf/HashMap.h>
 #include <wtf/Hasher.h>
 #include <wtf/Vector.h>

 namespace WebCore {
 namespace ContentExtensions {

 namespace {

 template<typename VectorType, typename Iterable, typename Function>
 static inline void iterateIntersections(const VectorType& singularTransitionsFirsts, const Iterable& iterableTransitionList, const Function& intersectionHandler)
 {
     ASSERT(!singularTransitionsFirsts.isEmpty());
     auto otherIterator = iterableTransitionList.begin();
     auto otherEnd = iterableTransitionList.end();

     if (otherIterator == otherEnd)
         return;

     unsigned singularTransitionsLength = singularTransitionsFirsts.size();
     unsigned singularTransitionsFirstsIndex = 0;
     for (; otherIterator != otherEnd; ++otherIterator) {
         auto firstCharacter = otherIterator.first();
         while (singularTransitionsFirstsIndex < singularTransitionsLength
             && singularTransitionsFirsts[singularTransitionsFirstsIndex] != firstCharacter)
             ++singularTransitionsFirstsIndex;

         intersectionHandler(singularTransitionsFirstsIndex, otherIterator);
         ++singularTransitionsFirstsIndex;

         auto lastCharacter = otherIterator.last();
         while (singularTransitionsFirstsIndex < singularTransitionsLength
             && singularTransitionsFirsts[singularTransitionsFirstsIndex] <= lastCharacter) {
             intersectionHandler(singularTransitionsFirstsIndex, otherIterator);
             ++singularTransitionsFirstsIndex;
         }
     }
 }

 class Partition {
 public:
     void initialize(unsigned size)
     {
         if (!size)
             return;

         m_sets.reserveInitialCapacity(size);
         m_partitionedElements.resize(size);
         m_elementPositionInPartitionedNodes.resize(size);
         m_elementToSetMap.resize(size);

         for (unsigned i = 0; i < size; ++i) {
             m_partitionedElements[i] = i;
             m_elementPositionInPartitionedNodes[i] = i;
             m_elementToSetMap[i] = 0;
         }
         m_sets.uncheckedAppend(SetDescriptor { 0, size, 0 });
     }

     void reserveUninitializedCapacity(unsigned elementCount)
     {
         m_partitionedElements.resize(elementCount);
         m_elementPositionInPartitionedNodes.resize(elementCount);
         m_elementToSetMap.resize(elementCount);
     }

     void addSetUnchecked(unsigned start, unsigned size)
     {
         m_sets.append(SetDescriptor { start, size, 0 });
     }

     void setElementUnchecked(unsigned elementIndex, unsigned positionInPartition, unsigned setIndex)
     {
         ASSERT(setIndex < m_sets.size());
         m_partitionedElements[positionInPartition] = elementIndex;
         m_elementPositionInPartitionedNodes[elementIndex] = positionInPartition;
         m_elementToSetMap[elementIndex] = setIndex;
     }

     unsigned startOffsetOfSet(unsigned setIndex) const
     {
         return m_sets[setIndex].start;
     }

     ALWAYS_INLINE void markElementInCurrentGeneration(unsigned elementIndex)
     {
         // Swap the node with the first unmarked node.
         unsigned setIndex = m_elementToSetMap[elementIndex];
         SetDescriptor& setDescriptor = m_sets[setIndex];

         unsigned elementPositionInPartition = m_elementPositionInPartitionedNodes[elementIndex];
         ASSERT(elementPositionInPartition >= setDescriptor.start);
         ASSERT(elementPositionInPartition < setDescriptor.end());

         unsigned firstUnmarkedElementPositionInPartition = setDescriptor.indexAfterMarkedElements();
         ASSERT(firstUnmarkedElementPositionInPartition >= setDescriptor.start && firstUnmarkedElementPositionInPartition < setDescriptor.end());
         ASSERT(firstUnmarkedElementPositionInPartition >= firstUnmarkedElementPositionInPartition);

         // Swap the nodes in the set.
         unsigned firstUnmarkedElement = m_partitionedElements[firstUnmarkedElementPositionInPartition];
         m_partitionedElements[firstUnmarkedElementPositionInPartition] = elementIndex;
         m_partitionedElements[elementPositionInPartition] = firstUnmarkedElement;

         // Update their index.
         m_elementPositionInPartitionedNodes[elementIndex] = firstUnmarkedElementPositionInPartition;
         m_elementPositionInPartitionedNodes[firstUnmarkedElement] = elementPositionInPartition;

         if (!setDescriptor.markedCount) {
             ASSERT(!m_setsMarkedInCurrentGeneration.contains(setIndex));
             m_setsMarkedInCurrentGeneration.append(setIndex);
         }
         ++setDescriptor.markedCount;
     }

     // The function passed as argument MUST not modify the partition.
     template<typename Function>
     void refineGeneration(const Function& function)
     {
         for (unsigned setIndex : m_setsMarkedInCurrentGeneration) {
             SetDescriptor& setDescriptor = m_sets[setIndex];
             if (setDescriptor.markedCount == setDescriptor.size) {
                 // Everything is marked, there is nothing to refine.
                 setDescriptor.markedCount = 0;
                 continue;
             }

             SetDescriptor newSet;
             bool newSetIsMarkedSet = setDescriptor.markedCount * 2 <= setDescriptor.size;
             if (newSetIsMarkedSet) {
                 // Less than half of the nodes have been marked.
                 newSet = { setDescriptor.start, setDescriptor.markedCount, 0 };
                 setDescriptor.start = setDescriptor.start + setDescriptor.markedCount;
             } else
                 newSet = { setDescriptor.start + setDescriptor.markedCount, setDescriptor.size - setDescriptor.markedCount, 0 };
             setDescriptor.size -= newSet.size;
             setDescriptor.markedCount = 0;

             unsigned newSetIndex = m_sets.size();
             m_sets.append(newSet);

             for (unsigned i = newSet.start; i < newSet.end(); ++i)
                 m_elementToSetMap[m_partitionedElements[i]] = newSetIndex;

             function(newSetIndex);
         }
         m_setsMarkedInCurrentGeneration.clear();
     }

     // Call Function() on every node of a given subset.
     template<typename Function>
     void iterateSet(unsigned setIndex, const Function& function)
     {
         SetDescriptor& setDescriptor = m_sets[setIndex];
         for (unsigned i = setDescriptor.start; i < setDescriptor.end(); ++i)
             function(m_partitionedElements[i]);
     }

     // Index of the set containing the Node.
     unsigned setIndex(unsigned elementIndex) const
     {
         return m_elementToSetMap[elementIndex];
     }

     // NodeIndex of the first element in the set.
     unsigned firstElementInSet(unsigned setIndex) const
     {
         return m_partitionedElements[m_sets[setIndex].start];
     }

     unsigned size() const
     {
         return m_sets.size();
     }

 private:
     struct SetDescriptor {
         unsigned start;
         unsigned size;
         unsigned markedCount;

         unsigned indexAfterMarkedElements() const { return start + markedCount; }
         unsigned end() const { return start + size; }
     };

     // List of sets.
     Vector<SetDescriptor, 0, ContentExtensionsOverflowHandler> m_sets;

     // All the element indices such that two elements of the same set never have a element of a different set between them.
     Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_partitionedElements;

     // Map elementIndex->position in the partitionedElements.
     Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_elementPositionInPartitionedNodes;

     // Map elementIndex->SetIndex.
     Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_elementToSetMap;

     // List of sets with any marked node. Each set can appear at most once.
     // FIXME: find a good inline size for this.
     Vector<unsigned, 128, ContentExtensionsOverflowHandler> m_setsMarkedInCurrentGeneration;
 };

 class FullGraphPartition {
     typedef MutableRangeList<char, uint32_t, 128> SingularTransitionsMutableRangeList;
 public:
     FullGraphPartition(const DFA& dfa)
     {
         m_nodePartition.initialize(dfa.nodes.size());

         SingularTransitionsMutableRangeList singularTransitions;
         CounterConverter counterConverter;
         for (const DFANode& node : dfa.nodes) {
             if (node.isKilled())
                 continue;
             auto transitions = node.transitions(dfa);
             singularTransitions.extend(transitions.begin(), transitions.end(), counterConverter);
         }

         // Count the number of transition for each singular range. This will give us the bucket size
         // for the transition partition, where transitions are partitioned by "symbol".
         unsigned rangeIndexAccumulator = 0;
         for (const auto& transition : singularTransitions) {
             m_transitionPartition.addSetUnchecked(rangeIndexAccumulator, transition.data);
             rangeIndexAccumulator += transition.data;
         }

         // Count the number of incoming transitions per node.
         m_flattenedTransitionsStartOffsetPerNode.resize(dfa.nodes.size());
         memset(m_flattenedTransitionsStartOffsetPerNode.data(), 0, m_flattenedTransitionsStartOffsetPerNode.size() * sizeof(unsigned));

         Vector<char, 0, ContentExtensionsOverflowHandler> singularTransitionsFirsts;
         singularTransitionsFirsts.reserveInitialCapacity(singularTransitions.m_ranges.size());
         for (const auto& transition : singularTransitions)
             singularTransitionsFirsts.uncheckedAppend(transition.first);

         for (const DFANode& node : dfa.nodes) {
             if (node.isKilled())
                 continue;
             auto transitions = node.transitions(dfa);
             iterateIntersections(singularTransitionsFirsts, transitions, [&](unsigned, const DFANode::ConstRangeIterator& origin) {
                 uint32_t targetNodeIndex = origin.target();
                 ++m_flattenedTransitionsStartOffsetPerNode[targetNodeIndex];
             });
         }

         // Accumulate the offsets. This gives us the start position of each bucket.
         unsigned transitionAccumulator = 0;
         for (unsigned i = 0; i < m_flattenedTransitionsStartOffsetPerNode.size(); ++i) {
             unsigned transitionsCountForNode = m_flattenedTransitionsStartOffsetPerNode[i];
             m_flattenedTransitionsStartOffsetPerNode[i] = transitionAccumulator;
             transitionAccumulator += transitionsCountForNode;
         }
         unsigned flattenedTransitionsSize = transitionAccumulator;
         ASSERT_WITH_MESSAGE(flattenedTransitionsSize == rangeIndexAccumulator, "The number of transitions should be the same, regardless of how they are arranged in buckets.");

         m_transitionPartition.reserveUninitializedCapacity(flattenedTransitionsSize);

         // Next, let's fill the transition table and set up the size of each group at the same time.
         m_flattenedTransitionsSizePerNode.resize(dfa.nodes.size());
         for (unsigned& counter : m_flattenedTransitionsSizePerNode)
             counter = 0;
         m_flattenedTransitions.resize(flattenedTransitionsSize);

         Vector<uint32_t> transitionPerRangeOffset(m_transitionPartition.size());
         memset(transitionPerRangeOffset.data(), 0, transitionPerRangeOffset.size() * sizeof(uint32_t));

         for (unsigned i = 0; i < dfa.nodes.size(); ++i) {
             const DFANode& node = dfa.nodes[i];
             if (node.isKilled())
                 continue;

             auto transitions = node.transitions(dfa);
             iterateIntersections(singularTransitionsFirsts, transitions, [&](unsigned singularTransitonIndex, const DFANode::ConstRangeIterator& origin) {
                 uint32_t targetNodeIndex = origin.target();

                 unsigned start = m_flattenedTransitionsStartOffsetPerNode[targetNodeIndex];
                 unsigned offset = m_flattenedTransitionsSizePerNode[targetNodeIndex];
                 unsigned positionInFlattenedTransitions = start + offset;
                 m_flattenedTransitions[positionInFlattenedTransitions] = Transition({ i });

                 uint32_t& inRangeOffset = transitionPerRangeOffset[singularTransitonIndex];
                 unsigned positionInTransitionPartition = m_transitionPartition.startOffsetOfSet(singularTransitonIndex) + inRangeOffset;
                 ++inRangeOffset;

                 m_transitionPartition.setElementUnchecked(positionInFlattenedTransitions, positionInTransitionPartition, singularTransitonIndex);

                 ++m_flattenedTransitionsSizePerNode[targetNodeIndex];
             });
         }
     }

     void markNode(unsigned nodeIndex)
     {
         m_nodePartition.markElementInCurrentGeneration(nodeIndex);
     }

     void refinePartitions()
     {
         m_nodePartition.refineGeneration([&](unsigned smallestSetIndex) {
             m_nodePartition.iterateSet(smallestSetIndex, [&](unsigned nodeIndex) {
                 unsigned incomingTransitionsStartForNode = m_flattenedTransitionsStartOffsetPerNode[nodeIndex];
                 unsigned incomingTransitionsSizeForNode = m_flattenedTransitionsSizePerNode[nodeIndex];

                 for (unsigned i = 0; i < incomingTransitionsSizeForNode; ++i)
                     m_transitionPartition.markElementInCurrentGeneration(incomingTransitionsStartForNode + i);
             });

             // We only need to split the transitions, we handle the new sets through the main loop.
             m_transitionPartition.refineGeneration([](unsigned) { });
         });
     }

     void splitByUniqueTransitions()
     {
         for (; m_nextTransitionSetToProcess < m_transitionPartition.size(); ++m_nextTransitionSetToProcess) {
             // We use the known splitters to refine the set.
             m_transitionPartition.iterateSet(m_nextTransitionSetToProcess, [&](unsigned transitionIndex) {
                 unsigned sourceNodeIndex = m_flattenedTransitions[transitionIndex].source;
                 m_nodePartition.markElementInCurrentGeneration(sourceNodeIndex);
             });

             refinePartitions();
         }
     }

     unsigned nodeReplacement(unsigned nodeIndex)
     {
         unsigned setIndex = m_nodePartition.setIndex(nodeIndex);
         return m_nodePartition.firstElementInSet(setIndex);
     }

 private:
     struct Transition {
         unsigned source;
     };

     struct CounterConverter {
         uint32_t convert(uint32_t)
         {
             return 1;
         }

         void extend(uint32_t& destination, uint32_t)
         {
             ++destination;
         }
     };

     Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_flattenedTransitionsStartOffsetPerNode;
     Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_flattenedTransitionsSizePerNode;
     Vector<Transition, 0, ContentExtensionsOverflowHandler> m_flattenedTransitions;

     Partition m_nodePartition;
     Partition m_transitionPartition;

     unsigned m_nextTransitionSetToProcess { 0 };
 };

 struct ActionKey {
     enum DeletedValueTag { DeletedValue };
     explicit ActionKey(DeletedValueTag) { state = Deleted; }

     enum EmptyValueTag { EmptyValue };
     explicit ActionKey(EmptyValueTag) { state = Empty; }

     explicit ActionKey(const DFA* dfa, uint32_t actionsStart, uint16_t actionsLength)
         : dfa(dfa)
         , actionsStart(actionsStart)
         , actionsLength(actionsLength)
         , state(Valid)
     {
         StringHasher hasher;
         hasher.addCharactersAssumingAligned(reinterpret_cast<const UChar*>(&dfa->actions[actionsStart]), actionsLength * sizeof(uint64_t) / sizeof(UChar));
         hash = hasher.hash();
     }

     bool isEmptyValue() const { return state == Empty; }
     bool isDeletedValue() const { return state == Deleted; }

     unsigned hash;

     const DFA* dfa;
     uint32_t actionsStart;
     uint16_t actionsLength;

     enum {
         Valid,
         Empty,
         Deleted
     } state;
 };

 struct ActionKeyHash {
     static unsigned hash(const ActionKey& actionKey)
     {
         return actionKey.hash;
     }

     static bool equal(const ActionKey& a, const ActionKey& b)
     {
         if (a.state != b.state
             || a.dfa != b.dfa
             || a.actionsLength != b.actionsLength)
             return false;
         for (uint16_t i = 0; i < a.actionsLength; ++i) {
             if (a.dfa->actions[a.actionsStart + i] != a.dfa->actions[b.actionsStart + i])
                 return false;
         }
         return true;
     }
     static const bool safeToCompareToEmptyOrDeleted = false;
 };

 struct ActionKeyHashTraits : public WTF::CustomHashTraits<ActionKey> {
     static const bool emptyValueIsZero = true;
 };

 } // anonymous namespace.

 void DFAMinimizer::minimize(DFA& dfa)
 {
     FullGraphPartition fullGraphPartition(dfa);

     // Unlike traditional minimization final states can be differentiated by their action.
     // Instead of creating a single set for the final state, we partition by actions from
     // the start.
     HashMap<ActionKey, Vector<unsigned>, ActionKeyHash, ActionKeyHashTraits> finalStates;
     for (unsigned i = 0; i < dfa.nodes.size(); ++i) {
         const DFANode& node = dfa.nodes[i];
         if (node.hasActions()) {
             // FIXME: Sort the actions in the dfa to make nodes that have the same actions in different order equal.
             auto addResult = finalStates.add(ActionKey(&dfa, node.actionsStart(), node.actionsLength()), Vector<unsigned>());
             addResult.iterator->value.append(i);
         }
     }

     for (const auto& slot : finalStates) {
         for (unsigned finalStateIndex : slot.value)
             fullGraphPartition.markNode(finalStateIndex);
         fullGraphPartition.refinePartitions();
     }

     // Use every splitter to refine the node partitions.
     fullGraphPartition.splitByUniqueTransitions();

     Vector<unsigned> relocationVector;
     relocationVector.reserveInitialCapacity(dfa.nodes.size());
     for (unsigned i = 0; i < dfa.nodes.size(); ++i)
         relocationVector.uncheckedAppend(i);

     // Update all the transitions.
     for (unsigned i = 0; i < dfa.nodes.size(); ++i) {
         unsigned replacement = fullGraphPartition.nodeReplacement(i);
         if (i != replacement) {
             relocationVector[i] = replacement;
             dfa.nodes[i].kill(dfa);
         }
     }

     dfa.root = relocationVector[dfa.root];
     for (DFANode& node : dfa.nodes) {
         if (node.isKilled())
             continue;

         for (auto& transition : node.transitions(dfa)) {
             uint32_t target = transition.target();
             uint32_t relocatedTarget = relocationVector[target];
             if (target != relocatedTarget)
                 transition.resetTarget(relocatedTarget);
         }
     }
 }

 } // namespace ContentExtensions
 } // namespace WebCore

 #endif // ENABLE(CONTENT_EXTENSIONS)
	/*
	* Copyright (C) 2015 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
	* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
	* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
	* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
	* THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "DFAMinimizer.h"

	#if ENABLE(CONTENT_EXTENSIONS)

	#include "DFA.h"
	#include "DFANode.h"
	#include "MutableRangeList.h"
	#include <wtf/HashMap.h>
	#include <wtf/Hasher.h>
	#include <wtf/Vector.h>

	namespace WebCore {
	namespace ContentExtensions {

	namespace {

	template<typename VectorType, typename Iterable, typename Function>
	static inline void iterateIntersections(const VectorType& singularTransitionsFirsts, const Iterable& iterableTransitionList, const Function& intersectionHandler)
	{
	ASSERT(!singularTransitionsFirsts.isEmpty());
	auto otherIterator = iterableTransitionList.begin();
	auto otherEnd = iterableTransitionList.end();

	if (otherIterator == otherEnd)
	return;

	unsigned singularTransitionsLength = singularTransitionsFirsts.size();
	unsigned singularTransitionsFirstsIndex = 0;
	for (; otherIterator != otherEnd; ++otherIterator) {
	auto firstCharacter = otherIterator.first();
	while (singularTransitionsFirstsIndex < singularTransitionsLength
	&& singularTransitionsFirsts[singularTransitionsFirstsIndex] != firstCharacter)
	++singularTransitionsFirstsIndex;

	intersectionHandler(singularTransitionsFirstsIndex, otherIterator);
	++singularTransitionsFirstsIndex;

	auto lastCharacter = otherIterator.last();
	while (singularTransitionsFirstsIndex < singularTransitionsLength
	&& singularTransitionsFirsts[singularTransitionsFirstsIndex] <= lastCharacter) {
	intersectionHandler(singularTransitionsFirstsIndex, otherIterator);
	++singularTransitionsFirstsIndex;
	}
	}
	}

	class Partition {
	public:
	void initialize(unsigned size)
	{
	if (!size)
	return;

	m_sets.reserveInitialCapacity(size);
	m_partitionedElements.resize(size);
	m_elementPositionInPartitionedNodes.resize(size);
	m_elementToSetMap.resize(size);

	for (unsigned i = 0; i < size; ++i) {
	m_partitionedElements[i] = i;
	m_elementPositionInPartitionedNodes[i] = i;
	m_elementToSetMap[i] = 0;
	}
	m_sets.uncheckedAppend(SetDescriptor { 0, size, 0 });
	}

	void reserveUninitializedCapacity(unsigned elementCount)
	{
	m_partitionedElements.resize(elementCount);
	m_elementPositionInPartitionedNodes.resize(elementCount);
	m_elementToSetMap.resize(elementCount);
	}

	void addSetUnchecked(unsigned start, unsigned size)
	{
	m_sets.append(SetDescriptor { start, size, 0 });
	}

	void setElementUnchecked(unsigned elementIndex, unsigned positionInPartition, unsigned setIndex)
	{
	ASSERT(setIndex < m_sets.size());
	m_partitionedElements[positionInPartition] = elementIndex;
	m_elementPositionInPartitionedNodes[elementIndex] = positionInPartition;
	m_elementToSetMap[elementIndex] = setIndex;
	}

	unsigned startOffsetOfSet(unsigned setIndex) const
	{
	return m_sets[setIndex].start;
	}

	ALWAYS_INLINE void markElementInCurrentGeneration(unsigned elementIndex)
	{
	// Swap the node with the first unmarked node.
	unsigned setIndex = m_elementToSetMap[elementIndex];
	SetDescriptor& setDescriptor = m_sets[setIndex];

	unsigned elementPositionInPartition = m_elementPositionInPartitionedNodes[elementIndex];
	ASSERT(elementPositionInPartition >= setDescriptor.start);
	ASSERT(elementPositionInPartition < setDescriptor.end());

	unsigned firstUnmarkedElementPositionInPartition = setDescriptor.indexAfterMarkedElements();
	ASSERT(firstUnmarkedElementPositionInPartition >= setDescriptor.start && firstUnmarkedElementPositionInPartition < setDescriptor.end());
	ASSERT(firstUnmarkedElementPositionInPartition >= firstUnmarkedElementPositionInPartition);

	// Swap the nodes in the set.
	unsigned firstUnmarkedElement = m_partitionedElements[firstUnmarkedElementPositionInPartition];
	m_partitionedElements[firstUnmarkedElementPositionInPartition] = elementIndex;
	m_partitionedElements[elementPositionInPartition] = firstUnmarkedElement;

	// Update their index.
	m_elementPositionInPartitionedNodes[elementIndex] = firstUnmarkedElementPositionInPartition;
	m_elementPositionInPartitionedNodes[firstUnmarkedElement] = elementPositionInPartition;

	if (!setDescriptor.markedCount) {
	ASSERT(!m_setsMarkedInCurrentGeneration.contains(setIndex));
	m_setsMarkedInCurrentGeneration.append(setIndex);
	}
	++setDescriptor.markedCount;
	}

	// The function passed as argument MUST not modify the partition.
	template<typename Function>
	void refineGeneration(const Function& function)
	{
	for (unsigned setIndex : m_setsMarkedInCurrentGeneration) {
	SetDescriptor& setDescriptor = m_sets[setIndex];
	if (setDescriptor.markedCount == setDescriptor.size) {
	// Everything is marked, there is nothing to refine.
	setDescriptor.markedCount = 0;
	continue;
	}

	SetDescriptor newSet;
	bool newSetIsMarkedSet = setDescriptor.markedCount * 2 <= setDescriptor.size;
	if (newSetIsMarkedSet) {
	// Less than half of the nodes have been marked.
	newSet = { setDescriptor.start, setDescriptor.markedCount, 0 };
	setDescriptor.start = setDescriptor.start + setDescriptor.markedCount;
	} else
	newSet = { setDescriptor.start + setDescriptor.markedCount, setDescriptor.size - setDescriptor.markedCount, 0 };
	setDescriptor.size -= newSet.size;
	setDescriptor.markedCount = 0;

	unsigned newSetIndex = m_sets.size();
	m_sets.append(newSet);

	for (unsigned i = newSet.start; i < newSet.end(); ++i)
	m_elementToSetMap[m_partitionedElements[i]] = newSetIndex;

	function(newSetIndex);
	}
	m_setsMarkedInCurrentGeneration.clear();
	}

	// Call Function() on every node of a given subset.
	template<typename Function>
	void iterateSet(unsigned setIndex, const Function& function)
	{
	SetDescriptor& setDescriptor = m_sets[setIndex];
	for (unsigned i = setDescriptor.start; i < setDescriptor.end(); ++i)
	function(m_partitionedElements[i]);
	}

	// Index of the set containing the Node.
	unsigned setIndex(unsigned elementIndex) const
	{
	return m_elementToSetMap[elementIndex];
	}

	// NodeIndex of the first element in the set.
	unsigned firstElementInSet(unsigned setIndex) const
	{
	return m_partitionedElements[m_sets[setIndex].start];
	}

	unsigned size() const
	{
	return m_sets.size();
	}

	private:
	struct SetDescriptor {
	unsigned start;
	unsigned size;
	unsigned markedCount;

	unsigned indexAfterMarkedElements() const { return start + markedCount; }
	unsigned end() const { return start + size; }
	};

	// List of sets.
	Vector<SetDescriptor, 0, ContentExtensionsOverflowHandler> m_sets;

	// All the element indices such that two elements of the same set never have a element of a different set between them.
	Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_partitionedElements;

	// Map elementIndex->position in the partitionedElements.
	Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_elementPositionInPartitionedNodes;

	// Map elementIndex->SetIndex.
	Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_elementToSetMap;

	// List of sets with any marked node. Each set can appear at most once.
	// FIXME: find a good inline size for this.
	Vector<unsigned, 128, ContentExtensionsOverflowHandler> m_setsMarkedInCurrentGeneration;
	};

	class FullGraphPartition {
	typedef MutableRangeList<char, uint32_t, 128> SingularTransitionsMutableRangeList;
	public:
	FullGraphPartition(const DFA& dfa)
	{
	m_nodePartition.initialize(dfa.nodes.size());

	SingularTransitionsMutableRangeList singularTransitions;
	CounterConverter counterConverter;
	for (const DFANode& node : dfa.nodes) {
	if (node.isKilled())
	continue;
	auto transitions = node.transitions(dfa);
	singularTransitions.extend(transitions.begin(), transitions.end(), counterConverter);
	}

	// Count the number of transition for each singular range. This will give us the bucket size
	// for the transition partition, where transitions are partitioned by "symbol".
	unsigned rangeIndexAccumulator = 0;
	for (const auto& transition : singularTransitions) {
	m_transitionPartition.addSetUnchecked(rangeIndexAccumulator, transition.data);
	rangeIndexAccumulator += transition.data;
	}

	// Count the number of incoming transitions per node.
	m_flattenedTransitionsStartOffsetPerNode.resize(dfa.nodes.size());
	memset(m_flattenedTransitionsStartOffsetPerNode.data(), 0, m_flattenedTransitionsStartOffsetPerNode.size() * sizeof(unsigned));

	Vector<char, 0, ContentExtensionsOverflowHandler> singularTransitionsFirsts;
	singularTransitionsFirsts.reserveInitialCapacity(singularTransitions.m_ranges.size());
	for (const auto& transition : singularTransitions)
	singularTransitionsFirsts.uncheckedAppend(transition.first);

	for (const DFANode& node : dfa.nodes) {
	if (node.isKilled())
	continue;
	auto transitions = node.transitions(dfa);
	iterateIntersections(singularTransitionsFirsts, transitions, [&](unsigned, const DFANode::ConstRangeIterator& origin) {
	uint32_t targetNodeIndex = origin.target();
	++m_flattenedTransitionsStartOffsetPerNode[targetNodeIndex];
	});
	}

	// Accumulate the offsets. This gives us the start position of each bucket.
	unsigned transitionAccumulator = 0;
	for (unsigned i = 0; i < m_flattenedTransitionsStartOffsetPerNode.size(); ++i) {
	unsigned transitionsCountForNode = m_flattenedTransitionsStartOffsetPerNode[i];
	m_flattenedTransitionsStartOffsetPerNode[i] = transitionAccumulator;
	transitionAccumulator += transitionsCountForNode;
	}
	unsigned flattenedTransitionsSize = transitionAccumulator;
	ASSERT_WITH_MESSAGE(flattenedTransitionsSize == rangeIndexAccumulator, "The number of transitions should be the same, regardless of how they are arranged in buckets.");

	m_transitionPartition.reserveUninitializedCapacity(flattenedTransitionsSize);

	// Next, let's fill the transition table and set up the size of each group at the same time.
	m_flattenedTransitionsSizePerNode.resize(dfa.nodes.size());
	for (unsigned& counter : m_flattenedTransitionsSizePerNode)
	counter = 0;
	m_flattenedTransitions.resize(flattenedTransitionsSize);

	Vector<uint32_t> transitionPerRangeOffset(m_transitionPartition.size());
	memset(transitionPerRangeOffset.data(), 0, transitionPerRangeOffset.size() * sizeof(uint32_t));

	for (unsigned i = 0; i < dfa.nodes.size(); ++i) {
	const DFANode& node = dfa.nodes[i];
	if (node.isKilled())
	continue;

	auto transitions = node.transitions(dfa);
	iterateIntersections(singularTransitionsFirsts, transitions, [&](unsigned singularTransitonIndex, const DFANode::ConstRangeIterator& origin) {
	uint32_t targetNodeIndex = origin.target();

	unsigned start = m_flattenedTransitionsStartOffsetPerNode[targetNodeIndex];
	unsigned offset = m_flattenedTransitionsSizePerNode[targetNodeIndex];
	unsigned positionInFlattenedTransitions = start + offset;
	m_flattenedTransitions[positionInFlattenedTransitions] = Transition({ i });

	uint32_t& inRangeOffset = transitionPerRangeOffset[singularTransitonIndex];
	unsigned positionInTransitionPartition = m_transitionPartition.startOffsetOfSet(singularTransitonIndex) + inRangeOffset;
	++inRangeOffset;

	m_transitionPartition.setElementUnchecked(positionInFlattenedTransitions, positionInTransitionPartition, singularTransitonIndex);

	++m_flattenedTransitionsSizePerNode[targetNodeIndex];
	});
	}
	}

	void markNode(unsigned nodeIndex)
	{
	m_nodePartition.markElementInCurrentGeneration(nodeIndex);
	}

	void refinePartitions()
	{
	m_nodePartition.refineGeneration([&](unsigned smallestSetIndex) {
	m_nodePartition.iterateSet(smallestSetIndex, [&](unsigned nodeIndex) {
	unsigned incomingTransitionsStartForNode = m_flattenedTransitionsStartOffsetPerNode[nodeIndex];
	unsigned incomingTransitionsSizeForNode = m_flattenedTransitionsSizePerNode[nodeIndex];

	for (unsigned i = 0; i < incomingTransitionsSizeForNode; ++i)
	m_transitionPartition.markElementInCurrentGeneration(incomingTransitionsStartForNode + i);
	});

	// We only need to split the transitions, we handle the new sets through the main loop.
	m_transitionPartition.refineGeneration([](unsigned) { });
	});
	}

	void splitByUniqueTransitions()
	{
	for (; m_nextTransitionSetToProcess < m_transitionPartition.size(); ++m_nextTransitionSetToProcess) {
	// We use the known splitters to refine the set.
	m_transitionPartition.iterateSet(m_nextTransitionSetToProcess, [&](unsigned transitionIndex) {
	unsigned sourceNodeIndex = m_flattenedTransitions[transitionIndex].source;
	m_nodePartition.markElementInCurrentGeneration(sourceNodeIndex);
	});

	refinePartitions();
	}
	}

	unsigned nodeReplacement(unsigned nodeIndex)
	{
	unsigned setIndex = m_nodePartition.setIndex(nodeIndex);
	return m_nodePartition.firstElementInSet(setIndex);
	}

	private:
	struct Transition {
	unsigned source;
	};

	struct CounterConverter {
	uint32_t convert(uint32_t)
	{
	return 1;
	}

	void extend(uint32_t& destination, uint32_t)
	{
	++destination;
	}
	};

	Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_flattenedTransitionsStartOffsetPerNode;
	Vector<unsigned, 0, ContentExtensionsOverflowHandler> m_flattenedTransitionsSizePerNode;
	Vector<Transition, 0, ContentExtensionsOverflowHandler> m_flattenedTransitions;

	Partition m_nodePartition;
	Partition m_transitionPartition;

	unsigned m_nextTransitionSetToProcess { 0 };
	};

	struct ActionKey {
	enum DeletedValueTag { DeletedValue };
	explicit ActionKey(DeletedValueTag) { state = Deleted; }

	enum EmptyValueTag { EmptyValue };
	explicit ActionKey(EmptyValueTag) { state = Empty; }

	explicit ActionKey(const DFA* dfa, uint32_t actionsStart, uint16_t actionsLength)
	: dfa(dfa)
	, actionsStart(actionsStart)
	, actionsLength(actionsLength)
	, state(Valid)
	{
	StringHasher hasher;
	hasher.addCharactersAssumingAligned(reinterpret_cast<const UChar>(&dfa->actions[actionsStart]), actionsLength sizeof(uint64_t) / sizeof(UChar));
	hash = hasher.hash();
	}

	bool isEmptyValue() const { return state == Empty; }
	bool isDeletedValue() const { return state == Deleted; }

	unsigned hash;

	const DFA* dfa;
	uint32_t actionsStart;
	uint16_t actionsLength;

	enum {
	Valid,
	Empty,
	Deleted
	} state;
	};

	struct ActionKeyHash {
	static unsigned hash(const ActionKey& actionKey)
	{
	return actionKey.hash;
	}

	static bool equal(const ActionKey& a, const ActionKey& b)
	{
	if (a.state != b.state
	\|\| a.dfa != b.dfa
	\|\| a.actionsLength != b.actionsLength)
	return false;
	for (uint16_t i = 0; i < a.actionsLength; ++i) {
	if (a.dfa->actions[a.actionsStart + i] != a.dfa->actions[b.actionsStart + i])
	return false;
	}
	return true;
	}
	static const bool safeToCompareToEmptyOrDeleted = false;
	};

	struct ActionKeyHashTraits : public WTF::CustomHashTraits<ActionKey> {
	static const bool emptyValueIsZero = true;
	};

	} // anonymous namespace.

	void DFAMinimizer::minimize(DFA& dfa)
	{
	FullGraphPartition fullGraphPartition(dfa);

	// Unlike traditional minimization final states can be differentiated by their action.
	// Instead of creating a single set for the final state, we partition by actions from
	// the start.
	HashMap<ActionKey, Vector<unsigned>, ActionKeyHash, ActionKeyHashTraits> finalStates;
	for (unsigned i = 0; i < dfa.nodes.size(); ++i) {
	const DFANode& node = dfa.nodes[i];
	if (node.hasActions()) {
	// FIXME: Sort the actions in the dfa to make nodes that have the same actions in different order equal.
	auto addResult = finalStates.add(ActionKey(&dfa, node.actionsStart(), node.actionsLength()), Vector<unsigned>());
	addResult.iterator->value.append(i);
	}
	}

	for (const auto& slot : finalStates) {
	for (unsigned finalStateIndex : slot.value)
	fullGraphPartition.markNode(finalStateIndex);
	fullGraphPartition.refinePartitions();
	}

	// Use every splitter to refine the node partitions.
	fullGraphPartition.splitByUniqueTransitions();

	Vector<unsigned> relocationVector;
	relocationVector.reserveInitialCapacity(dfa.nodes.size());
	for (unsigned i = 0; i < dfa.nodes.size(); ++i)
	relocationVector.uncheckedAppend(i);

	// Update all the transitions.
	for (unsigned i = 0; i < dfa.nodes.size(); ++i) {
	unsigned replacement = fullGraphPartition.nodeReplacement(i);
	if (i != replacement) {
	relocationVector[i] = replacement;
	dfa.nodes[i].kill(dfa);
	}
	}

	dfa.root = relocationVector[dfa.root];
	for (DFANode& node : dfa.nodes) {
	if (node.isKilled())
	continue;

	for (auto& transition : node.transitions(dfa)) {
	uint32_t target = transition.target();
	uint32_t relocatedTarget = relocationVector[target];
	if (target != relocatedTarget)
	transition.resetTarget(relocatedTarget);
	}
	}
	}

	} // namespace ContentExtensions
	} // namespace WebCore

	#endif // ENABLE(CONTENT_EXTENSIONS)