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/*
* 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 "DFACombiner.h"
#if ENABLE(CONTENT_EXTENSIONS)
#include "MutableRangeList.h"
#include <wtf/HashMap.h>
#include <wtf/HashSet.h>
namespace WebCore {
namespace ContentExtensions {
class DFAMerger {
typedef MutableRangeList<char, uint64_t, 128> CombinedTransitionsMutableRangeList;
enum class WhichDFA {
A,
B
};
template<WhichDFA whichDFA>
struct TargetConverter {
uint64_t convert(uint32_t target)
{
uint64_t value = 0xffffffffffffffff;
extend(value, target);
return value;
}
void extend(uint64_t& destination, uint32_t target)
{
setHalfSignature(destination, target);
}
private:
void setHalfSignature(uint64_t& signature, uint32_t value)
{
unsigned shiftAmount = (whichDFA == WhichDFA::A) ? 32 : 0;
uint64_t mask = static_cast<uint64_t>(0xffffffff) << (32 - shiftAmount);
signature = (signature & mask) | static_cast<uint64_t>(value) << shiftAmount;
}
};
public:
DFAMerger(const DFA& a, const DFA& b)
: m_dfaA(a)
, m_dfaB(b)
{
}
DFA merge()
{
if (!m_nodeMapping.isEmpty())
return m_output;
uint64_t rootSignature = signatureForIndices(m_dfaA.root, m_dfaB.root);
getOrCreateCombinedNode(rootSignature);
CombinedTransitionsMutableRangeList combinedTransitions;
while (!m_unprocessedNodes.isEmpty()) {
combinedTransitions.clear();
uint64_t unprocessedNode = m_unprocessedNodes.takeLast();
uint32_t indexA = extractIndexA(unprocessedNode);
if (indexA != invalidNodeIndex) {
const DFANode& nodeA = m_dfaA.nodes[indexA];
auto transitionsA = nodeA.transitions(m_dfaA);
TargetConverter<WhichDFA::A> converterA;
combinedTransitions.extend(transitionsA.begin(), transitionsA.end(), converterA);
}
uint32_t indexB = extractIndexB(unprocessedNode);
if (indexB != invalidNodeIndex) {
const DFANode& nodeB = m_dfaB.nodes[indexB];
auto transitionsB = nodeB.transitions(m_dfaB);
TargetConverter<WhichDFA::B> converterB;
combinedTransitions.extend(transitionsB.begin(), transitionsB.end(), converterB);
}
unsigned transitionsStart = m_output.transitionRanges.size();
for (const auto& range : combinedTransitions) {
unsigned targetNodeId = getOrCreateCombinedNode(range.data);
m_output.transitionRanges.append({ range.first, range.last });
m_output.transitionDestinations.append(targetNodeId);
}
unsigned transitionsEnd = m_output.transitionRanges.size();
unsigned transitionsLength = transitionsEnd - transitionsStart;
uint32_t sourceNodeId = m_nodeMapping.get(unprocessedNode);
DFANode& dfaSourceNode = m_output.nodes[sourceNodeId];
dfaSourceNode.setTransitions(transitionsStart, static_cast<uint8_t>(transitionsLength));
}
return m_output;
}
private:
uint32_t invalidNodeIndex = 0xffffffff;
static uint64_t signatureForIndices(uint32_t aIndex, uint32_t bIndex)
{
return static_cast<uint64_t>(aIndex) << 32 | bIndex;
}
static uint32_t extractIndexA(uint64_t signature)
{
return static_cast<uint32_t>(signature >> 32);
}
static uint32_t extractIndexB(uint64_t signature)
{
return static_cast<uint32_t>(signature);
}
uint32_t getOrCreateCombinedNode(uint64_t newNodeSignature)
{
auto addResult = m_nodeMapping.add(newNodeSignature, invalidNodeIndex);
if (!addResult.isNewEntry)
return addResult.iterator->value;
m_output.nodes.append(DFANode());
uint32_t newNodeIndex = m_output.nodes.size() - 1;
addResult.iterator->value = newNodeIndex;
m_unprocessedNodes.append(newNodeSignature);
uint32_t indexA = extractIndexA(newNodeSignature);
uint32_t indexB = extractIndexB(newNodeSignature);
HashSet<uint64_t, DefaultHash<uint64_t>::Hash, WTF::UnsignedWithZeroKeyHashTraits<uint64_t>> actions;
if (indexA != invalidNodeIndex) {
const DFANode& node = m_dfaA.nodes[indexA];
uint32_t actionsStart = node.actionsStart();
uint32_t actionsEnd = actionsStart + node.actionsLength();
for (uint32_t i = actionsStart; i < actionsEnd; ++i)
actions.add(m_dfaA.actions[i]);
}
if (indexB != invalidNodeIndex) {
const DFANode& node = m_dfaB.nodes[indexB];
uint32_t actionsStart = node.actionsStart();
uint32_t actionsEnd = actionsStart + node.actionsLength();
for (uint32_t i = actionsStart; i < actionsEnd; ++i)
actions.add(m_dfaB.actions[i]);
}
uint32_t actionsStart = m_output.actions.size();
for (uint64_t action : actions)
m_output.actions.append(action);
uint32_t actionsEnd = m_output.actions.size();
uint16_t actionsLength = static_cast<uint16_t>(actionsEnd - actionsStart);
m_output.nodes.last().setActions(actionsStart, actionsLength);
return newNodeIndex;
}
const DFA& m_dfaA;
const DFA& m_dfaB;
DFA m_output;
HashMap<uint64_t, uint32_t, DefaultHash<uint64_t>::Hash, WTF::UnsignedWithZeroKeyHashTraits<uint64_t>> m_nodeMapping;
Vector<uint64_t, 0, ContentExtensionsOverflowHandler> m_unprocessedNodes;
};
void DFACombiner::combineDFAs(unsigned minimumSize, std::function<void(DFA&&)> handler)
{
if (m_dfas.isEmpty())
return;
for (unsigned i = m_dfas.size(); i--;) {
if (m_dfas[i].graphSize() > minimumSize) {
handler(WTFMove(m_dfas[i]));
m_dfas.remove(i);
}
}
while (!m_dfas.isEmpty()) {
if (m_dfas.size() == 1) {
handler(WTFMove(m_dfas.first()));
return;
}
DFA a = m_dfas.takeLast();
DFA b = m_dfas.takeLast();
DFAMerger dfaMerger(a, b);
DFA c = dfaMerger.merge();
if (c.graphSize() > minimumSize || m_dfas.isEmpty()) {
// Minimizing is somewhat expensive. We only do it in bulk when we reach the threshold
// to reduce the load.
c.minimize();
}
if (c.graphSize() > minimumSize)
handler(WTFMove(c));
else
m_dfas.append(c);
}
}
}
} // namespace WebCore
#endif
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