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/*
* Copyright (C) 2010 Google 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 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 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.
*/
#ifndef PODIntervalTree_h
#define PODIntervalTree_h
#include "PODArena.h"
#include "PODInterval.h"
#include "PODRedBlackTree.h"
#include <wtf/Assertions.h>
#include <wtf/Noncopyable.h>
#include <wtf/Vector.h>
namespace WebCore {
#ifndef NDEBUG
template<class T>
struct ValueToString;
#endif
// An interval tree, which is a form of augmented red-black tree. It
// supports efficient (O(lg n)) insertion, removal and querying of
// intervals in the tree.
template<class T, class UserData = void*>
class PODIntervalTree : public PODRedBlackTree<PODInterval<T, UserData> > {
WTF_MAKE_NONCOPYABLE(PODIntervalTree);
public:
// Typedef to reduce typing when declaring intervals to be stored in
// this tree.
typedef PODInterval<T, UserData> IntervalType;
PODIntervalTree()
: PODRedBlackTree<IntervalType>()
{
init();
}
explicit PODIntervalTree(PassRefPtr<PODArena> arena)
: PODRedBlackTree<IntervalType>(arena)
{
init();
}
// Returns all intervals in the tree which overlap the given query
// interval. The returned intervals are sorted by increasing low
// endpoint.
Vector<IntervalType> allOverlaps(const IntervalType& interval) const
{
Vector<IntervalType> result;
allOverlaps(interval, result);
return result;
}
// Returns all intervals in the tree which overlap the given query
// interval. The returned intervals are sorted by increasing low
// endpoint.
void allOverlaps(const IntervalType& interval, Vector<IntervalType>& result) const
{
// Explicit dereference of "this" required because of
// inheritance rules in template classes.
searchForOverlapsFrom(this->root(), interval, result);
}
// Helper to create interval objects.
static IntervalType createInterval(const T& low, const T& high, const UserData data = 0)
{
return IntervalType(low, high, data);
}
virtual bool checkInvariants() const
{
if (!PODRedBlackTree<IntervalType>::checkInvariants())
return false;
if (!this->root())
return true;
return checkInvariantsFromNode(this->root(), 0);
}
private:
typedef typename PODRedBlackTree<IntervalType>::Node IntervalNode;
// Initializes the tree.
void init()
{
// Explicit dereference of "this" required because of
// inheritance rules in template classes.
this->setNeedsFullOrderingComparisons(true);
}
// Starting from the given node, adds all overlaps with the given
// interval to the result vector. The intervals are sorted by
// increasing low endpoint.
void searchForOverlapsFrom(IntervalNode* node, const IntervalType& interval, Vector<IntervalType>& res) const
{
if (!node)
return;
// Because the intervals are sorted by left endpoint, inorder
// traversal produces results sorted as desired.
// See whether we need to traverse the left subtree.
IntervalNode* left = node->left();
if (left
// This is phrased this way to avoid the need for operator
// <= on type T.
&& !(left->data().maxHigh() < interval.low()))
searchForOverlapsFrom(left, interval, res);
// Check for overlap with current node.
if (node->data().overlaps(interval))
res.append(node->data());
// See whether we need to traverse the right subtree.
// This is phrased this way to avoid the need for operator <=
// on type T.
if (!(interval.high() < node->data().low()))
searchForOverlapsFrom(node->right(), interval, res);
}
virtual bool updateNode(IntervalNode* node)
{
// Would use const T&, but need to reassign this reference in this
// function.
const T* curMax = &node->data().high();
IntervalNode* left = node->left();
if (left) {
if (*curMax < left->data().maxHigh())
curMax = &left->data().maxHigh();
}
IntervalNode* right = node->right();
if (right) {
if (*curMax < right->data().maxHigh())
curMax = &right->data().maxHigh();
}
// This is phrased like this to avoid needing operator!= on type T.
if (!(*curMax == node->data().maxHigh())) {
node->data().setMaxHigh(*curMax);
return true;
}
return false;
}
bool checkInvariantsFromNode(IntervalNode* node, T* currentMaxValue) const
{
// These assignments are only done in order to avoid requiring
// a default constructor on type T.
T leftMaxValue(node->data().maxHigh());
T rightMaxValue(node->data().maxHigh());
IntervalNode* left = node->left();
IntervalNode* right = node->right();
if (left) {
if (!checkInvariantsFromNode(left, &leftMaxValue))
return false;
}
if (right) {
if (!checkInvariantsFromNode(right, &rightMaxValue))
return false;
}
if (!left && !right) {
// Base case.
if (currentMaxValue)
*currentMaxValue = node->data().high();
return (node->data().high() == node->data().maxHigh());
}
T localMaxValue(node->data().maxHigh());
if (!left || !right) {
if (left)
localMaxValue = leftMaxValue;
else
localMaxValue = rightMaxValue;
} else
localMaxValue = (leftMaxValue < rightMaxValue) ? rightMaxValue : leftMaxValue;
if (localMaxValue < node->data().high())
localMaxValue = node->data().high();
if (!(localMaxValue == node->data().maxHigh())) {
#ifndef NDEBUG
String localMaxValueString = ValueToString<T>::string(localMaxValue);
LOG_ERROR("PODIntervalTree verification failed at node 0x%p: localMaxValue=%s and data=%s",
node, localMaxValueString.utf8().data(), node->data().toString().utf8().data());
#endif
return false;
}
if (currentMaxValue)
*currentMaxValue = localMaxValue;
return true;
}
};
#ifndef NDEBUG
// Support for printing PODIntervals at the PODRedBlackTree level.
template<class T, class UserData>
struct ValueToString<PODInterval<T, UserData> > {
static String string(const PODInterval<T, UserData>& interval)
{
return interval.toString();
}
};
#endif
} // namespace WebCore
#endif // PODIntervalTree_h
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