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diff --git a/WebCore/platform/Timer.cpp b/WebCore/platform/Timer.cpp
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+/*
+ * Copyright (C) 2006, 2008 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 COMPUTER, INC. ``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 COMPUTER, INC. OR
+ * 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 "Timer.h"
+
+#include "SharedTimer.h"
+#include "SystemTime.h"
+#include <limits.h>
+#include <limits>
+#include <math.h>
+#include <wtf/HashSet.h>
+#include <wtf/Vector.h>
+
+using namespace std;
+
+namespace WebCore {
+
+// Timers are stored in a heap data structure, used to implement a priority queue.
+// This allows us to efficiently determine which timer needs to fire the soonest.
+// Then we set a single shared system timer to fire at that time.
+//
+// When a timer's "next fire time" changes, we need to move it around in the priority queue.
+
+// ----------------
+
+static bool deferringTimers;
+static Vector<TimerBase*>* timerHeap;
+static HashSet<const TimerBase*>* timersReadyToFire;
+
+// ----------------
+
+// Class to represent elements in the heap when calling the standard library heap algorithms.
+// Maintains the m_heapIndex value in the timers themselves, which allows us to do efficient
+// modification of the heap.
+class TimerHeapElement {
+public:
+    explicit TimerHeapElement(int i) : m_index(i), m_timer((*timerHeap)[m_index]) { checkConsistency(); }
+
+    TimerHeapElement(const TimerHeapElement&);
+    TimerHeapElement& operator=(const TimerHeapElement&);
+
+    TimerBase* timer() const { return m_timer; }
+
+    void checkConsistency() const {
+        ASSERT(m_index >= 0);
+        ASSERT(m_index < (timerHeap ? static_cast<int>(timerHeap->size()) : 0));
+    }
+
+private:
+    TimerHeapElement();
+
+    int m_index;
+    TimerBase* m_timer;
+};
+
+inline TimerHeapElement::TimerHeapElement(const TimerHeapElement& o)
+    : m_index(-1), m_timer(o.timer())
+{
+}
+
+inline TimerHeapElement& TimerHeapElement::operator=(const TimerHeapElement& o)
+{
+    TimerBase* t = o.timer();
+    m_timer = t;
+    if (m_index != -1) {
+        checkConsistency();
+        (*timerHeap)[m_index] = t;
+        t->m_heapIndex = m_index;
+    }
+    return *this;
+}
+
+inline bool operator<(const TimerHeapElement& a, const TimerHeapElement& b)
+{
+    // The comparisons below are "backwards" because the heap puts the largest 
+    // element first and we want the lowest time to be the first one in the heap.
+    double aFireTime = a.timer()->m_nextFireTime;
+    double bFireTime = b.timer()->m_nextFireTime;
+    if (bFireTime != aFireTime)
+        return bFireTime < aFireTime;
+    
+    // We need to look at the difference of the insertion orders instead of comparing the two 
+    // outright in case of overflow. 
+    unsigned difference = a.timer()->m_heapInsertionOrder - b.timer()->m_heapInsertionOrder;
+    return difference < UINT_MAX / 2;
+}
+
+// ----------------
+
+// Class to represent iterators in the heap when calling the standard library heap algorithms.
+// Returns TimerHeapElement for elements in the heap rather than the TimerBase pointers themselves.
+class TimerHeapIterator : public iterator<random_access_iterator_tag, TimerHeapElement, int> {
+public:
+    TimerHeapIterator() : m_index(-1) { }
+    TimerHeapIterator(int i) : m_index(i) { checkConsistency(); }
+
+    TimerHeapIterator& operator++() { checkConsistency(); ++m_index; checkConsistency(); return *this; }
+    TimerHeapIterator operator++(int) { checkConsistency(); checkConsistency(1); return m_index++; }
+
+    TimerHeapIterator& operator--() { checkConsistency(); --m_index; checkConsistency(); return *this; }
+    TimerHeapIterator operator--(int) { checkConsistency(); checkConsistency(-1); return m_index--; }
+
+    TimerHeapIterator& operator+=(int i) { checkConsistency(); m_index += i; checkConsistency(); return *this; }
+    TimerHeapIterator& operator-=(int i) { checkConsistency(); m_index -= i; checkConsistency(); return *this; }
+
+    TimerHeapElement operator*() const { return TimerHeapElement(m_index); }
+    TimerHeapElement operator[](int i) const { return TimerHeapElement(m_index + i); }
+
+    int index() const { return m_index; }
+
+    void checkConsistency(int offset = 0) const {
+        ASSERT(m_index + offset >= 0);
+        ASSERT(m_index + offset <= (timerHeap ? static_cast<int>(timerHeap->size()) : 0));
+    }
+
+private:
+    int m_index;
+};
+
+inline bool operator==(TimerHeapIterator a, TimerHeapIterator b) { return a.index() == b.index(); }
+inline bool operator!=(TimerHeapIterator a, TimerHeapIterator b) { return a.index() != b.index(); }
+inline bool operator<(TimerHeapIterator a, TimerHeapIterator b) { return a.index() < b.index(); }
+
+inline TimerHeapIterator operator+(TimerHeapIterator a, int b) { return a.index() + b; }
+inline TimerHeapIterator operator+(int a, TimerHeapIterator b) { return a + b.index(); }
+
+inline TimerHeapIterator operator-(TimerHeapIterator a, int b) { return a.index() - b; }
+inline int operator-(TimerHeapIterator a, TimerHeapIterator b) { return a.index() - b.index(); }
+
+// ----------------
+
+void updateSharedTimer()
+{
+    if (timersReadyToFire || deferringTimers || !timerHeap || timerHeap->isEmpty())
+        stopSharedTimer();
+    else
+        setSharedTimerFireTime(timerHeap->first()->m_nextFireTime);
+}
+
+// ----------------
+
+TimerBase::TimerBase()
+    : m_nextFireTime(0), m_repeatInterval(0), m_heapIndex(-1)
+{
+    // We only need to do this once, but probably not worth trying to optimize it.
+    setSharedTimerFiredFunction(sharedTimerFired);
+}
+
+TimerBase::~TimerBase()
+{
+    stop();
+
+    ASSERT(!inHeap());
+}
+
+void TimerBase::start(double nextFireInterval, double repeatInterval)
+{
+    m_repeatInterval = repeatInterval;
+    setNextFireTime(currentTime() + nextFireInterval);
+}
+
+void TimerBase::stop()
+{
+    m_repeatInterval = 0;
+    setNextFireTime(0);
+
+    ASSERT(m_nextFireTime == 0);
+    ASSERT(m_repeatInterval == 0);
+    ASSERT(!inHeap());
+}
+
+bool TimerBase::isActive() const
+{
+    return m_nextFireTime || (timersReadyToFire && timersReadyToFire->contains(this));
+}
+
+double TimerBase::nextFireInterval() const
+{
+    ASSERT(isActive());
+    double current = currentTime();
+    if (m_nextFireTime < current)
+        return 0;
+    return m_nextFireTime - current;
+}
+
+inline void TimerBase::checkHeapIndex() const
+{
+    ASSERT(timerHeap);
+    ASSERT(!timerHeap->isEmpty());
+    ASSERT(m_heapIndex >= 0);
+    ASSERT(m_heapIndex < static_cast<int>(timerHeap->size()));
+    ASSERT((*timerHeap)[m_heapIndex] == this);
+}
+
+inline void TimerBase::checkConsistency() const
+{
+    // Timers should be in the heap if and only if they have a non-zero next fire time.
+    ASSERT(inHeap() == (m_nextFireTime != 0));
+    if (inHeap())
+        checkHeapIndex();
+}
+
+void TimerBase::heapDecreaseKey()
+{
+    ASSERT(m_nextFireTime != 0);
+    checkHeapIndex();
+    push_heap(TimerHeapIterator(0), TimerHeapIterator(m_heapIndex + 1));
+    checkHeapIndex();
+}
+
+inline void TimerBase::heapDelete()
+{
+    ASSERT(m_nextFireTime == 0);
+    heapPop();
+    timerHeap->removeLast();
+    m_heapIndex = -1;
+}
+
+inline void TimerBase::heapDeleteMin()
+{
+    ASSERT(m_nextFireTime == 0);
+    heapPopMin();
+    timerHeap->removeLast();
+    m_heapIndex = -1;
+}
+
+inline void TimerBase::heapIncreaseKey()
+{
+    ASSERT(m_nextFireTime != 0);
+    heapPop();
+    heapDecreaseKey();
+}
+
+inline void TimerBase::heapInsert()
+{
+    ASSERT(!inHeap());
+    if (!timerHeap)
+        timerHeap = new Vector<TimerBase*>;
+    timerHeap->append(this);
+    m_heapIndex = timerHeap->size() - 1;
+    heapDecreaseKey();
+}
+
+inline void TimerBase::heapPop()
+{
+    // Temporarily force this timer to have the minimum key so we can pop it.
+    double fireTime = m_nextFireTime;
+    m_nextFireTime = -numeric_limits<double>::infinity();
+    heapDecreaseKey();
+    heapPopMin();
+    m_nextFireTime = fireTime;
+}
+
+void TimerBase::heapPopMin()
+{
+    ASSERT(this == timerHeap->first());
+    checkHeapIndex();
+    pop_heap(TimerHeapIterator(0), TimerHeapIterator(timerHeap->size()));
+    checkHeapIndex();
+    ASSERT(this == timerHeap->last());
+}
+
+void TimerBase::setNextFireTime(double newTime)
+{
+    // Keep heap valid while changing the next-fire time.
+
+    if (timersReadyToFire)
+        timersReadyToFire->remove(this);
+
+    double oldTime = m_nextFireTime;
+    if (oldTime != newTime) {
+        m_nextFireTime = newTime;
+        static unsigned currentHeapInsertionOrder;
+        m_heapInsertionOrder = currentHeapInsertionOrder++;
+
+        bool wasFirstTimerInHeap = m_heapIndex == 0;
+
+        if (oldTime == 0)
+            heapInsert();
+        else if (newTime == 0)
+            heapDelete();
+        else if (newTime < oldTime)
+            heapDecreaseKey();
+        else
+            heapIncreaseKey();
+
+        bool isFirstTimerInHeap = m_heapIndex == 0;
+
+        if (wasFirstTimerInHeap || isFirstTimerInHeap)
+            updateSharedTimer();
+    }
+
+    checkConsistency();
+}
+
+void TimerBase::collectFiringTimers(double fireTime, Vector<TimerBase*>& firingTimers)
+{
+    while (!timerHeap->isEmpty() && timerHeap->first()->m_nextFireTime <= fireTime) {
+        TimerBase* timer = timerHeap->first();
+        firingTimers.append(timer);
+        timersReadyToFire->add(timer);
+        timer->m_nextFireTime = 0;
+        timer->heapDeleteMin();
+    }
+}
+
+void TimerBase::fireTimers(double fireTime, const Vector<TimerBase*>& firingTimers)
+{
+    int size = firingTimers.size();
+    for (int i = 0; i != size; ++i) {
+        TimerBase* timer = firingTimers[i];
+
+        // If not in the set, this timer has been deleted or re-scheduled in another timer's fired function.
+        // So either we don't want to fire it at all or we will fire it next time the shared timer goes off.
+        // It might even have been deleted; that's OK because we won't do anything else with the pointer.
+        if (!timersReadyToFire->contains(timer))
+            continue;
+
+        // Setting the next fire time has a side effect of removing the timer from the firing timers set.
+        double interval = timer->repeatInterval();
+        timer->setNextFireTime(interval ? fireTime + interval : 0);
+
+        // Once the timer has been fired, it may be deleted, so do nothing else with it after this point.
+        timer->fired();
+
+        // Catch the case where the timer asked timers to fire in a nested event loop.
+        if (!timersReadyToFire)
+            break;
+    }
+}
+
+void TimerBase::sharedTimerFired()
+{
+    // Do a re-entrancy check.
+    if (timersReadyToFire)
+        return;
+
+    double fireTime = currentTime();
+    Vector<TimerBase*> firingTimers;
+    HashSet<const TimerBase*> firingTimersSet;
+
+    timersReadyToFire = &firingTimersSet;
+
+    collectFiringTimers(fireTime, firingTimers);
+    fireTimers(fireTime, firingTimers);
+
+    timersReadyToFire = 0;
+
+    updateSharedTimer();
+}
+
+void TimerBase::fireTimersInNestedEventLoop()
+{
+    timersReadyToFire = 0;
+    updateSharedTimer();
+}
+
+// ----------------
+
+bool isDeferringTimers()
+{
+    return deferringTimers;
+}
+
+void setDeferringTimers(bool shouldDefer)
+{
+    if (shouldDefer == deferringTimers)
+        return;
+    deferringTimers = shouldDefer;
+    updateSharedTimer();
+}
+
+}