WIP - not ready for review

Source/platform/Timer.cpp

Index: Source/platform/Timer.cpp
diff --git a/Source/platform/Timer.cpp b/Source/platform/Timer.cpp
index c6ad0cbd0593fcee2742973723d121da95aa4f71..5c523043a08a02f7416043b83adda129140368e3 100644
--- a/Source/platform/Timer.cpp
+++ b/Source/platform/Timer.cpp
@@ -29,167 +29,15 @@
 
 #include "platform/PlatformThreadData.h"
 #include "platform/ThreadTimers.h"
-#include "wtf/Atomics.h"
+#include "platform/TimerHeap.h"
 #include "wtf/CurrentTime.h"
-#include "wtf/HashSet.h"
-#include <limits.h>
-#include <math.h>
-#include <limits>
 
 namespace blink {
 
-class TimerHeapReference;
-
-// 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 Vector<TimerBase*>& threadGlobalTimerHeap()
-{
-    return PlatformThreadData::current().threadTimers().timerHeap();
-}
-// ----------------
-
-class TimerHeapPointer {
-public:
-    TimerHeapPointer(TimerBase** pointer) : m_pointer(pointer) { }
-    TimerHeapReference operator*() const;
-    TimerBase* operator->() const { return *m_pointer; }
-private:
-    TimerBase** m_pointer;
-};
-
-class TimerHeapReference {
-public:
-    TimerHeapReference(TimerBase*& reference) : m_reference(reference) { }
-    operator TimerBase*() const { return m_reference; }
-    TimerHeapPointer operator&() const { return &m_reference; }
-    TimerHeapReference& operator=(TimerBase*);
-    TimerHeapReference& operator=(TimerHeapReference);
-private:
-    TimerBase*& m_reference;
-};
-
-inline TimerHeapReference TimerHeapPointer::operator*() const
-{
-    return *m_pointer;
-}
-
-inline TimerHeapReference& TimerHeapReference::operator=(TimerBase* timer)
-{
-    m_reference = timer;
-    Vector<TimerBase*>& heap = timer->timerHeap();
-    if (&m_reference >= heap.data() && &m_reference < heap.data() + heap.size())
-        timer->m_heapIndex = &m_reference - heap.data();
-    return *this;
-}
-
-inline TimerHeapReference& TimerHeapReference::operator=(TimerHeapReference b)
-{
-    TimerBase* timer = b;
-    return *this = timer;
-}
-
-inline void swap(TimerHeapReference a, TimerHeapReference b)
-{
-    TimerBase* timerA = a;
-    TimerBase* timerB = b;
-
-    // Invoke the assignment operator, since that takes care of updating m_heapIndex.
-    a = timerB;
-    b = timerA;
-}
-
-// ----------------
-
-// Class to represent iterators in the heap when calling the standard library heap algorithms.
-// Uses a custom pointer and reference type that update indices for pointers in the heap.
-class TimerHeapIterator : public std::iterator<std::random_access_iterator_tag, TimerBase*, ptrdiff_t, TimerHeapPointer, TimerHeapReference> {
-public:
-    explicit TimerHeapIterator(TimerBase** pointer) : m_pointer(pointer) { checkConsistency(); }
-
-    TimerHeapIterator& operator++() { checkConsistency(); ++m_pointer; checkConsistency(); return *this; }
-    TimerHeapIterator operator++(int) { checkConsistency(1); return TimerHeapIterator(m_pointer++); }
-
-    TimerHeapIterator& operator--() { checkConsistency(); --m_pointer; checkConsistency(); return *this; }
-    TimerHeapIterator operator--(int) { checkConsistency(-1); return TimerHeapIterator(m_pointer--); }
-
-    TimerHeapIterator& operator+=(ptrdiff_t i) { checkConsistency(); m_pointer += i; checkConsistency(); return *this; }
-    TimerHeapIterator& operator-=(ptrdiff_t i) { checkConsistency(); m_pointer -= i; checkConsistency(); return *this; }
-
-    TimerHeapReference operator*() const { return TimerHeapReference(*m_pointer); }
-    TimerHeapReference operator[](ptrdiff_t i) const { return TimerHeapReference(m_pointer[i]); }
-    TimerBase* operator->() const { return *m_pointer; }
-
-private:
-    void checkConsistency(ptrdiff_t offset = 0) const
-    {
-        ASSERT(m_pointer >= threadGlobalTimerHeap().data());
-        ASSERT(m_pointer <= threadGlobalTimerHeap().data() + threadGlobalTimerHeap().size());
-        ASSERT_UNUSED(offset, m_pointer + offset >= threadGlobalTimerHeap().data());
-        ASSERT_UNUSED(offset, m_pointer + offset <= threadGlobalTimerHeap().data() + threadGlobalTimerHeap().size());
-    }
-
-    friend bool operator==(TimerHeapIterator, TimerHeapIterator);
-    friend bool operator!=(TimerHeapIterator, TimerHeapIterator);
-    friend bool operator<(TimerHeapIterator, TimerHeapIterator);
-    friend bool operator>(TimerHeapIterator, TimerHeapIterator);
-    friend bool operator<=(TimerHeapIterator, TimerHeapIterator);
-    friend bool operator>=(TimerHeapIterator, TimerHeapIterator);
-
-    friend TimerHeapIterator operator+(TimerHeapIterator, size_t);
-    friend TimerHeapIterator operator+(size_t, TimerHeapIterator);
-
-    friend TimerHeapIterator operator-(TimerHeapIterator, size_t);
-    friend ptrdiff_t operator-(TimerHeapIterator, TimerHeapIterator);
-
-    TimerBase** m_pointer;
-};
-
-inline bool operator==(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer == b.m_pointer; }
-inline bool operator!=(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer != b.m_pointer; }
-inline bool operator<(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer < b.m_pointer; }
-inline bool operator>(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer > b.m_pointer; }
-inline bool operator<=(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer <= b.m_pointer; }
-inline bool operator>=(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer >= b.m_pointer; }
-
-inline TimerHeapIterator operator+(TimerHeapIterator a, size_t b) { return TimerHeapIterator(a.m_pointer + b); }
-inline TimerHeapIterator operator+(size_t a, TimerHeapIterator b) { return TimerHeapIterator(a + b.m_pointer); }
-
-inline TimerHeapIterator operator-(TimerHeapIterator a, size_t b) { return TimerHeapIterator(a.m_pointer - b); }
-inline ptrdiff_t operator-(TimerHeapIterator a, TimerHeapIterator b) { return a.m_pointer - b.m_pointer; }
-
-// ----------------
-
-class TimerHeapLessThanFunction {
-public:
-    bool operator()(const TimerBase*, const TimerBase*) const;
-};
-
-inline bool TimerHeapLessThanFunction::operator()(const TimerBase* a, const TimerBase* b) const
-{
-    // 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->m_nextFireTime;
-    double bFireTime = b->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->m_heapInsertionOrder - b->m_heapInsertionOrder;
-    return difference < std::numeric_limits<unsigned>::max() / 2;
-}
-
-// ----------------
-
 TimerBase::TimerBase()
-    : m_nextFireTime(0)
-    , m_unalignedNextFireTime(0)
+    : m_unalignedNextFireTime(0)
     , m_repeatInterval(0)
-    , m_heapIndex(-1)
-    , m_cachedThreadGlobalTimerHeap(0)
+    , m_heapEntry(&TimerHeap::get())
 #if ENABLE(ASSERT)
     , m_thread(currentThread())
 #endif
@@ -199,7 +47,7 @@ TimerBase::TimerBase()
 TimerBase::~TimerBase()
 {
     stop();
-    ASSERT(!inHeap());
+    ASSERT(!m_heapEntry.inHeap());
 }
 
 void TimerBase::start(double nextFireInterval, double repeatInterval, const WebTraceLocation& caller)
@@ -218,148 +66,18 @@ void TimerBase::stop()
     m_repeatInterval = 0;
     setNextFireTime(0);
 
-    ASSERT(m_nextFireTime == 0);
+    ASSERT(nextFireTime() == 0);
     ASSERT(m_repeatInterval == 0);
-    ASSERT(!inHeap());
+    ASSERT(!m_heapEntry.inHeap());
 }
 
 double TimerBase::nextFireInterval() const
 {
     ASSERT(isActive());
     double current = monotonicallyIncreasingTime();
-    if (m_nextFireTime < current)
+    if (nextFireTime() < current)
         return 0;
-    return m_nextFireTime - current;
-}
-
-inline void TimerBase::checkHeapIndex() const
-{
-    ASSERT(timerHeap() == threadGlobalTimerHeap());
-    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();
-    TimerBase** heapData = timerHeap().data();
-    push_heap(TimerHeapIterator(heapData), TimerHeapIterator(heapData + m_heapIndex + 1), TimerHeapLessThanFunction());
-    checkHeapIndex();
-}
-
-inline void TimerBase::heapDelete()
-{
-    ASSERT(m_nextFireTime == 0);
-    heapPop();
-    timerHeap().removeLast();
-    m_heapIndex = -1;
-}
-
-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());
-    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 = -std::numeric_limits<double>::infinity();
-    heapDecreaseKey();
-    heapPopMin();
-    m_nextFireTime = fireTime;
-}
-
-void TimerBase::heapPopMin()
-{
-    ASSERT(this == timerHeap().first());
-    checkHeapIndex();
-    Vector<TimerBase*>& heap = timerHeap();
-    TimerBase** heapData = heap.data();
-    pop_heap(TimerHeapIterator(heapData), TimerHeapIterator(heapData + heap.size()), TimerHeapLessThanFunction());
-    checkHeapIndex();
-    ASSERT(this == timerHeap().last());
-}
-
-static inline bool parentHeapPropertyHolds(const TimerBase* current, const Vector<TimerBase*>& heap, unsigned currentIndex)
-{
-    if (!currentIndex)
-        return true;
-    unsigned parentIndex = (currentIndex - 1) / 2;
-    TimerHeapLessThanFunction compareHeapPosition;
-    return compareHeapPosition(current, heap[parentIndex]);
-}
-
-static inline bool childHeapPropertyHolds(const TimerBase* current, const Vector<TimerBase*>& heap, unsigned childIndex)
-{
-    if (childIndex >= heap.size())
-        return true;
-    TimerHeapLessThanFunction compareHeapPosition;
-    return compareHeapPosition(heap[childIndex], current);
-}
-
-bool TimerBase::hasValidHeapPosition() const
-{
-    ASSERT(m_nextFireTime);
-    if (!inHeap())
-        return false;
-    // Check if the heap property still holds with the new fire time. If it does we don't need to do anything.
-    // This assumes that the STL heap is a standard binary heap. In an unlikely event it is not, the assertions
-    // in updateHeapIfNeeded() will get hit.
-    const Vector<TimerBase*>& heap = timerHeap();
-    if (!parentHeapPropertyHolds(this, heap, m_heapIndex))
-        return false;
-    unsigned childIndex1 = 2 * m_heapIndex + 1;
-    unsigned childIndex2 = childIndex1 + 1;
-    return childHeapPropertyHolds(this, heap, childIndex1) && childHeapPropertyHolds(this, heap, childIndex2);
-}
-
-void TimerBase::updateHeapIfNeeded(double oldTime)
-{
-    if (m_nextFireTime && hasValidHeapPosition())
-        return;
-#if ENABLE(ASSERT)
-    int oldHeapIndex = m_heapIndex;
-#endif
-    if (!oldTime)
-        heapInsert();
-    else if (!m_nextFireTime)
-        heapDelete();
-    else if (m_nextFireTime < oldTime)
-        heapDecreaseKey();
-    else
-        heapIncreaseKey();
-    ASSERT(m_heapIndex != oldHeapIndex);
-    ASSERT(!inHeap() || hasValidHeapPosition());
+    return nextFireTime() - current;
 }
 
 void TimerBase::setNextFireTime(double newUnalignedTime)
@@ -369,29 +87,10 @@ void TimerBase::setNextFireTime(double newUnalignedTime)
     if (m_unalignedNextFireTime != newUnalignedTime)
         m_unalignedNextFireTime = newUnalignedTime;
 
-    // Accessing thread global data is slow. Cache the heap pointer.
-    if (!m_cachedThreadGlobalTimerHeap)
-        m_cachedThreadGlobalTimerHeap = &threadGlobalTimerHeap();
-
-    // Keep heap valid while changing the next-fire time.
-    double oldTime = m_nextFireTime;
+    double oldTime = nextFireTime();
     double newTime = alignedFireTime(newUnalignedTime);
-    if (oldTime != newTime) {
-        m_nextFireTime = newTime;
-        static unsigned currentHeapInsertionOrder;
-        m_heapInsertionOrder = atomicAdd(&currentHeapInsertionOrder, 1);
-
-        bool wasFirstTimerInHeap = m_heapIndex == 0;
-
-        updateHeapIfNeeded(oldTime);
-
-        bool isFirstTimerInHeap = m_heapIndex == 0;
-
-        if (wasFirstTimerInHeap || isFirstTimerInHeap)
-            PlatformThreadData::current().threadTimers().updateSharedTimer();
-    }
-
-    checkConsistency();
+    if (oldTime != newTime)
+        m_heapEntry.setValue(*this, newTime);
 }
 
 void TimerBase::fireTimersInNestedEventLoop()