mirror of
https://github.com/mozilla/gecko-dev.git
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174 lines
6.3 KiB
C++
174 lines
6.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_dom_OrderedTimeoutIterator_h__
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#define mozilla_dom_OrderedTimeoutIterator_h__
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#include "mozilla/RefPtr.h"
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#include "mozilla/dom/Timeout.h"
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#include "mozilla/dom/TimeoutManager.h"
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namespace mozilla {
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namespace dom {
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// This class implements and iterator which iterates the normal and tracking
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// timeouts lists simultaneously in the mWhen order.
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class MOZ_STACK_CLASS OrderedTimeoutIterator final {
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public:
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typedef TimeoutManager::Timeouts Timeouts;
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typedef Timeouts::TimeoutList TimeoutList;
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OrderedTimeoutIterator(Timeouts& aNormalTimeouts,
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Timeouts& aTrackingTimeouts)
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: mNormalTimeouts(aNormalTimeouts.mTimeoutList),
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mTrackingTimeouts(aTrackingTimeouts.mTimeoutList),
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mNormalIter(mNormalTimeouts.getFirst()),
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mTrackingIter(mTrackingTimeouts.getFirst()),
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mKind(Kind::None),
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mUpdateIteratorCalled(true)
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{
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}
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// Return the current timeout and move to the next one.
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// Unless this is the first time calling Next(), you must call
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// UpdateIterator() before calling this method.
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Timeout* Next()
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{
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MOZ_ASSERT(mUpdateIteratorCalled);
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MOZ_ASSERT_IF(mNormalIter, mNormalIter->isInList());
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MOZ_ASSERT_IF(mTrackingIter, mTrackingIter->isInList());
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mUpdateIteratorCalled = false;
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mKind = Kind::None;
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Timeout* timeout = nullptr;
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if (!mNormalIter) {
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if (!mTrackingIter) {
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// We have reached the end of both lists. Bail out!
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return nullptr;
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} else {
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// We have reached the end of the normal timeout list, select the next
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// tracking timeout.
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timeout = mTrackingIter;
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mKind = Kind::Tracking;
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}
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} else if (!mTrackingIter) {
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// We have reached the end of the tracking timeout list, select the next
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// normal timeout.
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timeout = mNormalIter;
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mKind = Kind::Normal;
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} else {
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// If we have a normal and a tracking timer, return the one with the
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// smaller mWhen (and prefer the timeout with a lower ID in case they are
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// equal.) Otherwise, return whichever iterator has an item left,
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// preferring a non-tracking timeout again. Note that in practice, even
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// if a web page calls setTimeout() twice in a row, it should get
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// different mWhen values, so in practice we shouldn't fall back to
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// comparing timeout IDs.
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if (mNormalIter && mTrackingIter &&
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(mTrackingIter->When() < mNormalIter->When() ||
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(mTrackingIter->When() == mNormalIter->When() &&
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mTrackingIter->mTimeoutId < mNormalIter->mTimeoutId))) {
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timeout = mTrackingIter;
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mKind = Kind::Tracking;
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} else if (mNormalIter) {
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timeout = mNormalIter;
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mKind = Kind::Normal;
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} else if (mTrackingIter) {
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timeout = mTrackingIter;
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mKind = Kind::Tracking;
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}
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}
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if (!timeout) {
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// We didn't find any suitable iterator. This can happen for example
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// when getNext() in UpdateIterator() returns nullptr and then Next()
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// gets called. Bail out!
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return nullptr;
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}
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MOZ_ASSERT(mKind != Kind::None);
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// Record the current timeout we just found.
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mCurrent = timeout;
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MOZ_ASSERT(mCurrent);
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return mCurrent;
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}
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// Prepare the iterator for the next call to Next().
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// This method can be called as many times as needed. Calling this more than
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// once is helpful in cases where we expect the timeouts list has been
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// modified before we got a chance to call Next().
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void UpdateIterator()
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{
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MOZ_ASSERT(mKind != Kind::None);
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// Update the winning iterator to point to the next element. Also check to
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// see if the other iterator is still valid, otherwise reset it to the
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// beginning of the list. This is needed in case a timeout handler removes
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// the timeout pointed to from one of our iterators.
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if (mKind == Kind::Normal) {
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mNormalIter = mCurrent->getNext();
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if (mTrackingIter && !mTrackingIter->isInList()) {
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mTrackingIter = mTrackingTimeouts.getFirst();
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}
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} else {
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mTrackingIter = mCurrent->getNext();
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if (mNormalIter && !mNormalIter->isInList()) {
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mNormalIter = mNormalTimeouts.getFirst();
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}
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}
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mUpdateIteratorCalled = true;
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}
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// This function resets the iterator to a defunct state. It should only be
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// used when we want to forcefully sever all of the strong references this
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// class holds.
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void Clear()
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{
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// Release all strong references.
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mNormalIter = nullptr;
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mTrackingIter = nullptr;
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mCurrent = nullptr;
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mKind = Kind::None;
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mUpdateIteratorCalled = true;
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}
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// Returns true if the previous call to Next() picked a normal timeout.
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// Cannot be called before Next() has been called. Note that the result of
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// this method is only affected by Next() and not UpdateIterator(), so calling
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// UpdateIterator() before calling this is allowed.
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bool PickedNormalIter() const
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{
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MOZ_ASSERT(mKind != Kind::None);
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return mKind == Kind::Normal;
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}
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// Returns true if the previous call to Next() picked a tracking timeout.
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// Cannot be called before Next() has been called. Note that the result of
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// this method is only affected by Next() and not UpdateIterator(), so calling
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// UpdateIterator() before calling this is allowed.
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bool PickedTrackingIter() const
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{
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MOZ_ASSERT(mKind != Kind::None);
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return mKind == Kind::Tracking;
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}
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private:
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TimeoutList& mNormalTimeouts; // The list of normal timeouts.
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TimeoutList& mTrackingTimeouts; // The list of tracking timeouts.
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RefPtr<Timeout> mNormalIter; // The iterator over the normal timeout list.
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RefPtr<Timeout> mTrackingIter; // The iterator over the tracking timeout list.
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RefPtr<Timeout> mCurrent; // The current timeout that Next() just found.
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enum class Kind { Normal, Tracking, None };
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Kind mKind; // The kind of iterator picked the last time.
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DebugOnly<bool> mUpdateIteratorCalled; // Whether we have called UpdateIterator() before calling Next().
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};
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}
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}
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#endif
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