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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsEventQueue.h"
#include "nsAutoPtr.h"
#include "mozilla/Logging.h"
#include "nsThreadUtils.h"
#include "prthread.h"
#include "mozilla/ChaosMode.h"
using namespace mozilla;
static LazyLogModule sEventQueueLog("nsEventQueue");
#ifdef LOG
#undef LOG
#endif
#define LOG(args) MOZ_LOG(sEventQueueLog, mozilla::LogLevel::Debug, args)
nsEventQueue::nsEventQueue(mozilla::CondVar& aCondVar, EventQueueType aType)
: mHead(nullptr)
, mTail(nullptr)
, mOffsetHead(0)
, mOffsetTail(0)
, mEventsAvailable(aCondVar)
, mType(aType)
{
}
nsEventQueue::~nsEventQueue()
{
// It'd be nice to be able to assert that no one else is holding the lock,
// but NSPR doesn't really expose APIs for it.
NS_ASSERTION(IsEmpty(),
"Non-empty event queue being destroyed; events being leaked.");
if (mHead) {
FreePage(mHead);
}
}
bool
nsEventQueue::GetEvent(bool aMayWait, nsIRunnable** aResult,
MutexAutoLock& aProofOfLock)
{
if (aResult) {
*aResult = nullptr;
}
while (IsEmpty()) {
if (!aMayWait) {
return false;
}
LOG(("EVENTQ(%p): wait begin\n", this));
mEventsAvailable.Wait();
LOG(("EVENTQ(%p): wait end\n", this));
if (mType == eSharedCondVarQueue) {
if (IsEmpty()) {
return false;
}
break;
}
}
if (aResult) {
MOZ_ASSERT(mOffsetHead < EVENTS_PER_PAGE);
MOZ_ASSERT_IF(mHead == mTail, mOffsetHead <= mOffsetTail);
*aResult = mHead->mEvents[mOffsetHead++];
MOZ_ASSERT(*aResult);
MOZ_ASSERT(mOffsetHead <= EVENTS_PER_PAGE);
// Check if mHead points to empty Page
if (mOffsetHead == EVENTS_PER_PAGE) {
Page* dead = mHead;
mHead = mHead->mNext;
FreePage(dead);
mOffsetHead = 0;
}
}
return true;
}
void
nsEventQueue::PutEvent(already_AddRefed<nsIRunnable>&& aRunnable,
MutexAutoLock& aProofOfLock)
{
if (!mHead) {
mHead = NewPage();
MOZ_ASSERT(mHead);
mTail = mHead;
mOffsetHead = 0;
mOffsetTail = 0;
} else if (mOffsetTail == EVENTS_PER_PAGE) {
Page* page = NewPage();
MOZ_ASSERT(page);
mTail->mNext = page;
mTail = page;
mOffsetTail = 0;
}
nsIRunnable*& queueLocation = mTail->mEvents[mOffsetTail];
MOZ_ASSERT(!queueLocation);
queueLocation = aRunnable.take();
++mOffsetTail;
LOG(("EVENTQ(%p): notify\n", this));
mEventsAvailable.Notify();
}
void
nsEventQueue::PutEvent(nsIRunnable* aRunnable, MutexAutoLock& aProofOfLock)
{
nsCOMPtr<nsIRunnable> event(aRunnable);
PutEvent(event.forget(), aProofOfLock);
}
size_t
nsEventQueue::Count(MutexAutoLock& aProofOfLock) const
{
// It is obvious count is 0 when the queue is empty.
if (!mHead) {
return 0;
}
/* How we count the number of events in the queue:
* 1. Let pageCount(x, y) denote the number of pages excluding the tail page
* where x is the index of head page and y is the index of the tail page.
* 2. Then we have pageCount(x, y) = y - x.
*
* Ex: pageCount(0, 0) = 0 where both head and tail pages point to page 0.
* pageCount(0, 1) = 1 where head points to page 0 and tail points page 1.
*
* 3. number of events = (EVENTS_PER_PAGE * pageCount(x, y))
* - (empty slots in head page) + (non-empty slots in tail page)
* = (EVENTS_PER_PAGE * pageCount(x, y)) - mOffsetHead + mOffsetTail
*/
int count = -mOffsetHead;
// Compute (EVENTS_PER_PAGE * pageCount(x, y))
for (Page* page = mHead; page != mTail; page = page->mNext) {
count += EVENTS_PER_PAGE;
}
count += mOffsetTail;
MOZ_ASSERT(count >= 0);
return count;
}
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