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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/. */
#ifndef mozilla_dom_workerinternal_Queue_h
#define mozilla_dom_workerinternal_Queue_h
#include "mozilla/Mutex.h"
#include "nsTArray.h"
namespace mozilla::dom::workerinternals {
template <typename T, int TCount>
struct StorageWithTArray {
typedef AutoTArray<T, TCount> StorageType;
static void Reverse(StorageType& aStorage) {
uint32_t length = aStorage.Length();
for (uint32_t index = 0; index < length / 2; index++) {
uint32_t reverseIndex = length - 1 - index;
T t1 = aStorage.ElementAt(index);
T t2 = aStorage.ElementAt(reverseIndex);
aStorage.ReplaceElementsAt(index, 1, t2);
aStorage.ReplaceElementsAt(reverseIndex, 1, t1);
}
}
static bool IsEmpty(const StorageType& aStorage) {
return !!aStorage.IsEmpty();
}
static void Push(StorageType& aStorage, const T& aEntry) {
aStorage.AppendElement(aEntry);
}
static bool Pop(StorageType& aStorage, T& aEntry) {
if (IsEmpty(aStorage)) {
return false;
}
aEntry = aStorage.PopLastElement();
return true;
}
static void Clear(StorageType& aStorage) { aStorage.Clear(); }
static void Compact(StorageType& aStorage) { aStorage.Compact(); }
};
class MOZ_CAPABILITY("mutex") LockingWithMutex {
mozilla::Mutex mMutex;
protected:
LockingWithMutex() : mMutex("LockingWithMutex::mMutex") {}
void Lock() MOZ_CAPABILITY_ACQUIRE() { mMutex.Lock(); }
void Unlock() MOZ_CAPABILITY_RELEASE() { mMutex.Unlock(); }
class MOZ_SCOPED_CAPABILITY AutoLock {
LockingWithMutex& mHost;
public:
explicit AutoLock(LockingWithMutex& aHost) MOZ_CAPABILITY_ACQUIRE(aHost)
: mHost(aHost) {
mHost.Lock();
}
~AutoLock() MOZ_CAPABILITY_RELEASE() { mHost.Unlock(); }
};
friend class AutoLock;
};
class NoLocking {
protected:
void Lock() {}
void Unlock() {}
class AutoLock {
public:
explicit AutoLock(NoLocking& aHost) {}
~AutoLock() = default;
};
};
template <typename T, int TCount = 256, class LockingPolicy = NoLocking,
class StoragePolicy =
StorageWithTArray<T, TCount % 2 ? TCount / 2 + 1 : TCount / 2> >
class Queue : public LockingPolicy {
typedef typename StoragePolicy::StorageType StorageType;
typedef typename LockingPolicy::AutoLock AutoLock;
StorageType mStorage1;
StorageType mStorage2;
StorageType* mFront;
StorageType* mBack;
public:
Queue() : mFront(&mStorage1), mBack(&mStorage2) {}
bool IsEmpty() {
AutoLock lock(*this);
return StoragePolicy::IsEmpty(*mFront) && StoragePolicy::IsEmpty(*mBack);
}
void Push(const T& aEntry) {
AutoLock lock(*this);
StoragePolicy::Push(*mBack, aEntry);
}
bool Pop(T& aEntry) {
AutoLock lock(*this);
if (StoragePolicy::IsEmpty(*mFront)) {
StoragePolicy::Compact(*mFront);
StoragePolicy::Reverse(*mBack);
StorageType* tmp = mFront;
mFront = mBack;
mBack = tmp;
}
return StoragePolicy::Pop(*mFront, aEntry);
}
void Clear() {
AutoLock lock(*this);
StoragePolicy::Clear(*mFront);
StoragePolicy::Clear(*mBack);
}
// XXX Do we need this?
void Lock() { LockingPolicy::Lock(); }
// XXX Do we need this?
void Unlock() { LockingPolicy::Unlock(); }
private:
// Queue is not copyable.
Queue(const Queue&);
Queue& operator=(const Queue&);
};
} // namespace mozilla::dom::workerinternals
#endif /* mozilla_dom_workerinternals_Queue_h*/
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