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/*
File: CAAtomicStack.h
Abstract: Part of CoreAudio Utility Classes
Version: 1.1
Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple
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terms, and your use, installation, modification or redistribution of
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In consideration of your agreement to abide by the following terms, and
subject to these terms, Apple grants you a personal, non-exclusive
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Software, with or without modifications, in source and/or binary forms;
provided that if you redistribute the Apple Software in its entirety and
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Neither the name, trademarks, service marks or logos of Apple Inc. may
be used to endorse or promote products derived from the Apple Software
without specific prior written permission from Apple. Except as
expressly stated in this notice, no other rights or licenses, express or
implied, are granted by Apple herein, including but not limited to any
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The Apple Software is provided by Apple on an "AS IS" basis. APPLE
MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND
OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL
OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,
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AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),
STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
Copyright (C) 2014 Apple Inc. All Rights Reserved.
*/
#ifndef __CAAtomicStack_h__
#define __CAAtomicStack_h__
#if !defined(__COREAUDIO_USE_FLAT_INCLUDES__)
#include <libkern/OSAtomic.h>
#else
#include <CAAtomic.h>
#endif
#if MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_4
#include <CoreServices/CoreServices.h>
#endif
// linked list LIFO or FIFO (pop_all_reversed) stack, elements are pushed and popped atomically
// class T must implement T *& next().
template <class T>
class TAtomicStack {
public:
TAtomicStack() : mHead(NULL) { }
// non-atomic routines, for use when initializing/deinitializing, operate NON-atomically
void push_NA(T *item)
{
item->next() = mHead;
mHead = item;
}
T * pop_NA()
{
T *result = mHead;
if (result)
mHead = result->next();
return result;
}
bool empty() const { return mHead == NULL; }
T * head() { return mHead; }
// atomic routines
void push_atomic(T *item)
{
T *head_;
do {
head_ = mHead;
item->next() = head_;
} while (!compare_and_swap(head_, item, &mHead));
}
void push_multiple_atomic(T *item)
// pushes entire linked list headed by item
{
T *head_, *p = item, *tail;
// find the last one -- when done, it will be linked to head
do {
tail = p;
p = p->next();
} while (p);
do {
head_ = mHead;
tail->next() = head_;
} while (!compare_and_swap(head_, item, &mHead));
}
T * pop_atomic_single_reader()
// this may only be used when only one thread may potentially pop from the stack.
// if multiple threads may pop, this suffers from the ABA problem.
// <rdar://problem/4606346> TAtomicStack suffers from the ABA problem
{
T *result;
do {
if ((result = mHead) == NULL)
break;
} while (!compare_and_swap(result, result->next(), &mHead));
return result;
}
T * pop_atomic()
// This is inefficient for large linked lists.
// prefer pop_all() to a series of calls to pop_atomic.
// push_multiple_atomic has to traverse the entire list.
{
T *result = pop_all();
if (result) {
T *next = result->next();
if (next)
// push all the remaining items back onto the stack
push_multiple_atomic(next);
}
return result;
}
T * pop_all()
{
T *result;
do {
if ((result = mHead) == NULL)
break;
} while (!compare_and_swap(result, NULL, &mHead));
return result;
}
T* pop_all_reversed()
{
TAtomicStack<T> reversed;
T *p = pop_all(), *next;
while (p != NULL) {
next = p->next();
reversed.push_NA(p);
p = next;
}
return reversed.mHead;
}
static bool compare_and_swap(T *oldvalue, T *newvalue, T **pvalue)
{
#if TARGET_OS_MAC
#if __LP64__
return ::OSAtomicCompareAndSwap64Barrier(int64_t(oldvalue), int64_t(newvalue), (int64_t *)pvalue);
#elif MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
return ::OSAtomicCompareAndSwap32Barrier(int32_t(oldvalue), int32_t(newvalue), (int32_t *)pvalue);
#else
return ::CompareAndSwap(UInt32(oldvalue), UInt32(newvalue), (UInt32 *)pvalue);
#endif
#else
//return ::CompareAndSwap(UInt32(oldvalue), UInt32(newvalue), (UInt32 *)pvalue);
return CAAtomicCompareAndSwap32Barrier(SInt32(oldvalue), SInt32(newvalue), (SInt32*)pvalue);
#endif
}
protected:
T * mHead;
};
#if ((MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5) && !TARGET_OS_WIN32)
#include <libkern/OSAtomic.h>
class CAAtomicStack {
public:
CAAtomicStack(size_t nextPtrOffset) : mNextPtrOffset(nextPtrOffset) {
/*OSQueueHead h = OS_ATOMIC_QUEUE_INIT; mHead = h;*/
mHead.opaque1 = 0; mHead.opaque2 = 0;
}
// a subset of the above
void push_atomic(void *p) { OSAtomicEnqueue(&mHead, p, mNextPtrOffset); }
void push_NA(void *p) { push_atomic(p); }
void * pop_atomic() { return OSAtomicDequeue(&mHead, mNextPtrOffset); }
void * pop_atomic_single_reader() { return pop_atomic(); }
void * pop_NA() { return pop_atomic(); }
private:
OSQueueHead mHead;
size_t mNextPtrOffset;
};
// a more efficient subset of TAtomicStack using OSQueue.
template <class T>
class TAtomicStack2 {
public:
TAtomicStack2() {
/*OSQueueHead h = OS_ATOMIC_QUEUE_INIT; mHead = h;*/
mHead.opaque1 = 0; mHead.opaque2 = 0;
mNextPtrOffset = -1;
}
void push_atomic(T *item) {
if (mNextPtrOffset < 0) {
T **pnext = &item->next(); // hack around offsetof not working with C++
mNextPtrOffset = (Byte *)pnext - (Byte *)item;
}
OSAtomicEnqueue(&mHead, item, mNextPtrOffset);
}
void push_NA(T *item) { push_atomic(item); }
T * pop_atomic() { return (T *)OSAtomicDequeue(&mHead, mNextPtrOffset); }
T * pop_atomic_single_reader() { return pop_atomic(); }
T * pop_NA() { return pop_atomic(); }
// caution: do not try to implement pop_all_reversed here. the writer could add new elements
// while the reader is trying to pop old ones!
private:
OSQueueHead mHead;
ssize_t mNextPtrOffset;
};
#else
#define TAtomicStack2 TAtomicStack
#endif // MAC_OS_X_VERSION_MAX_ALLOWED && !TARGET_OS_WIN32
#endif // __CAAtomicStack_h__
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