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/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* $Source: src/include/util/lockfree/stack.H $ */
/* */
/* OpenPOWER HostBoot Project */
/* */
/* COPYRIGHT International Business Machines Corp. 2010,2014 */
/* */
/* Licensed under the Apache License, Version 2.0 (the "License"); */
/* you may not use this file except in compliance with the License. */
/* You may obtain a copy of the License at */
/* */
/* http://www.apache.org/licenses/LICENSE-2.0 */
/* */
/* Unless required by applicable law or agreed to in writing, software */
/* distributed under the License is distributed on an "AS IS" BASIS, */
/* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or */
/* implied. See the License for the specific language governing */
/* permissions and limitations under the License. */
/* */
/* IBM_PROLOG_END_TAG */
#ifndef __UTIL_LOCKFREE_STACK_H
#define __UTIL_LOCKFREE_STACK_H
#include <stddef.h>
#include <assert.h>
namespace Util
{
namespace Lockfree
{
template <typename _T>
class Stack
{
public:
Stack() : head(NULL) {};
_T* pop();
void push(_T*);
/**
* Get a pointer to the first element in the stack
* @return the pointer to the first element
* @Note: SMP safety of this pointer is not guaranteed.
*/
_T* first();
private:
_T* head;
};
template <typename _T>
_T* Stack<_T>::first()
{
_T * _head = head;
return (_T*) (((uint64_t)_head) & 0x00000000FFFFFFFF);
}
template <typename _T>
_T* Stack<_T>::pop()
{
_T * _head = head;
_T * h = (_T*) (((uint64_t)_head) & 0x00000000FFFFFFFF);
if (NULL == h) return h;
uint64_t token = ((uint64_t)_head) >> 32;
token++;
uint64_t h_next_v = (uint64_t)(h->next);
_T * h_next = (_T*) ((h_next_v & 0x00000000FFFFFFFF) |
(token << 32));
if (!__sync_bool_compare_and_swap(&head,
_head,
h_next))
return pop();
crit_assert((h_next_v >> 32) == 0x5354414B);
return h;
}
template <typename _T>
void Stack<_T>::push(_T* p)
{
_T* _head = head;
p->next = (_T*) ((((uint64_t)_head) & 0x00000000FFFFFFFF) |
0x5354414B00000000);
uint64_t token = ((uint64_t)_head) >> 32;
token++;
_T* _p = (_T*) (((uint64_t)p) | (token << 32));
if (!__sync_bool_compare_and_swap(&head,
_head,
_p))
push(p);
}
}
}
#endif
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