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/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* $Source: src/include/util/nolockfree/stack.H $ */
/* */
/* OpenPOWER HostBoot Project */
/* */
/* Contributors Listed Below - COPYRIGHT 2010,2019 */
/* [+] International Business Machines Corp. */
/* */
/* */
/* 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_NOLOCKFREE_STACK_H
#define __UTIL_NOLOCKFREE_STACK_H
#include <stddef.h>
#include <assert.h>
namespace Util
{
namespace NoLockFree
{
/**
* @brief Non-lockfree stack implementation
*
* This is an intrusive container design, meaning elements being
* added to the stack must have a 'next' member of _T* type. This
* container is not threadsafe.
*
* @note: For a lockfree stack implementation, see Util::LockFree::Stack
*/
template <typename _T>
class Stack
{
public:
/**
* @brief Constructor
*/
Stack()
: head(nullptr)
{
}
/**
* @brief Pop an element from the stack.
*
* @return _T* The pointer to the element popped from the stack
*/
_T* pop();
/**
* @brief Push an element to the stack.
*
* @param[in] p Pointer to the element to add to the stack.
*/
void push(_T* p);
/**
* @brief Get a pointer to the first element in the stack
*
* @return _T* 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()
{
return head;
}
template <typename _T>
_T* Stack<_T>::pop()
{
auto original = head;
if (unlikely(nullptr == original))
{
return nullptr;
}
head = original->next;
return original;
}
template <typename _T>
void Stack<_T>::push(_T* p)
{
p->next = head;
head = p;
}
} // End NoLockFree namespace
} // End Util namespace
#endif // __UTIL_NOLOCKFREE_STACK_H
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