cpp-ipc/include/libconcur/intrusive_stack.h

/**
 * \file libconcur/intrusive_stack.h
 * \author mutouyun (orz@orzz.org)
 * \brief Define concurrent intrusive stack.
 * \date 2023-11-18
 */
#pragma once

#include <atomic>

#include "libconcur/def.h"

LIBCONCUR_NAMESPACE_BEG_

template <typename T>
class intrusive_stack {
public:
  struct node {
    T value;
    std::atomic<node *> next{nullptr};
  };

private:
  std::atomic<node *> top_{nullptr};

public:
  intrusive_stack(intrusive_stack const &) = delete;
  intrusive_stack(intrusive_stack &&) = delete;
  intrusive_stack &operator=(intrusive_stack const &) = delete;
  intrusive_stack &operator=(intrusive_stack &&) = delete;

  constexpr intrusive_stack() noexcept = default;

  bool empty() const noexcept {
    return top_.load(std::memory_order_acquire) == nullptr;
  }

  void push(node *n) noexcept {
    node *old_top = top_.load(std::memory_order_acquire);
    do {
      n->next.store(old_top, std::memory_order_relaxed);
    } while (!top_.compare_exchange_weak(old_top, n, std::memory_order_release
                                                   , std::memory_order_acquire));
  }

  node *pop() noexcept {
    node *old_top = top_.load(std::memory_order_acquire);
    do {
      if (old_top == nullptr) {
        return nullptr;
      }
    } while (!top_.compare_exchange_weak(old_top, old_top->next.load(std::memory_order_relaxed)
                                                   , std::memory_order_release
                                                   , std::memory_order_acquire));
    return old_top;
  }
};

LIBCONCUR_NAMESPACE_END_