mcas_buffer.h

Go to the documentation of this file.

/*
The MIT License (MIT)

Copyright (c) 2015 University of Central Florida's Computer Software Engineering
Scalable & Secure Systems (CSE - S3) Lab

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
#ifndef __TERVEL_CONTAINERS_LF_MCAS_BUFFER_MCAS_BUFFER_H__
#define __TERVEL_CONTAINERS_LF_MCAS_BUFFER_MCAS_BUFFER_H__

#include <atomic>
#include <cstdint>
#include <algorithm>

#include <tervel/util/info.h>
#include <tervel/util/memory/rc/descriptor_util.h>
#include <tervel/util/descriptor.h>

#include <tervel/algorithms/wf/mcas/mcas.h>

namespace tervel {
namespace containers {
namespace lf {
namespace mcas_buffer {

template<typename T>
class Node : public util::Descriptor {
 public:
  explicit Node(T val)
    : val_(val) {}

  ~Node() {}

  T value() {
    return val_;
  };

  using util::Descriptor::complete;
  void * complete(void *current, std::atomic<void *> *address) {
    assert(false);
    return nullptr;
  };

  using util::Descriptor::get_logical_value;
  void * get_logical_value() {
    assert(false);
    return nullptr;
  };

 private:
  const T val_;
};  // class Node

template<typename T>
class RingBuffer {
 public:
  explicit RingBuffer(uint64_t s)
    : capacity_(s)
    , buff_(new std::atomic<Node<T> *>[s]) {
      buff_[0].store(c_tail_value);
      buff_[1].store(c_head_value);
      head_.store(1);
      tail_.store(0);
      for (uint64_t i = 2; i < capacity_; i++) {
        buff_[i].store(c_not_value);
      }
    };

  ~RingBuffer() {
    for (uint64_t i = 0; i < capacity_; i++) {
      Node<T> * cvalue = buff_[i].load();
      if (cvalue == c_tail_value) {
        continue;
      } else if (cvalue == c_head_value) {
        continue;
      } else if (cvalue == c_not_value) {
        continue;
      } else {
        delete cvalue;
      }
    }
  };


  bool enqueue(T value);
  bool dequeue(T &value);

  bool is_empty() {
    uint64_t t = tail();
    uint64_t h = head();

    if (h > t+1) {
      return false;
    } else {
      return true;
    }
  };

  bool is_full() {
    uint64_t t = tail();
    uint64_t h = head();

    if (h+1 >= t+capacity_) {
      return true;
    } else {
      return false;
    }
  };

  size_t capacity() {
    return capacity_;
  };

  void print_queue() {
    for (uint64_t i = 0; i < capacity_; i++) {
      Node<T> * cvalue = buff_[i].load();
      if (cvalue == c_tail_value) {
        printf("[%lu, TAIL(%p) ] ", i, cvalue);
      } else if (cvalue == c_head_value) {
        printf("[%lu, HEAD(%p) ] ", i, cvalue);
      } else if (cvalue == c_not_value) {
        printf("[%lu, NOT(%p) ] ", i, cvalue);
      } else {
        printf("[%lu, VAL(%p)] ", i, reinterpret_cast<void *>(cvalue->value()));
      }
    }
    printf("\n");
  };

 private:
  Node<T> *at(uint64_t pos) {
    if (pos >= capacity_) {
      pos = pos % capacity_;
    }
    while (true) {
      Node<T> *node = buff_[pos].load();

      if (util::memory::rc::is_descriptor_first(reinterpret_cast<void *>(
            node))) {
        util::memory::rc::remove_descriptor(reinterpret_cast<void *>(node),
            reinterpret_cast<std::atomic<void *> *>(&(buff_[pos])));
      } else {
        return node;
      }
    }
  }

  std::atomic<Node<T> *> *address(uint64_t pos) {
    if (pos >= capacity_) {
      pos = pos % capacity_;
    }
    return &(buff_[pos]);
  }

  uint64_t head() {
    return head_.load();
  }

  uint64_t head(uint64_t i) {
    return head_.fetch_add(i);
  }

  uint64_t tail() {
    return tail_.load();
  }

  uint64_t tail(uint64_t i) {
    return tail_.fetch_add(i);
  }

  bool enqueue(Node<T> * node) {
    if (is_full()) {
      return false;
    }

    uint64_t h = head();

    while (true) {
      Node<T> *current = at(h);
      if (current == c_head_value) {
        Node<T> *next = at(h+1);

        if (next == c_tail_value) {
          return false;
        } else {
          tervel::algorithms::wf::mcas::MCAS<Node<T> *> *mcas =
              new tervel::algorithms::wf::mcas::MCAS<Node<T> *>(2);
          bool success;
          success = mcas->add_cas_triple(address(h), c_head_value, node);
          assert(success);

          success = mcas->add_cas_triple(address(h+1), c_not_value, c_head_value);
          assert(success);

          success = mcas->execute();
          mcas->safe_delete();

          if (success) {
            head(1);
            return true;
          } else {
            continue;
          }
        }

      } else if (current == c_not_value) {
        h = head();
      } else {
        h++;
      }
    }
  }  

  Node<T> * dequeue() {
    if (is_empty()) {
      return c_not_value;
    }

    uint64_t t = tail();

    while (true) {
      Node<T> *current = at(t);
      if (current == c_tail_value) {
        Node<T> *next = at(t+1);

        if (next == c_head_value) {
          return c_not_value;
        } else if (next == c_tail_value) {
          t++;
        } else if (next == c_not_value) {
          t = tail();
        } else {  // some node *
          tervel::algorithms::wf::mcas::MCAS<Node<T> *> *mcas =
              new tervel::algorithms::wf::mcas::MCAS<Node<T> *>(2);
          bool success;
          success = mcas->add_cas_triple(address(t), c_tail_value, c_not_value);
          assert(success);

          success = mcas->add_cas_triple(address(t+1), next, c_tail_value);
          assert(success);

          success = mcas->execute();
          mcas->safe_delete();

          if (success) {
            tail(1);
            return next;
          } else {
            continue;
          }
        }

      } else if (current == c_not_value) {
        t = tail();
      } else {
        t++;
      }
    }
  }  // dequeue

  const uint64_t capacity_;
  std::atomic<uint64_t> head_;
  std::atomic<uint64_t> tail_;
  std::unique_ptr<std::atomic<Node<T> *>[]> buff_;

  Node<T> * c_not_value = reinterpret_cast<Node<T> *>(0x0L);
  Node<T> * c_head_value = reinterpret_cast<Node<T> *>(0x10L);
  Node<T> * c_tail_value = reinterpret_cast<Node<T> *>(0x20L);
};  // class RingBuffer



template<typename T>
bool RingBuffer<T>::enqueue(T value) {
  Node<T> *node = tervel::util::memory::rc::get_descriptor<Node<T>>(value);

  if (enqueue(node)) {
    return true;
  } else {
    util::memory::rc::free_descriptor(node);
    return false;
  }
};

template<typename T>
bool RingBuffer<T>::dequeue(T &value) {
  Node<T> *node = dequeue();
  if (node == c_not_value) {
    return false;
  } else {
    value = node->value();
    util::memory::rc::free_descriptor(node);
    return true;
  }
};

}  // namespace tervel
}  // namespace containers
}  // namespace lf
}  // namespace mcas_buffer

#endif  // __TERVEL_CONTAINERS_LF_MCAS_BUFFER_MCAS_BUFFER_H__