mcas.h

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/*
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_MCAS_MCAS_H_
#define TERVEL_MCAS_MCAS_H_

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

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

namespace tervel {
namespace algorithms {
namespace wf {
namespace mcas {
template<class T>
inline T read(std::atomic<T> *address) {
  void *value = util::memory::rc::descriptor_read_first(address);
  return reinterpret_cast<T>(value);
}

template<class T>
class MultiWordCompareAndSwap : public util::OpRecord {
 public:
  static constexpr void * MCAS_FAIL_CONST = reinterpret_cast<void *>(0x1L);

  explicit MultiWordCompareAndSwap<T>(int max_rows)
      : cas_rows_(new CasRow<T>[max_rows])
      , max_rows_ {max_rows} {}

  ~MultiWordCompareAndSwap<T>() {
    state_.store(MCasState::DELETED);
    for (int i = 0; i < row_count_; i++) {
      Helper<T>* helper = cas_rows_[i].helper_.load();
      // The No check flag is true because each was check prior
      // to the call of this descructor.
      if (helper == reinterpret_cast<Helper<T> *>(MCAS_FAIL_CONST)) {
        break;
      }
      util::memory::rc::free_descriptor(helper, true);
    }
  }

  bool add_cas_triple(std::atomic<T> *address, T expected_value, T new_value);

  bool execute();

  void help_complete() {
    mcas_complete(0, true);
  }

  bool on_is_watched() {
    for (int i = 0; i < row_count_; i++) {
      Helper<T>* helper = cas_rows_[i].helper_.load();
      // The No check flag is true because each was check prior
      // to the call of this destructor.
      if (helper == reinterpret_cast<Helper<T> *>(MCAS_FAIL_CONST)) {
        break;
      } else if (util::memory::rc::is_watched(helper)) {
        return true;
      }
    }
    return false;
  }

 private:
  enum class MCasState : std::int8_t {IN_PROGRESS = 0, PASS = 1 , FAIL = 2,
      DELETED = 3};
  bool mcas_complete(int start_pos, bool wfmode = false);

  bool mcas_complete(CasRow<T> *current_row);

  void cleanup(bool success);

  T mcas_remove(const int pos, T value);

  // ------
  // Member Data
  // ------

  /* THe array of CAS triples to complete*/
  std::unique_ptr<CasRow<T>[]> cas_rows_;
  /* The state of the mcas operation */
  std::atomic<MCasState> state_ {MCasState::IN_PROGRESS};
  /* The number of cas rows */
  int row_count_ {0};
  /* The max number of rows supported this instance is expecting*/
  int max_rows_;

  friend Helper<T>;
  friend CasRow<T>;
};  // MCAS class


}  // namespace mcas
}  // namespace wf
}  // namespace algorithms
}  // namespace tervel

#include <tervel/algorithms/wf/mcas/mcas_imp.h>
#endif  // TERVEL_MCAS_MCAS_H_