Line data    Source code

       1             : //
       2             : // immer: immutable data structures for C++
       3             : // Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
       4             : //
       5             : // This software is distributed under the Boost Software License, Version 1.0.
       6             : // See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
       7             : //
       8             : 
       9             : #pragma once
      10             : 
      11             : #include <immer/refcount/no_refcount_policy.hpp>
      12             : 
      13             : #include <atomic>
      14             : #include <cassert>
      15             : #include <utility>
      16             : 
      17             : namespace immer {
      18             : 
      19             : /*!
      20             :  * A reference counting policy implemented using an *atomic* `int`
      21             :  * count.  It is **thread-safe**.
      22             :  */
      23             : struct refcount_policy
      24             : {
      25             :     mutable std::atomic<int> refcount;
      26             : 
      27       66954 :     refcount_policy()
      28       30239 :         : refcount{1} {};
      29             :     refcount_policy(disowned)
      30             :         : refcount{0}
      31             :     {}
      32             : 
      33     1583384 :     void inc() { refcount.fetch_add(1, std::memory_order_relaxed); }
      34             : 
      35       35321 :     bool dec() { return 1 == refcount.fetch_sub(1, std::memory_order_acq_rel); }
      36             : 
      37        5297 :     void dec_unsafe()
      38             :     {
      39        5297 :         assert(refcount.load() > 1);
      40        5297 :         refcount.fetch_sub(1, std::memory_order_relaxed);
      41        5297 :     }
      42             : 
      43             :     bool unique() { return refcount == 1; }
      44             : };
      45             : 
      46             : } // namespace immer