1  // Mutex pool used to limit contention -*- C++ -*-
       2  
       3  // Copyright (C) 2016-2023 Free Software Foundation, Inc.
       4  //
       5  // This file is part of the GNU ISO C++ Library.  This library is free
       6  // software; you can redistribute it and/or modify it under the
       7  // terms of the GNU General Public License as published by the
       8  // Free Software Foundation; either version 3, or (at your option)
       9  // any later version.
      10  
      11  // This library is distributed in the hope that it will be useful,
      12  // but WITHOUT ANY WARRANTY; without even the implied warranty of
      13  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14  // GNU General Public License for more details.
      15  
      16  // Under Section 7 of GPL version 3, you are granted additional
      17  // permissions described in the GCC Runtime Library Exception, version
      18  // 3.1, as published by the Free Software Foundation.
      19  
      20  // You should have received a copy of the GNU General Public License and
      21  // a copy of the GCC Runtime Library Exception along with this program;
      22  // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23  // <http://www.gnu.org/licenses/>.
      24  
      25  namespace __gnu_internal _GLIBCXX_VISIBILITY(hidden)
      26  {
      27    const unsigned char mask = 0xf;
      28    const unsigned char invalid = mask + 1;
      29  
      30    /* Returns different instances of __mutex depending on the passed index
      31     * in order to limit contention.
      32     */
      33    __gnu_cxx::__mutex& get_mutex(unsigned char i);
      34  }