libcxx/src/random_shuffle.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include <algorithm>
  10 #include <random>
  11
  12 #if _LIBCPP_HAS_THREADS
  13 #  include <mutex>
  14 #  if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
  15 #    pragma comment(lib, "pthread")
  16 #  endif
  17 #endif
  18
  19 _LIBCPP_BEGIN_NAMESPACE_STD
  20
  21 #if _LIBCPP_HAS_THREADS
  22 static constinit __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
  23 #endif
  24 unsigned __rs_default::__c_ = 0;
  25
  26 __rs_default::__rs_default() {
  27 #if _LIBCPP_HAS_THREADS
  28   __libcpp_mutex_lock(&__rs_mut);
  29 #endif
  30   __c_ = 1;
  31 }
  32
  33 __rs_default::__rs_default(const __rs_default&) { ++__c_; }
  34
  35 __rs_default::~__rs_default() {
  36 #if _LIBCPP_HAS_THREADS
  37   if (--__c_ == 0)
  38     __libcpp_mutex_unlock(&__rs_mut);
  39 #else
  40   --__c_;
  41 #endif
  42 }
  43
  44 __rs_default::result_type __rs_default::operator()() {
  45   static mt19937 __rs_g;
  46   return __rs_g();
  47 }
  48
  49 __rs_default __rs_get() { return __rs_default(); }
  50
  51 _LIBCPP_END_NAMESPACE_STD