1//===---------------------- shared_mutex.cpp ------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is dual licensed under the MIT and the University of Illinois Open 6// Source Licenses. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9 10#define _LIBCPP_BUILDING_SHARED_MUTEX 11#include "shared_mutex" 12 13_LIBCPP_BEGIN_NAMESPACE_STD 14 15shared_timed_mutex::shared_timed_mutex() 16 : __state_(0) 17{ 18} 19 20// Exclusive ownership 21 22void 23shared_timed_mutex::lock() 24{ 25 unique_lock<mutex> lk(__mut_); 26 while (__state_ & __write_entered_) 27 __gate1_.wait(lk); 28 __state_ |= __write_entered_; 29 while (__state_ & __n_readers_) 30 __gate2_.wait(lk); 31} 32 33bool 34shared_timed_mutex::try_lock() 35{ 36 unique_lock<mutex> lk(__mut_); 37 if (__state_ == 0) 38 { 39 __state_ = __write_entered_; 40 return true; 41 } 42 return false; 43} 44 45void 46shared_timed_mutex::unlock() 47{ 48 lock_guard<mutex> _(__mut_); 49 __state_ = 0; 50 __gate1_.notify_all(); 51} 52 53// Shared ownership 54 55void 56shared_timed_mutex::lock_shared() 57{ 58 unique_lock<mutex> lk(__mut_); 59 while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_) 60 __gate1_.wait(lk); 61 unsigned num_readers = (__state_ & __n_readers_) + 1; 62 __state_ &= ~__n_readers_; 63 __state_ |= num_readers; 64} 65 66bool 67shared_timed_mutex::try_lock_shared() 68{ 69 unique_lock<mutex> lk(__mut_); 70 unsigned num_readers = __state_ & __n_readers_; 71 if (!(__state_ & __write_entered_) && num_readers != __n_readers_) 72 { 73 ++num_readers; 74 __state_ &= ~__n_readers_; 75 __state_ |= num_readers; 76 return true; 77 } 78 return false; 79} 80 81void 82shared_timed_mutex::unlock_shared() 83{ 84 lock_guard<mutex> _(__mut_); 85 unsigned num_readers = (__state_ & __n_readers_) - 1; 86 __state_ &= ~__n_readers_; 87 __state_ |= num_readers; 88 if (__state_ & __write_entered_) 89 { 90 if (num_readers == 0) 91 __gate2_.notify_one(); 92 } 93 else 94 { 95 if (num_readers == __n_readers_ - 1) 96 __gate1_.notify_one(); 97 } 98} 99 100 101_LIBCPP_END_NAMESPACE_STD 102