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