1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// (C) Copyright 2013 Vicente J. Botet Escriba
#ifndef BOOST_THREAD_LATCH_HPP
#define BOOST_THREAD_LATCH_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/thread/detail/delete.hpp>
#include <boost/thread/detail/counter.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/lock_types.hpp>
#include <boost/thread/condition_variable.hpp>
#include <boost/chrono/duration.hpp>
#include <boost/chrono/time_point.hpp>
#include <boost/assert.hpp>
#include <boost/config/abi_prefix.hpp>
namespace boost
{
class latch
{
/// @Requires: count_ must be greater than 0
/// Effect: Decrement the count. Unlocks the lock and notify anyone waiting if we reached zero.
/// Returns: true if count_ reached the value 0.
/// @ThreadSafe ensured by the @c lk parameter
bool count_down(unique_lock<mutex> &)
/// pre_condition (count_ > 0)
{
BOOST_ASSERT(count_ > 0);
if (--count_ == 0)
{
++generation_;
//lk.unlock();
cond_.notify_all();
return true;
}
return false;
}
/// Effect: Decrement the count is > 0. Unlocks the lock notify anyone waiting if we reached zero.
/// Returns: true if count_ is 0.
/// @ThreadSafe ensured by the @c lk parameter
bool try_count_down(unique_lock<mutex> &lk)
{
if (count_ > 0)
{
return count_down(lk);
}
return true;
}
public:
BOOST_THREAD_NO_COPYABLE( latch)
/// Constructs a latch with a given count.
latch(std::size_t count) :
count_(count), generation_(0)
{
}
/// Destructor
/// Precondition: No threads are waiting or invoking count_down on @c *this.
~latch()
{
}
/// Blocks until the latch has counted down to zero.
void wait()
{
boost::unique_lock<boost::mutex> lk(mutex_);
if (count_ == 0) return;
std::size_t generation(generation_);
cond_.wait(lk, detail::not_equal(generation, generation_));
}
/// @return true if the internal counter is already 0, false otherwise
bool try_wait()
{
boost::unique_lock<boost::mutex> lk(mutex_);
return (count_ == 0);
}
/// try to wait for a specified amount of time is elapsed.
/// @return whether there is a timeout or not.
template <class Rep, class Period>
cv_status wait_for(const chrono::duration<Rep, Period>& rel_time)
{
boost::unique_lock<boost::mutex> lk(mutex_);
if (count_ == 0) return cv_status::no_timeout;
std::size_t generation(generation_);
return cond_.wait_for(lk, rel_time, detail::not_equal(generation, generation_))
? cv_status::no_timeout
: cv_status::timeout;
}
/// try to wait until the specified time_point is reached
/// @return whether there were a timeout or not.
template <class Clock, class Duration>
cv_status wait_until(const chrono::time_point<Clock, Duration>& abs_time)
{
boost::unique_lock<boost::mutex> lk(mutex_);
if (count_ == 0) return cv_status::no_timeout;
std::size_t generation(generation_);
return cond_.wait_until(lk, abs_time, detail::not_equal(generation, generation_))
? cv_status::no_timeout
: cv_status::timeout;
}
/// Decrement the count and notify anyone waiting if we reach zero.
/// @Requires count must be greater than 0
void count_down()
{
boost::unique_lock<boost::mutex> lk(mutex_);
count_down(lk);
}
/// Effect: Decrement the count if it is > 0 and notify anyone waiting if we reached zero.
/// Returns: true if count_ was 0 or reached 0.
bool try_count_down()
{
boost::unique_lock<boost::mutex> lk(mutex_);
return try_count_down(lk);
}
void signal()
{
count_down();
}
/// Decrement the count and notify anyone waiting if we reach zero.
/// Blocks until the latch has counted down to zero.
/// @Requires count must be greater than 0
void count_down_and_wait()
{
boost::unique_lock<boost::mutex> lk(mutex_);
std::size_t generation(generation_);
if (count_down(lk))
{
return;
}
cond_.wait(lk, detail::not_equal(generation, generation_));
}
void sync()
{
count_down_and_wait();
}
/// Reset the counter
/// #Requires This method may only be invoked when there are no other threads currently inside the count_down_and_wait() method.
void reset(std::size_t count)
{
boost::lock_guard<boost::mutex> lk(mutex_);
//BOOST_ASSERT(count_ == 0);
count_ = count;
}
private:
mutex mutex_;
condition_variable cond_;
std::size_t count_;
std::size_t generation_;
};
} // namespace boost
#include <boost/config/abi_suffix.hpp>
#endif
|
