std::unique_lock<Mutex>::unique_lock
unique_lock() noexcept; |
(1) | (since C++11) |
unique_lock( unique_lock&& other ) noexcept; |
(2) | (since C++11) |
explicit unique_lock( mutex_type& m ); |
(3) | (since C++11) |
unique_lock( mutex_type& m, std::defer_lock_t t ) noexcept; |
(4) | (since C++11) |
unique_lock( mutex_type& m, std::try_to_lock_t t ); |
(5) | (since C++11) |
unique_lock( mutex_type& m, std::adopt_lock_t t ); |
(6) | (since C++11) |
template< class Rep, class Period >
unique_lock( mutex_type& m,
const std::chrono::duration<Rep,Period>& timeout_duration ); |
(7) | (since C++11) |
template< class Clock, class Duration >
unique_lock( mutex_type& m,
const std::chrono::time_point<Clock,Duration>& timeout_time ); |
(8) | (since C++11) |
Constructs a unique_lock, optionally locking the supplied mutex.
1) Constructs a
unique_lock with no associated mutex.
2) Move constructor. Initializes the
unique_lock with the contents of
other. Leaves
other with no associated mutex.
3-8) Constructs a
unique_lock with
m as the associated mutex. Additionally:
3) Locks the associated mutex by calling
m.lock().
4) Does not lock the associated mutex.
5) Tries to lock the associated mutex without blocking by calling
m.try_lock(). The behavior is undefined if
Mutex does not satisfy
Lockable.
6) Assumes the calling thread already holds an non-shared lock (i.e., a lock acquired by
lock,
try_lock,
try_lock_for, or
try_lock_until) on
m. The behavior is undefined if not so.
7) Tries to lock the associated mutex by calling
m.try_lock_for(timeout_duration). Blocks until specified
timeout_duration has elapsed or the lock is acquired, whichever comes first. May block for longer than
timeout_duration. The behavior is undefined if
Mutex does not satisfy
TimedLockable.
8) Tries to lock the associated mutex by calling
m.try_lock_until(timeout_time). Blocks until specified
timeout_time has been reached or the lock is acquired, whichever comes first. May block for longer than until
timeout_time has been reached. The behavior is undefined if
Mutex does not satisfy
TimedLockable.
Parameters
| other | - | another unique_lock to initialize the state with |
| m | - | mutex to associate with the lock and optionally acquire ownership of |
| t | - | tag parameter used to select constructors with different locking strategies |
| timeout_duration | - | maximum duration to block for |
| timeout_time | - | maximum time point to block until |
Example
#include <iostream>
#include <thread>
#include <vector>
#include <mutex>
std::mutex m_a, m_b, m_c;
int a, b, c = 1;
void update()
{
{ // Note: std::lock_guard or atomic<int> can be used instead
std::unique_lock<std::mutex> lk(m_a);
a++;
}
{ // Note: see std::lock and std::scoped_lock for details and alternatives
std::unique_lock<std::mutex> lk_b(m_b, std::defer_lock);
std::unique_lock<std::mutex> lk_c(m_c, std::defer_lock);
std::lock(lk_b, lk_c);
b = std::exchange(c, b+c);
}
}
int main()
{
std::vector<std::thread> threads;
for (unsigned i = 0; i < 12; ++i)
threads.emplace_back(update);
for (auto& i: threads)
i.join();
std::cout << a << "'th and " << a+1 << "'th Fibonacci numbers: "
<< b << " and " << c << '\n';
}
Output:
12'th and 13'th Fibonacci numbers: 144 and 233
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