xtd::threading::lock_guard Class Reference

Inheritance diagram for xtd::threading::lock_guard:

Definition

Provides a mechanism that synchronizes access to objects with xtd::threading::mutex.

class core_export_ lock_guard final : public xtd::object

Inheritance

xtd::object → xtd::lock_guard

Header

#include <xtd/threading/lock_guard>

Namespace

xtd::threading

Library

xtd.core

Examples

The following example uses the xtd::threading::lock_guard class to synchronize access to a single instance of a random number generator represented by the xtd::random class. The example creates ten threads, each of which executes asynchronously on a thread pool thread. Each thread generates 10,000 random numbers, calculates their average, and updates two procedure-level variables that maintain a running total of the number of random numbers generated and their sum. After all threads have executed, these two values are then used to calculate the overall mean.

#include <xtd/xtd>
 
namespace lock_guard_example {
  class program {
  public:
    static void main() {
      auto threads = list<thread> {};
      auto rnd = xtd::random {};
      auto total = 0_s64;
      auto n = 0;
      
      for (auto thread_ctr = 0; thread_ctr < 10; ++thread_ctr)
        threads.add(thread::start_new([&] {
          auto values = std::array<int, 10000> {};
          auto thread_total = 0;
          auto thread_n = 0;
          auto ctr = 0;
          block_scope_(lock_guard lock {rnd}) {
            // Generate 10,000 random integers
            for (ctr = 0; ctr < 10000; ++ctr)
              values[ctr] = rnd.next(0, 1001);
          }
          thread_n = ctr;
          for (auto value : values)
            thread_total += value;
          
          console::write_line("Mean for task {0,2}: {1:N2} (N={2:N0})",
                              thread::current_thread().managed_thread_id(),
                              (thread_total * 1.0) / thread_n, thread_n);
          interlocked::add(n, thread_n);
          interlocked::add(total, thread_total);
        }));
      try {
        for (auto& thread : threads)
          thread.join();
        console::write_line("\nMean for all tasks: {0:N2} (N={1:N0})",
                            (total * 1.0)/n, n);
      }
      catch (const system_exception& e) {
        console::write_line("{0}: {1}", e.get_type().name(), e.message());
      }
    }
  };
}
 
startup_(lock_guard_example::program::main);
 
// This example produces output similar to the following:
//
// Mean for task  4: 498.90 (N=10000)
// Mean for task  2: 499.92 (N=10000)
// Mean for task  7: 503.12 (N=10000)
// Mean for task  5: 499.41 (N=10000)
// Mean for task  3: 498.58 (N=10000)
// Mean for task  8: 496.71 (N=10000)
// Mean for task 10: 501.49 (N=10000)
// Mean for task  6: 498.84 (N=10000)
// Mean for task  9: 502.72 (N=10000)
// Mean for task 11: 498.69 (N=10000)
//
// Mean for all tasks: 499.84 (N=100000)

Remarks

See xtd::threading::mutex for more information.

Public Constructors
template<class object_t>
	lock_guard (const object_t &obj)
	Create a xtd::threading::lock_guard object and acquires an exclusive lock_guard on the specified obj.
	lock_guard (const xtd::string &str)
	Create a xtd::threading::lock_guard object and acquires an exclusive lock_guard on the specified string.

Public Methods
void	enter ()
	Enters the lock_guard, waiting if necessary until the lock_guard can be entered.
void	exit ()
	Exits the lock_guard.

Additional Inherited Members
	object ()=default
	Create a new instance of the ultimate base class object.
virtual bool	equals (const object &obj) const noexcept
	Determines whether the specified object is equal to the current object.
virtual xtd::size	get_hash_code () const noexcept
	Serves as a hash function for a particular type.
virtual type_object	get_type () const noexcept
	Gets the type of the current instance.
template<class object_t>
xtd::unique_ptr_object< object_t >	memberwise_clone () const
	Creates a shallow copy of the current object.
virtual xtd::string	to_string () const noexcept
	Returns a xtd::string that represents the current object.
template<class object_a_t, class object_b_t>
static bool	equals (const object_a_t &object_a, const object_b_t &object_b) noexcept
	Determines whether the specified object instances are considered equal.
template<class object_a_t, class object_b_t>
static bool	reference_equals (const object_a_t &object_a, const object_b_t &object_b) noexcept
	Determines whether the specified object instances are the same instance.

Constructor & Destructor Documentation

lock_guard() [1/2]

template<class object_t>

xtd::threading::lock_guard::lock_guard ( const object_t & obj )

inlineexplicit

Create a xtd::threading::lock_guard object and acquires an exclusive lock_guard on the specified obj.

Parameters

obj	The object on which to acquire the mutex lock_guard.

Remarks

When the xtd::threading::lock_guard destroyed it releases the exclusive lock_guard specified in the constructor.

lock_guard() [2/2]

xtd::threading::lock_guard::lock_guard ( const xtd::string & str )

explicit

Create a xtd::threading::lock_guard object and acquires an exclusive lock_guard on the specified string.

Parameters

str	The string on which to acquire the mutex lock_guard.

Remarks

When the xtd::threading::lock_guard destroyed it releases the exclusive lock_guard specified in the constructor.

Member Function Documentation

enter()

void xtd::threading::lock_guard::enter

(

)

Enters the lock_guard, waiting if necessary until the lock_guard can be entered.

Remarks

When the method returns, the current thread is the only thread that holds the lock_guard. If the lock_guard can't be entered immediately, the method waits until the lock_guard can be entered. If the lock_guard is already held by the current thread, the lock_guard is entered again. To fully exit the lock_guard and allow other threads to enter the lock_guard, the current thread should exit the lock_guard as many times as it has entered the lock_guard.

exit()

void xtd::threading::lock_guard::exit

(

)

Exits the lock_guard.

Exceptions

xtd::object_closed_exception

the handle is invalid

Remarks

If the current thread holds the lock_guard multiple times, such as recursively, the lock_guard is exited only once. The current thread should ensure that each enter is matched with an exit.

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The documentation for this class was generated from the following file:

• xtd.core/include/xtd/threading/lock_guard.hpp