xtd 0.2.0
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semaphore.cpp

Shows how to use xtd::threading::semaphore class.

#include <xtd/collections/generic/list>
#include <xtd/threading/interlocked>
#include <xtd/threading/semaphore>
#include <xtd/threading/thread>
#include <xtd/console>
#include <xtd/startup>
using namespace xtd;
using namespace xtd::collections::generic;
using namespace xtd::threading;
namespace mutex_example {
class program {
public:
static void main() {
// Create a semaphore that can satisfy up to three
// concurrent requests. Use an initial count of zero,
// so that the entire semaphore count is initially
// owned by the main program thread.
//
pool = semaphore {0, 3};
// Create and start five numbered threads.
//
for(auto i = 1; i <= 5; ++i) {
threads.emplace_back(worker);
// Start the thread, passing the number.
//
threads.back().start(i);
}
// Wait for half a second, to allow all the
// threads to start and to block on the semaphore.
//
thread::sleep(500);
// The main thread starts out holding the entire
// semaphore count. Calling Release(3) brings the
// semaphore count back to its maximum value, and
// allows the waiting threads to enter the semaphore,
// up to three at a time.
//
console::write_line("Main thread calls Release(3).");
pool.release(3);
thread::sleep(100);
console::write_line("Main thread exits.");
// Join all threads with timeout because the pool
// semaphore released only for 3 threads.
thread::join_all(threads, 100);
}
static void worker(std::any num) {
// Each worker thread begins by requesting the
// semaphore.
console::write_line("thread {0} begins "
"and waits for the semaphore.", num);
pool.wait_one();
// A padding interval to make the output more orderly.
int padding = interlocked::add(padding, 100);
console::write_line("thread {0} enters the semaphore.", num);
// The thread's "work" consists of sleeping for
// about a second. Each thread "works" a little
// longer, just to make the output more orderly.
//
thread::sleep(1000 + padding);
console::write_line("thread {0} releases the semaphore.", num);
console::write_line("thread {0} previous semaphore count: {1}",
num, pool.release());
}
private:
inline static list<thread> threads = list<thread>(5);
// A semaphore that simulates a limited resource pool.
//
inline static semaphore pool;
// A padding interval to make the output more orderly.
inline static int padding;
};
}
startup_(mutex_example::program::main);
// This example produces output similar to the following:
//
// thread 2 begins and waits for the semaphore.
// thread 5 begins and waits for the semaphore.
// thread 4 begins and waits for the semaphore.
// thread 1 begins and waits for the semaphore.
// thread 3 begins and waits for the semaphore.
// Main thread calls Release(3).
// thread 5 enters the semaphore.
// thread 2 enters the semaphore.
// thread 1 enters the semaphore.
// thread 5 releases the semaphore.
// thread 5 previous semaphore count: 0
// thread 4 enters the semaphore.
// thread 2 releases the semaphore.
// thread 2 previous semaphore count: 0
// thread 3 enters the semaphore.
// thread 1 releases the semaphore.
// thread 1 previous semaphore count: 0
// thread 4 releases the semaphore.
// thread 4 previous semaphore count: 1
// thread 3 releases the semaphore.
// thread 3 previous semaphore count: 2
// Main thread exits.
Represents a strongly typed list of objects that can be accessed by index. Provides methods to search...
Definition list.h:71
Limits the number of threads that can access a resource or pool of resources concurrently.
Definition semaphore.h:38
#define startup_(main_method)
Defines the entry point to be called when the application loads. Generally this is set either to the ...
Definition startup.h:175
The xtd::collections::generic namespace contains interfaces and classes that define generic collectio...
Definition comparer.h:15
The xtd::threading namespace provides classes and interfaces that enable multithreaded programming....
Definition abandoned_mutex_exception.h:11
The xtd namespace contains all fundamental classes to access Hardware, Os, System,...
Definition xtd_about_box.h:10