How to: Send a Message at a Regular Interval
This example shows how to use the concurrency::timer class to send a message at a regular interval.
Example
The following example uses a timer object to report progress during a lengthy operation. This example links the timer object to a concurrency::call object. The call object prints a progress indicator to the console at a regular interval. The concurrency::timer::start method runs the timer on a separate context. The perform_lengthy_operation function calls the concurrency::wait function on the main context to simulate a time-consuming operation.
// report-progress.cpp
// compile with: /EHsc
#include <agents.h>
#include <iostream>
using namespace concurrency;
using namespace std;
// Simulates a lengthy operation.
void perform_lengthy_operation()
{
// Yield the current context for one second.
wait(1000);
}
int wmain()
{
// Create a call object that prints a single character to the console.
call<wchar_t> report_progress([](wchar_t c) {
wcout << c;
});
// Create a timer object that sends the dot character to the
// call object every 100 milliseconds.
timer<wchar_t> progress_timer(100, L'.', &report_progress, true);
wcout << L"Performing a lengthy operation";
// Start the timer on a separate context.
progress_timer.start();
// Perform a lengthy operation on the main context.
perform_lengthy_operation();
// Stop the timer and print a message.
progress_timer.stop();
wcout << L"done.";
}
This example produces the following sample output:
Performing a lengthy operation..........done.
Compiling the Code
Copy the example code and paste it in a Visual Studio project, or paste it in a file that is named report-progress.cpp and then run the following command in a Visual Studio Command Prompt window.
cl.exe /EHsc report-progress.cpp