C++

Cancel Async Task if not Completed after a Max Time

See more Async Examples

Demonstrates how to wait a maximum amount of time for an asynchronous task to completed. If not completed in the allotted amount of time, the task is cancelled. C++

#include <CkHttp.h>
#include <CkTask.h>

void ChilkatSample(void)
    {
    bool success = false;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkHttp http;

    // Set some timeouts, in seconds:
    http.put_ConnectTimeout(15);
    http.put_ReadTimeout(15);

    // Wait a max time of 2 seconds for the task.
    // In this example, it's an unreasonably small amount of time,
    // which means the task will get cancelled.
    int waitMaxMs = 2000;

    // We're just going to download for 2 seconds and then cancel.
    // Substitute your own URL with a large enough file for testing..
    const char *downloadUrl = "http://download.mono-project.com/archive/4.6.1/windows-installer/mono-4.6.1.5-gtksharp-2.12.38-win32-0.msi";

    CkTask *task = http.DownloadAsync(downloadUrl,"qa_output/mono.msi");
    task->Run();

    // Wait a maximum of waitMaxMs for the task (i.e. the HTTP download) to complete.
    // The Wait method returns when the task has been canceled, aborted, or completed, or when the max allotted time has passed.
    task->Wait(waitMaxMs);

    // At this point, the download may or may not have completed.  
    // Rather than checking the Task status, we can call task.Cancel because
    // if the Task is no longer running (because it already completed, was canceled or aborted), then the 
    // call to Cancel is a NO-OP (meaning it does nothing and the Task's status is unaffected).
    // Also, task.Cancel returns true if the task was in the "queued" or "running" state and was canceled or aborted. 
    // The method returns false if the task has any other status.
    bool wasCanceled = task->Cancel();
    if (wasCanceled == true) {
        std::cout << "The HTTP download took too long and was canceled." << "\r\n";
    }
    else {
        // Find out what happened.
        if (task->get_StatusInt() == 7) {
            // The task completed, which means the background thread's call to Download completed
            // with success or failure.  Find out which...
            success = task->GetResultBool();
            if (success == true) {
                std::cout << "Download successful!" << "\r\n";
            }
            else {
                std::cout << "Download failed prior to waitMaxMs..." << "\r\n";
                std::cout << task->resultErrorText() << "\r\n";
            }

        }
        else {
            // The task must've been canceled or aborted by some other means..
            std::cout << "Task did not complete.  Final status: " << task->status() << "\r\n";
        }

    }

    delete task;
    }