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(C++) Cancel Async Task if not Completed after a Max TimeDemonstrates 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.
#include <CkHttp.h> #include <CkTask.h> void ChilkatSample(void) { // This example requires the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. bool success; 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; } |
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