Tcl

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. Tcl

load ./chilkat.dll

set success 0

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

set http [new_CkHttp]

# Set some timeouts, in seconds:
CkHttp_put_ConnectTimeout $http 15
CkHttp_put_ReadTimeout $http 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.
set 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..
set downloadUrl "http://download.mono-project.com/archive/4.6.1/windows-installer/mono-4.6.1.5-gtksharp-2.12.38-win32-0.msi"

# task is a CkTask
set task [CkHttp_DownloadAsync $http $downloadUrl "qa_output/mono.msi"]
CkTask_Run $task

# 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.
CkTask_Wait $task $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 1 if the task was in the "queued" or "running" state and was canceled or aborted. 
# The method returns 0 if the task has any other status.
set wasCanceled [CkTask_Cancel $task]
if {$wasCanceled == 1} then {
    puts "The HTTP download took too long and was canceled."
} else {
    # Find out what happened.
    if {[CkTask_get_StatusInt $task] == 7} then {
        # The task completed, which means the background thread's call to Download completed
        # with success or failure.  Find out which...
        set success [CkTask_GetResultBool $task]
        if {$success == 1} then {
            puts "Download successful!"
        }         else {
            puts "Download failed prior to waitMaxMs..."
            puts [CkTask_resultErrorText $task]
        }

    }     else {
        # The task must've been canceled or aborted by some other means..
        puts "Task did not complete.  Final status: [CkTask_status $task]"
    }

}

delete_CkTask $task


delete_CkHttp $http