C

Async Task Chain

See more Async Examples

Demonstrates how to combine a sequence of asynchronous tasks into a single task chain to be run in a background thread. C

#include <C_CkMailMan.h>
#include <C_CkTaskChain.h>
#include <C_CkTask.h>
#include <C_CkEmail.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkMailMan mailman;
    int numMessages;
    HCkTaskChain taskChain;
    int i;
    HCkTask task;
    HCkEmail email;
    int numTasks;
    int taskIdx;

    success = FALSE;

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

    success = FALSE;

    mailman = CkMailMan_Create();

    // Set the POP3 server's hostname
    CkMailMan_putMailHost(mailman,"pop.example.com");

    // Set the POP3 login/password and any other requirements..
    CkMailMan_putPopUsername(mailman,"myLogin");
    CkMailMan_putPopPassword(mailman,"myPassword");
    CkMailMan_putPopSsl(mailman,TRUE);
    CkMailMan_putMailPort(mailman,995);

    // Connect to the POP3 server:
    success = CkMailMan_Pop3BeginSession(mailman);
    if (!success) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        CkMailMan_Dispose(mailman);
        return;
    }

    // Get the number of messages in the mailbox.
    numMessages = CkMailMan_GetMailboxCount(mailman);
    if (numMessages == 0) {
        printf("No email messages in the POP3 mailbox.\n");
        CkMailMan_Dispose(mailman);
        return;
    }

    taskChain = CkTaskChain_Create();

    // Create async task objects to fetch each email message
    // by its sequence number

    for (i = 1; i <= numMessages; i++) {

        task = CkMailMan_FetchByMsgnumAsync(mailman,i);
        if (CkMailMan_getLastMethodSuccess(mailman) == FALSE) {
            printf("%s\n",CkMailMan_lastErrorText(mailman));
            CkMailMan_Dispose(mailman);
            CkTaskChain_Dispose(taskChain);
            return;
        }

        // Append each task to the task chain.
        success = CkTaskChain_Append(taskChain,task);
        if (!success) {
            printf("%s\n",CkTaskChain_lastErrorText(taskChain));
            CkMailMan_Dispose(mailman);
            CkTaskChain_Dispose(taskChain);
            return;
        }

        CkTask_Dispose(task);

    }

    // At this point, no tasks have actually started running.
    // All we've done so far is to create tasks for the work that will be done
    // when the task chain is run.

    // Start the task chain running in a background thread.
    // Each task is run one after the other (on the same background thread) until all tasks have completed.
    // The task chain will stop at the first task that fails.
    CkTaskChain_putStopOnFailedTask(taskChain,TRUE);
    success = CkTaskChain_Run(taskChain);
    if (!success) {
        printf("%s\n",CkTaskChain_lastErrorText(taskChain));
        CkMailMan_Dispose(mailman);
        CkTaskChain_Dispose(taskChain);
        return;
    }

    // The application is now free to do anything else
    // while the emails are being downloaded

    // For this example, we'll simply sleep and periodically
    // check to see if the taskchain if finished. 
    while (CkTaskChain_getFinished(taskChain) != TRUE) {

        // Sleep 100 ms.
        CkTaskChain_SleepMs(taskChain,100);

    }

    // A finished task chain could be one that was canceled, aborted, or truly finished.  

    // If the task chain "completed", then it ran to completion.  A "completed" task will
    // have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
    // been aborted or canceled:
    if (CkTaskChain_getStatusInt(taskChain) != 7) {
        printf("Task did not complete.\n");
        printf("task chain status: %s\n",CkTaskChain_status(taskChain));
        CkMailMan_Dispose(mailman);
        CkTaskChain_Dispose(taskChain);
        return;
    }

    email = CkEmail_Create();

    numTasks = CkTaskChain_getNumTasks(taskChain);
    taskIdx = 0;

    while ((taskIdx < numTasks)) {

        task = CkTaskChain_GetTask(taskChain,taskIdx);

        // Load the email object with email downloaded by this task.
        success = CkEmail_LoadTaskResult(email,task);
        if (!success) {
            printf("Failed to load email object for task.\n");
        }
        else {
            printf("%s; %s\n",CkEmail_ck_from(email),CkEmail_subject(email));
        }

        CkTask_Dispose(task);

        taskIdx = taskIdx + 1;
    }



    CkMailMan_Dispose(mailman);
    CkTaskChain_Dispose(taskChain);
    CkEmail_Dispose(email);

    }