TaskChain C Reference Documentation

TaskChain

Current Version: 9.5.0.73

Represents a chain of asynchronous tasks to be run in sequence in a background thread.

Create/Dispose

HCkTaskChain instance = CkTaskChain_Create();
// ...
CkTaskChain_Dispose(instance);
HCkTaskChain CkTaskChain_Create(void);

Creates an instance of the HCkTaskChain object and returns a handle ("void *" pointer). The handle is passed in the 1st argument for the functions listed on this page.

void CkTaskChain_Dispose(HCkTaskChain handle);

Objects created by calling CkTaskChain_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function. Also, any handle returned by a Chilkat "C" function must also be freed by the application by calling the appropriate Dispose method, such as CkTaskChain_Dispose.

Properties

DebugLogFilePath
void CkTaskChain_getDebugLogFilePath(HCkTaskChain cHandle, HCkString retval);
void CkTaskChain_putDebugLogFilePath(HCkTaskChain cHandle, const char *newVal);
const char *CkTaskChain_debugLogFilePath(HCkTaskChain cHandle);

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

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Finished
BOOL CkTaskChain_getFinished(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

TRUE if the task status is "canceled", "aborted", or "completed". A task chain can only reach the "canceled" status if it was activated via the Run method, made it onto the internal thread pool thread's queue, was waiting for a pool thread to become available, and was then canceled prior to the task actually starting.

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HeartbeatMs
int CkTaskChain_getHeartbeatMs(HCkTaskChain cHandle);
void CkTaskChain_putHeartbeatMs(HCkTaskChain cHandle, int newVal);
Introduced in version 9.5.0.52

The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort the Wait method. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire. Note: An asynchronous task chain running in a background thread (in one of the thread pool threads) does not fire events. The task chain's event callbacks pertain only to the Wait method.

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Inert
BOOL CkTaskChain_getInert(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

TRUE if the task status is "empty" or "loaded". When a task chain is inert, it has been loaded but is not scheduled to run yet.

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LastErrorHtml
void CkTaskChain_getLastErrorHtml(HCkTaskChain cHandle, HCkString retval);
const char *CkTaskChain_lastErrorHtml(HCkTaskChain cHandle);

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorText
void CkTaskChain_getLastErrorText(HCkTaskChain cHandle, HCkString retval);
const char *CkTaskChain_lastErrorText(HCkTaskChain cHandle);

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorXml
void CkTaskChain_getLastErrorXml(HCkTaskChain cHandle, HCkString retval);
const char *CkTaskChain_lastErrorXml(HCkTaskChain cHandle);

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastMethodSuccess
BOOL CkTaskChain_getLastMethodSuccess(HCkTaskChain cHandle);
void CkTaskChain_putLastMethodSuccess(HCkTaskChain cHandle, BOOL newVal);
Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of TRUE indicates success, a value of FALSE indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = TRUE and failure = FALSE.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to TRUE. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

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Live
BOOL CkTaskChain_getLive(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

TRUE if the task status is "queued" or "running". When a task chain is live, it is either already running, or is on the thread pool thread's queue waiting for a thread to become available.

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NumTasks
int CkTaskChain_getNumTasks(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

The number of tasks contained within the task chain.

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Status
void CkTaskChain_getStatus(HCkTaskChain cHandle, HCkString retval);
const char *CkTaskChain_status(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

The current status of the task chain. Possible values are:

  • "empty" -- No tasks have yet been appended to the task chain.
  • "loaded" -- The task chain has been loaded (appended) with one or more task objects.
  • "queued" -- The task chain is in the thread pool's queue of tasks awaiting to be run.
  • "running" -- The task chain is currently running.
  • "canceled" -- The task chain was canceled before it entered the "running" state.
  • "aborted" -- The task chain was canceled while it was in the running state.
  • "completed" -- The task chain completed.

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StatusInt
int CkTaskChain_getStatusInt(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

The current status of the task as an integer value. Possible values are:

  • 1 -- "empty" -- No tasks have yet been appended to the task chain.
  • 2 -- "loaded" -- The task chain has been loaded (appended) with one or more task objects.
  • 3 -- "queued" -- The task chain is in the thread pool's queue of tasks awaiting to be run.
  • 4 -- "running" -- The task chain is currently running.
  • 5 -- "canceled" -- The task chain was canceled before it entered the "running" state.
  • 6 -- "aborted" -- The task chain was canceled while it was in the running state.
  • 7 -- "completed" -- The task chain completed.

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StopOnFailedTask
BOOL CkTaskChain_getStopOnFailedTask(HCkTaskChain cHandle);
void CkTaskChain_putStopOnFailedTask(HCkTaskChain cHandle, BOOL newVal);
Introduced in version 9.5.0.52

If TRUE then stops execution of the task chain if any individual task fails. Task failure is defined by the standard LastMethodSuccess property. If FALSE, then all of the tasks in the chain will be run even if some fail. The default value of this property is TRUE.

More Information and Examples
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Utf8
BOOL CkTaskChain_getUtf8(HCkTaskChain cHandle);
void CkTaskChain_putUtf8(HCkTaskChain cHandle, BOOL newVal);

When set to TRUE, all "const char *" arguments are interpreted as utf-8 strings. If set to FALSE (the default), then "const char *" arguments are interpreted as ANSI strings. Also, when set to TRUE, and Chilkat method returning a "const char *" is returning the utf-8 representation. If set to FALSE, all "const char *" return values are ANSI strings.

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VerboseLogging
BOOL CkTaskChain_getVerboseLogging(HCkTaskChain cHandle);
void CkTaskChain_putVerboseLogging(HCkTaskChain cHandle, BOOL newVal);

If set to TRUE, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is FALSE. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
void CkTaskChain_getVersion(HCkTaskChain cHandle, HCkString retval);
const char *CkTaskChain_version(HCkTaskChain cHandle);

Version of the component/library, such as "9.5.0.63"

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Methods

Append
BOOL CkTaskChain_Append(HCkTaskChain cHandle, HCkTask task);
Introduced in version 9.5.0.52

Appends a task to the task chain. Can fail if the task is already part of another chain. (A task can only be part of a single chain.)

Returns TRUE for success, FALSE for failure.

More Information and Examples
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Cancel
BOOL CkTaskChain_Cancel(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

Cancels execution of the asynchronous task chain.

Returns TRUE for success, FALSE for failure.

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GetTask
HCkTask CkTaskChain_GetTask(HCkTaskChain cHandle, int index);
Introduced in version 9.5.0.52

Returns the Nth task in the chain. The 1st task is at index 0.

Returns NULL on failure

More Information and Examples
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Run
BOOL CkTaskChain_Run(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

Queues the task chain to run on the internal Chilkat thread pool. Each task in the chain will run, one after the other.

Returns TRUE for success, FALSE for failure.

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RunSynchronously
BOOL CkTaskChain_RunSynchronously(HCkTaskChain cHandle);
Introduced in version 9.5.0.52

Runs the task chain synchronously. Then this method returns after all the tasks in the chain have been run.

Returns TRUE for success, FALSE for failure.

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SaveLastError
BOOL CkTaskChain_SaveLastError(HCkTaskChain cHandle, const char *path);

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns TRUE for success, FALSE for failure.

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SleepMs
void CkTaskChain_SleepMs(HCkTaskChain cHandle, int numMs);
Introduced in version 9.5.0.52

Convenience method to force the calling thread to sleep for a number of milliseconds.

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Wait
BOOL CkTaskChain_Wait(HCkTaskChain cHandle, int maxWaitMs);
Introduced in version 9.5.0.52

Waits for the task chain to complete. Returns when all of the tasks in the chain have completed, or after maxWaitMs milliseconds have elapsed. (A maxWaitMs value of 0 is to wait indefinitely.) Returns (FALSE) if the task chain has not yet been started by calling the Run method, or if the maxWaitMs expired. If the task chain completed, was already completed, was canceled, or aborted, then this method returns TRUE.

Returns TRUE for success, FALSE for failure.

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