TaskChain Unicode C Reference Documentation

TaskChain

Current Version: 9.5.0.97

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

Create/Dispose

HCkTaskChainW instance = CkTaskChainW_Create();
// ...
CkTaskChainW_Dispose(instance);
HCkTaskChainW CkTaskChainW_Create(void);

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

void CkTaskChainW_Dispose(HCkTaskChainW handle);

Objects created by calling CkTaskChainW_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 CkTaskChainW_Dispose.

Callback Functions

Callback Functions introduced in Chilkat v9.5.0.56
void CkTaskChainW_setAbortCheck(HCkTaskChainW cHandle, BOOL (*fnAbortCheck)(void));

Provides the opportunity for a method call to be aborted. If TRUE is returned, the operation in progress is aborted. Return FALSE to allow the current method call to continue. This callback function is called periodically based on the value of the HeartbeatMs property. (If HeartbeatMs is 0, then no callbacks are made.) As an example, to make 5 AbortCheck callbacks per second, set the HeartbeatMs property equal to 200.

void CkTaskChainW_setPercentDone(HCkTaskChainW cHandle, BOOL (*fnPercentDone)(int pctDone));

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This callback is only called when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For methods that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

This callback counts as an AbortCheck callback, and takes the place of the AbortCheck event when it fires.

The return value indicates whether the method call should be aborted, or whether it should proceed. Return TRUE to abort, and FALSE to proceed.

void CkTaskChainW_setProgressInfo(HCkTaskChainW cHandle, void (*fnProgressInfo)(const wchar_t *name, const wchar_t *value));

This is a general callback that provides name/value information about what is happening at certain points during a method call. To see the information provided in ProgressInfo callbacks, if any, write code to handle this event and log the name/value pairs. Most are self-explanatory.

void CkTaskChainW_setTaskCompleted(HCkTaskChainW cHandle, void (*fnTaskCompleted)(HCkTaskW hTask));

Called in the background thread when an asynchronous task completes. (Note: When an async method is running, all callbacks are in the background thread.)

Properties

DebugLogFilePath
void CkTaskChainW_getDebugLogFilePath(HCkTaskChainW cHandle, HCkString retval);
void CkTaskChainW_putDebugLogFilePath(HCkTaskChainW cHandle, const wchar_t *newVal);
const wchar_t *CkTaskChainW_debugLogFilePath(HCkTaskChainW 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 CkTaskChainW_getFinished(HCkTaskChainW 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 CkTaskChainW_getHeartbeatMs(HCkTaskChainW cHandle);
void CkTaskChainW_putHeartbeatMs(HCkTaskChainW 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 CkTaskChainW_getInert(HCkTaskChainW 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 CkTaskChainW_getLastErrorHtml(HCkTaskChainW cHandle, HCkString retval);
const wchar_t *CkTaskChainW_lastErrorHtml(HCkTaskChainW 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 CkTaskChainW_getLastErrorText(HCkTaskChainW cHandle, HCkString retval);
const wchar_t *CkTaskChainW_lastErrorText(HCkTaskChainW 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 CkTaskChainW_getLastErrorXml(HCkTaskChainW cHandle, HCkString retval);
const wchar_t *CkTaskChainW_lastErrorXml(HCkTaskChainW 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 CkTaskChainW_getLastMethodSuccess(HCkTaskChainW cHandle);
void CkTaskChainW_putLastMethodSuccess(HCkTaskChainW cHandle, BOOL newVal);

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 CkTaskChainW_getLive(HCkTaskChainW 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 CkTaskChainW_getNumTasks(HCkTaskChainW cHandle);
Introduced in version 9.5.0.52

The number of tasks contained within the task chain.

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Status
void CkTaskChainW_getStatus(HCkTaskChainW cHandle, HCkString retval);
const wchar_t *CkTaskChainW_status(HCkTaskChainW 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 CkTaskChainW_getStatusInt(HCkTaskChainW 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 CkTaskChainW_getStopOnFailedTask(HCkTaskChainW cHandle);
void CkTaskChainW_putStopOnFailedTask(HCkTaskChainW 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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VerboseLogging
BOOL CkTaskChainW_getVerboseLogging(HCkTaskChainW cHandle);
void CkTaskChainW_putVerboseLogging(HCkTaskChainW 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 CkTaskChainW_getVersion(HCkTaskChainW cHandle, HCkString retval);
const wchar_t *CkTaskChainW_version(HCkTaskChainW cHandle);

Version of the component/library, such as "9.5.0.94"

More Information and Examples
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Methods

Append
BOOL CkTaskChainW_Append(HCkTaskChainW cHandle, HCkTaskW 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 CkTaskChainW_Cancel(HCkTaskChainW 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
HCkTaskW CkTaskChainW_GetTask(HCkTaskChainW 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 CkTaskChainW_Run(HCkTaskChainW 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 CkTaskChainW_RunSynchronously(HCkTaskChainW 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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SleepMs
void CkTaskChainW_SleepMs(HCkTaskChainW 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 CkTaskChainW_Wait(HCkTaskChainW 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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