Adds an element to the front of a queue.


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Inputs/Outputs

  • cqueuern.png queue —

    queue is a reference to a queue.

    Use the Obtain Queue function to obtain a queue reference.
  • cstr.png element —

    element is the element you want to add to the front of the queue.

    This data type changes to match the subtype of queue.
  • ci32.png timeout in ms (-1) —

    timeout in ms specifies the time, in milliseconds, that the function waits for available space in the queue if the queue is full.

    The default is –1, indicating never to time out.

    If the function waits timeout in ms and the queue remains full, timed out? is TRUE.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • iqueuern.png queue out —

    queue out returns the reference to the queue unchanged.

  • ibool.png timed out? —

    timed out? returns TRUE if space in the queue did not become available before the function times out. timed out? also returns TRUE if this function encounters an error.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

    • This function is similar to the Enqueue Element function. If the queue is full, the function waits timeout in ms before continuing. If queue becomes invalid (for example, the queue reference is released), the function stops waiting and returns error code 1122.

    Queues typically use a first-in-first-out flow of data. In rare situations, you might want to interrupt this normal flow of data by adding an element to the front of the queue. After you add an element to the front of a queue, the next Dequeue Element function you call removes the element you added to the front. For example, you could use this function if you want to use the queue as a stack structure or add high-priority elements to the front of the queue.

    Examples

    Refer to the following example files included with LabVIEW.

    • labview\examples\Synchronization\Queue\Queue Stack Maze Solver.vi