Enqueue Element At Opposite End (G Dataflow)

Adds an element to the front of a queue.

Queues typically use a first-in-first-out flow where data is enqueued at the back of the queue and dequeued in the front of the queue. In rare situations, you might want to interrupt this normal flow of data by adding an element to the front of the queue. For example, you may want to use the queue as a stack structure or add high-priority elements to the front of the queue. After you add an element to the front of a queue, the next Dequeue Element node you call removes and returns that element.

If the queue becomes invalid because the queue reference is released, then this node stops waiting and returns an error.

Programming Patterns

Use Dequeue Element to remove and return the element after you enqueue it.

• Inputs/Outputs
• Compatibility

queue

A reference to a queue.

element

The element you want to add to the front of the queue. The data type of this input changes to match the data type of the elements in the queue.

timeout in milliseconds

The number of milliseconds that the node waits for available space in the queue if the queue is full.

If space becomes available in the queue during the wait, the node inserts the element and does not time out.

Note

This node waits if a maximum size has been set for the queue and the queue is full. Use Obtain Queue to set the maximum size of the queue.

Default: -1 — The node never times out.

error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error	error in contains an error
If no error occurred before the node runs, the node begins execution normally. If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.	If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

queue out

Reference to the queue.

timed out?

A Boolean value that indicates whether there is space available in the queue before the node times out or an error occurs.

True	There was no space available in the queue before the node timed out, or this node generated an error.
False	There was space available in the queue before the node timed out, or an error occurred before this node executed.

error out

The node produces this output according to standard error behavior.

This node can return the following error codes.

1122	The reference became invalid while the node was waiting for it.

Note

This is not a comprehensive list of errors this node can return.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error	error in contains an error
If no error occurred before the node runs, the node begins execution normally. If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.	If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Supported in VIs that run in a web application