TLazThreadedQueue class

In unit LazCollections

Implements a thread-safe FIFO queue for items of a generic type.

Declaration

pascal

TLazThreadedQueue<T> = class

Description

TLazThreadedQueue is generic class which implements a thread-safe FIFO queue using a generic type for its items. The class requires specialization to specify the type stored in the items for the queue. For example:

TLazThreadedQueueString = specialize TLazThreadedQueue<String>;
TLazThreadedQueueInt = specialize TLazThreadedQueue<Integer>;
TLazThreadedQueueRect = specialize TLazThreadedQueue<TRectangle>;

TLazThreadedQueue uses an internal TLazMonitor member to synchronize access to resources in the queue between executing threads. Methods in the class which require thread-safe access use the monitor to enable/disable resource protection. Items in the queue are maintained using the PushItem, PopItem, and PopItemTimeout methods. Properties are provided to determine the size of the queue, and the number of items added or removed.

TLazThreadedQueue specializations are used in the implementation of the fpdserver component, and its integration into the Lazarus IDE.

Properties

`FifoQueue`	protected	Provides access to the TLazTypedFifoQueue instance used in the class.
`QueueSize`	public	Number of storage slots for items in the queue.
`TotalItemsPopped`	public	Total number of items removed from the queue.
`TotalItemsPushed`	public	Total number of items added to the queue.
`ShutDown`	public	Indicates if the DoShutdown method has been called but not finished.

Methods

`TryPushItemUnprotected`	protected	Tries to push an item onto the queue without resource protection.
`TryPopItemUnprotected`	protected	Tries to pop an item off of the queue without resource protection.
`Lock`	protected	Enters the Monitor used for resource protection.
`Unlock`	protected	Leaves the Monitor used for resource protection.
`CreateFifoQueue`	protected	Creates the TLazTypedFifoQueue instance used in the class.
`create`	public	Constructor for the class instance.
`Destroy`	public	Destructor for the class instance.
`Grow`	public	Expands (or shrinks) the allocated storage for the queue by the specified size.
`PushItem`	public	Adds the specified item to the queue.
`PopItem`	public	Pops the next item from the queue.
`PopItemTimeout`	public	Pops an item off the queue with a timeout value.
`DoShutDown`	public	Performs actions required when the thread-safe queue is freed.

Types and constants

TLazTypedFifoQueue protected Type used to the specialize the internal TLazFifoQueue instance for the class.

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.