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Thread Safe Generic Queue Class

, 2 Oct 2009 CPOL
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I've been doing a lot of mult-threading work, recently, using the standard Thead class, the Worker Queue, and the new PLINQ (Parallel LINQ). The problem with most of the built-in generic collections (Queue<>, List<>, Dictionary<>, etc), is that they are not thread safe.

I've been doing a lot of multi-threading work recently using the standard Thread class, the Worker Queue, and the new PLINQ (Parallel LINQ). The problem with most of the built-in generic collections (Queue<>, List<>, Dictionary<>, etc.), is that they are not thread safe.

I created a library of thread safe collections which allow me to use the standard generic collection actions (foreach, LINQ, etc.), while at the same time being thread safe.

The classes in this library inherit from the appropriate collection interface (IEnumerable, ICollection, etc.). Each class also has all the functions and properties that its original non-thread safe class has.

You can download a copy of the entire library, which includes support for a thread safe List<>, Dictionary<>, and Queue<>, here: Thread Safe Generic Collections.

TQueue<> Example

The first thing we need to do is create a container for the TQueue and a thread lock object. I generally prefer to use the ReaderWriterLockSlim because it is light weight and fast.

/// <span class="code-SummaryComment"><summary> 

Just like a standard Queue, we have three overloads for the Initialization. These overloads allow an empty Queue to be created, a Queue with a specified capacity, or a Queue with an initial IEnumerable collection to populate the Queue.

/// <span class="code-SummaryComment"><summary> 

This next function is probably the most important one. The GetEnumerator() is used during ForEach loops, and returns the next item in the collection. Following Microsoft's example of a thread-safe enumerator, we first get a copy of the current container Queue, then use this copy for iterating. You'll notice the use of the Read lock before acquiring the container Queue copy.

/// <span class="code-SummaryComment"><summary> 

A Queue must include an Enqueue and a Dequeue, used for adding and removing items from the collection. Just as in every other function, we're using the locks to protect our data access.

/// <span class="code-SummaryComment"><summary> 

I found that many times, I have a need to enqueue multiple items at once. This leads to the creation of the EnqueueAll functions. You'll notice the second overload is using the thread safe List (TList).

/// <span class="code-SummaryComment"><summary> 

And, since we have an EnqueueAll, I also found a need to dequeue everything at once. DequeueAll returns a thread safe list (TList), instead of the standard List.

/// <span class="code-SummaryComment"><summary> 

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About Philip Pierce:

I am a software developer with twenty years experience in game development, mobile, web, desktop, server, and database. My extensive background highlights an expertise in rapid application development using the latest Microsoft, Mobile, and Game Development technologies, along with the ability to create AI for games and business software, redesign existing software, develop multi-threaded software, and create client/server applications.

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Comments and Discussions

QuestionWhy not use lock{}, its faster? Pin
kauseeman3-Dec-10 10:56
memberkauseeman3-Dec-10 10:56 
AnswerRe: Why not use lock{}, its faster? Pin
merlin9814-Dec-10 1:43
membermerlin9814-Dec-10 1:43 
GeneralRe: Why not use lock{}, its faster? Pin
kauseeman4-Dec-10 3:03
memberkauseeman4-Dec-10 3:03 
GeneralRe: Why not use lock{}, its faster? Pin
merlin9815-Dec-10 1:13
membermerlin9815-Dec-10 1:13 
GeneralA small Bug Pin
philippe dykmans6-Sep-10 5:39
memberphilippe dykmans6-Sep-10 5:39 

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