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Loyc.Threading.ScratchBuffer< T > Struct Template Reference

Holds a single Value that is associated with the thread that assigned it. More...

Source file:
Inheritance diagram for Loyc.Threading.ScratchBuffer< T >:
Loyc.IHasValue< T >


Holds a single Value that is associated with the thread that assigned it.

ScratchBuffer is typically used as a static variable to hold a temporary object used for operations that are done frequently and require a temporary memory space–but only during the operation, not afterward.

For example, CPTrie may require a temporary byte array during searches. Re-creating the byte array for every search might cause a too much time to be spent garbage-collecting. On the other hand, if CPTrie keeps a reference to the temporary buffer in itself, what if a program contains many instances of CPTrie? Each one would have its own separate temporary buffer, wasting memory. The buffer can't be a straightforward global variable, either, in case two threads need a scratch buffer at once. ScratchBuffer, then, exists to prevent two threads from using the same buffer.

ScratchBuffer is designed with the assumption that creating a scratch buffer is fast, but re-using an existing buffer is faster. Since creating a scratch buffer is cheap already, this class is worthless unless it is even cheaper. Therefore, it does not hold a buffer for each thread, since managing multiple buffers would be too expensive; and volatile variable access is used instead of locking.

ScratchBuffer originally returned null if the scratch buffer had not been initialized or was associated with a different thread, requiring the caller to create a new buffer manually. Now there is a new constructor that takes a factory function, which is called automatically by the Value property if the scratch buffer is null or belongs to another thread. If you use this constructor, then you do longer have to worry about Value returning null.

static ScratchBuffer<byte[]> _buf = new ScratchBuffer<byte[]>(() => new byte[40]);

// A method called a million times that needs a scratch buffer each time void FrequentOperation() { byte[] buf = _buf.Value;

// do something here involving the buffer ... }

Arguably it is better to use a [ThreadStatic] variable is instead of ScratchBuffer, but FWIW [ThreadStatic] is not available on the .NET Compact Framework.

Type Constraints
T :class 

Public fields

volatile int _threadID
volatile T _buffer
Func< T > _factory


Value [get, set]
 Please see the documentation of ScratchBuffer<T> itself. More...
- Properties inherited from Loyc.IHasValue< T >
Value [get]

Public Member Functions

 ScratchBuffer (Func< T > factory)

Property Documentation

◆ Value

T Loyc.Threading.ScratchBuffer< T >.Value

Please see the documentation of ScratchBuffer<T> itself.