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Using TFifo


FIFO (First In, First Out) registers are mainly used in programs where some asynchronous data stream has to be managed. A FIFO can be seen as circular buffers of a given fixed length. Any FIFO has a method to input data at one end and to read data from it at the other end. The figure below shows a typical implementation of a FIFO buffer.

FIFOSTRK.gif

In order to use it, first an instance of the class TFifo has to be created - either by drag and drop from the component palette, or by creating an instance at runtime:

 
const 
  SizeOfFifo = 1000; 
... 
AnyFifo := TFifo.Create (Form1); 
AnyFifo.Size := SizeOfFifo; 
... 

Thereafter data can be written to the FIFO by using the method PutByte:

 
repeat 
until PutByte (cc) = True; 

The loop ensures that the byte in parameter cc is delivered in any case. Note, that such a loop could also have some advert effect by blocking the system when the FIFO is not emptied by some other process.

In order to retrieve data from a FIFO, you should use the method GetData:

 
if GetByte (cc) then 
  begin 
  {... here goes some user code} 
  end; 


Last Update: 2013-May-14