JAVA-BASED REAL-TIME PROGRAMMING

3. Multi-Threaded Programming
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RTEvent[] buffer
currSize==7
postAt
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fetchAt
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growth
Figure 3.10: Ring buffer as an array with size 12, currently filled with 7 objects
(referenced from the gray elements).
tor, if the operation of the buffer needs to be synchronized with some
other objects (such as an other buffer).
The actual buffer/array is, as shown in Figure 3-10, declared as
protected RTEvent[] buffer;
Construction A new buffer is created by the following constructors, where
the default maxSize is some system dependent DEFAULT_SIZE (currently
64 in our system), and the default lock object is allocated and internally.
The parameters maxSize and lock overrides the defaults:
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public RTEventBuffer()
public RTEventBuffer(int maxSize)
public RTEventBuffer(int maxSize , Object lock)
Posting The methods for posting events to the buffer are named doPost,
tryPost, or simply post. The doPost method simply blocks the caller
until the posting is completed. The tryPost gives up if the buffer is full,
either immediately if no timeout is given or after the specified timeout (in
ms). The method post is the generic one that is subject to replacement
in subclasses, whereas the other methods are declared final for reasons
of efficiency.
The post method by default simply calls doPost and returns null. The
return (of type RTEvent) value is useful when subclassing and changing
post to call one of the tryPost methods, which return null when the
event was successfully posted. The event supplied as an argument to
tryPost is returned if not posted (due to the buffer being full). Returning
the unposted event simplifies the calling code. The public posting
methods are:
92 2012-08-29 16:05