Class OverWritingBuffer
- java.lang.Object
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- org.jcsp.util.OverWritingBuffer
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- All Implemented Interfaces:
java.io.Serializable
,java.lang.Cloneable
,ChannelDataStore
public class OverWritingBuffer extends java.lang.Object implements ChannelDataStore, java.io.Serializable
This is used to create a buffered object channel that always accepts input, overwriting its last entered data if full.Description
It is an implementation of ChannelDataStore that yields a FIFO buffered semantics for a channel. When empty, the channel blocks readers. When full, a writer will overwrite the latest item written to the channel. See the static construction methods ofChannel
(Channel.one2one(org.jcsp.util.ChannelDataStore)
etc.).The getState method returns EMPTY or NONEMPTYFULL, but never FULL.
- Author:
- P.D. Austin
- See Also:
ZeroBuffer
,Buffer
,OverWriteOldestBuffer
,OverFlowingBuffer
,InfiniteBuffer
,Channel
, Serialized Form
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Field Summary
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Fields inherited from interface org.jcsp.util.ChannelDataStore
EMPTY, FULL, NONEMPTYFULL
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Constructor Summary
Constructors Constructor Description OverWritingBuffer(int size)
Construct a new OverWritingBuffer with the specified size.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
clone()
Returns a new (and EMPTY) OverWritingBuffer with the same creation parameters as this one.void
endGet()
This ends an extended rendezvous by the reader.java.lang.Object
get()
Returns the oldest Object from the OverWritingBuffer and removes it.int
getState()
Returns the current state of the OverWritingBuffer.void
put(java.lang.Object value)
Puts a new Object into the OverWritingBuffer.void
removeAll()
Deletes all items in the buffer, leaving it empty.java.lang.Object
startGet()
This begins an extended rendezvous by the reader.
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Constructor Detail
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OverWritingBuffer
public OverWritingBuffer(int size)
Construct a new OverWritingBuffer with the specified size.- Parameters:
size
- the number of Objects the OverWritingBuffer can store.- Throws:
BufferSizeError
- if size is zero or negative. Note: no action should be taken to try/catch this exception - application code generating it is in error and needs correcting.
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Method Detail
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get
public java.lang.Object get()
Returns the oldest Object from the OverWritingBuffer and removes it.Pre-condition: getState must not currently return EMPTY.
- Specified by:
get
in interfaceChannelDataStore
- Returns:
- the oldest Object from the OverWritingBuffer
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put
public void put(java.lang.Object value)
Puts a new Object into the OverWritingBuffer.If OverWritingBuffer is full, the last item previously put into the buffer will be overwritten.
- Specified by:
put
in interfaceChannelDataStore
- Parameters:
value
- the Object to put into the OverWritingBuffer
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startGet
public java.lang.Object startGet()
This begins an extended rendezvous by the reader. The semantics of an extended rendezvous on an overwrite-newest buffer are slightly complicated, but hopefully intuitive.If the buffer is of size 2 or larger, the semantics are as follows. Beginning an extended rendezvous will return the oldest value in the buffer, but not remove it. If the writer writes to the buffer during the rendezvous, it will grow the buffer and end up overwriting the newest value as normal. At the end of the extended rendezvous, the oldest value is removed.
If the buffer is of size 1, the semantics are identical to those of an
OverWriteOldestBuffer
. For a complete description, refer to the documentation for theOverWriteOldestBuffer.startGet()
method.- Specified by:
startGet
in interfaceChannelDataStore
- Returns:
- The oldest value in the buffer at this time
- See Also:
ChannelDataStore.endGet()
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endGet
public void endGet()
This ends an extended rendezvous by the reader.- Specified by:
endGet
in interfaceChannelDataStore
- See Also:
startGet()
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getState
public int getState()
Returns the current state of the OverWritingBuffer.- Specified by:
getState
in interfaceChannelDataStore
- Returns:
- the current state of the OverWritingBuffer (EMPTY or NONEMPTYFULL)
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clone
public java.lang.Object clone()
Returns a new (and EMPTY) OverWritingBuffer with the same creation parameters as this one.Note: Only the size and structure of the OverWritingBuffer is cloned, not any stored data.
- Specified by:
clone
in interfaceChannelDataStore
- Overrides:
clone
in classjava.lang.Object
- Returns:
- the cloned instance of this OverWritingBuffer.
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removeAll
public void removeAll()
Description copied from interface:ChannelDataStore
Deletes all items in the buffer, leaving it empty.- Specified by:
removeAll
in interfaceChannelDataStore
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