simtools.util
Class StreamMemoryBuffer

java.lang.Object
  simtools.util.StreamMemoryBuffer

public class StreamMemoryBuffer
extends java.lang.Object

A memory buffer to be filled by one writer and read by several readers The readers do not empty the buffer, they acces data in it using an index The writer is filling the circular buffer it writes at a given index and increments a minimum index value to prevent access from the readers on overwritten data due to the cyclic buffer. Thus the writer is never constrained by the readers. The readers have to be fast enough to read the buffer. The buffer is allocated into native memory and thus can be quite large. This implementation is based on the assumption that packets size has a maximum value and that the minimum value is not too much different from the maximum value. If not efficient in terms of memory usage, it is assumed that a subclass will manage it.

Author:

cazenave_c

Nested Class Summary

class

StreamMemoryBuffer.StreamReader A buffer reader

Field Summary

protected java.nio.ByteBuffer	buffer The memory circular buffer
protected long	bufferSize The size of the circular buffer= number of packets in memory
protected int	counter The numbe of times the circular buffer is filled (starting at 1)
protected long	index The index of the next packet to be written
protected int[]	lengths A circular array with packets length
protected long	minIndex The last availble packet index (-1 at the beginning)
protected int	streamMaxSize The maximum size for one packet
protected java.lang.Object	synchro A syncho to allow readers to synchrosize on the buffer updates

Constructor Summary

StreamMemoryBuffer(int bufferSize, int streamMaxSize)
Create a new memory buffer

Method Summary

void	clean() Clean the StreamMemoryBuffer
StreamMemoryBuffer.StreamReader	createReader() Create a reader on this buffer This method is overwritten to implement specific readers
long	write(byte[] b, int offset, int length) Write a packet into the buffer
long	write(java.nio.ByteBuffer b) Write a byte buffer into the buffer

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

buffer

protected java.nio.ByteBuffer buffer

The memory circular buffer

lengths

protected int[] lengths

A circular array with packets length

bufferSize

protected final long bufferSize

The size of the circular buffer= number of packets in memory

streamMaxSize

protected final int streamMaxSize

The maximum size for one packet

index

protected long index

The index of the next packet to be written

minIndex

protected long minIndex

The last availble packet index (-1 at the beginning)

counter

protected int counter

The numbe of times the circular buffer is filled (starting at 1)

synchro

protected java.lang.Object synchro

A syncho to allow readers to synchrosize on the buffer updates

Constructor Detail

StreamMemoryBuffer

public StreamMemoryBuffer(int bufferSize,
                          int streamMaxSize)

Create a new memory buffer

Parameters:

bufferSize - the number of packets to store

streamMaxSize - the max size for one packet

Method Detail

write

public long write(byte[] b,
                  int offset,
                  int length)

Write a packet into the buffer

Parameters:

b - The array from which bytes are to be read

offset - The offset within the array of the first byte to be read

length - The number of bytes to be read from the given array

Returns:

the written packet index

write

public long write(java.nio.ByteBuffer b)

Write a byte buffer into the buffer

Parameters:

b - the byte buffer

Returns:

the written packet index

createReader

public StreamMemoryBuffer.StreamReader createReader()

Create a reader on this buffer This method is overwritten to implement specific readers

Returns:

the new reader

clean

public void clean()

Clean the StreamMemoryBuffer