Package org.epics.archiverappliance

Class ByteArray

java.lang.Object
org.epics.archiverappliance.ByteArray
public class ByteArray extends Object
A version of byte[] that is used to provide some optimization for data retrieval and the like. This is very similar to NIO's ByteBuffer but has all its internal's exposed and is meant to pass a byte[]+offset+length around within the appliance archiver. Many event streams reuse the same ByteArray across events in order to minimize memory allocation costs. And as we reuse ByteArray instances so we have a reset method. The convention for ByteArrays within Events is that they stored the escaped bytes (@see LineEscaper) and the inPlaceUnescape method is used to unescape these bytes. For example, in summary, the PB code will ByteArray bar = new ByteArray(); LineByteStream lbs = new LineByteStream(path...); lbs.readLine(bar); while(!bar.isEmpty()) { SomeType.newBuilder().mergeFrom(bar.inPlaceUnescape().unescapedData, bar.off, bar.unescapedLen).build(); lbs.readLine(bar); } The readLine logic in lbs has the code necessary to increase the length of the data field as required. Because many event streams reuse the same ByteArray across events, life becomes interesting as we need to remember to use makeClone anytime we want to span the Event across the iterator that generated it. Spoke with Luofeng about this and we both came to the conclusion that we should try to make this work as much as possible as the GC gains itself are quite a bit.
Author:
mshankar

  • Field Details

    • data

      public byte[] data

    • off

      public int off

    • len

      public int len

    • unescapedData

      public byte[] unescapedData

    • unescapedLen

      public int unescapedLen

  • Constructor Details

    • ByteArray

      public ByteArray(int size)

    • ByteArray

      public ByteArray(byte[] src)

  • Method Details

    • reset

      public void reset()

    • toBytes

      public byte[] toBytes()
      Use this for unit tests and the like...
      Returns:
       
      See Also:

    • unescapedBytes

      public byte[] unescapedBytes()

    • doubleBufferSize

      public void doubleBufferSize() throws LineTooLongException
      Increases the size of the array to twice what it is currently subject to a maximum
      Throws:
      LineTooLongException -  

    • isEmpty

      public boolean isEmpty()

    • inPlaceUnescape

      public ByteArray inPlaceUnescape()