org.apache.nifi.util

Class NaiveSearchRingBuffer

java.lang.Object

org.apache.nifi.util.NaiveSearchRingBuffer

public class NaiveSearchRingBuffer
extends Object

A RingBuffer that can be used to scan byte sequences for subsequences.

This class implements an efficient naive search algorithm, which allows the user of the library to identify byte sequences in a stream on-the-fly so that the stream can be segmented without having to buffer the data.

The intended usage paradigm is:

 final byte[] searchSequence = ...;
 final CircularBuffer buffer = new CircularBuffer(searchSequence);
 while ((int nextByte = in.read()) > 0) {
      if ( buffer.addAndCompare(nextByte) ) {
          // This byte is the last byte in the given sequence
      } else {
          // This byte does not complete the given sequence
      }
 }
 

Field Summary

Fields

Modifier and Type	Field and Description
private int[]	buffer
private int	bufferSize
private int	insertionPointer
private byte[]	lookingFor

Constructor Summary

Constructors

Constructor and Description
NaiveSearchRingBuffer(byte[] lookingFor)

Method Summary

Modifier and Type	Method and Description
boolean	addAndCompare(byte data) Add the given byte to the buffer and notify whether or not the byte completes the desired byte sequence.
void	clear() Clears the internal buffer so that a new search may begin
byte[]	getBufferContents()
int	getOldestByte()
boolean	isFilled()

Methods inherited from class java.lang.Object

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

Field Detail

lookingFor

private final byte[] lookingFor

buffer

private final int[] buffer

insertionPointer

private int insertionPointer

bufferSize

private int bufferSize

Constructor Detail

NaiveSearchRingBuffer

public NaiveSearchRingBuffer(byte[] lookingFor)

Method Detail

getBufferContents

public byte[] getBufferContents()

Returns:

the contents of the internal buffer, which represents the last X bytes added to the buffer, where X is the minimum of the number of bytes added to the buffer or the length of the byte sequence for which we are looking

getOldestByte

public int getOldestByte()

Returns:

the oldest byte in the buffer

isFilled

public boolean isFilled()

Returns:

true if the number of bytes that have been added to the buffer is at least equal to the length of the byte sequence for which we are searching

clear

public void clear()

Clears the internal buffer so that a new search may begin

addAndCompare

public boolean addAndCompare(byte data)

Add the given byte to the buffer and notify whether or not the byte completes the desired byte sequence.

Parameters:

data - the data to add to the buffer

Returns:

true if this byte completes the byte sequence, false otherwise.