org.apache.lucene.util.encoding
Class NOnesIntEncoder

java.lang.Object
  org.apache.lucene.util.encoding.IntEncoder
      org.apache.lucene.util.encoding.ChunksIntEncoder
          org.apache.lucene.util.encoding.FourFlagsIntEncoder
              org.apache.lucene.util.encoding.NOnesIntEncoder

public class NOnesIntEncoder
extends FourFlagsIntEncoder

A variation of FourFlagsIntEncoder which translates the data as follows:

• Values ≥ 2 are trnalsated to value+1 (2 ⇒ 3, 3 ⇒ 4 and so forth).
• Any N occurrences of 1 are encoded as a single 2.
• Otherwise, each 1 is encoded as 1.

Encoding examples:

• N = 4: the data 1,1,1,1,1 is translated to: 2, 1
• N = 3: the data 1,2,3,4,1,1,1,1,5 is translated to 1,3,4,5,2,1,6

NOTE: this encoder does not support values ≤ 0 and Integer.MAX_VALUE. 0 is not supported because it's not supported by FourFlagsIntEncoder and Integer.MAX_VALUE because this encoder translates N to N+1, which will cause an overflow and Integer.MAX_VALUE will become a negative number, which is not supported as well.
This does not mean you cannot encode Integer.MAX_VALUE. If it is not the first value to encode, and you wrap this encoder with DGapIntEncoder, then the value that will be sent to this encoder will be MAX_VAL - prev.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields inherited from class org.apache.lucene.util.encoding.ChunksIntEncoder

encodeQueue, encodeQueueSize, encoder, indicator, ordinal

Fields inherited from class org.apache.lucene.util.encoding.IntEncoder

out

Constructor Summary

NOnesIntEncoder(int n)
Constructs an encoder with a given value of N (N: Number of consecutive '1's to be translated into single target value '2').

Method Summary

void	close() Instructs the encoder to finish the encoding process.
IntDecoder	createMatchingDecoder() Returns an IntDecoder which matches this encoder.
void	encode(int value) Small values (<=3) are stored in the indicator while larger values are saved for later encoding in the ChunksIntEncoder.encodeQueue.
void	reInit(OutputStream out) Reinitializes the encoder with the give OutputStream.
String	toString()

Methods inherited from class org.apache.lucene.util.encoding.ChunksIntEncoder

encodeChunk

Methods inherited from class java.lang.Object

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

Constructor Detail

NOnesIntEncoder

public NOnesIntEncoder(int n)

Constructs an encoder with a given value of N (N: Number of consecutive '1's to be translated into single target value '2').

Method Detail

close

public void close()
           throws IOException

Description copied from class: IntEncoder

Instructs the encoder to finish the encoding process. This method closes the output stream which was specified by reInit. An implementation may do here additional cleanup required to complete the encoding, such as flushing internal buffers, etc.
Once this method was called, no further calls to encode should be made before first calling reInit.

NOTE: overriding classes should make sure they either call super.close() or close the output stream themselves.

Overrides:

close in class ChunksIntEncoder

Throws:

IOException

encode

public void encode(int value)
            throws IOException

Description copied from class: FourFlagsIntEncoder

Small values (<=3) are stored in the indicator while larger values are saved for later encoding in the ChunksIntEncoder.encodeQueue. Since Vint8 will only encode values larger or equal to 4, the values saves for encoded are transformed to (value - 4).
When a chunk is ready (got 4 values), the ChunksIntEncoder.encodeChunk() takes control.

Overrides:

encode in class FourFlagsIntEncoder

Throws:

IOException

createMatchingDecoder

public IntDecoder createMatchingDecoder()

Description copied from class: IntEncoder

Returns an IntDecoder which matches this encoder. Every encoder must return an IntDecoder and null is not a valid value. If an encoder is just a filter, it should at least return its wrapped encoder's matching decoder.

NOTE: this method should create a new instance of the matching decoder and leave the instance sharing to the caller. Returning the same instance over and over is risky because encoders and decoders are not thread safe.

Overrides:

createMatchingDecoder in class FourFlagsIntEncoder

reInit

public void reInit(OutputStream out)

Description copied from class: IntEncoder

Reinitializes the encoder with the give OutputStream. For re-usability it can be changed without the need to reconstruct a new object.

NOTE: after calling IntEncoder.close(), one must call this method even if the output stream itself hasn't changed. An example case is that the output stream wraps a byte[], and the output stream itself is reset, but its instance hasn't changed. Some implementations of IntEncoder may write some metadata about themselves to the output stream, and therefore it is imperative that one calls this method before encoding any data.

Overrides:

reInit in class ChunksIntEncoder

toString

public String toString()

Overrides:

toString in class FourFlagsIntEncoder