Package org.apache.commons.compress.harmony.pack200

Class PopulationCodec

java.lang.Object

org.apache.commons.compress.harmony.pack200.Codec

org.apache.commons.compress.harmony.pack200.PopulationCodec

public class PopulationCodec
extends Codec

A PopulationCodec is a Codec that is well suited to encoding data that shows statistical or repetitive patterns, containing for example a few numbers which are repeated a lot throughout the set, but not necessarily sequentially.

Field Summary

Fields inherited from class org.apache.commons.compress.harmony.pack200.Codec

BCI5, BRANCH5, BYTE1, CHAR3, DELTA5, lastBandLength, MDELTA5, SIGNED5, UDELTA5, UNSIGNED5

Constructor Summary

Constructors

Constructor	Description
PopulationCodec(Codec favouredCodec, int l, Codec unfavouredCodec)
PopulationCodec(Codec favouredCodec, Codec tokenCodec, Codec unvafouredCodec)

Method Summary

Modifier and Type	Method	Description
int	decode(InputStream in)	Decodes a sequence of bytes from the given input stream, returning the value as a long.
int	decode(InputStream in, long last)	Decodes a sequence of bytes from the given input stream, returning the value as a long.
int[]	decodeInts(int n, InputStream in)	Decodes a sequence of n values from in.
byte[]	encode(int value)	Encodes a single value into a sequence of bytes.
byte[]	encode(int[] favoured, int[] tokens, int[] unfavoured)
byte[]	encode(int value, int last)	Encodes a single value into a sequence of bytes.
int[]	getFavoured()
Codec	getFavouredCodec()
Codec	getTokenCodec()
Codec	getUnfavouredCodec()

Methods inherited from class org.apache.commons.compress.harmony.pack200.Codec

decodeInts, encode

Methods inherited from class java.lang.Object

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

Constructor Details

PopulationCodec

public PopulationCodec(Codec favouredCodec,
 Codec tokenCodec,
 Codec unvafouredCodec)

PopulationCodec

public PopulationCodec(Codec favouredCodec,
 int l,
 Codec unfavouredCodec)

Method Details

decode

public int decode(InputStream in)
           throws IOException,
Pack200Exception

Description copied from class: Codec

Decodes a sequence of bytes from the given input stream, returning the value as a long. Note that this method can only be applied for non-delta encodings.

Specified by:

decode in class Codec

Parameters:

in - the input stream to read from

Returns:

the value as a long

Throws:

IOException - if there is a problem reading from the underlying input stream

Pack200Exception - if the encoding is a delta encoding

decode

public int decode(InputStream in,
 long last)
           throws IOException,
Pack200Exception

Description copied from class: Codec

Decodes a sequence of bytes from the given input stream, returning the value as a long. If this encoding is a delta encoding (d=1) then the previous value must be passed in as a parameter. If it is a non-delta encoding, then it does not matter what value is passed in, so it makes sense for the value to be passed in by default using code similar to:

 long last = 0;
 while (condition) {
     last = codec.decode(in, last);
     // do something with last
 }
 

Specified by:

decode in class Codec

Parameters:

in - the input stream to read from

last - the previous value read, which must be supplied if the codec is a delta encoding

Returns:

the value as a long

Throws:

IOException - if there is a problem reading from the underlying input stream

Pack200Exception - if there is a problem decoding the value or that the value is invalid

decodeInts

public int[] decodeInts(int n,
 InputStream in)
                 throws IOException,
Pack200Exception

Description copied from class: Codec

Decodes a sequence of n values from in. This should probably be used in most cases, since some codecs (such as PopulationCodec) only work when the number of values to be read is known.

Overrides:

decodeInts in class Codec

Parameters:

n - the number of values to decode

in - the input stream to read from

Returns:

an array of int values corresponding to values decoded

Throws:

IOException - if there is a problem reading from the underlying input stream

Pack200Exception - if there is a problem decoding the value or that the value is invalid

encode

public byte[] encode(int value)
              throws Pack200Exception

Description copied from class: Codec

Encodes a single value into a sequence of bytes. Note that this method can only be used for non-delta encodings.

Specified by:

encode in class Codec

Parameters:

value - the value to encode

Returns:

the encoded bytes

Throws:

Pack200Exception - TODO

encode

public byte[] encode(int value,
 int last)
              throws Pack200Exception

Description copied from class: Codec

Encodes a single value into a sequence of bytes.

Specified by:

encode in class Codec

Parameters:

value - the value to encode

last - the previous value encoded (for delta encodings)

Returns:

the encoded bytes

Throws:

Pack200Exception - TODO

encode

public byte[] encode(int[] favoured,
 int[] tokens,
 int[] unfavoured)
              throws Pack200Exception

Throws:

Pack200Exception

getFavoured

public int[] getFavoured()

getFavouredCodec

public Codec getFavouredCodec()

getTokenCodec

public Codec getTokenCodec()

getUnfavouredCodec

public Codec getUnfavouredCodec()