org.apache.nutch.io
Class WritableComparator

java.lang.Object
  org.apache.nutch.io.WritableComparator

All Implemented Interfaces:

Comparator

Direct Known Subclasses:

BooleanWritable.Comparator, DeleteDuplicates.IndexedDoc.ByHashDoc, DeleteDuplicates.IndexedDoc.ByHashScore, DistributedWebDBWriter.LinkInstruction.MD5Comparator, DistributedWebDBWriter.LinkInstruction.UrlComparator, DistributedWebDBWriter.PageInstruction.PageComparator, DistributedWebDBWriter.PageInstruction.UrlComparator, FloatWritable.Comparator, IntWritable.Comparator, Link.MD5Comparator, Link.UrlComparator, LongWritable.Comparator, MD5Hash.Comparator, Page.Comparator, Page.UrlComparator, UpdateSegmentsFromDb.BySegmentComparator, UpdateSegmentsFromDb.ByUrlComparator, UTF8.Comparator, WebDBWriter.LinkInstruction.MD5Comparator, WebDBWriter.LinkInstruction.UrlComparator, WebDBWriter.PageInstruction.PageComparator, WebDBWriter.PageInstruction.UrlComparator

public class WritableComparator

extends Object

implements Comparator

A Comparator for WritableComparables.

This base implemenation uses the natural ordering. To define alternate orderings, override compare(WritableComparable,WritableComparable).

One may optimize compare-intensive operations by overriding compare(byte[],int,int,byte[],int,int). Static utility methods are provided to assist in optimized implementations of this method.

Constructor Summary

protected

WritableComparator(Class keyClass) Construct for a WritableComparable implementation.

Method Summary

int	compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) Optimization hook.
int	compare(Object a, Object b)
int	compare(WritableComparable a, WritableComparable b) Compare two WritableComparables.
static int	compareBytes(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) Lexicographic order of binary data.
static void	define(Class c, WritableComparator comparator) Register an optimized comparator for a WritableComparable implementation.
static WritableComparator	get(Class c) Get a comparator for a WritableComparable implementation.
Class	getKeyClass() Returns the WritableComparable implementation class.
WritableComparable	newKey() Construct a new WritableComparable instance.
static float	readFloat(byte[] bytes, int start) Parse a float from a byte array.
static int	readInt(byte[] bytes, int start) Parse an integer from a byte array.
static long	readLong(byte[] bytes, int start) Parse a long from a byte array.
static int	readUnsignedShort(byte[] bytes, int start) Parse an unsigned short from a byte array.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

equals

Constructor Detail

WritableComparator

protected WritableComparator(Class keyClass)

Construct for a WritableComparable implementation.

Method Detail

get

public static WritableComparator get(Class c)

Get a comparator for a WritableComparable implementation.

define

public static void define(Class c,
                          WritableComparator comparator)

Register an optimized comparator for a WritableComparable implementation.

getKeyClass

public Class getKeyClass()

Returns the WritableComparable implementation class.

newKey

public WritableComparable newKey()

Construct a new WritableComparable instance.

compare

public int compare(byte[] b1,
                   int s1,
                   int l1,
                   byte[] b2,
                   int s2,
                   int l2)

Optimization hook. Override this to make SequenceFile.Sorter's scream.

The default implementation reads the data into two WritableComparables (using Writable.readFields(DataInput), then calls compare(WritableComparable,WritableComparable).

compare

public int compare(WritableComparable a,
                   WritableComparable b)

Compare two WritableComparables.

The default implementation uses the natural ordering, calling Comparable.compareTo(Object).

compare

public int compare(Object a,
                   Object b)

Specified by:

compare in interface Comparator

compareBytes

public static int compareBytes(byte[] b1,
                               int s1,
                               int l1,
                               byte[] b2,
                               int s2,
                               int l2)

Lexicographic order of binary data.

readUnsignedShort

public static int readUnsignedShort(byte[] bytes,
                                    int start)

Parse an unsigned short from a byte array.

readInt

public static int readInt(byte[] bytes,
                          int start)

Parse an integer from a byte array.

readFloat

public static float readFloat(byte[] bytes,
                              int start)

Parse a float from a byte array.

readLong

public static long readLong(byte[] bytes,
                            int start)

Parse a long from a byte array.