org.apache.hadoop.io

类 WritableComparator

java.lang.Object

org.apache.hadoop.io.WritableComparator

所有已实现的接口:

Comparator, RawComparator

直接已知子类:

BooleanWritable.Comparator, BytesWritable.Comparator, ByteWritable.Comparator, DoubleWritable.Comparator, FloatWritable.Comparator, IntWritable.Comparator, KeyFieldBasedComparator, KeyFieldBasedComparator, LongWritable.Comparator, MD5Hash.Comparator, NullWritable.Comparator, RecordComparator, SecondarySort.IntPair.Comparator, Text.Comparator, UTF8.Comparator

public class WritableComparator
extends Object
implements RawComparator

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.

构造器概要

构造器

限定符	构造器和说明
protected	WritableComparator(Class<? extends WritableComparable> keyClass) Construct for a WritableComparable implementation.
protected	WritableComparator(Class<? extends WritableComparable> keyClass, boolean createInstances)

方法概要

方法

限定符和类型	方法和说明
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<? extends WritableComparable> c) Get a comparator for a WritableComparable implementation.
Class<? extends WritableComparable>	getKeyClass() Returns the WritableComparable implementation class.
static int	hashBytes(byte[] bytes, int length) Compute hash for binary data.
static int	hashBytes(byte[] bytes, int offset, int length) Compute hash for binary data.
WritableComparable	newKey() Construct a new WritableComparable instance.
static double	readDouble(byte[] bytes, int start) Parse a double from a byte array.
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.
static int	readVInt(byte[] bytes, int start) Reads a zero-compressed encoded integer from a byte array and returns it.
static long	readVLong(byte[] bytes, int start) Reads a zero-compressed encoded long from a byte array and returns it.

从类继承的方法 java.lang.Object

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

从接口继承的方法 java.util.Comparator

equals

构造器详细资料

WritableComparator

protected WritableComparator(Class<? extends WritableComparable> keyClass)

Construct for a WritableComparable implementation.

WritableComparator

protected WritableComparator(Class<? extends WritableComparable> keyClass,
                  boolean createInstances)

方法详细资料

get

public static WritableComparator get(Class<? extends WritableComparable> 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<? extends WritableComparable> 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).

指定者:

compare 在接口中 RawComparator

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)

指定者:

compare 在接口中 Comparator

compareBytes

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

Lexicographic order of binary data.

hashBytes

public static int hashBytes(byte[] bytes,
            int offset,
            int length)

Compute hash for binary data.

hashBytes

public static int hashBytes(byte[] bytes,
            int length)

Compute hash for 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.

readDouble

public static double readDouble(byte[] bytes,
                int start)

Parse a double from a byte array.

readVLong

public static long readVLong(byte[] bytes,
             int start)
                      throws IOException

Reads a zero-compressed encoded long from a byte array and returns it.

参数:

bytes - byte array with decode long

start - starting index

返回:

deserialized long

抛出:

IOException

readVInt

public static int readVInt(byte[] bytes,
           int start)
                    throws IOException

Reads a zero-compressed encoded integer from a byte array and returns it.

参数:

bytes - byte array with the encoded integer

start - start index

返回:

deserialized integer

抛出:

IOException