org.apache.hadoop.io

Class BytesWritable

java.lang.Object

org.apache.hadoop.io.BinaryComparable

org.apache.hadoop.io.BytesWritable

All Implemented Interfaces:

Comparable<BinaryComparable>, Writable, WritableComparable<BinaryComparable>

@InterfaceAudience.Public
@InterfaceStability.Stable
public class BytesWritable
extends BinaryComparable
implements WritableComparable<BinaryComparable>

A byte sequence that is usable as a key or value. It is resizable and distinguishes between the size of the sequence and the current capacity. The hash function is the front of the md5 of the buffer. The sort order is the same as memcmp.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BytesWritable.Comparator A Comparator optimized for BytesWritable.

Constructor Summary

Constructors

Constructor and Description
BytesWritable() Create a zero-size sequence.
BytesWritable(byte[] bytes) Create a BytesWritable using the byte array as the initial value.
BytesWritable(byte[] bytes, int length) Create a BytesWritable using the byte array as the initial value and length as the length.

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	copyBytes() Get a copy of the bytes that is exactly the length of the data.
boolean	equals(Object right_obj) Are the two byte sequences equal?
byte[]	get() Deprecated. Use getBytes() instead.
byte[]	getBytes() Get the data backing the BytesWritable.
int	getCapacity() Get the capacity, which is the maximum size that could handled without resizing the backing storage.
int	getLength() Get the current size of the buffer.
int	getSize() Deprecated. Use getLength() instead.
int	hashCode() Return a hash of the bytes returned from {#getBytes()}.
void	readFields(DataInput in) Deserialize the fields of this object from in.
void	set(byte[] newData, int offset, int length) Set the value to a copy of the given byte range
void	set(BytesWritable newData) Set the BytesWritable to the contents of the given newData.
void	setCapacity(int new_cap) Change the capacity of the backing storage.
void	setSize(int size) Change the size of the buffer.
String	toString() Generate the stream of bytes as hex pairs separated by ' '.
void	write(DataOutput out) Serialize the fields of this object to out.

Methods inherited from class org.apache.hadoop.io.BinaryComparable

compareTo, compareTo

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Comparable

compareTo

Constructor Detail

BytesWritable

public BytesWritable()

Create a zero-size sequence.

BytesWritable

public BytesWritable(byte[] bytes)

Create a BytesWritable using the byte array as the initial value.

Parameters:

bytes - This array becomes the backing storage for the object.

BytesWritable

public BytesWritable(byte[] bytes,
             int length)

Create a BytesWritable using the byte array as the initial value and length as the length. Use this constructor if the array is larger than the value it represents.

Parameters:

bytes - This array becomes the backing storage for the object.

length - The number of bytes to use from array.

Method Detail

copyBytes

public byte[] copyBytes()

Get a copy of the bytes that is exactly the length of the data. See getBytes() for faster access to the underlying array.

getBytes

public byte[] getBytes()

Get the data backing the BytesWritable. Please use copyBytes() if you need the returned array to be precisely the length of the data.

Specified by:

getBytes in class BinaryComparable

Returns:

The data is only valid between 0 and getLength() - 1.

get

@Deprecated
public byte[] get()

Deprecated. Use getBytes() instead.

Get the data from the BytesWritable.

getLength

public int getLength()

Get the current size of the buffer.

Specified by:

getLength in class BinaryComparable

getSize

@Deprecated
public int getSize()

Deprecated. Use getLength() instead.

Get the current size of the buffer.

setSize

public void setSize(int size)

Change the size of the buffer. The values in the old range are preserved and any new values are undefined. The capacity is changed if it is necessary.

Parameters:

size - The new number of bytes

getCapacity

public int getCapacity()

Get the capacity, which is the maximum size that could handled without resizing the backing storage.

Returns:

The number of bytes

setCapacity

public void setCapacity(int new_cap)

Change the capacity of the backing storage. The data is preserved.

Parameters:

new_cap - The new capacity in bytes.

set

public void set(BytesWritable newData)

Set the BytesWritable to the contents of the given newData.

Parameters:

newData - the value to set this BytesWritable to.

set

public void set(byte[] newData,
       int offset,
       int length)

Set the value to a copy of the given byte range

Parameters:

newData - the new values to copy in

offset - the offset in newData to start at

length - the number of bytes to copy

readFields

public void readFields(DataInput in)
                throws IOException

Description copied from interface: Writable

Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:

readFields in interface Writable

Parameters:

in - DataInput to deseriablize this object from.

Throws:

IOException

write

public void write(DataOutput out)
           throws IOException

Description copied from interface: Writable

Serialize the fields of this object to out.

Specified by:

write in interface Writable

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException

hashCode

public int hashCode()

Description copied from class: BinaryComparable

Return a hash of the bytes returned from {#getBytes()}.

Overrides:

hashCode in class BinaryComparable

See Also:

WritableComparator.hashBytes(byte[],int)

equals

public boolean equals(Object right_obj)

Are the two byte sequences equal?

Overrides:

equals in class BinaryComparable

toString

public String toString()

Generate the stream of bytes as hex pairs separated by ' '.

Overrides:

toString in class Object