org.apache.hadoop.io.BytesWritable Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.io;
import java.io.IOException;
import java.io.DataInput;
import java.io.DataOutput;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* 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.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class BytesWritable extends BinaryComparable
implements WritableComparable {
private static final int LENGTH_BYTES = 4;
private static final byte[] EMPTY_BYTES = {};
private int size;
private byte[] bytes;
/**
* Create a zero-size sequence.
*/
public BytesWritable() {this(EMPTY_BYTES);}
/**
* Create a BytesWritable using the byte array as the initial value.
* @param bytes This array becomes the backing storage for the object.
*/
public BytesWritable(byte[] bytes) {
this(bytes, bytes.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.
* @param bytes This array becomes the backing storage for the object.
* @param length The number of bytes to use from array.
*/
public BytesWritable(byte[] bytes, int length) {
this.bytes = bytes;
this.size = length;
}
/**
* Get a copy of the bytes that is exactly the length of the data.
* See {@link #getBytes()} for faster access to the underlying array.
*/
public byte[] copyBytes() {
byte[] result = new byte[size];
System.arraycopy(bytes, 0, result, 0, size);
return result;
}
/**
* Get the data backing the BytesWritable. Please use {@link #copyBytes()}
* if you need the returned array to be precisely the length of the data.
* @return The data is only valid between 0 and getLength() - 1.
*/
@Override
public byte[] getBytes() {
return bytes;
}
/**
* Get the data from the BytesWritable.
* @deprecated Use {@link #getBytes()} instead.
*/
@Deprecated
public byte[] get() {
return getBytes();
}
/**
* Get the current size of the buffer.
*/
@Override
public int getLength() {
return size;
}
/**
* Get the current size of the buffer.
* @deprecated Use {@link #getLength()} instead.
*/
@Deprecated
public int getSize() {
return getLength();
}
/**
* 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.
* @param size The new number of bytes
*/
public void setSize(int size) {
if (size > getCapacity()) {
// Avoid overflowing the int too early by casting to a long.
long newSize = Math.min(Integer.MAX_VALUE, (3L * size) / 2L);
setCapacity((int) newSize);
}
this.size = size;
}
/**
* Get the capacity, which is the maximum size that could handled without
* resizing the backing storage.
* @return The number of bytes
*/
public int getCapacity() {
return bytes.length;
}
/**
* Change the capacity of the backing storage.
* The data is preserved.
* @param new_cap The new capacity in bytes.
*/
public void setCapacity(int new_cap) {
if (new_cap != getCapacity()) {
byte[] new_data = new byte[new_cap];
if (new_cap < size) {
size = new_cap;
}
if (size != 0) {
System.arraycopy(bytes, 0, new_data, 0, size);
}
bytes = new_data;
}
}
/**
* Set the BytesWritable to the contents of the given newData.
* @param newData the value to set this BytesWritable to.
*/
public void set(BytesWritable newData) {
set(newData.bytes, 0, newData.size);
}
/**
* Set the value to a copy of the given byte range
* @param newData the new values to copy in
* @param offset the offset in newData to start at
* @param length the number of bytes to copy
*/
public void set(byte[] newData, int offset, int length) {
setSize(0);
setSize(length);
System.arraycopy(newData, offset, bytes, 0, size);
}
// inherit javadoc
@Override
public void readFields(DataInput in) throws IOException {
setSize(0); // clear the old data
setSize(in.readInt());
in.readFully(bytes, 0, size);
}
// inherit javadoc
@Override
public void write(DataOutput out) throws IOException {
out.writeInt(size);
out.write(bytes, 0, size);
}
@Override
public int hashCode() {
return super.hashCode();
}
/**
* Are the two byte sequences equal?
*/
@Override
public boolean equals(Object right_obj) {
if (right_obj instanceof BytesWritable)
return super.equals(right_obj);
return false;
}
/**
* Generate the stream of bytes as hex pairs separated by ' '.
*/
@Override
public String toString() {
StringBuilder sb = new StringBuilder(3*size);
for (int idx = 0; idx < size; idx++) {
// if not the first, put a blank separator in
if (idx != 0) {
sb.append(' ');
}
String num = Integer.toHexString(0xff & bytes[idx]);
// if it is only one digit, add a leading 0.
if (num.length() < 2) {
sb.append('0');
}
sb.append(num);
}
return sb.toString();
}
/** A Comparator optimized for BytesWritable. */
public static class Comparator extends WritableComparator {
public Comparator() {
super(BytesWritable.class);
}
/**
* Compare the buffers in serialized form.
*/
@Override
public int compare(byte[] b1, int s1, int l1,
byte[] b2, int s2, int l2) {
return compareBytes(b1, s1+LENGTH_BYTES, l1-LENGTH_BYTES,
b2, s2+LENGTH_BYTES, l2-LENGTH_BYTES);
}
}
static { // register this comparator
WritableComparator.define(BytesWritable.class, new Comparator());
}
}
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