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Common functionality for HBase
/**
* 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.hbase.io;
import java.io.IOException;
import java.io.DataInput;
import java.io.DataOutput;
import java.util.Arrays;
import java.util.List;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
/**
* A byte sequence that is usable as a key or value. Based on
* {@link org.apache.hadoop.io.BytesWritable} only this class is NOT resizable
* and DOES NOT distinguish between the size of the sequence and the current
* capacity as {@link org.apache.hadoop.io.BytesWritable} does. Hence its
* comparatively 'immutable'. When creating a new instance of this class,
* the underlying byte [] is not copied, just referenced. The backing
* buffer is accessed when we go to serialize.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
@edu.umd.cs.findbugs.annotations.SuppressWarnings(
value="EQ_CHECK_FOR_OPERAND_NOT_COMPATIBLE_WITH_THIS",
justification="It has been like this forever")
public class ImmutableBytesWritable
implements WritableComparable {
private byte[] bytes;
private int offset;
private int length;
/**
* Create a zero-size sequence.
*/
public ImmutableBytesWritable() {
super();
}
/**
* Create a ImmutableBytesWritable using the byte array as the initial value.
* @param bytes This array becomes the backing storage for the object.
*/
public ImmutableBytesWritable(byte[] bytes) {
this(bytes, 0, bytes.length);
}
/**
* Set the new ImmutableBytesWritable to the contents of the passed
* ibw.
* @param ibw the value to set this ImmutableBytesWritable to.
*/
public ImmutableBytesWritable(final ImmutableBytesWritable ibw) {
this(ibw.get(), ibw.getOffset(), ibw.getLength());
}
/**
* Set the value to a given byte range
* @param bytes the new byte range to set to
* @param offset the offset in newData to start at
* @param length the number of bytes in the range
*/
public ImmutableBytesWritable(final byte[] bytes, final int offset,
final int length) {
this.bytes = bytes;
this.offset = offset;
this.length = length;
}
/**
* Get the data from the BytesWritable.
* @return The data is only valid between offset and offset+length.
*/
public byte [] get() {
if (this.bytes == null) {
throw new IllegalStateException("Uninitialiized. Null constructor " +
"called w/o accompaying readFields invocation");
}
return this.bytes;
}
/**
* @param b Use passed bytes as backing array for this instance.
*/
public void set(final byte [] b) {
set(b, 0, b.length);
}
/**
* @param b Use passed bytes as backing array for this instance.
* @param offset
* @param length
*/
public void set(final byte [] b, final int offset, final int length) {
this.bytes = b;
this.offset = offset;
this.length = length;
}
/**
* @return the number of valid bytes in the buffer
* @deprecated use {@link #getLength()} instead
*/
@Deprecated
public int getSize() {
if (this.bytes == null) {
throw new IllegalStateException("Uninitialiized. Null constructor " +
"called w/o accompaying readFields invocation");
}
return this.length;
}
/**
* @return the number of valid bytes in the buffer
*/
public int getLength() {
if (this.bytes == null) {
throw new IllegalStateException("Uninitialiized. Null constructor " +
"called w/o accompaying readFields invocation");
}
return this.length;
}
/**
* @return offset
*/
public int getOffset(){
return this.offset;
}
@Override
public void readFields(final DataInput in) throws IOException {
this.length = in.readInt();
this.bytes = new byte[this.length];
in.readFully(this.bytes, 0, this.length);
this.offset = 0;
}
@Override
public void write(final DataOutput out) throws IOException {
out.writeInt(this.length);
out.write(this.bytes, this.offset, this.length);
}
// Below methods copied from BytesWritable
@Override
public int hashCode() {
int hash = 1;
for (int i = offset; i < offset + length; i++)
hash = (31 * hash) + (int)bytes[i];
return hash;
}
/**
* Define the sort order of the BytesWritable.
* @param that The other bytes writable
* @return Positive if left is bigger than right, 0 if they are equal, and
* negative if left is smaller than right.
*/
@Override
public int compareTo(ImmutableBytesWritable that) {
return WritableComparator.compareBytes(
this.bytes, this.offset, this.length,
that.bytes, that.offset, that.length);
}
/**
* Compares the bytes in this object to the specified byte array
* @param that
* @return Positive if left is bigger than right, 0 if they are equal, and
* negative if left is smaller than right.
*/
public int compareTo(final byte [] that) {
return WritableComparator.compareBytes(
this.bytes, this.offset, this.length,
that, 0, that.length);
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object right_obj) {
if (right_obj instanceof byte []) {
return compareTo((byte [])right_obj) == 0;
}
if (right_obj instanceof ImmutableBytesWritable) {
return compareTo((ImmutableBytesWritable)right_obj) == 0;
}
return false;
}
/**
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
StringBuilder sb = new StringBuilder(3*this.length);
final int endIdx = this.offset + this.length;
for (int idx = this.offset; idx < endIdx ; idx++) {
sb.append(' ');
String num = Integer.toHexString(0xff & this.bytes[idx]);
// if it is only one digit, add a leading 0.
if (num.length() < 2) {
sb.append('0');
}
sb.append(num);
}
return sb.length() > 0 ? sb.substring(1) : "";
}
/** A Comparator optimized for ImmutableBytesWritable.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public static class Comparator extends WritableComparator {
private BytesWritable.Comparator comparator =
new BytesWritable.Comparator();
/** constructor */
public Comparator() {
super(ImmutableBytesWritable.class);
}
/**
* @see org.apache.hadoop.io.WritableComparator#compare(byte[], int, int, byte[], int, int)
*/
@Override
public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
return comparator.compare(b1, s1, l1, b2, s2, l2);
}
}
static { // register this comparator
WritableComparator.define(ImmutableBytesWritable.class, new Comparator());
}
/**
* @param array List of byte [].
* @return Array of byte [].
*/
public static byte [][] toArray(final List array) {
// List#toArray doesn't work on lists of byte [].
byte[][] results = new byte[array.size()][];
for (int i = 0; i < array.size(); i++) {
results[i] = array.get(i);
}
return results;
}
/**
* Returns a copy of the bytes referred to by this writable
*/
public byte[] copyBytes() {
return Arrays.copyOfRange(bytes, offset, offset+length);
}
}