BytesWritable.java
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上传日期:2018-01-08
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- /**
- * 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.commons.logging.Log;
- import org.apache.commons.logging.LogFactory;
- /**
- * A byte sequence that is usable as a key or value.
- * It is resizable and distinguishes between the size of the seqeunce and
- * the current capacity. The hash function is the front of the md5 of the
- * buffer. The sort order is the same as memcmp.
- */
- public class BytesWritable extends BinaryComparable
- implements WritableComparable<BinaryComparable> {
- private static final Log LOG = LogFactory.getLog(BytesWritable.class);
- 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;
- this.size = bytes.length;
- }
-
- /**
- * Get the data from the BytesWritable.
- * @return The data is only valid between 0 and getLength() - 1.
- */
- 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.
- */
- 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()) {
- setCapacity(size * 3 / 2);
- }
- 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
- public void readFields(DataInput in) throws IOException {
- setSize(0); // clear the old data
- setSize(in.readInt());
- in.readFully(bytes, 0, size);
- }
-
- // inherit javadoc
- public void write(DataOutput out) throws IOException {
- out.writeInt(size);
- out.write(bytes, 0, size);
- }
-
- public int hashCode() {
- return super.hashCode();
- }
- /**
- * Are the two byte sequences equal?
- */
- 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 ' '.
- */
- public String toString() {
- StringBuffer sb = new StringBuffer(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.
- */
- 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());
- }
-
- }