org.apache.hadoop.io.DataInputBuffer 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 org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
/** A reusable {@link java.io.DataInput} implementation
* that reads from an in-memory buffer.
*
* This saves memory over creating a new DataInputStream and
* ByteArrayInputStream each time data is read.
*
*
Typical usage is something like the following:
*
* DataInputBuffer buffer = new DataInputBuffer();
* while (... loop condition ...) {
* byte[] data = ... get data ...;
* int dataLength = ... get data length ...;
* buffer.reset(data, dataLength);
* ... read buffer using DataInput methods ...
* }
*
*
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
public class DataInputBuffer extends DataInputStream {
private static class Buffer extends ByteArrayInputStream {
public Buffer() {
super(new byte[] {});
}
public void reset(byte[] input, int start, int length) {
this.buf = input;
this.count = start+length;
this.mark = start;
this.pos = start;
}
public byte[] getData() {
return buf;
}
public int getPosition() {
return pos;
}
public int getLength() {
return count;
}
/* functions below comes verbatim from
hive.common.io.NonSyncByteArrayInputStream */
/**
* {@inheritDoc}
*/
@Override
public int read() {
return (pos < count) ? (buf[pos++] & 0xff) : -1;
}
/**
* {@inheritDoc}
*/
@Override
public int read(byte[] b, int off, int len) {
if (b == null) {
throw new NullPointerException();
} else if (off < 0 || len < 0 || len > b.length - off) {
throw new IndexOutOfBoundsException();
}
if (pos >= count) {
return -1;
}
if (pos + len > count) {
len = count - pos;
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, pos, b, off, len);
pos += len;
return len;
}
/**
* {@inheritDoc}
*/
@Override
public long skip(long n) {
if (pos + n > count) {
n = count - pos;
}
if (n < 0) {
return 0;
}
pos += n;
return n;
}
/**
* {@inheritDoc}
*/
@Override
public int available() {
return count - pos;
}
}
private Buffer buffer;
/** Constructs a new empty buffer. */
public DataInputBuffer() {
this(new Buffer());
}
private DataInputBuffer(Buffer buffer) {
super(buffer);
this.buffer = buffer;
}
/** Resets the data that the buffer reads. */
public void reset(byte[] input, int length) {
buffer.reset(input, 0, length);
}
/** Resets the data that the buffer reads. */
public void reset(byte[] input, int start, int length) {
buffer.reset(input, start, length);
}
public byte[] getData() {
return buffer.getData();
}
/** Returns the current position in the input. */
public int getPosition() { return buffer.getPosition(); }
/**
* Returns the index one greater than the last valid character in the input
* stream buffer.
*/
public int getLength() { return buffer.getLength(); }
}