org.apache.hadoop.io.OutputBuffer 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.*;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/** A reusable {@link OutputStream} implementation that writes to an in-memory
* buffer.
*
* This saves memory over creating a new OutputStream and
* ByteArrayOutputStream each time data is written.
*
*
Typical usage is something like the following:
*
* OutputBuffer buffer = new OutputBuffer();
* while (... loop condition ...) {
* buffer.reset();
* ... write buffer using OutputStream methods ...
* byte[] data = buffer.getData();
* int dataLength = buffer.getLength();
* ... write data to its ultimate destination ...
* }
*
* @see DataOutputBuffer
* @see InputBuffer
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
public class OutputBuffer extends FilterOutputStream {
private static class Buffer extends ByteArrayOutputStream {
public byte[] getData() { return buf; }
public int getLength() { return count; }
@Override
public void reset() { count = 0; }
public void write(InputStream in, int len) throws IOException {
int newcount = count + len;
if (newcount > buf.length) {
byte newbuf[] = new byte[Math.max(buf.length << 1, newcount)];
System.arraycopy(buf, 0, newbuf, 0, count);
buf = newbuf;
}
IOUtils.readFully(in, buf, count, len);
count = newcount;
}
}
private Buffer buffer;
/** Constructs a new empty buffer. */
public OutputBuffer() {
this(new Buffer());
}
private OutputBuffer(Buffer buffer) {
super(buffer);
this.buffer = buffer;
}
/** Returns the current contents of the buffer.
* Data is only valid to {@link #getLength()}.
*/
public byte[] getData() { return buffer.getData(); }
/** Returns the length of the valid data currently in the buffer. */
public int getLength() { return buffer.getLength(); }
/** Resets the buffer to empty. */
public OutputBuffer reset() {
buffer.reset();
return this;
}
/** Writes bytes from a InputStream directly into the buffer. */
public void write(InputStream in, int length) throws IOException {
buffer.write(in, length);
}
}