/**
* 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.*;
/** A reusable {@link DataOutput} implementation that writes to an in-memory
* buffer.
*
* <p>This saves memory over creating a new DataOutputStream and
* ByteArrayOutputStream each time data is written.
*
* <p>Typical usage is something like the following:<pre>
*
* DataOutputBuffer buffer = new DataOutputBuffer();
* while (... loop condition ...) {
* buffer.reset();
* ... write buffer using DataOutput methods ...
* byte[] data = buffer.getData();
* int dataLength = buffer.getLength();
* ... write data to its ultimate destination ...
* }
* </pre>
*
*/
public class DataOutputBuffer extends DataOutputStream {
private static class Buffer extends ByteArrayOutputStream {
public byte[] getData() { return buf; }
public int getLength() { return count; }
public Buffer() {
super();
}
public Buffer(int size) {
super(size);
}
public void write(DataInput 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;
}
in.readFully(buf, count, len);
count = newcount;
}
}
private Buffer buffer;
/** Constructs a new empty buffer. */
public DataOutputBuffer() {
this(new Buffer());
}
public DataOutputBuffer(int size) {
this(new Buffer(size));
}
private DataOutputBuffer(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 DataOutputBuffer reset() {
this.written = 0;
buffer.reset();
return this;
}
/** Writes bytes from a DataInput directly into the buffer. */
public void write(DataInput in, int length) throws IOException {
buffer.write(in, length);
}
/** Write to a file stream */
public void writeTo(OutputStream out) throws IOException {
buffer.writeTo(out);
}
}
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