| /** |
| * 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. |
| * |
| * <p>This saves memory over creating a new OutputStream and |
| * ByteArrayOutputStream each time data is written. |
| * |
| * <p>Typical usage is something like the following:<pre> |
| * |
| * 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 ... |
| * } |
| * </pre> |
| * @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); |
| } |
| } |