| /** |
| * 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; |
| |
| import org.apache.hadoop.thirdparty.com.google.common.base.Preconditions; |
| |
| /** 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> |
| * |
| */ |
| @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"}) |
| @InterfaceStability.Unstable |
| 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; |
| } |
| |
| /** |
| * Set the count for the current buf. |
| * @param newCount the new count to set |
| * @return the original count |
| */ |
| private int setCount(int newCount) { |
| Preconditions.checkArgument(newCount >= 0 && newCount <= buf.length); |
| int oldCount = count; |
| count = newCount; |
| return oldCount; |
| } |
| } |
| |
| 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); |
| } |
| |
| /** |
| * Overwrite an integer into the internal buffer. Note that this call can only |
| * be used to overwrite existing data in the buffer, i.e., buffer#count cannot |
| * be increased, and DataOutputStream#written cannot be increased. |
| */ |
| public void writeInt(int v, int offset) throws IOException { |
| Preconditions.checkState(offset + 4 <= buffer.getLength()); |
| byte[] b = new byte[4]; |
| b[0] = (byte) ((v >>> 24) & 0xFF); |
| b[1] = (byte) ((v >>> 16) & 0xFF); |
| b[2] = (byte) ((v >>> 8) & 0xFF); |
| b[3] = (byte) ((v >>> 0) & 0xFF); |
| int oldCount = buffer.setCount(offset); |
| buffer.write(b); |
| buffer.setCount(oldCount); |
| } |
| } |