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