hadoop InputBuffer 源码
haddop InputBuffer 代码
文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/InputBuffer.java
/**
* 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 InputStream} implementation that reads from an in-memory
* buffer.
*
* <p>This saves memory over creating a new InputStream and
* ByteArrayInputStream each time data is read.
*
* <p>Typical usage is something like the following:<pre>
*
* InputBuffer buffer = new InputBuffer();
* while (... loop condition ...) {
* byte[] data = ... get data ...;
* int dataLength = ... get data length ...;
* buffer.reset(data, dataLength);
* ... read buffer using InputStream methods ...
* }
* </pre>
* @see DataInputBuffer
* @see DataOutput
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
public class InputBuffer extends FilterInputStream {
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 int getPosition() { return pos; }
public int getLength() { return count; }
}
private Buffer buffer;
/** Constructs a new empty buffer. */
public InputBuffer() {
this(new Buffer());
}
private InputBuffer(Buffer buffer) {
super(buffer);
this.buffer = buffer;
}
/**
* Resets the data that the buffer reads.
* @param input input.
* @param length length.
*/
public void reset(byte[] input, int length) {
buffer.reset(input, 0, length);
}
/**
* Resets the data that the buffer reads.
* @param input input.
* @param start start.
* @param length length.
*/
public void reset(byte[] input, int start, int length) {
buffer.reset(input, start, length);
}
/**
* Returns the current position in the input.
* @return the current position in the input.
*/
public int getPosition() { return buffer.getPosition(); }
/**
* Returns the length of the input.
* @return length of the input.
*/
public int getLength() { return buffer.getLength(); }
}
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