com.aliyun.odps.io.DataInputBuffer Maven / Gradle / Ivy
/**
* 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 com.aliyun.odps.io;
import java.io.ByteArrayInputStream;
import java.io.DataInput;
import java.io.DataInputStream;
/**
* DataInputBuffer 提供一个可复用的 {@link DataInput} 实现.
*
*
* DataInputBuffer 继承自 {@link DataInputStream} ，提供了 {@link DataInput}
* 的实现，可以方便的将内存数据作为输入，并提供 reset 系列方法支持对象复用。
*
*
* 代码示例：
*
*
* DataInputBuffer buffer = new DataInputBuffer();
* while (... loop condition ...) {
* byte[] data = ... get data ...;
* int dataLength = ... get data length ...;
* buffer.reset(data, dataLength); //重用 buffer，无需再new 对象
* ... read buffer using DataInput methods ...
* }
*
*
* @see Writable#readFields(DataInput)
* @see DataOutputBuffer
*/
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;
}
}
private Buffer buffer;
/**
* 构建一个空 DataInputBuffer
*/
public DataInputBuffer() {
this(new Buffer());
}
private DataInputBuffer(Buffer buffer) {
super(buffer);
this.buffer = buffer;
}
/**
* 重置内存数据输入.
*
*
* 将 input[0,...,length-1] 作为数据输入
*
* @param input
* 字节数组
* @param length
* 数据内容长度
*/
public void reset(byte[] input, int length) {
buffer.reset(input, 0, length);
}
/**
* 重置内存数据输入.
*
*
* 将 input[start,...,start+length-1] 作为数据输入
*
* @param input
* 字节数组
* @param start
* 数据起始位置
* @param length
* 数据内容长度
*/
public void reset(byte[] input, int start, int length) {
buffer.reset(input, start, length);
}
/**
* 获取当前数据内容的字节数组
*
* @return 当前数据内容的字节数组
*/
public byte[] getData() {
return buffer.getData();
}
/**
* 获取数据输入流的当前位置
*
* @return 数据输入流的当前位置
*/
public int getPosition() {
return buffer.getPosition();
}
/**
* 获取数据输入的内容长度
*
* @return 数据输入的内容长度
*/
public int getLength() {
return buffer.getLength();
}
}