BufferedFSInputStream.java
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上传日期:2018-01-08
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文件大小:3k
- /**
- * 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.fs;
- import java.io.BufferedInputStream;
- import java.io.IOException;
- /**
- * A class optimizes reading from FSInputStream by bufferring
- */
- public class BufferedFSInputStream extends BufferedInputStream
- implements Seekable, PositionedReadable {
- /**
- * Creates a <code>BufferedFSInputStream</code>
- * with the specified buffer size,
- * and saves its argument, the input stream
- * <code>in</code>, for later use. An internal
- * buffer array of length <code>size</code>
- * is created and stored in <code>buf</code>.
- *
- * @param in the underlying input stream.
- * @param size the buffer size.
- * @exception IllegalArgumentException if size <= 0.
- */
- public BufferedFSInputStream(FSInputStream in, int size) {
- super(in, size);
- }
- public long getPos() throws IOException {
- return ((FSInputStream)in).getPos()-(count-pos);
- }
- public long skip(long n) throws IOException {
- if (n <= 0) {
- return 0;
- }
- seek(getPos()+n);
- return n;
- }
- public void seek(long pos) throws IOException {
- if( pos<0 ) {
- return;
- }
- // optimize: check if the pos is in the buffer
- long end = ((FSInputStream)in).getPos();
- long start = end - count;
- if( pos>=start && pos<end) {
- this.pos = (int)(pos-start);
- return;
- }
- // invalidate buffer
- this.pos = 0;
- this.count = 0;
- ((FSInputStream)in).seek(pos);
- }
- public boolean seekToNewSource(long targetPos) throws IOException {
- pos = 0;
- count = 0;
- return ((FSInputStream)in).seekToNewSource(targetPos);
- }
- public int read(long position, byte[] buffer, int offset, int length) throws IOException {
- return ((FSInputStream)in).read(position, buffer, offset, length) ;
- }
- public void readFully(long position, byte[] buffer, int offset, int length) throws IOException {
- ((FSInputStream)in).readFully(position, buffer, offset, length);
- }
- public void readFully(long position, byte[] buffer) throws IOException {
- ((FSInputStream)in).readFully(position, buffer);
- }
- }