[120] | 1 | /** |
---|
| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
---|
| 3 | * or more contributor license agreements. See the NOTICE file |
---|
| 4 | * distributed with this work for additional information |
---|
| 5 | * regarding copyright ownership. The ASF licenses this file |
---|
| 6 | * to you under the Apache License, Version 2.0 (the |
---|
| 7 | * "License"); you may not use this file except in compliance |
---|
| 8 | * with the License. You may obtain a copy of the License at |
---|
| 9 | * |
---|
| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
---|
| 11 | * |
---|
| 12 | * Unless required by applicable law or agreed to in writing, software |
---|
| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
---|
| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
---|
| 15 | * See the License for the specific language governing permissions and |
---|
| 16 | * limitations under the License. |
---|
| 17 | */ |
---|
| 18 | package org.apache.hadoop.fs; |
---|
| 19 | |
---|
| 20 | import java.io.BufferedInputStream; |
---|
| 21 | import java.io.IOException; |
---|
| 22 | |
---|
| 23 | |
---|
| 24 | /** |
---|
| 25 | * A class optimizes reading from FSInputStream by bufferring |
---|
| 26 | */ |
---|
| 27 | |
---|
| 28 | |
---|
| 29 | public class BufferedFSInputStream extends BufferedInputStream |
---|
| 30 | implements Seekable, PositionedReadable { |
---|
| 31 | /** |
---|
| 32 | * Creates a <code>BufferedFSInputStream</code> |
---|
| 33 | * with the specified buffer size, |
---|
| 34 | * and saves its argument, the input stream |
---|
| 35 | * <code>in</code>, for later use. An internal |
---|
| 36 | * buffer array of length <code>size</code> |
---|
| 37 | * is created and stored in <code>buf</code>. |
---|
| 38 | * |
---|
| 39 | * @param in the underlying input stream. |
---|
| 40 | * @param size the buffer size. |
---|
| 41 | * @exception IllegalArgumentException if size <= 0. |
---|
| 42 | */ |
---|
| 43 | public BufferedFSInputStream(FSInputStream in, int size) { |
---|
| 44 | super(in, size); |
---|
| 45 | } |
---|
| 46 | |
---|
| 47 | public long getPos() throws IOException { |
---|
| 48 | return ((FSInputStream)in).getPos()-(count-pos); |
---|
| 49 | } |
---|
| 50 | |
---|
| 51 | public long skip(long n) throws IOException { |
---|
| 52 | if (n <= 0) { |
---|
| 53 | return 0; |
---|
| 54 | } |
---|
| 55 | |
---|
| 56 | seek(getPos()+n); |
---|
| 57 | return n; |
---|
| 58 | } |
---|
| 59 | |
---|
| 60 | public void seek(long pos) throws IOException { |
---|
| 61 | if( pos<0 ) { |
---|
| 62 | return; |
---|
| 63 | } |
---|
| 64 | // optimize: check if the pos is in the buffer |
---|
| 65 | long end = ((FSInputStream)in).getPos(); |
---|
| 66 | long start = end - count; |
---|
| 67 | if( pos>=start && pos<end) { |
---|
| 68 | this.pos = (int)(pos-start); |
---|
| 69 | return; |
---|
| 70 | } |
---|
| 71 | |
---|
| 72 | // invalidate buffer |
---|
| 73 | this.pos = 0; |
---|
| 74 | this.count = 0; |
---|
| 75 | |
---|
| 76 | ((FSInputStream)in).seek(pos); |
---|
| 77 | } |
---|
| 78 | |
---|
| 79 | public boolean seekToNewSource(long targetPos) throws IOException { |
---|
| 80 | pos = 0; |
---|
| 81 | count = 0; |
---|
| 82 | return ((FSInputStream)in).seekToNewSource(targetPos); |
---|
| 83 | } |
---|
| 84 | |
---|
| 85 | public int read(long position, byte[] buffer, int offset, int length) throws IOException { |
---|
| 86 | return ((FSInputStream)in).read(position, buffer, offset, length) ; |
---|
| 87 | } |
---|
| 88 | |
---|
| 89 | public void readFully(long position, byte[] buffer, int offset, int length) throws IOException { |
---|
| 90 | ((FSInputStream)in).readFully(position, buffer, offset, length); |
---|
| 91 | } |
---|
| 92 | |
---|
| 93 | public void readFully(long position, byte[] buffer) throws IOException { |
---|
| 94 | ((FSInputStream)in).readFully(position, buffer); |
---|
| 95 | } |
---|
| 96 | } |
---|