[120] | 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 3 | * or more contributor license agreements. See the NOTICE file |
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| 4 | * distributed with this work for additional information |
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| 5 | * regarding copyright ownership. The ASF licenses this file |
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| 6 | * to you under the Apache License, Version 2.0 (the |
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| 7 | * "License"); you may not use this file except in compliance |
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| 8 | * with the License. You may obtain a copy of the License at |
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| 9 | * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 11 | * |
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| 12 | * Unless required by applicable law or agreed to in writing, software |
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| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 15 | * See the License for the specific language governing permissions and |
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| 16 | * limitations under the License. |
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| 17 | */ |
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| 18 | package org.apache.hadoop.fs; |
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| 19 | |
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| 20 | import java.io.*; |
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| 21 | |
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| 22 | /**************************************************************** |
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| 23 | * FSInputStream is a generic old InputStream with a little bit |
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| 24 | * of RAF-style seek ability. |
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| 25 | * |
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| 26 | *****************************************************************/ |
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| 27 | public abstract class FSInputStream extends InputStream |
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| 28 | implements Seekable, PositionedReadable { |
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| 29 | /** |
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| 30 | * Seek to the given offset from the start of the file. |
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| 31 | * The next read() will be from that location. Can't |
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| 32 | * seek past the end of the file. |
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| 33 | */ |
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| 34 | public abstract void seek(long pos) throws IOException; |
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| 35 | |
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| 36 | /** |
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| 37 | * Return the current offset from the start of the file |
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| 38 | */ |
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| 39 | public abstract long getPos() throws IOException; |
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| 40 | |
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| 41 | /** |
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| 42 | * Seeks a different copy of the data. Returns true if |
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| 43 | * found a new source, false otherwise. |
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| 44 | */ |
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| 45 | public abstract boolean seekToNewSource(long targetPos) throws IOException; |
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| 46 | |
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| 47 | public int read(long position, byte[] buffer, int offset, int length) |
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| 48 | throws IOException { |
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| 49 | synchronized (this) { |
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| 50 | long oldPos = getPos(); |
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| 51 | int nread = -1; |
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| 52 | try { |
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| 53 | seek(position); |
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| 54 | nread = read(buffer, offset, length); |
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| 55 | } finally { |
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| 56 | seek(oldPos); |
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| 57 | } |
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| 58 | return nread; |
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| 59 | } |
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| 60 | } |
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| 61 | |
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| 62 | public void readFully(long position, byte[] buffer, int offset, int length) |
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| 63 | throws IOException { |
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| 64 | int nread = 0; |
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| 65 | while (nread < length) { |
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| 66 | int nbytes = read(position+nread, buffer, offset+nread, length-nread); |
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| 67 | if (nbytes < 0) { |
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| 68 | throw new EOFException("End of file reached before reading fully."); |
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| 69 | } |
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| 70 | nread += nbytes; |
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| 71 | } |
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| 72 | } |
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| 73 | |
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| 74 | public void readFully(long position, byte[] buffer) |
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| 75 | throws IOException { |
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| 76 | readFully(position, buffer, 0, buffer.length); |
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| 77 | } |
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| 78 | } |
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