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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