[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.hdfs.server.namenode; |
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| 19 | |
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| 20 | import java.util.Arrays; |
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| 21 | |
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| 22 | /** |
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| 23 | * File name generator. |
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| 24 | * |
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| 25 | * Each directory contains not more than a fixed number (filesPerDir) |
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| 26 | * of files and directories. |
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| 27 | * When the number of files in one directory reaches the maximum, |
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| 28 | * the generator creates a new directory and proceeds generating files in it. |
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| 29 | * The generated namespace tree is balanced that is any path to a leaf |
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| 30 | * file is not less than the height of the tree minus one. |
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| 31 | */ |
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| 32 | public class FileNameGenerator { |
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| 33 | private static final int DEFAULT_FILES_PER_DIRECTORY = 32; |
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| 34 | |
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| 35 | private int[] pathIndecies = new int[20]; // this will support up to 32**20 = 2**100 = 10**30 files |
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| 36 | private String baseDir; |
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| 37 | private String currentDir; |
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| 38 | private int filesPerDirectory; |
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| 39 | private long fileCount; |
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| 40 | |
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| 41 | FileNameGenerator(String baseDir) { |
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| 42 | this(baseDir, DEFAULT_FILES_PER_DIRECTORY); |
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| 43 | } |
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| 44 | |
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| 45 | FileNameGenerator(String baseDir, int filesPerDir) { |
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| 46 | this.baseDir = baseDir; |
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| 47 | this.filesPerDirectory = filesPerDir; |
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| 48 | reset(); |
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| 49 | } |
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| 50 | |
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| 51 | String getNextDirName(String prefix) { |
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| 52 | int depth = 0; |
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| 53 | while(pathIndecies[depth] >= 0) |
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| 54 | depth++; |
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| 55 | int level; |
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| 56 | for(level = depth-1; |
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| 57 | level >= 0 && pathIndecies[level] == filesPerDirectory-1; level--) |
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| 58 | pathIndecies[level] = 0; |
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| 59 | if(level < 0) |
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| 60 | pathIndecies[depth] = 0; |
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| 61 | else |
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| 62 | pathIndecies[level]++; |
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| 63 | level = 0; |
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| 64 | String next = baseDir; |
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| 65 | while(pathIndecies[level] >= 0) |
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| 66 | next = next + "/" + prefix + pathIndecies[level++]; |
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| 67 | return next; |
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| 68 | } |
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| 69 | |
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| 70 | synchronized String getNextFileName(String fileNamePrefix) { |
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| 71 | long fNum = fileCount % filesPerDirectory; |
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| 72 | if(fNum == 0) { |
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| 73 | currentDir = getNextDirName(fileNamePrefix + "Dir"); |
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| 74 | } |
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| 75 | String fn = currentDir + "/" + fileNamePrefix + fileCount; |
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| 76 | fileCount++; |
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| 77 | return fn; |
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| 78 | } |
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| 79 | |
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| 80 | private synchronized void reset() { |
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| 81 | Arrays.fill(pathIndecies, -1); |
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| 82 | fileCount = 0L; |
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| 83 | currentDir = ""; |
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| 84 | } |
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| 85 | |
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| 86 | synchronized int getFilesPerDirectory() { |
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| 87 | return filesPerDirectory; |
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| 88 | } |
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| 89 | |
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| 90 | synchronized String getCurrentDir() { |
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| 91 | return currentDir; |
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| 92 | } |
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| 93 | } |
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