src/main/java/eu/svjatoslav/sixth/data/store/file/VacuumContext.java

   1 /*
   2  * Sixth - System for data storage, computation, exploration and interaction.
   3  * Copyright ©2012-2016, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 3 of the GNU Lesser General Public License
   7  * or later as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.sixth.data.store.file;
  11
  12 public class VacuumContext {
  13     private final FileDataStore vacuumContext;
  14     private final int targetFragmentationPercent;
  15     long analyzedBytesCount = 0;
  16     long freeBytesCount = 0;
  17     long lastRecordStartAddress;
  18     long defragmentationStartAddress;
  19
  20     public VacuumContext(final FileDataStore fileDataStore,
  21                          final long currentFreeAddress, final int targetFragmentationPercent) {
  22
  23         vacuumContext = fileDataStore;
  24         lastRecordStartAddress = currentFreeAddress;
  25         defragmentationStartAddress = currentFreeAddress;
  26         this.targetFragmentationPercent = targetFragmentationPercent;
  27     }
  28
  29     public void analyzeEntry(final EntryRecord record) {
  30         final long bytesSinceLastEntry = lastRecordStartAddress
  31                 - record.location;
  32
  33         final long freeSpace = bytesSinceLastEntry - record.length;
  34         freeBytesCount += freeSpace;
  35         analyzedBytesCount += freeSpace;
  36
  37         checkDefragmentationPointer(record.location + record.length);
  38
  39         analyzedBytesCount += record.length;
  40         lastRecordStartAddress = record.location;
  41     }
  42
  43     public void analyzeStartOfDataArea() {
  44         freeBytesCount += lastRecordStartAddress
  45                 - vacuumContext.metaData.getEntriesStorageAreaStart();
  46
  47         checkDefragmentationPointer(vacuumContext.metaData
  48                 .getEntriesStorageAreaStart());
  49     }
  50
  51     public void checkDefragmentationPointer(
  52             final long defragmentationStartAddress) {
  53
  54         if (analyzedBytesCount == 0) {
  55             this.defragmentationStartAddress = defragmentationStartAddress;
  56             return;
  57         }
  58
  59         final int fragmentationPercentage = (int) ((100L * freeBytesCount) / analyzedBytesCount);
  60
  61         if (fragmentationPercentage >= targetFragmentationPercent)
  62             this.defragmentationStartAddress = defragmentationStartAddress;
  63     }
  64 }