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annotate Core/Cache/MemoryCache.cpp @ 284:06aa7b7b6723

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implementation of a single-threaded cache mechanism
author Sebastien Jodogne <s.jodogne@gmail.com>
date Wed, 12 Dec 2012 15:40:18 +0100
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children 4031f73fe0e4
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06aa7b7b6723 implementation of a single-threaded cache mechanism
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1 /**
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2 * Orthanc - A Lightweight, RESTful DICOM Store
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3 * Copyright (C) 2012 Medical Physics Department, CHU of Liege,
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4 * Belgium
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5 *
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6 * This program is free software: you can redistribute it and/or
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7 * modify it under the terms of the GNU General Public License as
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8 * published by the Free Software Foundation, either version 3 of the
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9 * License, or (at your option) any later version.
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10 *
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11 * In addition, as a special exception, the copyright holders of this
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12 * program give permission to link the code of its release with the
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13 * OpenSSL project's "OpenSSL" library (or with modified versions of it
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14 * that use the same license as the "OpenSSL" library), and distribute
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15 * the linked executables. You must obey the GNU General Public License
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16 * in all respects for all of the code used other than "OpenSSL". If you
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17 * modify file(s) with this exception, you may extend this exception to
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18 * your version of the file(s), but you are not obligated to do so. If
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19 * you do not wish to do so, delete this exception statement from your
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20 * version. If you delete this exception statement from all source files
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21 * in the program, then also delete it here.
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22 *
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23 * This program is distributed in the hope that it will be useful, but
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24 * WITHOUT ANY WARRANTY; without even the implied warranty of
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25 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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26 * General Public License for more details.
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27 *
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28 * You should have received a copy of the GNU General Public License
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29 * along with this program. If not, see <http://www.gnu.org/licenses/>.
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30 **/
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31
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32
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33 #include "MemoryCache.h"
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34
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35 namespace Orthanc
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36 {
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37 MemoryCache::Page& MemoryCache::Load(const std::string& id)
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38 {
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39 // Reuse the cache entry if it already exists
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40 Page* p = NULL;
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41 if (index_.Contains(id, p))
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42 {
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43 assert(p != NULL);
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44 index_.TagAsMostRecent(id);
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45 return *p;
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46 }
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47
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48 // The id is not in the cache yet. Make some room if the cache
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49 // is full.
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50 if (index_.GetSize() == cacheSize_)
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51 {
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52 index_.RemoveOldest(p);
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53 delete p;
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54 }
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55
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56 // Create a new cache page
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57 std::auto_ptr<Page> result(new Page);
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58 result->id_ = id;
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59 result->content_.reset(provider_.Provide(id));
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60
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61 // Add the newly create page to the cache
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62 p = result.release();
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63 index_.Add(id, p);
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64 return *p;
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65 }
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66
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67 MemoryCache::MemoryCache(ICachePageProvider& provider,
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68 size_t cacheSize) :
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69 provider_(provider),
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70 cacheSize_(cacheSize)
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71 {
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72 }
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73
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74 MemoryCache::~MemoryCache()
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75 {
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76 while (!index_.IsEmpty())
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77 {
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78 Page* element = NULL;
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79 index_.RemoveOldest(element);
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80 assert(element != NULL);
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81 delete element;
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82 }
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83 }
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84
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85 MemoryCache::Accessor* MemoryCache::Access(const std::string& id)
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86 {
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87 Page& element = Load(id);
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88 return new Accessor(element);
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89 }
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90 }