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comparison 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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283:c9977db00e1d 284:06aa7b7b6723
1 /**
2 * Orthanc - A Lightweight, RESTful DICOM Store
3 * Copyright (C) 2012 Medical Physics Department, CHU of Liege,
4 * Belgium
5 *
6 * This program is free software: you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation, either version 3 of the
9 * License, or (at your option) any later version.
10 *
11 * In addition, as a special exception, the copyright holders of this
12 * program give permission to link the code of its release with the
13 * OpenSSL project's "OpenSSL" library (or with modified versions of it
14 * that use the same license as the "OpenSSL" library), and distribute
15 * the linked executables. You must obey the GNU General Public License
16 * in all respects for all of the code used other than "OpenSSL". If you
17 * modify file(s) with this exception, you may extend this exception to
18 * your version of the file(s), but you are not obligated to do so. If
19 * you do not wish to do so, delete this exception statement from your
20 * version. If you delete this exception statement from all source files
21 * in the program, then also delete it here.
22 *
23 * This program is distributed in the hope that it will be useful, but
24 * WITHOUT ANY WARRANTY; without even the implied warranty of
25 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
26 * General Public License for more details.
27 *
28 * You should have received a copy of the GNU General Public License
29 * along with this program. If not, see <http://www.gnu.org/licenses/>.
30 **/
31
32
33 #include "MemoryCache.h"
34
35 namespace Orthanc
36 {
37 MemoryCache::Page& MemoryCache::Load(const std::string& id)
38 {
39 // Reuse the cache entry if it already exists
40 Page* p = NULL;
41 if (index_.Contains(id, p))
42 {
43 assert(p != NULL);
44 index_.TagAsMostRecent(id);
45 return *p;
46 }
47
48 // The id is not in the cache yet. Make some room if the cache
49 // is full.
50 if (index_.GetSize() == cacheSize_)
51 {
52 index_.RemoveOldest(p);
53 delete p;
54 }
55
56 // Create a new cache page
57 std::auto_ptr<Page> result(new Page);
58 result->id_ = id;
59 result->content_.reset(provider_.Provide(id));
60
61 // Add the newly create page to the cache
62 p = result.release();
63 index_.Add(id, p);
64 return *p;
65 }
66
67 MemoryCache::MemoryCache(ICachePageProvider& provider,
68 size_t cacheSize) :
69 provider_(provider),
70 cacheSize_(cacheSize)
71 {
72 }
73
74 MemoryCache::~MemoryCache()
75 {
76 while (!index_.IsEmpty())
77 {
78 Page* element = NULL;
79 index_.RemoveOldest(element);
80 assert(element != NULL);
81 delete element;
82 }
83 }
84
85 MemoryCache::Accessor* MemoryCache::Access(const std::string& id)
86 {
87 Page& element = Load(id);
88 return new Accessor(element);
89 }
90 }