Line data Source code
1 : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 : /*
3 : * This file is part of the LibreOffice project.
4 : *
5 : * This Source Code Form is subject to the terms of the Mozilla Public
6 : * License, v. 2.0. If a copy of the MPL was not distributed with this
7 : * file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 : *
9 : * This file incorporates work covered by the following license notice:
10 : *
11 : * Licensed to the Apache Software Foundation (ASF) under one or more
12 : * contributor license agreements. See the NOTICE file distributed
13 : * with this work for additional information regarding copyright
14 : * ownership. The ASF licenses this file to you under the Apache
15 : * License, Version 2.0 (the "License"); you may not use this file
16 : * except in compliance with the License. You may obtain a copy of
17 : * the License at http://www.apache.org/licenses/LICENSE-2.0 .
18 : */
19 : #ifndef _LRU_CACHE_HXX_
20 : #define _LRU_CACHE_HXX_
21 :
22 : // __CACHE_DIAGNOSE forces cache size to 4 and works only for OUString keys
23 : // #define __CACHE_DIAGNOSE 1
24 :
25 : #include <osl/mutex.hxx>
26 : #include "rtl/ustring.hxx"
27 :
28 : #include <boost/unordered_map.hpp>
29 :
30 :
31 : /** Implementation of a least recently used (lru) cache.
32 : <br>
33 : @author Daniel Boelzle
34 : */
35 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
36 : class LRU_Cache
37 : {
38 144896 : struct CacheEntry
39 : {
40 : t_Key aKey;
41 : t_Val aVal;
42 : CacheEntry * pPred;
43 : CacheEntry * pSucc;
44 : };
45 : typedef ::boost::unordered_map< t_Key, CacheEntry *, t_KeyHash, t_KeyEqual > t_Key2Element;
46 :
47 : mutable ::osl::Mutex _aCacheMutex;
48 : sal_Int32 _nCachedElements;
49 : t_Key2Element _aKey2Element;
50 :
51 : CacheEntry * _pBlock;
52 : mutable CacheEntry * _pHead;
53 : mutable CacheEntry * _pTail;
54 : inline void toFront( CacheEntry * pEntry ) const;
55 :
56 : public:
57 : /** Constructor:
58 : <br>
59 : @param nCachedElements number of elements to be cached; default param set to 128
60 : */
61 : inline LRU_Cache( sal_Int32 nCachedElements = 128 );
62 : /** Destructor: releases all cached elements and keys.
63 : <br>
64 : */
65 : inline ~LRU_Cache();
66 :
67 : /** Retrieves a value from the cache. Returns default constructed value,
68 : if none was found.
69 : <br>
70 : @param rKey a key
71 : @return value
72 : */
73 : inline t_Val getValue( t_Key const & rKey ) const;
74 : /** Sets a value to be cached for given key.
75 : <br>
76 : @param rKey a key
77 : @param rValue a value
78 : */
79 : inline void setValue( t_Key const & rKey, t_Val const & rValue );
80 : /** Tests whether a value is cached for given key.
81 : <br>
82 : @param rKey a key
83 : @return true, if value is cached
84 : */
85 : inline sal_Bool hasValue( t_Key const & rKey ) const;
86 : /** Clears the cache, thus releasing all cached elements and keys.
87 : <br>
88 : */
89 : inline void clear();
90 : };
91 : //__________________________________________________________________________________________________
92 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
93 259 : inline LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::LRU_Cache( sal_Int32 nCachedElements )
94 : #ifdef __CACHE_DIAGNOSE
95 : : _nCachedElements( 4 )
96 : #else
97 : : _nCachedElements( nCachedElements )
98 : #endif
99 259 : , _pBlock( 0 )
100 : {
101 259 : if (_nCachedElements > 0)
102 : {
103 259 : _pBlock = new CacheEntry[_nCachedElements];
104 259 : _pHead = _pBlock;
105 259 : _pTail = _pBlock + _nCachedElements -1;
106 133126 : for ( sal_Int32 nPos = _nCachedElements; nPos--; )
107 : {
108 132608 : _pBlock[nPos].pPred = _pBlock + nPos -1;
109 132608 : _pBlock[nPos].pSucc = _pBlock + nPos +1;
110 : }
111 : }
112 259 : }
113 : //__________________________________________________________________________________________________
114 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
115 24 : inline LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::~LRU_Cache()
116 : {
117 24 : delete [] _pBlock;
118 24 : }
119 : //__________________________________________________________________________________________________
120 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
121 17521 : inline void LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::toFront(
122 : CacheEntry * pEntry ) const
123 : {
124 17521 : if (pEntry != _pHead)
125 : {
126 : // cut out element
127 15574 : if (pEntry == _pTail)
128 : {
129 6425 : _pTail = pEntry->pPred;
130 : }
131 : else
132 : {
133 9149 : pEntry->pSucc->pPred = pEntry->pPred;
134 9149 : pEntry->pPred->pSucc = pEntry->pSucc;
135 : }
136 : // push to front
137 15574 : _pHead->pPred = pEntry;
138 15574 : pEntry->pSucc = _pHead;
139 15574 : _pHead = pEntry;
140 : }
141 17521 : }
142 : //__________________________________________________________________________________________________
143 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
144 : inline sal_Bool LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::hasValue(
145 : t_Key const & rKey ) const
146 : {
147 : ::osl::MutexGuard aGuard( _aCacheMutex );
148 : typename t_Key2Element::const_iterator const iFind( _aKey2Element.find( rKey ) );
149 : return (iFind != _aKey2Element.end());
150 : }
151 : //__________________________________________________________________________________________________
152 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
153 17522 : inline t_Val LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::getValue(
154 : t_Key const & rKey ) const
155 : {
156 17522 : ::osl::MutexGuard aGuard( _aCacheMutex );
157 17522 : const typename t_Key2Element::const_iterator iFind( _aKey2Element.find( rKey ) );
158 17522 : if (iFind != _aKey2Element.end())
159 : {
160 11096 : CacheEntry * pEntry = (*iFind).second;
161 11096 : toFront( pEntry );
162 : #ifdef __CACHE_DIAGNOSE
163 : OSL_TRACE( "> retrieved element \"" );
164 : OSL_TRACE( "%s", ::rtl::OUStringToOString( pEntry->aKey, RTL_TEXTENCODING_ASCII_US ).getStr() );
165 : OSL_TRACE( "\" from cache <" );
166 : #endif
167 11096 : return pEntry->aVal;
168 : }
169 6426 : return t_Val();
170 : }
171 : //__________________________________________________________________________________________________
172 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
173 6425 : inline void LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::setValue(
174 : t_Key const & rKey, t_Val const & rValue )
175 : {
176 6425 : if (_nCachedElements > 0)
177 : {
178 6425 : ::osl::MutexGuard aGuard( _aCacheMutex );
179 6425 : typename t_Key2Element::const_iterator const iFind( _aKey2Element.find( rKey ) );
180 :
181 : CacheEntry * pEntry;
182 6425 : if (iFind == _aKey2Element.end())
183 : {
184 6425 : pEntry = _pTail; // erase last element
185 : #ifdef __CACHE_DIAGNOSE
186 : if (pEntry->aKey.getLength())
187 : {
188 : OSL_TRACE( "> kicking element \"" );
189 : OSL_TRACE( "%s", ::rtl::OUStringToOString( pEntry->aKey, RTL_TEXTENCODING_ASCII_US ).getStr() );
190 : OSL_TRACE( "\" from cache <" );
191 : }
192 : #endif
193 6425 : _aKey2Element.erase( pEntry->aKey );
194 6425 : _aKey2Element[ pEntry->aKey = rKey ] = pEntry;
195 : }
196 : else
197 : {
198 0 : pEntry = (*iFind).second;
199 : #ifdef __CACHE_DIAGNOSE
200 : OSL_TRACE( "> replacing element \"" );
201 : OSL_TRACE( "%s", ::rtl::OUStringToOString( pEntry->aKey, RTL_TEXTENCODING_ASCII_US ).getStr() );
202 : OSL_TRACE( "\" in cache <" );
203 : #endif
204 : }
205 6425 : pEntry->aVal = rValue;
206 6425 : toFront( pEntry );
207 : }
208 6425 : }
209 : //__________________________________________________________________________________________________
210 : template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
211 39 : inline void LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::clear()
212 : {
213 39 : ::osl::MutexGuard aGuard( _aCacheMutex );
214 39 : _aKey2Element.clear();
215 20046 : for ( sal_Int32 nPos = _nCachedElements; nPos--; )
216 : {
217 19968 : _pBlock[nPos].aKey = t_Key();
218 20007 : _pBlock[nPos].aVal = t_Val();
219 : }
220 : #ifdef __CACHE_DIAGNOSE
221 : OSL_TRACE( "> cleared cache <" );
222 : #endif
223 39 : }
224 :
225 : //==================================================================================================
226 : struct FctHashOUString : public ::std::unary_function< ::rtl::OUString const &, size_t >
227 : {
228 36692 : size_t operator()( ::rtl::OUString const & rKey ) const
229 36692 : { return (size_t)rKey.hashCode(); }
230 : };
231 :
232 : /** Template instance for OUString keys, Any values.<br>
233 : */
234 : typedef LRU_Cache< ::rtl::OUString, ::com::sun::star::uno::Any,
235 : FctHashOUString, ::std::equal_to< ::rtl::OUString > >
236 : LRU_CacheAnyByOUString;
237 :
238 :
239 : #endif
240 :
241 : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
|
