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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 _STOC_SEC_LRU_CACHE_H_
20 : #define _STOC_SEC_LRU_CACHE_H_
21 :
22 : #include <boost/unordered_map.hpp>
23 :
24 : // __CACHE_DIAGNOSE works only for OUString keys
25 : #ifdef __CACHE_DIAGNOSE
26 : #include <osl/diagnose.h>
27 : #include <rtl/ustrbuf.hxx>
28 : #include <rtl/ustring.hxx>
29 : #include <rtl/string.hxx>
30 : #endif
31 :
32 :
33 : namespace stoc_sec
34 : {
35 :
36 : /** Implementation of a least recently used (lru) cache.
37 : */
38 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
39 : class lru_cache
40 : {
41 0 : struct Entry
42 : {
43 : t_key m_key;
44 : t_val m_val;
45 : Entry * m_pred;
46 : Entry * m_succ;
47 : };
48 : typedef ::boost::unordered_map< t_key, Entry *, t_hashKey, t_equalKey > t_key2element;
49 : t_key2element m_key2element;
50 : ::std::size_t m_size;
51 :
52 : Entry * m_block;
53 : mutable Entry * m_head;
54 : mutable Entry * m_tail;
55 : inline void toFront( Entry * entry ) const SAL_THROW(());
56 :
57 : public:
58 : /** Default Ctor. Does not cache.
59 : */
60 : inline lru_cache() SAL_THROW(());
61 : /** Ctor.
62 :
63 : @param size number of elements to be cached; default param set to 128
64 : */
65 : inline lru_cache( ::std::size_t size ) SAL_THROW(());
66 :
67 : /** Destructor: releases all cached elements and keys.
68 : */
69 : inline ~lru_cache() SAL_THROW(());
70 :
71 : /** Retrieves a pointer to value in cache. Returns 0, if none was found.
72 :
73 : @param key a key
74 : @return pointer to value or 0
75 : */
76 : inline t_val const * lookup( t_key const & key ) const SAL_THROW(());
77 :
78 : /** Sets a value to be cached for given key.
79 :
80 : @param key a key
81 : @param val a value
82 : */
83 : inline void set( t_key const & key, t_val const & val ) SAL_THROW(());
84 :
85 : /** Tests whether a value is cached for given key.
86 :
87 : @param key a key
88 : @return true, if value is cached
89 : */
90 : inline bool has( t_key const & key ) const SAL_THROW(());
91 :
92 : /** Clears the cache, releasing all cached elements and keys.
93 : */
94 : inline void clear() SAL_THROW(());
95 :
96 : /** Sets the number of elements to be cached. This will clear previous entries.
97 :
98 : @param cacheSize number of elements to be cached
99 : */
100 : inline void setSize( ::std::size_t size ) SAL_THROW(());
101 : };
102 :
103 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
104 0 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::setSize(
105 : ::std::size_t size ) SAL_THROW(())
106 : {
107 0 : m_key2element.clear();
108 0 : delete [] m_block;
109 0 : m_block = 0;
110 0 : m_size = size;
111 :
112 0 : if (0 < m_size)
113 : {
114 0 : m_block = new Entry[ m_size ];
115 0 : m_head = m_block;
116 0 : m_tail = m_block + m_size -1;
117 0 : for ( ::std::size_t nPos = m_size; nPos--; )
118 : {
119 0 : m_block[ nPos ].m_pred = m_block + nPos -1;
120 0 : m_block[ nPos ].m_succ = m_block + nPos +1;
121 : }
122 : }
123 0 : }
124 :
125 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
126 : inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache(
127 : ::std::size_t size ) SAL_THROW(())
128 : : m_size( 0 )
129 : , m_block( 0 )
130 : , m_tail( 0 )
131 : {
132 : setSize( size );
133 : }
134 :
135 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
136 0 : inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache() SAL_THROW(())
137 : : m_size( 0 )
138 0 : , m_block( 0 )
139 : {
140 0 : }
141 :
142 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
143 0 : inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::~lru_cache()
144 : SAL_THROW(())
145 : {
146 0 : delete [] m_block;
147 0 : }
148 :
149 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
150 0 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::toFront(
151 : Entry * entry ) const SAL_THROW(())
152 : {
153 0 : if (entry != m_head)
154 : {
155 : // cut out element
156 0 : if (entry == m_tail)
157 : {
158 0 : m_tail = entry->m_pred;
159 : }
160 : else
161 : {
162 0 : entry->m_succ->m_pred = entry->m_pred;
163 0 : entry->m_pred->m_succ = entry->m_succ;
164 : }
165 : // push to front
166 0 : m_head->m_pred = entry;
167 0 : entry->m_succ = m_head;
168 0 : m_head = entry;
169 : }
170 0 : }
171 :
172 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
173 : inline bool lru_cache< t_key, t_val, t_hashKey, t_equalKey >::has(
174 : t_key const & key ) const SAL_THROW(())
175 : {
176 : typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
177 : return (iFind != m_key2element.end());
178 : }
179 :
180 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
181 0 : inline t_val const * lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lookup(
182 : t_key const & key ) const SAL_THROW(())
183 : {
184 0 : if (0 < m_size)
185 : {
186 0 : typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
187 0 : if (iFind != m_key2element.end())
188 : {
189 0 : Entry * entry = iFind->second;
190 0 : toFront( entry );
191 : #ifdef __CACHE_DIAGNOSE
192 : OUStringBuffer buf( 48 );
193 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> retrieved element \"") );
194 : buf.append( entry->m_key );
195 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
196 : OString str( OUStringToOString(
197 : buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
198 : OSL_TRACE( "%s", str.getStr() );
199 : #endif
200 0 : return &entry->m_val;
201 : }
202 : }
203 0 : return 0;
204 : }
205 :
206 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
207 0 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::set(
208 : t_key const & key, t_val const & val ) SAL_THROW(())
209 : {
210 0 : if (0 < m_size)
211 : {
212 0 : typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
213 :
214 : Entry * entry;
215 0 : if (iFind == m_key2element.end())
216 : {
217 0 : entry = m_tail; // erase last element
218 : #ifdef __CACHE_DIAGNOSE
219 : if (entry->m_key.getLength())
220 : {
221 : OUStringBuffer buf( 48 );
222 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> kicking element \"") );
223 : buf.append( entry->m_key );
224 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
225 : OString str( OUStringToOString(
226 : buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
227 : OSL_TRACE( "%s", str.getStr() );
228 : }
229 : #endif
230 0 : m_key2element.erase( entry->m_key );
231 0 : entry->m_key = key;
232 : ::std::pair< typename t_key2element::iterator, bool > insertion(
233 0 : m_key2element.insert( typename t_key2element::value_type( key, entry ) ) );
234 : #ifdef __CACHE_DIAGNOSE
235 : OSL_ENSURE( insertion.second, "### inserting new cache entry failed?!" );
236 : #endif
237 : (void) insertion; // avoid warnings
238 : }
239 : else
240 : {
241 0 : entry = iFind->second;
242 : #ifdef __CACHE_DIAGNOSE
243 : OUStringBuffer buf( 48 );
244 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> replacing element \"") );
245 : buf.append( entry->m_key );
246 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" in cache") );
247 : OString str( OUStringToOString(
248 : buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
249 : OSL_TRACE( "%s", str.getStr() );
250 : #endif
251 : }
252 0 : entry->m_val = val;
253 0 : toFront( entry );
254 : }
255 0 : }
256 :
257 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
258 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::clear() SAL_THROW(())
259 : {
260 : m_key2element.clear();
261 : for ( ::std::size_t nPos = m_size; nPos--; )
262 : {
263 : m_block[ nPos ].m_key = t_key();
264 : m_block[ nPos ].m_val = t_val();
265 : }
266 : #ifdef __CACHE_DIAGNOSE
267 : OSL_TRACE( "> cleared cache" );
268 : #endif
269 : }
270 :
271 : }
272 :
273 : #endif
274 :
275 : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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