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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 INCLUDED_STOC_SOURCE_SECURITY_LRU_CACHE_H
20 : #define INCLUDED_STOC_SOURCE_SECURITY_LRU_CACHE_H
21 :
22 : #include <unordered_map>
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 std::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;
56 :
57 : public:
58 : /** Default Ctor. Does not cache.
59 : */
60 : inline lru_cache();
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 );
66 :
67 : /** Destructor: releases all cached elements and keys.
68 : */
69 : inline ~lru_cache();
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;
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 );
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;
91 :
92 : /** Clears the cache, releasing all cached elements and keys.
93 : */
94 : inline void clear();
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 );
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 )
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 )
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 2 : inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache()
137 : : m_size( 0 )
138 : , m_block( 0 )
139 : , m_head( 0 )
140 2 : , m_tail( 0 )
141 : {
142 2 : }
143 :
144 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
145 2 : inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::~lru_cache()
146 : {
147 2 : delete [] m_block;
148 2 : }
149 :
150 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
151 0 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::toFront(
152 : Entry * entry ) const
153 : {
154 0 : if (entry != m_head)
155 : {
156 : // cut out element
157 0 : if (entry == m_tail)
158 : {
159 0 : m_tail = entry->m_pred;
160 : }
161 : else
162 : {
163 0 : entry->m_succ->m_pred = entry->m_pred;
164 0 : entry->m_pred->m_succ = entry->m_succ;
165 : }
166 : // push to front
167 0 : m_head->m_pred = entry;
168 0 : entry->m_succ = m_head;
169 0 : m_head = entry;
170 : }
171 0 : }
172 :
173 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
174 : inline bool lru_cache< t_key, t_val, t_hashKey, t_equalKey >::has(
175 : t_key const & key ) const
176 : {
177 : typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
178 : return (iFind != m_key2element.end());
179 : }
180 :
181 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
182 0 : inline t_val const * lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lookup(
183 : t_key const & key ) const
184 : {
185 0 : if (0 < m_size)
186 : {
187 0 : typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
188 0 : if (iFind != m_key2element.end())
189 : {
190 0 : Entry * entry = iFind->second;
191 0 : toFront( entry );
192 : #ifdef __CACHE_DIAGNOSE
193 : OUStringBuffer buf( 48 );
194 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> retrieved element \"") );
195 : buf.append( entry->m_key );
196 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
197 : OString str( OUStringToOString(
198 : buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
199 : OSL_TRACE( "%s", str.getStr() );
200 : #endif
201 0 : return &entry->m_val;
202 : }
203 : }
204 0 : return 0;
205 : }
206 :
207 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
208 0 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::set(
209 : t_key const & key, t_val const & val )
210 : {
211 0 : if (0 < m_size)
212 : {
213 0 : typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
214 :
215 : Entry * entry;
216 0 : if (iFind == m_key2element.end())
217 : {
218 0 : entry = m_tail; // erase last element
219 : #ifdef __CACHE_DIAGNOSE
220 : if (entry->m_key.getLength())
221 : {
222 : OUStringBuffer buf( 48 );
223 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> kicking element \"") );
224 : buf.append( entry->m_key );
225 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
226 : OString str( OUStringToOString(
227 : buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
228 : OSL_TRACE( "%s", str.getStr() );
229 : }
230 : #endif
231 0 : m_key2element.erase( entry->m_key );
232 0 : entry->m_key = key;
233 : ::std::pair< typename t_key2element::iterator, bool > insertion(
234 0 : m_key2element.insert( typename t_key2element::value_type( key, entry ) ) );
235 : #ifdef __CACHE_DIAGNOSE
236 : OSL_ENSURE( insertion.second, "### inserting new cache entry failed?!" );
237 : #endif
238 : (void) insertion; // avoid warnings
239 : }
240 : else
241 : {
242 0 : entry = iFind->second;
243 : #ifdef __CACHE_DIAGNOSE
244 : OUStringBuffer buf( 48 );
245 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> replacing element \"") );
246 : buf.append( entry->m_key );
247 : buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" in cache") );
248 : OString str( OUStringToOString(
249 : buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
250 : OSL_TRACE( "%s", str.getStr() );
251 : #endif
252 : }
253 0 : entry->m_val = val;
254 0 : toFront( entry );
255 : }
256 0 : }
257 :
258 : template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
259 : inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::clear()
260 : {
261 : m_key2element.clear();
262 : for ( ::std::size_t nPos = m_size; nPos--; )
263 : {
264 : m_block[ nPos ].m_key = t_key();
265 : m_block[ nPos ].m_val = t_val();
266 : }
267 : #ifdef __CACHE_DIAGNOSE
268 : OSL_TRACE( "> cleared cache" );
269 : #endif
270 : }
271 :
272 : }
273 :
274 : #endif
275 :
276 : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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