summaryrefslogtreecommitdiff
path: root/includes/libs/ProcessCacheLRU.php
blob: 8d80eb38671fab8b2f153c6e34508b8e757b3fff (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
<?php
/**
 * Per-process memory cache for storing items.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Cache
 */

/**
 * Handles per process caching of items
 * @ingroup Cache
 */
class ProcessCacheLRU {
	/** @var Array */
	protected $cache = array(); // (key => prop => value)

	/** @var Array */
	protected $cacheTimes = array(); // (key => prop => UNIX timestamp)

	protected $maxCacheKeys; // integer; max entries

	/**
	 * @param int $maxKeys Maximum number of entries allowed (min 1).
	 * @throws UnexpectedValueException When $maxCacheKeys is not an int or =< 0.
	 */
	public function __construct( $maxKeys ) {
		$this->resize( $maxKeys );
	}

	/**
	 * Set a property field for a cache entry.
	 * This will prune the cache if it gets too large based on LRU.
	 * If the item is already set, it will be pushed to the top of the cache.
	 *
	 * @param string $key
	 * @param string $prop
	 * @param mixed $value
	 * @return void
	 */
	public function set( $key, $prop, $value ) {
		if ( isset( $this->cache[$key] ) ) {
			$this->ping( $key ); // push to top
		} elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
			reset( $this->cache );
			$evictKey = key( $this->cache );
			unset( $this->cache[$evictKey] );
			unset( $this->cacheTimes[$evictKey] );
		}
		$this->cache[$key][$prop] = $value;
		$this->cacheTimes[$key][$prop] = microtime( true );
	}

	/**
	 * Check if a property field exists for a cache entry.
	 *
	 * @param string $key
	 * @param string $prop
	 * @param float $maxAge Ignore items older than this many seconds (since 1.21)
	 * @return bool
	 */
	public function has( $key, $prop, $maxAge = 0.0 ) {
		if ( isset( $this->cache[$key][$prop] ) ) {
			return ( $maxAge <= 0 ||
				( microtime( true ) - $this->cacheTimes[$key][$prop] ) <= $maxAge
			);
		}

		return false;
	}

	/**
	 * Get a property field for a cache entry.
	 * This returns null if the property is not set.
	 * If the item is already set, it will be pushed to the top of the cache.
	 *
	 * @param string $key
	 * @param string $prop
	 * @return mixed
	 */
	public function get( $key, $prop ) {
		if ( isset( $this->cache[$key][$prop] ) ) {
			// push to top
			$this->ping( $key );
			return $this->cache[$key][$prop];
		} else {
			return null;
		}
	}

	/**
	 * Clear one or several cache entries, or all cache entries.
	 *
	 * @param string|array $keys
	 * @return void
	 */
	public function clear( $keys = null ) {
		if ( $keys === null ) {
			$this->cache = array();
			$this->cacheTimes = array();
		} else {
			foreach ( (array)$keys as $key ) {
				unset( $this->cache[$key] );
				unset( $this->cacheTimes[$key] );
			}
		}
	}

	/**
	 * Resize the maximum number of cache entries, removing older entries as needed
	 *
	 * @param int $maxKeys
	 * @return void
	 * @throws UnexpectedValueException
	 */
	public function resize( $maxKeys ) {
		if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
			throw new UnexpectedValueException( __METHOD__ . " must be given an integer >= 1" );
		}
		$this->maxCacheKeys = $maxKeys;
		while ( count( $this->cache ) > $this->maxCacheKeys ) {
			reset( $this->cache );
			$evictKey = key( $this->cache );
			unset( $this->cache[$evictKey] );
			unset( $this->cacheTimes[$evictKey] );
		}
	}

	/**
	 * Push an entry to the top of the cache
	 *
	 * @param string $key
	 */
	protected function ping( $key ) {
		$item = $this->cache[$key];
		unset( $this->cache[$key] );
		$this->cache[$key] = $item;
	}
}