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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
|
<?php
/**
* TCache class file.
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @link http://www.pradosoft.com/
* @copyright Copyright © 2005 PradoSoft
* @license http://www.pradosoft.com/license/
* @version $Revision: $ $Date: $
* @package System.Web
*/
/**
* TCache class
*
* TCache is the base class for cache classes with different cache storage implementation.
*
* TCache implements the interface {@link ICache} with the following methods,
* - {@link get} : retrieve the value with a key (if any) from cache
* - {@link set} : store the value with a key into cache
* - {@link add} : store the value only if cache does not have this key
* - {@link delete} : delete the value with the specified key from cache
* - {@link flush} : delete all values from cache
*
* Each value is associated with an expiration time. The {@link get} operation
* ensures that any expired value will not be returned. The expiration time by
* the number of seconds. A expiration time 0 represents never expire.
*
* By definition, cache does not ensure the existence of a value
* even if it never expires. Cache is not meant to be an persistent storage.
*
* Child classes must implement the following methods:
* - {@link getValue}
* - {@link setValue}
* - {@link addValue}
* - {@link deleteValue}
* and optionally {@link flush}
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @version $Revision: $ $Date: $
* @package System.Caching
* @since 3.0
*/
abstract class TCache extends TModule implements ICache
{
private $_prefix=null;
/**
* Initializes the cache module.
* This method initializes the cache key prefix and registers the cache module
* with the application.
* @param TXmlElement the module configuration
*/
public function init($config)
{
if($this->_prefix===null)
$this->_prefix=$this->getApplication()->getUniqueID();
$this->getApplication()->setCache($this);
}
/**
* @return string a unique prefix for the keys of cached values.
* If it is not explicitly set, it will take the value of {@link TApplication::getUniqueID}.
*/
public function getPrefix()
{
return $this->_prefix;
}
/**
* @param string a unique prefix for the keys of cached values
*/
public function setPrefix($value)
{
$this->_prefix=$value;
}
/**
* @param string a key identifying a value to be cached
* @return sring a key generated from the provided key which ensures the uniqueness across applications
*/
protected function generateUniqueKey($key)
{
return md5($this->_prefix.$key);
}
/**
* Retrieves a value from cache with a specified key.
* @param string a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache or expired.
*/
public function get($id)
{
if(($value=$this->getValue($this->generateUniqueKey($id)))!==false)
{
$data=unserialize($value);
if(!($data[1] instanceof ICacheDependency) || !$data[1]->getHasChanged())
return $data[0];
}
return false;
}
/**
* Stores a value identified by a key into cache.
* If the cache already contains such a key, the existing value and
* expiration time will be replaced with the new ones.
*
* @param string the key identifying the value to be cached
* @param mixed the value to be cached
* @param integer the number of seconds in which the cached value will expire. 0 means never expire.
* @param ICacheDependency dependency of the cached item. If the dependency changes, the item is labelled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function set($id,$value,$expire=0,$dependency=null)
{
$data=array($value,$dependency);
$expire=($expire<=0)?0:time()+$expire;
return $this->setValue($this->generateUniqueKey($id),serialize($data),$expire);
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* Nothing will be done if the cache already contains the key.
* @param string the key identifying the value to be cached
* @param mixed the value to be cached
* @param integer the number of seconds in which the cached value will expire. 0 means never expire.
* @param ICacheDependency dependency of the cached item. If the dependency changes, the item is labelled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function add($id,$value,$expire=0,$dependency=null)
{
$data=array($value,$dependency);
$expire=($expire<=0)?0:time()+$expire;
return $this->addValue($this->generateUniqueKey($id),serialize($data),$expire);
}
/**
* Deletes a value with the specified key from cache
* @param string the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
public function delete($id)
{
return $this->deleteValue($this->generateUniqueKey($id));
}
/**
* Deletes all values from cache.
* Be careful of performing this operation if the cache is shared by multiple applications.
* Child classes may implement this method to realize the flush operation.
* @throws TNotSupportedException if this method is not overriden by child classes
*/
public function flush()
{
throw new TNotSupportedException('cache_flush_unsupported');
}
/**
* Retrieves a value from cache with a specified key.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link get()} already. So only the implementation of data retrieval
* is needed.
* @param string a unique key identifying the cached value
* @return string the value stored in cache, false if the value is not in the cache or expired.
*/
abstract protected function getValue($key);
/**
* Stores a value identified by a key in cache.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link set()} already. So only the implementation of data storage
* is needed.
*
* @param string the key identifying the value to be cached
* @param string the value to be cached
* @param integer the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
abstract protected function setValue($key,$value,$expire);
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link add()} already. So only the implementation of data storage
* is needed.
*
* @param string the key identifying the value to be cached
* @param string the value to be cached
* @param integer the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
abstract protected function addValue($key,$value,$expire);
/**
* Deletes a value with the specified key from cache
* This method should be implemented by child classes to delete the data from actual cache storage.
* @param string the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
abstract protected function deleteValue($key);
}
?>
|
