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
|
//
// UniqueAccessExpireCache.h
//
// Library: Foundation
// Package: Cache
// Module: UniqueAccessExpireCache
//
// Definition of the UniqueAccessExpireCache class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_UniqueAccessExpireCache_INCLUDED
#define Foundation_UniqueAccessExpireCache_INCLUDED
#include "Poco/AbstractCache.h"
#include "Poco/UniqueAccessExpireStrategy.h"
namespace Poco {
template <
class TKey,
class TValue,
class TMutex = FastMutex,
class TEventMutex = FastMutex
>
class UniqueAccessExpireCache: public AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue>, TMutex, TEventMutex>
/// An UniqueAccessExpireCache caches entries for a given time span. In contrast
/// to ExpireCache which only allows to set a per cache expiration value, it allows to define
/// expiration per CacheEntry.
/// Each TValue object must thus offer the following method:
///
/// const Poco::Timespan& getTimeout() const;
///
/// which returns the relative timespan for how long the entry should be valid without being accessed!
/// The absolute expire timepoint is calculated as now() + getTimeout().
/// Accessing an object will update this absolute expire timepoint.
/// You can use the Poco::AccessExpirationDecorator to add the getExpiration
/// method to values that do not have a getExpiration function.
///
/// Be careful when using an UniqueAccessExpireCache. A cache is often used
/// like cache.has(x) followed by cache.get x). Note that it could happen
/// that the "has" call works, then the current execution thread gets descheduled, time passes,
/// the entry gets invalid, thus leading to an empty SharedPtr being returned
/// when "get" is invoked.
{
public:
UniqueAccessExpireCache():
AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue>, TMutex, TEventMutex>(UniqueAccessExpireStrategy<TKey, TValue>())
{
}
~UniqueAccessExpireCache()
{
}
private:
UniqueAccessExpireCache(const UniqueAccessExpireCache& aCache);
UniqueAccessExpireCache& operator = (const UniqueAccessExpireCache& aCache);
};
} // namespace Poco
#endif // Foundation_UniqueAccessExpireCache_INCLUDED
|
