1 | // |
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2 | // UniqueAccessExpireCache.h |
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3 | // |
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4 | // $Id: //poco/1.3/Foundation/include/Poco/UniqueAccessExpireCache.h#1 $ |
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5 | // |
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6 | // Library: Foundation |
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7 | // Package: Cache |
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8 | // Module: UniqueAccessExpireCache |
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9 | // |
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10 | // Definition of the UniqueAccessExpireCache class. |
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11 | // |
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12 | // Copyright (c) 2006, Applied Informatics Software Engineering GmbH. |
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13 | // and Contributors. |
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14 | // |
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15 | // Permission is hereby granted, free of charge, to any person or organization |
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16 | // obtaining a copy of the software and accompanying documentation covered by |
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17 | // this license (the "Software") to use, reproduce, display, distribute, |
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18 | // execute, and transmit the Software, and to prepare derivative works of the |
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19 | // Software, and to permit third-parties to whom the Software is furnished to |
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20 | // do so, all subject to the following: |
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21 | // |
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22 | // The copyright notices in the Software and this entire statement, including |
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23 | // the above license grant, this restriction and the following disclaimer, |
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24 | // must be included in all copies of the Software, in whole or in part, and |
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25 | // all derivative works of the Software, unless such copies or derivative |
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26 | // works are solely in the form of machine-executable object code generated by |
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27 | // a source language processor. |
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28 | // |
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29 | // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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30 | // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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31 | // FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT |
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32 | // SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE |
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33 | // FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, |
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34 | // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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35 | // DEALINGS IN THE SOFTWARE. |
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36 | // |
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37 | |
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38 | |
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39 | #ifndef Foundation_UniqueAccessExpireCache_INCLUDED |
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40 | #define Foundation_UniqueAccessExpireCache_INCLUDED |
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41 | |
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42 | |
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43 | #include "Poco/AbstractCache.h" |
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44 | #include "Poco/UniqueAccessExpireStrategy.h" |
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45 | |
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46 | |
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47 | namespace Poco { |
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48 | |
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49 | |
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50 | template <class TKey, class TValue> |
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51 | class UniqueAccessExpireCache: public AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue> > |
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52 | /// An UniqueAccessExpireCache caches entries for a given time span. In contrast |
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53 | /// to ExpireCache which only allows to set a per cache expiration value, it allows to define |
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54 | /// expiration per CacheEntry. |
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55 | /// Each TValue object must thus offer the following method: |
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56 | /// |
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57 | /// const Poco::Timespan& getTimeout() const; |
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58 | /// |
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59 | /// which returns the relative timespan for how long the entry should be valid without being accessed! |
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60 | /// The absolute expire timepoint is calculated as now() + getTimeout(). |
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61 | /// Accessing an object will update this absolute expire timepoint. |
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62 | /// You can use the Poco::AccessExpirationDecorator to add the getExpiration |
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63 | /// method to values that do not have a getExpiration function. |
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64 | /// |
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65 | /// Be careful when using an UniqueAccessExpireCache. A cache is often used |
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66 | /// like cache.has(x) followed by cache.get x). Note that it could happen |
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67 | /// that the "has" call works, then the current execution thread gets descheduled, time passes, |
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68 | /// the entry gets invalid, thus leading to an empty SharedPtr being returned |
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69 | /// when "get" is invoked. |
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70 | { |
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71 | public: |
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72 | UniqueAccessExpireCache(): |
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73 | AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue> >(UniqueAccessExpireStrategy<TKey, TValue>()) |
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74 | { |
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75 | } |
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76 | |
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77 | ~UniqueAccessExpireCache() |
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78 | { |
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79 | } |
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80 | |
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81 | private: |
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82 | UniqueAccessExpireCache(const UniqueAccessExpireCache& aCache); |
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83 | UniqueAccessExpireCache& operator = (const UniqueAccessExpireCache& aCache); |
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84 | }; |
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85 | |
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86 | |
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87 | } // namespace Poco |
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88 | |
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89 | |
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90 | #endif // Foundation_UniqueAccessExpireCache_INCLUDED |
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