/src/yolk-cache-discrete_keys.ads
Ada | 86 lines | 22 code | 12 blank | 52 comment | 0 complexity | 732809aa07d12c5dca61649c350234ad MD5 | raw file
1------------------------------------------------------------------------------- 2-- -- 3-- Copyright (C) 2010-, Thomas Løcke -- 4-- -- 5-- This library is free software; you can redistribute it and/or modify -- 6-- it under terms of the GNU General Public License as published by the -- 7-- Free Software Foundation; either version 3, or (at your option) any -- 8-- later version. This library is distributed in the hope that it will be -- 9-- useful, but WITHOUT ANY WARRANTY; without even the implied warranty of -- 10-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. -- 11-- -- 12-- As a special exception under Section 7 of GPL version 3, you are -- 13-- granted additional permissions described in the GCC Runtime Library -- 14-- Exception, version 3.1, as published by the Free Software Foundation. -- 15-- -- 16-- You should have received a copy of the GNU General Public License and -- 17-- a copy of the GCC Runtime Library Exception along with this program; -- 18-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 19-- <http://www.gnu.org/licenses/>. -- 20-- -- 21------------------------------------------------------------------------------- 22 23-- A simple and fairly dumb cache. 24-- In order for an element to be valid, it must: 25-- 26-- 1. have been added to the cache using the Write procedure 27-- 2. be younger than Max_Element_Age 28-- 29-- WARNING! 30-- If your Key_Type is for example an Integer, then the cache _can_ grow to 31-- whatever the size of Integer is on your implementation. Obviously this 32-- can potentially use a lot of resources, so give some thought to Key_Type 33-- before you dump any old discrete type in there. 34-- 35-- Note that whenever an invalid element is found by the Read procedure 36-- (Is_Valid = False), it is automatically deleted from the cache. 37 38generic 39 40 type Key_Type is (<>); 41 type Element_Type is private; 42 Max_Element_Age : Duration := 3600.0; 43 -- Elements that are older than Max_Element_Age are considered invalid. 44 45package Yolk.Cache.Discrete_Keys is 46 47 procedure Cleanup; 48 -- Clear all stale elements from the cache. Basically this iterates over 49 -- every single object in the cache and deletes it if it is older than 50 -- Max_Element_Age. 51 -- Obviously this is a very expensive call if the cache is large. Use with 52 -- care. 53 54 procedure Clear; 55 -- Clear the entire cache. 56 57 procedure Clear 58 (Key : in Key_Type); 59 -- Remove the currently cached element associated with Key. 60 61 function Is_Valid 62 (Key : in Key_Type) 63 return Boolean; 64 -- Return True if the element associated with Key exists and is younger 65 -- than Max_Element_Age. 66 67 function Length 68 return Natural; 69 -- Return the amount of elements currently in the cache. This counts both 70 -- valid and invalid elements. 71 72 procedure Read 73 (Key : in Key_Type; 74 Is_Valid : out Boolean; 75 Value : out Element_Type); 76 -- Fetch the element associated with Key. 77 -- 78 -- WARNING! 79 -- Value will contain undefined garbage if Is_Valid is False. 80 81 procedure Write 82 (Key : in Key_Type; 83 Value : in Element_Type); 84 -- Add Value to the cache, and associate it with Key. 85 86end Yolk.Cache.Discrete_Keys;