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<title>Caching/ExpiringCacheMap/HashECM.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE OverloadedStrings #-}</span>
<a name="line-2"></a><span class='hs-comment'>-- |</span>
<a name="line-3"></a><span class='hs-comment'>-- Module : Caching.ExpiringCacheMap.HashECM</span>
<a name="line-4"></a><span class='hs-comment'>-- Copyright: (c) 2014 Edward L. Blake</span>
<a name="line-5"></a><span class='hs-comment'>-- License: BSD-style</span>
<a name="line-6"></a><span class='hs-comment'>-- Maintainer: Edward L. Blake <edwardlblake@gmail.com></span>
<a name="line-7"></a><span class='hs-comment'>-- Stability: experimental</span>
<a name="line-8"></a><span class='hs-comment'>-- Portability: portable</span>
<a name="line-9"></a><span class='hs-comment'>--</span>
<a name="line-10"></a><span class='hs-comment'>-- A cache that holds values for a length of time that uses 'Hashable' keys</span>
<a name="line-11"></a><span class='hs-comment'>-- with "Data.HashMap.Strict".</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a><span class='hs-comment'>-- An example of creating a cache for accessing files:</span>
<a name="line-14"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><span class='hs-comment'>-- > {-# LANGUAGE OverloadedStrings #-}</span>
<a name="line-16"></a><span class='hs-comment'>-- > </span>
<a name="line-17"></a><span class='hs-comment'>-- > import Caching.ExpiringCacheMap.HashECM (newECMIO, lookupECM, CacheSettings(..), consistentDuration)</span>
<a name="line-18"></a><span class='hs-comment'>-- > </span>
<a name="line-19"></a><span class='hs-comment'>-- > import qualified Data.Time.Clock.POSIX as POSIX (POSIXTime, getPOSIXTime)</span>
<a name="line-20"></a><span class='hs-comment'>-- > import qualified Data.ByteString.Char8 as BS</span>
<a name="line-21"></a><span class='hs-comment'>-- > import System.IO (withFile, IOMode(ReadMode))</span>
<a name="line-22"></a><span class='hs-comment'>-- > </span>
<a name="line-23"></a><span class='hs-comment'>-- > example = do</span>
<a name="line-24"></a><span class='hs-comment'>-- > filecache <- newECMIO</span>
<a name="line-25"></a><span class='hs-comment'>-- > (consistentDuration 100 -- Duration between access and expiry time of each item</span>
<a name="line-26"></a><span class='hs-comment'>-- > (\state id -> do BS.putStrLn "Reading a file again..."</span>
<a name="line-27"></a><span class='hs-comment'>-- > withFile (case id :: BS.ByteString of</span>
<a name="line-28"></a><span class='hs-comment'>-- > "file1" -> "file1.txt"</span>
<a name="line-29"></a><span class='hs-comment'>-- > "file2" -> "file2.txt")</span>
<a name="line-30"></a><span class='hs-comment'>-- > ReadMode $</span>
<a name="line-31"></a><span class='hs-comment'>-- > \fh -> do content <- BS.hGetContents fh</span>
<a name="line-32"></a><span class='hs-comment'>-- > return $! (state, content)))</span>
<a name="line-33"></a><span class='hs-comment'>-- > (do time <- POSIX.getPOSIXTime</span>
<a name="line-34"></a><span class='hs-comment'>-- > return (round (time * 100)))</span>
<a name="line-35"></a><span class='hs-comment'>-- > 1 -- Time check frequency: (accumulator `mod` this_number) == 0.</span>
<a name="line-36"></a><span class='hs-comment'>-- > (CacheWithLRUList</span>
<a name="line-37"></a><span class='hs-comment'>-- > 6 -- Expected size of key-value map when removing elements.</span>
<a name="line-38"></a><span class='hs-comment'>-- > 6 -- Size of map when to remove items from key-value map.</span>
<a name="line-39"></a><span class='hs-comment'>-- > 12 -- Size of list when to compact</span>
<a name="line-40"></a><span class='hs-comment'>-- > )</span>
<a name="line-41"></a><span class='hs-comment'>-- > </span>
<a name="line-42"></a><span class='hs-comment'>-- > -- Use lookupECM whenever the contents of "file1" is needed.</span>
<a name="line-43"></a><span class='hs-comment'>-- > b <- lookupECM filecache "file1"</span>
<a name="line-44"></a><span class='hs-comment'>-- > BS.putStrLn b</span>
<a name="line-45"></a><span class='hs-comment'>-- > return ()</span>
<a name="line-46"></a><span class='hs-comment'>-- > </span>
<a name="line-47"></a><span class='hs-comment'>-- </span>
<a name="line-48"></a>
<a name="line-49"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Caching</span><span class='hs-varop'>.</span><span class='hs-conid'>ExpiringCacheMap</span><span class='hs-varop'>.</span><span class='hs-conid'>HashECM</span> <span class='hs-layout'>(</span>
<a name="line-50"></a>
<a name="line-51"></a> <span class='hs-comment'>-- * Create cache</span>
<a name="line-52"></a> <span class='hs-varid'>newECMIO</span><span class='hs-layout'>,</span>
<a name="line-53"></a> <span class='hs-varid'>newECMForM</span><span class='hs-layout'>,</span>
<a name="line-54"></a> <span class='hs-varid'>consistentDuration</span><span class='hs-layout'>,</span>
<a name="line-55"></a>
<a name="line-56"></a> <span class='hs-comment'>-- * Request value from cache</span>
<a name="line-57"></a> <span class='hs-varid'>lookupECM</span><span class='hs-layout'>,</span>
<a name="line-58"></a>
<a name="line-59"></a> <span class='hs-comment'>-- * Value request function state</span>
<a name="line-60"></a> <span class='hs-varid'>getValReqState</span><span class='hs-layout'>,</span>
<a name="line-61"></a>
<a name="line-62"></a> <span class='hs-comment'>-- * Invalidate cache</span>
<a name="line-63"></a> <span class='hs-varid'>invalidate</span><span class='hs-layout'>,</span>
<a name="line-64"></a> <span class='hs-varid'>invalidateCache</span><span class='hs-layout'>,</span>
<a name="line-65"></a>
<a name="line-66"></a> <span class='hs-comment'>-- * List keys</span>
<a name="line-67"></a> <span class='hs-varid'>keysCached</span><span class='hs-layout'>,</span>
<a name="line-68"></a> <span class='hs-varid'>keysNotExpired</span><span class='hs-layout'>,</span>
<a name="line-69"></a>
<a name="line-70"></a> <span class='hs-comment'>-- * Type</span>
<a name="line-71"></a> <span class='hs-conid'>ECM</span><span class='hs-layout'>,</span>
<a name="line-72"></a> <span class='hs-conid'>CacheSettings</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-73"></a><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-74"></a>
<a name="line-75"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Concurrent</span><span class='hs-varop'>.</span><span class='hs-conid'>MVar</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>MV</span>
<a name="line-76"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span><span class='hs-varop'>.</span><span class='hs-conid'>Strict</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>HM</span>
<a name="line-77"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>List</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>L</span>
<a name="line-78"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Hashable</span> <span class='hs-layout'>(</span><span class='hs-conid'>Hashable</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-79"></a>
<a name="line-80"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Caching</span><span class='hs-varop'>.</span><span class='hs-conid'>ExpiringCacheMap</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span> <span class='hs-layout'>(</span><span class='hs-varid'>updateUses</span><span class='hs-layout'>,</span> <span class='hs-varid'>detECM</span><span class='hs-layout'>,</span> <span class='hs-varid'>detNotExpired</span><span class='hs-layout'>)</span>
<a name="line-81"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Caching</span><span class='hs-varop'>.</span><span class='hs-conid'>ExpiringCacheMap</span><span class='hs-varop'>.</span><span class='hs-conid'>Types</span>
<a name="line-82"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Caching</span><span class='hs-varop'>.</span><span class='hs-conid'>ExpiringCacheMap</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span><span class='hs-varop'>.</span><span class='hs-conid'>Types</span>
<a name="line-83"></a>
<a name="line-84"></a><a name="newECMIO"></a><span class='hs-comment'>-- | Create a new expiring cache for retrieving uncached values via 'IO'</span>
<a name="line-85"></a><span class='hs-comment'>-- interaction (such as in the case of reading a file from disk), with </span>
<a name="line-86"></a><span class='hs-comment'>-- a shared state lock via an 'MV.MVar' to manage cache state.</span>
<a name="line-87"></a><span class='hs-comment'>--</span>
<a name="line-88"></a><span class='hs-comment'>-- Value request and time check request functions are provided as arguments.</span>
<a name="line-89"></a><span class='hs-comment'>--</span>
<a name="line-90"></a><span class='hs-comment'>-- The time check frequency value has to be 1 or higher, with higher values</span>
<a name="line-91"></a><span class='hs-comment'>-- postponing time checks for longer periods of time.</span>
<a name="line-92"></a><span class='hs-comment'>-- </span>
<a name="line-93"></a><span class='hs-comment'>-- A cache setting specifies how the cache should remove entries when the</span>
<a name="line-94"></a><span class='hs-comment'>-- cache becomes a certain size. The only constructor for this is</span>
<a name="line-95"></a><span class='hs-comment'>-- 'CacheWithLRUList'.</span>
<a name="line-96"></a><span class='hs-comment'>--</span>
<a name="line-97"></a><span class='hs-definition'>newECMIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>TimeUnits</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>IO</span> <span class='hs-conid'>TimeUnits</span><span class='hs-layout'>)</span>
<a name="line-98"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ECMIncr</span>
<a name="line-99"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>CacheSettings</span>
<a name="line-100"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>ECM</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>MV</span><span class='hs-varop'>.</span><span class='hs-conid'>MVar</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-101"></a><span class='hs-definition'>newECMIO</span> <span class='hs-varid'>retr</span> <span class='hs-varid'>gettime</span> <span class='hs-varid'>timecheckmodulo</span> <span class='hs-varid'>cachesettings</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-102"></a> <span class='hs-varid'>newECMForM</span> <span class='hs-varid'>retr</span> <span class='hs-varid'>gettime</span> <span class='hs-varid'>timecheckmodulo</span> <span class='hs-varid'>cachesettings</span>
<a name="line-103"></a> <span class='hs-conid'>MV</span><span class='hs-varop'>.</span><span class='hs-varid'>newMVar</span> <span class='hs-conid'>MV</span><span class='hs-varop'>.</span><span class='hs-varid'>modifyMVar</span> <span class='hs-conid'>MV</span><span class='hs-varop'>.</span><span class='hs-varid'>readMVar</span>
<a name="line-104"></a>
<a name="line-105"></a><a name="newECMForM"></a><span class='hs-comment'>-- | Create a new expiring cache along arbitrary monads with provided</span>
<a name="line-106"></a><span class='hs-comment'>-- functions to create cache state in 'Monad' m2, and modify and read</span>
<a name="line-107"></a><span class='hs-comment'>-- cache state in 'Monad' m1.</span>
<a name="line-108"></a><span class='hs-comment'>--</span>
<a name="line-109"></a><span class='hs-comment'>-- 'newECMIO' is just a wrapper to this function with 'MV.MVar' functions:</span>
<a name="line-110"></a><span class='hs-comment'>--</span>
<a name="line-111"></a><span class='hs-comment'>-- @</span>
<a name="line-112"></a><span class='hs-comment'>-- newECMIO retr gettime timecheckmodulo cachesettings =</span>
<a name="line-113"></a><span class='hs-comment'>-- newECMForM retr gettime timecheckmodulo cachesettings</span>
<a name="line-114"></a><span class='hs-comment'>-- 'MV.newMVar' 'MV.modifyMVar' 'MV.readMVar'</span>
<a name="line-115"></a><span class='hs-comment'>-- @</span>
<a name="line-116"></a><span class='hs-comment'>--</span>
<a name="line-117"></a><span class='hs-comment'>-- Value request and time check request functions are provided as arguments.</span>
<a name="line-118"></a><span class='hs-comment'>--</span>
<a name="line-119"></a><span class='hs-comment'>-- The time check frequency value has to be 1 or higher, with higher values</span>
<a name="line-120"></a><span class='hs-comment'>-- postponing time checks for longer periods of time.</span>
<a name="line-121"></a><span class='hs-comment'>-- </span>
<a name="line-122"></a><span class='hs-comment'>-- A cache setting specifies how the cache should remove entries when the</span>
<a name="line-123"></a><span class='hs-comment'>-- cache becomes a certain size. The only constructor for this is</span>
<a name="line-124"></a><span class='hs-comment'>-- 'CacheWithLRUList'.</span>
<a name="line-125"></a><span class='hs-comment'>--</span>
<a name="line-126"></a><span class='hs-definition'>newECMForM</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m1</span><span class='hs-layout'>,</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m1</span> <span class='hs-layout'>(</span><span class='hs-conid'>TimeUnits</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>m1</span> <span class='hs-conid'>TimeUnits</span><span class='hs-layout'>)</span>
<a name="line-127"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ECMIncr</span>
<a name="line-128"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>CacheSettings</span>
<a name="line-129"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ECMNewState</span> <span class='hs-varid'>m2</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span>
<a name="line-130"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ECMEnterState</span> <span class='hs-varid'>m1</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span>
<a name="line-131"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ECMReadState</span> <span class='hs-varid'>m1</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span>
<a name="line-132"></a> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m2</span> <span class='hs-layout'>(</span><span class='hs-conid'>ECM</span> <span class='hs-varid'>m1</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-133"></a><span class='hs-definition'>newECMForM</span> <span class='hs-varid'>retr</span> <span class='hs-varid'>gettime</span> <span class='hs-varid'>timecheckmodulo</span> <span class='hs-layout'>(</span><span class='hs-conid'>CacheWithLRUList</span> <span class='hs-varid'>minimumkeep</span> <span class='hs-varid'>removalsize</span> <span class='hs-varid'>compactlistsize</span><span class='hs-layout'>)</span>
<a name="line-134"></a> <span class='hs-varid'>newstate</span> <span class='hs-varid'>enterstate</span> <span class='hs-varid'>readstate</span> <span class='hs-keyglyph'>=</span>
<a name="line-135"></a> <span class='hs-keyword'>if</span> <span class='hs-varid'>timecheckmodulo</span> <span class='hs-varop'><=</span> <span class='hs-num'>0</span>
<a name="line-136"></a> <span class='hs-keyword'>then</span> <span class='hs-varid'>error</span> <span class='hs-str'>"Modulo time check must be 1 or higher."</span>
<a name="line-137"></a> <span class='hs-keyword'>else</span> <span class='hs-keyword'>do</span>
<a name="line-138"></a> <span class='hs-varid'>m'maps</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newstate</span> <span class='hs-varop'>$</span> <span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span> <span class='hs-conid'>Nothing</span><span class='hs-layout'>,</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conid'>[]</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span> <span class='hs-layout'>)</span>
<a name="line-139"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>retr</span><span class='hs-layout'>,</span> <span class='hs-varid'>gettime</span><span class='hs-layout'>,</span> <span class='hs-varid'>minimumkeep</span><span class='hs-layout'>,</span>
<a name="line-140"></a> <span class='hs-varid'>timecheckmodulo</span><span class='hs-layout'>,</span> <span class='hs-varid'>removalsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>compactlistsize</span><span class='hs-layout'>,</span>
<a name="line-141"></a> <span class='hs-varid'>enterstate</span><span class='hs-layout'>,</span> <span class='hs-varid'>readstate</span> <span class='hs-layout'>)</span>
<a name="line-142"></a>
<a name="line-143"></a>
<a name="line-144"></a><a name="lookupECM"></a><span class='hs-comment'>-- | Request a value associated with a key from the cache.</span>
<a name="line-145"></a><span class='hs-comment'>--</span>
<a name="line-146"></a><span class='hs-comment'>-- * If the value is not in the cache, the value will be requested through the </span>
<a name="line-147"></a><span class='hs-comment'>-- function defined when the 'ECM' value was created, its computation</span>
<a name="line-148"></a><span class='hs-comment'>-- returned and the value stored in the cache state map.</span>
<a name="line-149"></a><span class='hs-comment'>-- </span>
<a name="line-150"></a><span class='hs-comment'>-- * If the value is in the cache and has not expired, it will be returned.</span>
<a name="line-151"></a><span class='hs-comment'>-- </span>
<a name="line-152"></a><span class='hs-comment'>-- * If the value is in the cache and a new time is computed in the same</span>
<a name="line-153"></a><span class='hs-comment'>-- lookup, and the value has been determined to have since expired, it </span>
<a name="line-154"></a><span class='hs-comment'>-- will be discarded and a new value will be requested for this computation.</span>
<a name="line-155"></a><span class='hs-comment'>--</span>
<a name="line-156"></a><span class='hs-comment'>-- Every 'lookupECM' computation increments an accumulator in the cache state</span>
<a name="line-157"></a><span class='hs-comment'>-- which is used to keep track of the succession of key accesses. Based on the</span>
<a name="line-158"></a><span class='hs-comment'>-- parameters provided with the 'CacheWithLRUList' constructor, this history </span>
<a name="line-159"></a><span class='hs-comment'>-- of key accesses is then used to remove entries from the cache back down to </span>
<a name="line-160"></a><span class='hs-comment'>-- a minimum size. Also, when the modulo of the accumulator and the modulo </span>
<a name="line-161"></a><span class='hs-comment'>-- value computes to 0, the time request function is invoked. In some cases the </span>
<a name="line-162"></a><span class='hs-comment'>-- accumulator may get incremented more than once in a 'lookupECM' computation.</span>
<a name="line-163"></a><span class='hs-comment'>--</span>
<a name="line-164"></a><span class='hs-comment'>-- As the accumulator is a bound unsigned integer, when the accumulator</span>
<a name="line-165"></a><span class='hs-comment'>-- increments back to 0, the cache state is completely cleared.</span>
<a name="line-166"></a><span class='hs-comment'>--</span>
<a name="line-167"></a><span class='hs-comment'>-- The time request function is invoked in one of two different conditions</span>
<a name="line-168"></a><span class='hs-comment'>-- </span>
<a name="line-169"></a><span class='hs-comment'>-- * When a new key-value entry is requested, the current time is also</span>
<a name="line-170"></a><span class='hs-comment'>-- requested during the same lookup, as a recent time determination is</span>
<a name="line-171"></a><span class='hs-comment'>-- needed for a new entry in the key-value cache.</span>
<a name="line-172"></a><span class='hs-comment'>-- </span>
<a name="line-173"></a><span class='hs-comment'>-- * When the modulo of the accumulator and a specified value equals to 0.</span>
<a name="line-174"></a><span class='hs-comment'>--</span>
<a name="line-175"></a><span class='hs-comment'>-- When the current time is determined during a lookup, access times of the</span>
<a name="line-176"></a><span class='hs-comment'>-- entries in the key-value cache are compared with the new time to filter</span>
<a name="line-177"></a><span class='hs-comment'>-- out expired entries from the key-value map.</span>
<a name="line-178"></a><span class='hs-comment'>-- </span>
<a name="line-179"></a><span class='hs-definition'>lookupECM</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ECM</span> <span class='hs-varid'>m</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>v</span>
<a name="line-180"></a><span class='hs-definition'>lookupECM</span> <span class='hs-varid'>ecm</span> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-181"></a> <span class='hs-varid'>enter</span> <span class='hs-varid'>m'maps</span> <span class='hs-varop'>$</span>
<a name="line-182"></a> <span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-183"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>incr'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>incr</span> <span class='hs-varop'>+</span> <span class='hs-num'>1</span>
<a name="line-184"></a> <span class='hs-keyword'>in</span> <span class='hs-keyword'>if</span> <span class='hs-varid'>incr'</span> <span class='hs-varop'><</span> <span class='hs-varid'>incr</span>
<a name="line-185"></a> <span class='hs-comment'>-- Word incrementor has cycled back to 0,</span>
<a name="line-186"></a> <span class='hs-comment'>-- so may as well clear the cache completely.</span>
<a name="line-187"></a> <span class='hs-keyword'>then</span> <span class='hs-varid'>lookupECM'</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conid'>[]</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-num'>0</span><span class='hs-varop'>+</span><span class='hs-num'>1</span><span class='hs-layout'>)</span>
<a name="line-188"></a> <span class='hs-keyword'>else</span> <span class='hs-varid'>lookupECM'</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr</span><span class='hs-layout'>)</span> <span class='hs-varid'>incr'</span>
<a name="line-189"></a> <span class='hs-keyword'>where</span>
<a name="line-190"></a>
<a name="line-191"></a> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>retr</span><span class='hs-layout'>,</span> <span class='hs-varid'>gettime</span><span class='hs-layout'>,</span> <span class='hs-varid'>minimumkeep</span><span class='hs-layout'>,</span> <span class='hs-varid'>timecheckmodulo</span><span class='hs-layout'>,</span> <span class='hs-varid'>removalsize</span><span class='hs-layout'>,</span>
<a name="line-192"></a> <span class='hs-varid'>compactlistsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>enter</span><span class='hs-layout'>,</span> <span class='hs-sel'>_ro</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ecm</span>
<a name="line-193"></a>
<a name="line-194"></a> <span class='hs-comment'>-- Reversing the list first before turning into a map, so the higher value</span>
<a name="line-195"></a> <span class='hs-comment'>-- which is at the beginning will be at the end. And fromList retains the</span>
<a name="line-196"></a> <span class='hs-comment'>-- last value for a key in the list.</span>
<a name="line-197"></a> <span class='hs-varid'>mnub</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>toList</span> <span class='hs-varop'>.</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>fromList</span> <span class='hs-varop'>.</span> <span class='hs-varid'>reverse</span>
<a name="line-198"></a> <span class='hs-varid'>lookupECM'</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr</span><span class='hs-layout'>)</span> <span class='hs-varid'>incr'</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-199"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>uses'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>updateUses</span> <span class='hs-varid'>uses</span> <span class='hs-varid'>id</span> <span class='hs-varid'>incr'</span> <span class='hs-varid'>compactlistsize</span> <span class='hs-varid'>mnub</span>
<a name="line-200"></a> <span class='hs-layout'>(</span><span class='hs-varid'>ret</span><span class='hs-layout'>,</span> <span class='hs-varid'>do_again</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>det</span> <span class='hs-varid'>retr_state</span> <span class='hs-varid'>maps</span> <span class='hs-varid'>mapsize</span> <span class='hs-varid'>uses'</span> <span class='hs-varid'>incr'</span>
<a name="line-201"></a> <span class='hs-keyword'>if</span> <span class='hs-varid'>do_again</span>
<a name="line-202"></a> <span class='hs-keyword'>then</span> <span class='hs-keyword'>do</span> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state'</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps'</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize'</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses''</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr''</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ret</span>
<a name="line-203"></a> <span class='hs-varid'>uses'''</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>updateUses</span> <span class='hs-varid'>uses''</span> <span class='hs-varid'>id</span> <span class='hs-varid'>incr''</span> <span class='hs-varid'>compactlistsize</span> <span class='hs-varid'>mnub</span>
<a name="line-204"></a> <span class='hs-layout'>(</span><span class='hs-varid'>ret'</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>det</span> <span class='hs-varid'>retr_state'</span> <span class='hs-varid'>maps'</span> <span class='hs-varid'>mapsize'</span> <span class='hs-varid'>uses'''</span> <span class='hs-varid'>incr''</span>
<a name="line-205"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>ret'</span>
<a name="line-206"></a> <span class='hs-keyword'>else</span> <span class='hs-varid'>return</span> <span class='hs-varid'>ret</span>
<a name="line-207"></a>
<a name="line-208"></a> <span class='hs-varid'>det</span> <span class='hs-varid'>retr_state</span> <span class='hs-varid'>maps</span> <span class='hs-varid'>mapsize</span> <span class='hs-varid'>uses'</span> <span class='hs-varid'>incr'</span> <span class='hs-keyglyph'>=</span>
<a name="line-209"></a> <span class='hs-varid'>detECM</span> <span class='hs-layout'>(</span><span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>lookup</span> <span class='hs-varid'>id</span> <span class='hs-varid'>maps</span><span class='hs-layout'>)</span> <span class='hs-varid'>retr_state</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr</span> <span class='hs-varid'>retr_state</span> <span class='hs-varid'>id</span><span class='hs-layout'>)</span>
<a name="line-210"></a> <span class='hs-layout'>(</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>time_r</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>insert</span> <span class='hs-varid'>id</span> <span class='hs-varid'>time_r</span> <span class='hs-varid'>maps</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-211"></a> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>time_r</span> <span class='hs-varid'>keepuses</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>insert</span> <span class='hs-varid'>id</span> <span class='hs-varid'>time_r</span> <span class='hs-varop'>$!</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>intersection</span> <span class='hs-varid'>maps</span> <span class='hs-varop'>$</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>fromList</span> <span class='hs-varid'>keepuses</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-212"></a> <span class='hs-varid'>mnub</span><span class='hs-layout'>,</span> <span class='hs-varid'>minimumkeep</span><span class='hs-layout'>,</span> <span class='hs-varid'>removalsize</span> <span class='hs-layout'>)</span>
<a name="line-213"></a> <span class='hs-varid'>gettime</span>
<a name="line-214"></a> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>filter</span>
<a name="line-215"></a> <span class='hs-varid'>mapsize</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>size</span>
<a name="line-216"></a> <span class='hs-varid'>uses'</span> <span class='hs-varid'>incr'</span> <span class='hs-varid'>timecheckmodulo</span> <span class='hs-varid'>maps</span>
<a name="line-217"></a>
<a name="line-218"></a>
<a name="line-219"></a><a name="getValReqState"></a><span class='hs-definition'>getValReqState</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ECM</span> <span class='hs-varid'>m</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-220"></a><span class='hs-definition'>getValReqState</span> <span class='hs-varid'>ecm</span> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-221"></a> <span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>read</span> <span class='hs-varid'>m'maps</span>
<a name="line-222"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>retr_state</span>
<a name="line-223"></a> <span class='hs-keyword'>where</span>
<a name="line-224"></a>
<a name="line-225"></a> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>read</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ecm</span>
<a name="line-226"></a>
<a name="line-227"></a>
<a name="line-228"></a><a name="invalidate"></a><span class='hs-comment'>-- | Invalidates a key from the cache and returns its value if any.</span>
<a name="line-229"></a><span class='hs-comment'>-- Note that this is a sequential composition of a read and modify of the</span>
<a name="line-230"></a><span class='hs-comment'>-- mutable cache container (e.g. 'MV.readMVar' followed by 'MV.modifyMVar'</span>
<a name="line-231"></a><span class='hs-comment'>-- with 'newECMIO' instances).</span>
<a name="line-232"></a><span class='hs-comment'>--</span>
<a name="line-233"></a><span class='hs-definition'>invalidate</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ECM</span> <span class='hs-varid'>m</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-234"></a><span class='hs-definition'>invalidate</span> <span class='hs-varid'>ecm</span> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-235"></a> <span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps0</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>read</span> <span class='hs-varid'>m'maps</span>
<a name="line-236"></a> <span class='hs-keyword'>case</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>lookup</span> <span class='hs-varid'>id</span> <span class='hs-varid'>maps0</span> <span class='hs-keyword'>of</span>
<a name="line-237"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>time_prev0</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-238"></a> <span class='hs-varid'>prev0'</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>enter</span> <span class='hs-varid'>m'maps</span> <span class='hs-varop'>$</span>
<a name="line-239"></a> <span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-240"></a> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>prev</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-241"></a> <span class='hs-keyword'>case</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>lookup</span> <span class='hs-varid'>id</span> <span class='hs-varid'>maps</span> <span class='hs-keyword'>of</span>
<a name="line-242"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>time_prev</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>time_prev</span>
<a name="line-243"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>time_prev0</span>
<a name="line-244"></a> <span class='hs-varid'>maps'</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>delete</span> <span class='hs-varid'>id</span> <span class='hs-varid'>maps</span>
<a name="line-245"></a> <span class='hs-keyword'>in</span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps'</span><span class='hs-layout'>,</span> <span class='hs-varid'>mapsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>uses</span><span class='hs-layout'>,</span> <span class='hs-varid'>incr</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>prev</span><span class='hs-layout'>)</span>
<a name="line-246"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>prev0'</span>
<a name="line-247"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-conid'>Nothing</span>
<a name="line-248"></a> <span class='hs-keyword'>where</span>
<a name="line-249"></a> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>compactlistsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>enter</span><span class='hs-layout'>,</span> <span class='hs-varid'>read</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ecm</span>
<a name="line-250"></a>
<a name="line-251"></a>
<a name="line-252"></a><a name="invalidateCache"></a><span class='hs-comment'>-- | Invalidates the entire cache and returns the last key and value if any.</span>
<a name="line-253"></a><span class='hs-comment'>-- Note that this is a sequential composition of a read and modify of the</span>
<a name="line-254"></a><span class='hs-comment'>-- mutable cache container (e.g. 'MV.readMVar' followed by 'MV.modifyMVar'</span>
<a name="line-255"></a><span class='hs-comment'>-- with 'newECMIO' instances).</span>
<a name="line-256"></a><span class='hs-comment'>--</span>
<a name="line-257"></a><span class='hs-definition'>invalidateCache</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ECM</span> <span class='hs-varid'>m</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-258"></a><span class='hs-definition'>invalidateCache</span> <span class='hs-varid'>ecm</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-259"></a> <span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps0</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-varid'>uses0</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>read</span> <span class='hs-varid'>m'maps</span>
<a name="line-260"></a> <span class='hs-keyword'>case</span> <span class='hs-layout'>(</span><span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>toList</span> <span class='hs-varop'>$</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>intersection</span> <span class='hs-layout'>(</span><span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>fromList</span> <span class='hs-varop'>$</span> <span class='hs-varid'>reverse</span> <span class='hs-varid'>uses0</span><span class='hs-layout'>)</span> <span class='hs-varid'>maps0</span><span class='hs-layout'>)</span> <span class='hs-keyword'>of</span>
<a name="line-261"></a> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-conid'>Nothing</span>
<a name="line-262"></a> <span class='hs-varid'>uses0'</span> <span class='hs-keyglyph'>-></span>
<a name="line-263"></a> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-varid'>id</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>L</span><span class='hs-varop'>.</span><span class='hs-varid'>maximumBy</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span><span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>compare</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-varid'>uses0'</span> <span class='hs-keyword'>in</span>
<a name="line-264"></a> <span class='hs-keyword'>case</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>lookup</span> <span class='hs-varid'>id</span> <span class='hs-varid'>maps0</span> <span class='hs-keyword'>of</span>
<a name="line-265"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>time_prev0</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-266"></a> <span class='hs-varid'>prev0'</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>enter</span> <span class='hs-varid'>m'maps</span> <span class='hs-varop'>$</span>
<a name="line-267"></a> <span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps</span><span class='hs-layout'>,</span> <span class='hs-sel'>_mapsize</span><span class='hs-layout'>,</span> <span class='hs-sel'>_uses</span><span class='hs-layout'>,</span> <span class='hs-sel'>_incr</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-268"></a> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>prev</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-269"></a> <span class='hs-keyword'>case</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>lookup</span> <span class='hs-varid'>id</span> <span class='hs-varid'>maps</span> <span class='hs-keyword'>of</span>
<a name="line-270"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>time_prev</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>time_prev</span>
<a name="line-271"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>time_prev0</span>
<a name="line-272"></a> <span class='hs-keyword'>in</span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-varid'>retr_state</span><span class='hs-layout'>,</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conid'>[]</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-num'>0</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>prev</span><span class='hs-layout'>)</span>
<a name="line-273"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>id</span><span class='hs-layout'>,</span> <span class='hs-varid'>prev0'</span><span class='hs-layout'>)</span>
<a name="line-274"></a> <span class='hs-keyword'>where</span>
<a name="line-275"></a> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>compactlistsize</span><span class='hs-layout'>,</span> <span class='hs-varid'>enter</span><span class='hs-layout'>,</span> <span class='hs-varid'>read</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ecm</span>
<a name="line-276"></a>
<a name="line-277"></a>
<a name="line-278"></a><a name="keysCached"></a><span class='hs-comment'>-- | List of keys in the cache map without performing a time check, returning</span>
<a name="line-279"></a><span class='hs-comment'>-- both stored keys that are expired and keys that are not expired. keys are</span>
<a name="line-280"></a><span class='hs-comment'>-- in an unspecified order.</span>
<a name="line-281"></a><span class='hs-comment'>--</span>
<a name="line-282"></a><span class='hs-definition'>keysCached</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ECM</span> <span class='hs-varid'>m</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>k</span><span class='hs-keyglyph'>]</span>
<a name="line-283"></a><span class='hs-definition'>keysCached</span> <span class='hs-varid'>ecm</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-284"></a> <span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps0</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>read</span> <span class='hs-varid'>m'maps</span>
<a name="line-285"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>keys</span> <span class='hs-varid'>maps0</span>
<a name="line-286"></a> <span class='hs-keyword'>where</span>
<a name="line-287"></a> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>read</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ecm</span>
<a name="line-288"></a>
<a name="line-289"></a>
<a name="line-290"></a><a name="keysNotExpired"></a><span class='hs-comment'>-- | List of keys in the cache map that are not expired values. A time check</span>
<a name="line-291"></a><span class='hs-comment'>-- is always performed to compare with the elapsed time left with each key.</span>
<a name="line-292"></a><span class='hs-comment'>-- The cache state is not modified and the time check is not performed from</span>
<a name="line-293"></a><span class='hs-comment'>-- within a modifying state context, e.g. not within 'MV.modifyMVar' with a </span>
<a name="line-294"></a><span class='hs-comment'>-- 'newECMIO' instance. Keys are in an unspecified order. </span>
<a name="line-295"></a><span class='hs-comment'>--</span>
<a name="line-296"></a><span class='hs-definition'>keysNotExpired</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ECM</span> <span class='hs-varid'>m</span> <span class='hs-varid'>mv</span> <span class='hs-varid'>s</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-conid'>HashMap</span> <span class='hs-varid'>k</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>k</span><span class='hs-keyglyph'>]</span>
<a name="line-297"></a><span class='hs-definition'>keysNotExpired</span> <span class='hs-varid'>ecm</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-298"></a> <span class='hs-conid'>CacheState</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>maps0</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>read</span> <span class='hs-varid'>m'maps</span>
<a name="line-299"></a> <span class='hs-varid'>current_time</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>gettime</span>
<a name="line-300"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-varid'>detNotExpired</span> <span class='hs-varid'>current_time</span> <span class='hs-varop'>$</span> <span class='hs-conid'>HM</span><span class='hs-varop'>.</span><span class='hs-varid'>toList</span> <span class='hs-varid'>maps0</span>
<a name="line-301"></a> <span class='hs-keyword'>where</span>
<a name="line-302"></a> <span class='hs-conid'>ECM</span> <span class='hs-layout'>(</span> <span class='hs-varid'>m'maps</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>gettime</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>read</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ecm</span>
<a name="line-303"></a>
<a name="line-304"></a>
<a name="line-305"></a>
<a name="line-306"></a><span class='hs-comment'>{-
<a name="line-307"></a>
<a name="line-308"></a>These functions would require inclusion of a enter_ function (like modifyMVar_)
<a name="line-309"></a>
<a name="line-310"></a>putValReqState :: (Monad m, Eq k, Hashable k) => ECM m mv s HM.HashMap k v -> k -> Maybe s -> m (Maybe s)
<a name="line-311"></a>putValReqState ecm id new_state = do
<a name="line-312"></a> enter m'maps $
<a name="line-313"></a> \(CacheState (retr_state, maps, mapsize, uses, incr)) ->
<a name="line-314"></a> return (CacheState (new_state, maps, mapsize, uses, incr), retr_state)
<a name="line-315"></a> where
<a name="line-316"></a>
<a name="line-317"></a> ECM ( m'maps, _, _, _, _, _, _, _, enter_ _ro ) = ecm
<a name="line-318"></a>
<a name="line-319"></a>--
<a name="line-320"></a>clearCache :: (Monad m, Eq k, Hashable k) => ECM m mv s HM.HashMap k v -> m ()
<a name="line-321"></a>clearCache ecm = do
<a name="line-322"></a> enter_ m'maps $
<a name="line-323"></a> \(CacheState (retr_state, maps, mapsize, uses, incr)) ->
<a name="line-324"></a> return $ CacheState (retr_state, HM.empty, 0, ([], 0), 0)
<a name="line-325"></a> where
<a name="line-326"></a> ECM ( m'maps, _, _, _, _, _, _, _, enter_, _ ) = ecm
<a name="line-327"></a>
<a name="line-328"></a>-}</span>
<a name="line-329"></a>
<a name="line-330"></a>
<a name="line-331"></a><span class='hs-comment'>{-
<a name="line-332"></a>-- This function differs from 'lookupECM' only in the case that the value
<a name="line-333"></a>-- being requested also causes a new time to have been computed during the
<a name="line-334"></a>-- same lookup, and have been found to be out of date. When the condition
<a name="line-335"></a>-- happens, this function returns the old cached value without attempting
<a name="line-336"></a>-- to request a new value, despite being out of date. However, it does
<a name="line-337"></a>-- clear the key from the key-value store for the next request.
<a name="line-338"></a>--
<a name="line-339"></a>lookupECMUse :: (Monad m, Eq k, Hashable k) => ECM m mv s HM.HashMap k v -> k -> m v
<a name="line-340"></a>lookupECMUse ecm id = do
<a name="line-341"></a> enter m'maps $
<a name="line-342"></a> \(CacheState (retr_state, maps, mapsize, uses, incr)) ->
<a name="line-343"></a> let incr' = incr + 1
<a name="line-344"></a> in if incr' < incr
<a name="line-345"></a> -- Word incrementor has cycled back to 0,
<a name="line-346"></a> -- so may as well clear the cache completely.
<a name="line-347"></a> then lookupECM' (retr_state, HM.empty, 0, ([], 0), 0) (0+1)
<a name="line-348"></a> else lookupECM' (retr_state, maps, mapsize, uses, incr) incr'
<a name="line-349"></a> where
<a name="line-350"></a>
<a name="line-351"></a> ECM ( m'maps, retr, gettime, minimumkeep, timecheckmodulo, removalsize,
<a name="line-352"></a> compactlistsize, enter, _ro ) = ecm
<a name="line-353"></a>
<a name="line-354"></a> mnub = HM.toList . HM.fromList . reverse
<a name="line-355"></a> lookupECM' (retr_state, maps, mapsize, uses, incr) incr' = do
<a name="line-356"></a> let uses' = updateUses uses id incr' compactlistsize mnub
<a name="line-357"></a> (ret, _) <-
<a name="line-358"></a> detECM (HM.lookup id maps) retr_state (retr retr_state id)
<a name="line-359"></a> ( (\time_r -> HM.insert id time_r maps),
<a name="line-360"></a> (\time_r keepuses -> HM.insert id time_r $! HM.intersection maps $ HM.fromList keepuses),
<a name="line-361"></a> mnub, minimumkeep, removalsize)
<a name="line-362"></a> gettime
<a name="line-363"></a> HM.filter mapsize HM.size
<a name="line-364"></a> uses' incr' timecheckmodulo maps
<a name="line-365"></a> return ret
<a name="line-366"></a>-}</span>
<a name="line-367"></a>
<a name="line-368"></a>
<a name="line-369"></a><a name="consistentDuration"></a><span class='hs-comment'>-- | Used with 'newECMIO' or 'newECMForM' to provide a consistent duration for requested values.</span>
<a name="line-370"></a><span class='hs-definition'>consistentDuration</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>k</span><span class='hs-layout'>,</span> <span class='hs-conid'>Hashable</span> <span class='hs-varid'>k</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>TimeUnits</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>TimeUnits</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-371"></a><span class='hs-definition'>consistentDuration</span> <span class='hs-varid'>duration</span> <span class='hs-varid'>fun</span> <span class='hs-keyglyph'>=</span>
<a name="line-372"></a> <span class='hs-keyglyph'>\</span><span class='hs-varid'>state</span> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-373"></a> <span class='hs-varid'>ret</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>fun</span> <span class='hs-varid'>state</span> <span class='hs-varid'>id</span>
<a name="line-374"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>duration</span><span class='hs-layout'>,</span> <span class='hs-varid'>ret</span><span class='hs-layout'>)</span>
<a name="line-375"></a>
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