60 lines
1.5 KiB
Haskell
60 lines
1.5 KiB
Haskell
{-|
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This modules defines the data structure used
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to store the URLs in memory and on disk.
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-}
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module Breve.UrlTable
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( UrlTable
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, load
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, save
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, insert
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, extract
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) where
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import Breve.Generator
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import Control.Monad (forever)
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import Control.Concurrent (forkIO, threadDelay)
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import Text.Read (readMaybe)
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import qualified Data.HashTable.IO as H
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-- | The hash table that stores URLs
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type UrlTable = H.CuckooHashTable Name Url
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-- | Periodically save a 'UrlTable' to a file
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sync :: UrlTable -> FilePath -> IO ()
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sync table file = forever $ do
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threadDelay (round 3.0e8)
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save table file
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-- | Writes a 'UrlTable' to a file
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--
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-- The table is stored in a text file
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-- as Haskell code for semplicity.
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save :: UrlTable -> FilePath -> IO ()
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save table file = do
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content <- show <$> H.toList table
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writeFile file content
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putStrLn "\n[breve] url table synced."
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-- | Loads a URL table from a file
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--
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-- Once the file is loaded it will be synced
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-- periodically (every 5min) on the disk.
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load :: FilePath -> IO UrlTable
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load file = do
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content <- readFile file
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table <- case readMaybe content of
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Just list -> H.fromList list
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Nothing -> H.new
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forkIO (sync table file)
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return table
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-- | Insert the URL in a table and return the name
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insert :: UrlTable -> Url -> IO Name
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insert table url = H.insert table new url >> return new
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where new = nameHash url
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-- | Lookup a table for the associated URL
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extract :: UrlTable -> Name -> IO (Maybe Url)
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extract = H.lookup
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