94 lines
2.8 KiB
Haskell
94 lines
2.8 KiB
Haskell
{- Caching a file's inode, size, and modification time to see when it's changed.
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-
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- Copyright 2013 Joey Hess <joey@kitenet.net>
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-
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- License: BSD-2-clause
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-}
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module Utility.InodeCache where
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import Common
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import System.PosixCompat.Types
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import Utility.QuickCheck
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data InodeCachePrim = InodeCachePrim FileID FileOffset EpochTime
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deriving (Show, Eq, Ord)
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newtype InodeCache = InodeCache InodeCachePrim
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deriving (Show)
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{- Inode caches can be compared in two different ways, either weakly
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- or strongly. -}
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data InodeComparisonType = Weakly | Strongly
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deriving (Eq, Ord)
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{- Strong comparison, including inodes. -}
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compareStrong :: InodeCache -> InodeCache -> Bool
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compareStrong (InodeCache x) (InodeCache y) = x == y
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{- Weak comparison of the inode caches, comparing the size and mtime,
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- but not the actual inode. Useful when inodes have changed, perhaps
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- due to some filesystems being remounted. -}
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compareWeak :: InodeCache -> InodeCache -> Bool
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compareWeak (InodeCache (InodeCachePrim _ size1 mtime1)) (InodeCache (InodeCachePrim _ size2 mtime2)) =
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size1 == size2 && mtime1 == mtime2
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compareBy :: InodeComparisonType -> InodeCache -> InodeCache -> Bool
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compareBy Strongly = compareStrong
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compareBy Weakly = compareWeak
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{- For use in a Map; it's determined at creation time whether this
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- uses strong or weak comparison for Eq. -}
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data InodeCacheKey = InodeCacheKey InodeComparisonType InodeCachePrim
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deriving (Ord)
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instance Eq InodeCacheKey where
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(InodeCacheKey ctx x) == (InodeCacheKey cty y) =
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compareBy (maximum [ctx,cty]) (InodeCache x ) (InodeCache y)
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inodeCacheToKey :: InodeComparisonType -> InodeCache -> InodeCacheKey
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inodeCacheToKey ct (InodeCache prim) = InodeCacheKey ct prim
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inodeCacheToMtime :: InodeCache -> EpochTime
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inodeCacheToMtime (InodeCache (InodeCachePrim _ _ mtime)) = mtime
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showInodeCache :: InodeCache -> String
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showInodeCache (InodeCache (InodeCachePrim inode size mtime)) = unwords
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[ show inode
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, show size
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, show mtime
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]
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readInodeCache :: String -> Maybe InodeCache
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readInodeCache s = case words s of
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(inode:size:mtime:_) ->
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let prim = InodeCachePrim
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<$> readish inode
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<*> readish size
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<*> readish mtime
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in InodeCache <$> prim
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_ -> Nothing
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genInodeCache :: FilePath -> IO (Maybe InodeCache)
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genInodeCache f = catchDefaultIO Nothing $ toInodeCache <$> getFileStatus f
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toInodeCache :: FileStatus -> Maybe InodeCache
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toInodeCache s
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| isRegularFile s = Just $ InodeCache $ InodeCachePrim
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(fileID s)
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(fileSize s)
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(modificationTime s)
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| otherwise = Nothing
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instance Arbitrary InodeCache where
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arbitrary =
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let prim = InodeCachePrim
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<$> arbitrary
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<*> arbitrary
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<*> arbitrary
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in InodeCache <$> prim
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prop_read_show_inodecache :: InodeCache -> Bool
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prop_read_show_inodecache c = case readInodeCache (showInodeCache c) of
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Nothing -> False
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Just c' -> compareStrong c c'
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