filecache

A multi-platform (Linux, Mac, Windows) cache system associating values to files. The values are automatically discarded when the files are modified.

Example usage:

module Main where

import Data.FileCache

countlines :: FilePath -> IO (Either String Int)
countlines = fmap (Right . length . lines) . readFile

main :: IO ()
main = do
    cache <- newFileCache :: IO (FileCache Int)
    let countlines' p = lazyQuery cache p (countlines p)
    countlines' "/tmp/somefile" >>= print

This should either print Left "/tmp/somefile: openFile: does not exist (No such file or directory)" or Right n, where n is the line count.

Subsequent calls to countlines' will read the data from the cache if the file hasn't been modified, or will run the original computation again.