69 lines
2 KiB
Haskell
69 lines
2 KiB
Haskell
{- Calculating a SHA checksum with an external command.
|
|
-
|
|
- This is typically a bit faster than using Haskell libraries,
|
|
- by around 1% to 10%. Worth it for really big files.
|
|
-
|
|
- Copyright 2011-2013 Joey Hess <id@joeyh.name>
|
|
-
|
|
- License: BSD-2-clause
|
|
-}
|
|
|
|
{-# OPTIONS_GHC -fno-warn-tabs #-}
|
|
|
|
module Utility.ExternalSHA (externalSHA) where
|
|
|
|
import Utility.SafeCommand
|
|
import Utility.Process
|
|
import Utility.FileSystemEncoding
|
|
import Utility.Misc
|
|
import Utility.Exception
|
|
|
|
import Data.List
|
|
import Data.Char
|
|
import System.IO
|
|
|
|
externalSHA :: String -> Int -> FilePath -> IO (Either String String)
|
|
externalSHA command shasize file = do
|
|
v <- tryNonAsync $ readsha $ toCommand [File file]
|
|
return $ case v of
|
|
Right s -> sanitycheck =<< parse (lines s)
|
|
Left _ -> Left (command ++ " failed")
|
|
where
|
|
readsha args = withHandle StdoutHandle createProcessSuccess p $ \h -> do
|
|
fileEncoding h
|
|
output <- hGetContentsStrict h
|
|
hClose h
|
|
return output
|
|
where
|
|
p = (proc command args) { std_out = CreatePipe }
|
|
|
|
{- The first word of the output is taken to be the sha. -}
|
|
parse [] = bad
|
|
parse (l:_)
|
|
| null sha = bad
|
|
-- sha is prefixed with \ when filename contains certian chars
|
|
| "\\" `isPrefixOf` sha = Right $ drop 1 sha
|
|
| otherwise = Right sha
|
|
where
|
|
sha = fst $ separate (== ' ') l
|
|
bad = Left $ command ++ " parse error"
|
|
|
|
{- Check that we've correctly parsing the output of the command,
|
|
- by making sure the sha we read is of the expected length
|
|
- and contains only the right characters. -}
|
|
sanitycheck sha
|
|
| length sha /= expectedSHALength shasize =
|
|
Left $ "Failed to parse the output of " ++ command
|
|
| any (`notElem` "0123456789abcdef") sha' =
|
|
Left $ "Unexpected character in output of " ++ command ++ "\"" ++ sha ++ "\""
|
|
| otherwise = Right sha'
|
|
where
|
|
sha' = map toLower sha
|
|
|
|
expectedSHALength :: Int -> Int
|
|
expectedSHALength 1 = 40
|
|
expectedSHALength 256 = 64
|
|
expectedSHALength 512 = 128
|
|
expectedSHALength 224 = 56
|
|
expectedSHALength 384 = 96
|
|
expectedSHALength _ = 0
|