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{- Some git commands output encoded filenames, in a rather annoyingly complex
- C-style encoding.
-
- Copyright 2010, 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git.Filename where
import qualified Codec.Binary.UTF8.String
import Data.Char
import Data.Word (Word8)
import Text.Printf
decode :: String -> FilePath
decode [] = []
decode f@(c:s)
-- encoded strings will be inside double quotes
| c == '"' = unescape ("", middle)
| otherwise = f
where
e = '\\'
middle = init s
unescape (b, []) = b
-- look for escapes starting with '\'
unescape (b, v) = b ++ beginning ++ unescape (handle rest)
where
pair = span (/= e) v
beginning = fst pair
rest = snd pair
isescape x = x == e
-- \NNN is an octal encoded character
handle (x:n1:n2:n3:rest)
| isescape x && alloctal = (fromoctal, rest)
where
alloctal = isOctDigit n1 &&
isOctDigit n2 &&
isOctDigit n3
fromoctal = [chr $ readoctal [n1, n2, n3]]
readoctal o = read $ "0o" ++ o :: Int
-- \C is used for a few special characters
handle (x:nc:rest)
| isescape x = ([echar nc], rest)
where
echar 'a' = '\a'
echar 'b' = '\b'
echar 'f' = '\f'
echar 'n' = '\n'
echar 'r' = '\r'
echar 't' = '\t'
echar 'v' = '\v'
echar a = a
handle n = ("", n)
{- Should not need to use this, except for testing decode. -}
encode :: FilePath -> String
encode s = foldl (++) "\"" (map echar s) ++ "\""
where
e c = '\\' : [c]
echar '\a' = e 'a'
echar '\b' = e 'b'
echar '\f' = e 'f'
echar '\n' = e 'n'
echar '\r' = e 'r'
echar '\t' = e 't'
echar '\v' = e 'v'
echar '\\' = e '\\'
echar '"' = e '"'
echar x
| ord x < 0x20 = e_num x -- low ascii
| ord x >= 256 = e_utf x
| ord x > 0x7E = e_num x -- high ascii
| otherwise = [x] -- printable ascii
where
showoctal i = '\\' : printf "%03o" i
e_num c = showoctal $ ord c
-- unicode character is decomposed to
-- Word8s and each is shown in octal
e_utf c = showoctal =<< (Codec.Binary.UTF8.String.encode [c] :: [Word8])
{- for quickcheck -}
prop_idempotent_deencode :: String -> Bool
prop_idempotent_deencode s = s == decode (encode s)
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