module Encoding where import Data.Char import Numeric -- tjc: TODO: Copied straight out of Encoding.hs. -- Ugh, maybe we can avoid this copy-pasta... -- ----------------------------------------------------------------------------- -- The Z-encoding {- This is the main name-encoding and decoding function. It encodes any string into a string that is acceptable as a C name. This is done right before we emit a symbol name into the compiled C or asm code. Z-encoding of strings is cached in the FastString interface, so we never encode the same string more than once. The basic encoding scheme is this. * Tuples (,,,) are coded as Z3T * Alphabetic characters (upper and lower) and digits all translate to themselves; except 'Z', which translates to 'ZZ' and 'z', which translates to 'zz' We need both so that we can preserve the variable/tycon distinction * Most other printable characters translate to 'zx' or 'Zx' for some alphabetic character x * The others translate as 'znnnU' where 'nnn' is the decimal number of the character Before After -------------------------- Trak Trak foo_wib foozuwib > zg >1 zg1 foo# foozh foo## foozhzh foo##1 foozhzh1 fooZ fooZZ :+ ZCzp () Z0T 0-tuple (,,,,) Z5T 5-tuple (# #) Z1H unboxed 1-tuple (note the space) (#,,,,#) Z5H unboxed 5-tuple (NB: There is no Z1T nor Z0H.) -} type UserString = String -- As the user typed it type EncodedString = String -- Encoded form zEncodeString :: UserString -> EncodedString zEncodeString cs = case maybe_tuple cs of Just n -> n -- Tuples go to Z2T etc Nothing -> go cs where go [] = [] go (c:cs) = encode_ch c ++ go cs unencodedChar :: Char -> Bool -- True for chars that don't need encoding unencodedChar 'Z' = False unencodedChar 'z' = False unencodedChar c = c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' encode_ch :: Char -> EncodedString encode_ch c | unencodedChar c = [c] -- Common case first -- Constructors encode_ch '(' = "ZL" -- Needed for things like (,), and (->) encode_ch ')' = "ZR" -- For symmetry with ( encode_ch '[' = "ZM" encode_ch ']' = "ZN" encode_ch ':' = "ZC" encode_ch 'Z' = "ZZ" -- Variables encode_ch 'z' = "zz" encode_ch '&' = "za" encode_ch '|' = "zb" encode_ch '^' = "zc" encode_ch '$' = "zd" encode_ch '=' = "ze" encode_ch '>' = "zg" encode_ch '#' = "zh" encode_ch '.' = "zi" encode_ch '<' = "zl" encode_ch '-' = "zm" encode_ch '!' = "zn" encode_ch '+' = "zp" encode_ch '\'' = "zq" encode_ch '\\' = "zr" encode_ch '/' = "zs" encode_ch '*' = "zt" encode_ch '_' = "zu" encode_ch '%' = "zv" encode_ch c = 'z' : if isDigit (head hex_str) then hex_str else '0':hex_str where hex_str = showHex (ord c) "U" -- ToDo: we could improve the encoding here in various ways. -- eg. strings of unicode characters come out as 'z1234Uz5678U', we -- could remove the 'U' in the middle (the 'z' works as a separator). showHex = showIntAtBase 16 intToDigit -- needed because prior to GHC 6.2, Numeric.showHex added a "0x" prefix zDecodeString :: EncodedString -> UserString zDecodeString [] = [] zDecodeString ('Z' : d : rest) | isDigit d = decode_tuple d rest | otherwise = decode_upper d : zDecodeString rest zDecodeString ('z' : d : rest) | isDigit d = decode_num_esc d rest | otherwise = decode_lower d : zDecodeString rest zDecodeString (c : rest) = c : zDecodeString rest decode_upper, decode_lower :: Char -> Char decode_upper 'L' = '(' decode_upper 'R' = ')' decode_upper 'M' = '[' decode_upper 'N' = ']' decode_upper 'C' = ':' decode_upper 'Z' = 'Z' decode_upper ch = {-pprTrace "decode_upper" (char ch)-} ch decode_lower 'z' = 'z' decode_lower 'a' = '&' decode_lower 'b' = '|' decode_lower 'c' = '^' decode_lower 'd' = '$' decode_lower 'e' = '=' decode_lower 'g' = '>' decode_lower 'h' = '#' decode_lower 'i' = '.' decode_lower 'l' = '<' decode_lower 'm' = '-' decode_lower 'n' = '!' decode_lower 'p' = '+' decode_lower 'q' = '\'' decode_lower 'r' = '\\' decode_lower 's' = '/' decode_lower 't' = '*' decode_lower 'u' = '_' decode_lower 'v' = '%' decode_lower ch = {-pprTrace "decode_lower" (char ch)-} ch -- Characters not having a specific code are coded as z224U (in hex) decode_num_esc :: Char -> EncodedString -> UserString decode_num_esc d rest = go (digitToInt d) rest where go n (c : rest) | isHexDigit c = go (16*n + digitToInt c) rest go n ('U' : rest) = chr n : zDecodeString rest go n other = error ("decode_num_esc: " ++ show n ++ ' ':other) decode_tuple :: Char -> EncodedString -> UserString decode_tuple d rest = go (digitToInt d) rest where -- NB. recurse back to zDecodeString after decoding the tuple, because -- the tuple might be embedded in a longer name. go n (c : rest) | isDigit c = go (10*n + digitToInt c) rest go 0 ('T':rest) = "()" ++ zDecodeString rest go n ('T':rest) = '(' : replicate (n-1) ',' ++ ")" ++ zDecodeString rest go 1 ('H':rest) = "(# #)" ++ zDecodeString rest go n ('H':rest) = '(' : '#' : replicate (n-1) ',' ++ "#)" ++ zDecodeString rest go n other = error ("decode_tuple: " ++ show n ++ ' ':other) {- Tuples are encoded as Z3T or Z3H for 3-tuples or unboxed 3-tuples respectively. No other encoding starts Z * "(# #)" is the tycon for an unboxed 1-tuple (not 0-tuple) There are no unboxed 0-tuples. * "()" is the tycon for a boxed 0-tuple. There are no boxed 1-tuples. -} maybe_tuple :: UserString -> Maybe EncodedString maybe_tuple "(# #)" = Just("Z1H") maybe_tuple ('(' : '#' : cs) = case count_commas (0::Int) cs of (n, '#' : ')' : _) -> Just ('Z' : shows (n+1) "H") _ -> Nothing maybe_tuple "()" = Just("Z0T") maybe_tuple ('(' : cs) = case count_commas (0::Int) cs of (n, ')' : _) -> Just ('Z' : shows (n+1) "T") _ -> Nothing maybe_tuple _ = Nothing count_commas :: Int -> String -> (Int, String) count_commas n (',' : cs) = count_commas (n+1) cs count_commas n cs = (n,cs)