--- /dev/null
+{-# OPTIONS -fno-warn-name-shadowing #-}
+
+module Language.Core.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<digit>
+
+* "(# #)" 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)
+
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