diff --git a/UTF8.lhs b/UTF8.lhs new file mode 100644 --- /dev/null +++ b/UTF8.lhs @@ -0,0 +1,340 @@ +Copyright (c) 2002, members of the Haskell Internationalisation Working +Group All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + +* Redistributions of source code must retain the above copyright notice, + this list of conditions and the following disclaimer. +* Redistributions in binary form must reproduce the above copyright notice, + this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. +* Neither the name of the Haskell Internationalisation Working Group nor + the names of its contributors may be used to endorse or promote products + derived from this software without specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" +AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE +LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +POSSIBILITY OF SUCH DAMAGE. + +This module provides lazy stream encoding/decoding facilities for UTF-8, +the Unicode Transformation Format with 8-bit words. + +2002-09-02 Sven Moritz Hallberg + + +> module UTF8 where + +> import Data.Char (ord, chr) +> import Data.Word (Word8, Word16, Word32) +> import Data.Bits (Bits, shiftL, shiftR, (.&.), (.|.)) + + + +///- UTF-8 in General -/// + +Adapted from the Unicode standard, version 3.2, +Table 3.1 "UTF-8 Bit Distribution" (excluded are UTF-16 encodings): + + Scalar 1st Byte 2nd Byte 3rd Byte 4th Byte + 000000000xxxxxxx 0xxxxxxx + 00000yyyyyxxxxxx 110yyyyy 10xxxxxx + zzzzyyyyyyxxxxxx 1110zzzz 10yyyyyy 10xxxxxx + 000uuuzzzzzzyyyyyyxxxxxx 11110uuu 10zzzzzz 10yyyyyy 10xxxxxx + +Also from the Unicode standard, version 3.2, +Table 3.1B "Legal UTF-8 Byte Sequences": + + Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte + U+0000..U+007F 00..7F + U+0080..U+07FF C2..DF 80..BF + U+0800..U+0FFF E0 A0..BF 80..BF + U+1000..U+CFFF E1..EC 80..BF 80..BF + U+D000..U+D7FF ED 80..9F 80..BF + U+D800..U+DFFF ill-formed + U+E000..U+FFFF EE..EF 80..BF 80..BF + U+10000..U+3FFFF F0 90..BF 80..BF 80..BF + U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF + U+100000..U+10FFFF F4 80..8F 80..BF 80..BF + + + +///- Encoding Functions -/// + +Must the encoder ensure that no illegal byte sequences are output or +can we trust the Haskell system to supply only legal values? +For now I include error case for the surrogate values U+D800..U+DFFF and +out-of-range scalars. + +The function is pretty much a transscript of table 3.1B with error checks. +It dispatches the actual encoding to functions specific to the number of +required bytes. + +> encodeOne :: Char -> [Word8] +> encodeOne c +>-- The report guarantees in (6.1.2) that this won't happen: +>-- | n < 0 = error "encodeUTF8: ord returned a negative value" +> | n < 0x0080 = encodeOne_onebyte n8 +> | n < 0x0800 = encodeOne_twobyte n16 +> | n < 0xD800 = encodeOne_threebyte n16 +> | n < 0xE000 = error "encodeUTF8: ord returned a surrogate value" +> | n < 0x10000 = encodeOne_threebyte n16 +>-- Haskell 98 only talks about 16 bit characters, but ghc handles 20.1. +> | n < 0x10FFFF = encodeOne_fourbyte n32 +> | otherwise = error "encodeUTF8: ord returned a value above 0x10FFFF" +> where +> n = ord c :: Int +> n8 = fromIntegral n :: Word8 +> n16 = fromIntegral n :: Word16 +> n32 = fromIntegral n :: Word32 + + +With the above, a stream decoder is trivial: + +> encode :: [Char] -> [Word8] +> encode = concatMap encodeOne + + +Now follow the individual encoders for certain numbers of bytes... + _ + / | __ ___ __ __ + / ^| // /__/ // // + /.==| \\ //_ // // +It's // || // \_/_//_//_ and it's here to stay! + +> encodeOne_onebyte :: Word8 -> [Word8] +> encodeOne_onebyte cp = [cp] + + +00000yyyyyxxxxxx -> 110yyyyy 10xxxxxx + +> encodeOne_twobyte :: Word16 -> [Word8] +> encodeOne_twobyte cp = [(0xC0.|.ys), (0x80.|.xs)] +> where +> xs, ys :: Word8 +> ys = fromIntegral (shiftR cp 6) +> xs = (fromIntegral cp) .&. 0x3F + + +zzzzyyyyyyxxxxxx -> 1110zzzz 10yyyyyy 10xxxxxx + +> encodeOne_threebyte :: Word16 -> [Word8] +> encodeOne_threebyte cp = [(0xE0.|.zs), (0x80.|.ys), (0x80.|.xs)] +> where +> xs, ys, zs :: Word8 +> xs = (fromIntegral cp) .&. 0x3F +> ys = (fromIntegral (shiftR cp 6)) .&. 0x3F +> zs = fromIntegral (shiftR cp 12) + + +000uuuzzzzzzyyyyyyxxxxxx -> 11110uuu 10zzzzzz 10yyyyyy 10xxxxxx + +> encodeOne_fourbyte :: Word32 -> [Word8] +> encodeOne_fourbyte cp = [0xF0.|.us, 0x80.|.zs, 0x80.|.ys, 0x80.|.xs] +> where +> xs, ys, zs, us :: Word8 +> xs = (fromIntegral cp) .&. 0x3F +> ys = (fromIntegral (shiftR cp 6)) .&. 0x3F +> zs = (fromIntegral (shiftR cp 12)) .&. 0x3F +> us = fromIntegral (shiftR cp 18) + + + +///- Decoding -/// + +The decoding is a bit more involved. The byte sequence could contain all +sorts of corruptions. The user must be able to either notice or ignore these +errors. + +I will first look at the decoding of a single character. The process +consumes a certain number of bytes from the input. It returns the +remaining input and either an error and the index of its occurance in the +byte sequence or the decoded character. + +> data Error + +The first byte in a sequence starts with either zero, two, three, or four +ones and one zero to indicate the length of the sequence. If it doesn't, +it is invalid. It is dropped and the next byte interpreted as the start +of a new sequence. + +> = InvalidFirstByte + +All bytes in the sequence except the first match the bit pattern 10xxxxxx. +If one doesn't, it is invalid. The sequence up to that point is dropped +and the "invalid" byte interpreted as the start of a new sequence. The error +includes the length of the partial sequence and the number of expected bytes. + +> | InvalidLaterByte Int -- the byte at relative index n was invalid + +If a sequence ends prematurely, it has been truncated. It dropped and +decoding stops. The error reports the actual and expected lengths of the +sequence. + +> | Truncated Int Int -- only n of m expected bytes were present + +Some sequences would represent code points which would be encoded as a +shorter sequence by a conformant encoder. Such non-shortest sequences are +considered erroneous and dropped. The error reports the actual and +expected number of bytes used. + +> | NonShortest Int Int -- n instead of m bytes were used + +Unicode code points are in the range of [0..0x10FFFF]. Any values outside +of those bounds are simply invalid. + +> | ValueOutOfBounds + +There is no such thing as "surrogate pairs" any more in UTF-8. The +corresponding code points now form illegal byte sequences. + +> | Surrogate +> deriving (Show, Eq) + + +Second, third, and fourth bytes share the common requirement to start +with the bit sequence 10. So, here's the function to check that property. + +> first_bits_not_10 :: Word8 -> Bool +> first_bits_not_10 b +> | (b.&.0xC0) /= 0x80 = True +> | otherwise = False + + +Erm, OK, the single-character decoding function's return type is a bit +longish. It is a tripel: + + - The first component contains the decoded character or an error + if the byte sequence was erroneous. + - The second component contains the number of bytes that were consumed + from the input. + - The third component contains the remaining bytes of input. + +> decodeOne :: [Word8] -> (Either Error Char, Int, [Word8]) +> decodeOne bs@(b1:rest) +> | b1 < 0x80 = decodeOne_onebyte bs +> | b1 < 0xC0 = (Left InvalidFirstByte, 1, rest) +> | b1 < 0xE0 = decodeOne_twobyte bs +> | b1 < 0xEE = decodeOne_threebyte bs +> | b1 < 0xF5 = decodeOne_fourbyte bs +> | otherwise = (Left ValueOutOfBounds, 1, rest) +> decodeOne [] = error "UTF8.decodeOne: No input" + + +0xxxxxxx -> 000000000xxxxxxx + +> decodeOne_onebyte :: [Word8] -> (Either Error Char, Int, [Word8]) +> decodeOne_onebyte (b:bs) = (Right (cpToChar b), 1, bs) +> decodeOne_onebyte[] = error "UTF8.decodeOne_onebyte: No input (can't happen)" + +> cpToChar :: Integral a => a -> Char +> cpToChar = chr . fromIntegral + + +110yyyyy 10xxxxxx -> 00000yyyyyxxxxxx + +> decodeOne_twobyte :: [Word8] -> (Either Error Char, Int, [Word8]) +> decodeOne_twobyte (_:[]) +> = (Left (Truncated 1 2), 1, []) +> decodeOne_twobyte (b1:b2:bs) +> | b1 < 0xC2 = (Left (NonShortest 2 1), 2, bs) +> | first_bits_not_10 b2 = (Left (InvalidLaterByte 1), 1, (b2:bs)) +> | otherwise = (Right (cpToChar result), 2, bs) +> where +> xs, ys, result :: Word32 +> xs = fromIntegral (b2.&.0x3F) +> ys = fromIntegral (b1.&.0x1F) +> result = shiftL ys 6 .|. xs +> decodeOne_twobyte[] = error "UTF8.decodeOne_twobyte: No input (can't happen)" + + +1110zzzz 10yyyyyy 10xxxxxx -> zzzzyyyyyyxxxxxx + +> decodeOne_threebyte :: [Word8] -> (Either Error Char, Int, [Word8]) +> decodeOne_threebyte (_:[]) = threebyte_truncated 1 +> decodeOne_threebyte (_:_:[]) = threebyte_truncated 2 +> decodeOne_threebyte bs@(b1:b2:b3:rest) +> | first_bits_not_10 b2 +> = (Left (InvalidLaterByte 1), 1, drop 1 bs) +> | first_bits_not_10 b3 +> = (Left (InvalidLaterByte 2), 2, drop 2 bs) +> | result < 0x0080 +> = (Left (NonShortest 3 1), 3, rest) +> | result < 0x0800 +> = (Left (NonShortest 3 2), 3, rest) +> | result >= 0xD800 && result < 0xE000 +> = (Left Surrogate, 3, rest) +> | otherwise +> = (Right (cpToChar result), 3, rest) +> where +> xs, ys, zs, result :: Word32 +> xs = fromIntegral (b3.&.0x3F) +> ys = fromIntegral (b2.&.0x3F) +> zs = fromIntegral (b1.&.0x0F) +> result = shiftL zs 12 .|. shiftL ys 6 .|. xs +> decodeOne_threebyte[] +> = error "UTF8.decodeOne_threebyte: No input (can't happen)" + +> threebyte_truncated :: Int -> (Either Error Char, Int, [Word8]) +> threebyte_truncated n = (Left (Truncated n 3), n, []) + + +11110uuu 10zzzzzz 10yyyyyy 10xxxxxx -> 000uuuzzzzzzyyyyyyxxxxxx + +> decodeOne_fourbyte :: [Word8] -> (Either Error Char, Int, [Word8]) +> decodeOne_fourbyte (_:[]) = fourbyte_truncated 1 +> decodeOne_fourbyte (_:_:[]) = fourbyte_truncated 2 +> decodeOne_fourbyte (_:_:_:[]) = fourbyte_truncated 3 +> decodeOne_fourbyte bs@(b1:b2:b3:b4:rest) +> | first_bits_not_10 b2 +> = (Left (InvalidLaterByte 1), 1, drop 1 bs) +> | first_bits_not_10 b3 +> = (Left (InvalidLaterByte 2), 2, drop 2 bs) +> | first_bits_not_10 b4 +> = (Left (InvalidLaterByte 3), 3, drop 3 bs) +> | result < 0x0080 +> = (Left (NonShortest 4 1), 4, rest) +> | result < 0x0800 +> = (Left (NonShortest 4 2), 4, rest) +> | result < 0x10000 +> = (Left (NonShortest 4 3), 4, rest) +> | result > 0x10FFFF +> = (Left ValueOutOfBounds, 4, rest) +> | otherwise +> = (Right (cpToChar result), 4, rest) +> where +> xs, ys, zs, us, result :: Word32 +> xs = fromIntegral (b4 .&. 0x3F) +> ys = fromIntegral (b3 .&. 0x3F) +> zs = fromIntegral (b2 .&. 0x3F) +> us = fromIntegral (b1 .&. 0x07) +> result = xs .|. shiftL ys 6 .|. shiftL zs 12 .|. shiftL us 18 +> decodeOne_fourbyte[] +> = error "UTF8.decodeOne_fourbyte: No input (can't happen)" + +> fourbyte_truncated :: Int -> (Either Error Char, Int, [Word8]) +> fourbyte_truncated n = (Left (Truncated n 4), n, []) + + +The decoder examines all input, recording decoded characters as well as +error-index pairs along the way. + +> decode :: [Word8] -> ([Char], [(Error,Int)]) +> decode bytes = iter 0 [] [] bytes +> where +> iter :: Int -> [Char] -> [(Error,Int)] -> [Word8] +> -> ([Char], [(Error,Int)]) +> iter _ cs es [] = (reverse cs, reverse es) +> iter idx cs es bs +> = case decodeOne bs of +> (Left e, n, rest) -> iter (idx+n) cs ((e,idx):es) rest +> (Right c, n, rest) -> iter (idx+n) (c:cs) es rest + diff --git a/uhexdump.cabal b/uhexdump.cabal --- a/uhexdump.cabal +++ b/uhexdump.cabal @@ -1,5 +1,5 @@ name: uhexdump -version: 0.2.2 +version: 0.2.3 synopsis: hex dumper for UTF-8 text description: hex dumper for UTF-8 text category: Text @@ -12,7 +12,7 @@ source-repository head type: darcs - location: http://patch-tag.com/kowey/uhexdump + location: http://patch-tag.com/r/kowey/uhexdump executable uhexdump build-Depends: base < 4.1, @@ -20,3 +20,4 @@ utf8-string == 0.3.* main-is: uhexdump.hs ghc-options: -Wall + other-modules: UTF8