191 lines
5.1 KiB
Haskell
191 lines
5.1 KiB
Haskell
{-# LANGUAGE NamedFieldPuns #-}
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module PDF.Object (
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Content(..)
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, DirectObject(..)
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, EOLStyle(..)
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, IndirectObjCoordinates(..)
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, Object(..)
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, Occurrence(..)
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, Parser
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, XRefEntry(..)
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, XRefSection
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, XRefSubSection(..)
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, blank
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, content
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, dictionary
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, directObject
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, eol
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, eolCharset
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, integer
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, line
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) where
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import Data.ByteString.Lazy.Char8 (ByteString)
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import Data.Int (Int64)
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import Data.Map (Map)
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import qualified Data.Map as Map (empty, fromList)
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import Text.Parsec
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type Parser u = Parsec ByteString u
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data EOLStyle = CR | LF | CRLF
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type Dictionary = Map String DirectObject
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data StringObj = Literal String | Hexadecimal String deriving Show
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data DirectObject =
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Boolean Bool
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| Number Float
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| String StringObj
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| Name String
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| Array [DirectObject]
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| Dictionary Dictionary
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| Null
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| Reference IndirectObjCoordinates
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deriving Show
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data Object =
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Direct DirectObject
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| Stream {
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header :: Dictionary
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, streamContent :: ByteString
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}
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deriving Show
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data IndirectObjCoordinates = IndirectObjCoordinates {
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objectId :: Int
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, versionNumber :: Int
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} deriving Show
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data Occurrence = Comment String | Indirect IndirectObjCoordinates deriving Show
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data XRefEntry = InUse {
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offset :: Int64
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, generation :: Int
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} | Free {
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nextFree :: Int64
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, generation :: Int
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} deriving Show
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data XRefSubSection = XRefSubSection {
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firstObjectId :: Int
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, entriesNumber :: Int
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, entries :: Map Int XRefEntry
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} deriving Show
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type XRefSection = [XRefSubSection]
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data Content = Content {
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startOffset :: Int64
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, body :: [Occurrence]
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, objects :: Map Int Object
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, xrefSection :: XRefSection
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, trailer :: Dictionary
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, startXrefPosition :: Int64
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} deriving Show
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eolCharset :: String
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eolCharset = "\r\n"
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eol :: Parser u EOLStyle
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eol =
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try (string "\r\n" >> return CRLF)
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<|> (string "\r" >> return CR)
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<|> (string "\n" >> return LF)
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line :: String -> Parser u ()
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line l = string l *> eol *> return ()
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whiteSpaceCharset :: String
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whiteSpaceCharset = "\0\t\12 "
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whiteSpace :: Parser u ()
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whiteSpace = oneOf whiteSpaceCharset *> return () <|> eol *> return ()
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blank :: Parser u ()
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blank = skipMany whiteSpace
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delimiterCharset :: String
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delimiterCharset = "()<>[]{}/%"
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regular :: Parser u Char
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regular = noneOf $ eolCharset ++ whiteSpaceCharset ++ delimiterCharset
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integer :: (Read a, Num a) => Parser u a
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integer = read <$> many1 digit <* whiteSpace
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directObject :: Parser u DirectObject
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directObject =
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Boolean <$> try boolean
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<|> Reference <$> try reference {- defined before Number because Number is a prefix of it -}
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<|> Number <$> try number
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<|> String <$> try stringObj
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<|> Name <$> try name
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<|> Array <$> try array
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<|> Dictionary <$> try dictionary
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<|> const Null <$> try nullObject
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boolean :: Parser u Bool
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boolean = (string "true" *> return True) <|> (string "false" *> return False)
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number :: Parser u Float
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number = read <$> (mappend <$> sign <*> (integerPart <|> ('0':) <$> floatPart))
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where
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sign = string "-" <|> option "" (char '+' >> return "")
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integerPart = mappend <$> many1 digit <*> option "" floatPart
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floatPart = (:) <$> char '.' <*> (option "0" $ many1 digit)
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stringObj :: Parser u StringObj
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stringObj =
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Literal <$> (char '(' *> (concat <$> many literalStringBlock) <* char ')')
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<|> Hexadecimal <$> (char '<' *> many hexDigit <* char '>')
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where
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literalStringBlock = many1 (noneOf "\\()") <|> matchingParenthesis <|> escapedChar
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matchingParenthesis =
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(++) <$> ((:) <$> char '(' <*> literalStringBlock) <*> string ")"
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escapedChar = (:) <$> char '\\' <*> ((:[]) <$> oneOf "nrtbf()\\" <|> octalCode)
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octalCode = choice $ (\n -> count n octDigit) <$> [1..3]
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name :: Parser u String
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name = char '/' *> many regular
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array :: Parser u [DirectObject]
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array = char '[' *> blank *> directObject `endBy` blank <* char ']'
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dictionary :: Parser u Dictionary
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dictionary =
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try (string "<<" *> blank *> keyValPairs <* string ">>")
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where
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keyVal = (,) <$> name <* blank <*> directObject
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keyValPairs = Map.fromList <$> keyVal `endBy` blank
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nullObject :: Parser u ()
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nullObject = string "null" *> return ()
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reference :: Parser u IndirectObjCoordinates
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reference = IndirectObjCoordinates <$> integer <*> integer <* char 'R'
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entry :: Parser u XRefEntry
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entry = do
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(big, small) <- (,) <$> integer <*> integer
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(inUse big small <|> free big small) <* blank
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where
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inUse :: Int64 -> Int -> Parser u XRefEntry
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inUse offset generation = char 'n' *> return (InUse {offset, generation})
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free :: Int64 -> Int -> Parser u XRefEntry
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free nextFree generation = char 'f' *> return (Free {nextFree, generation})
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xrefSubSection :: Parser u XRefSubSection
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xrefSubSection = do
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(firstObjectId, entriesNumber) <- (,) <$> integer <*> integer
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entries <- Map.fromList . zip [firstObjectId..] <$> count entriesNumber entry
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return $ XRefSubSection {firstObjectId, entriesNumber, entries}
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content :: Parser u Content
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content =
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Content 0 [] Map.empty
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<$> (line "xref" *> xrefSubSection `sepBy` eol)
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<*> (line "trailer" *> dictionary <* eol)
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<*> (line "startxref" *> integer)
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