path: root/haddock-api/src/Haddock/InterfaceFile.hs

{-# LANGUAGE CPP, RankNTypes, ScopedTypeVariables #-}
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Haddock.InterfaceFile
-- Copyright   :  (c) David Waern       2006-2009,
--                    Mateusz Kowalczyk 2013
-- License     :  BSD-like
--
-- Maintainer  :  haddock@projects.haskell.org
-- Stability   :  experimental
-- Portability :  portable
--
-- Reading and writing the .haddock interface file
-----------------------------------------------------------------------------
module Haddock.InterfaceFile (
  InterfaceFile(..), PackageInfo(..), ifUnitId, ifModule,
  PackageInterfaces(..), mkPackageInterfaces, ppPackageInfo, readInterfaceFile,
  nameCacheFromGhc, freshNameCache, NameCacheAccessor, writeInterfaceFile,
  binaryInterfaceVersion, binaryInterfaceVersionCompatibility
) where


import Haddock.Types

import Control.Monad
import Control.Monad.IO.Class ( MonadIO(..) )
import Data.Array
import Data.IORef
import Data.List (mapAccumR)
import qualified Data.Map as Map
import Data.Map (Map)
import Data.Version
import Data.Word
import Text.ParserCombinators.ReadP (readP_to_S)

import GHC.Iface.Binary (getSymtabName, getDictFastString)
import GHC.Unit.State
import GHC.Utils.Binary
import GHC.Data.FastMutInt
import GHC.Data.FastString
import GHC hiding (NoLink)
import GHC.Driver.Monad (withSession)
import GHC.Driver.Env
import GHC.Types.Name.Cache
import GHC.Iface.Env
import GHC.Types.Name
import GHC.Types.Unique.FM
import GHC.Types.Unique.Supply
import GHC.Types.Unique

import Haddock.Options (Visibility (..))

data InterfaceFile = InterfaceFile {
  ifLinkEnv         :: LinkEnv,
  -- | Package meta data.  Currently it only consist of a package name, which
  -- is not read from the interface file, but inferred from its name.
  --
  -- issue #
  ifPackageInfo     :: PackageInfo,
  ifInstalledIfaces :: [InstalledInterface]
}

data PackageInfo = PackageInfo {
  piPackageName    :: PackageName,
  piPackageVersion :: Data.Version.Version
}

ppPackageInfo :: PackageInfo -> String
ppPackageInfo (PackageInfo name version) | version == makeVersion []
                                         = unpackFS (unPackageName name)
ppPackageInfo (PackageInfo name version) = unpackFS (unPackageName name) ++ "-" ++ showVersion version

data PackageInterfaces = PackageInterfaces {
  piPackageInfo         :: PackageInfo,
  piVisibility          :: Visibility,
  piInstalledInterfaces :: [InstalledInterface]
}

mkPackageInterfaces :: Visibility -> InterfaceFile -> PackageInterfaces
mkPackageInterfaces piVisibility
                    InterfaceFile { ifPackageInfo
                                  , ifInstalledIfaces
                                  } = 
  PackageInterfaces { piPackageInfo = ifPackageInfo
                    , piVisibility
                    , piInstalledInterfaces = ifInstalledIfaces
                    }

ifModule :: InterfaceFile -> Module
ifModule if_ =
  case ifInstalledIfaces if_ of
    [] -> error "empty InterfaceFile"
    iface:_ -> instMod iface

ifUnitId :: InterfaceFile -> Unit
ifUnitId if_ =
  case ifInstalledIfaces if_ of
    [] -> error "empty InterfaceFile"
    iface:_ -> moduleUnit $ instMod iface


binaryInterfaceMagic :: Word32
binaryInterfaceMagic = 0xD0Cface

-- Note [The DocModule story]
--
-- Breaking changes to the DocH type result in Haddock being unable to read
-- existing interfaces. This is especially painful for interfaces shipped
-- with GHC distributions since there is no easy way to regenerate them!
--
-- PR #1315 introduced a breaking change to the DocModule constructor. To
-- maintain backward compatibility we
--
-- Parse the old DocModule constructor format (tag 5) and parse the contained
-- string into a proper ModLink structure. When writing interfaces we exclusively
-- use the new DocModule format (tag 24)

-- IMPORTANT: Since datatypes in the GHC API might change between major
-- versions, and because we store GHC datatypes in our interface files, we need
-- to make sure we version our interface files accordingly.
--
-- If you change the interface file format or adapt Haddock to work with a new
-- major version of GHC (so that the format changes indirectly) *you* need to
-- follow these steps:
--
-- (1) increase `binaryInterfaceVersion`
--
-- (2) set `binaryInterfaceVersionCompatibility` to [binaryInterfaceVersion]
--
binaryInterfaceVersion :: Word16
#if MIN_VERSION_ghc(9,2,0) && !MIN_VERSION_ghc(9,3,0)
binaryInterfaceVersion = 39

binaryInterfaceVersionCompatibility :: [Word16]
binaryInterfaceVersionCompatibility = [37, 38, binaryInterfaceVersion]
#elif defined(__HLINT__)
#else
#error Unsupported GHC version
#endif


initBinMemSize :: Int
initBinMemSize = 1024*1024


writeInterfaceFile :: FilePath -> InterfaceFile -> IO ()
writeInterfaceFile filename iface = do
  bh0 <- openBinMem initBinMemSize
  put_ bh0 binaryInterfaceMagic
  put_ bh0 binaryInterfaceVersion

  -- remember where the dictionary pointer will go
  dict_p_p <- tellBin bh0
  put_ bh0 dict_p_p

  -- remember where the symbol table pointer will go
  symtab_p_p <- tellBin bh0
  put_ bh0 symtab_p_p

  -- Make some intial state
  symtab_next <- newFastMutInt 0
  symtab_map <- newIORef emptyUFM
  let bin_symtab = BinSymbolTable {
                      bin_symtab_next = symtab_next,
                      bin_symtab_map  = symtab_map }
  dict_next_ref <- newFastMutInt 0
  dict_map_ref <- newIORef emptyUFM
  let bin_dict = BinDictionary {
                      bin_dict_next = dict_next_ref,
                      bin_dict_map  = dict_map_ref }

  -- put the main thing
  let bh = setUserData bh0 $ newWriteState (putName bin_symtab)
                                           (putName bin_symtab)
                                           (putFastString bin_dict)
  putInterfaceFile_ bh iface

  -- write the symtab pointer at the front of the file
  symtab_p <- tellBin bh
  putAt bh symtab_p_p symtab_p
  seekBin bh symtab_p

  -- write the symbol table itself
  symtab_next' <- readFastMutInt symtab_next
  symtab_map'  <- readIORef symtab_map
  putSymbolTable bh symtab_next' symtab_map'

  -- write the dictionary pointer at the fornt of the file
  dict_p <- tellBin bh
  putAt bh dict_p_p dict_p
  seekBin bh dict_p

  -- write the dictionary itself
  dict_next <- readFastMutInt dict_next_ref
  dict_map  <- readIORef dict_map_ref
  putDictionary bh dict_next dict_map

  -- and send the result to the file
  writeBinMem bh filename
  return ()


type NameCacheAccessor m = (m NameCache, NameCache -> m ())


nameCacheFromGhc :: forall m. GhcMonad m => NameCacheAccessor m
nameCacheFromGhc = ( read_from_session , write_to_session )
  where
    read_from_session = do
       ref <- withSession (return . hsc_NC)
       liftIO $ readIORef ref
    write_to_session nc' = do
       ref <- withSession (return . hsc_NC)
       liftIO $ writeIORef ref nc'


freshNameCache :: NameCacheAccessor IO
freshNameCache = ( create_fresh_nc , \_ -> return () )
  where
    create_fresh_nc = do
       u  <- mkSplitUniqSupply 'a' -- ??
       return (initNameCache u [])


-- | Read a Haddock (@.haddock@) interface file. Return either an
-- 'InterfaceFile' or an error message.
--
-- This function can be called in two ways.  Within a GHC session it will
-- update the use and update the session's name cache.  Outside a GHC session
-- a new empty name cache is used.  The function is therefore generic in the
-- monad being used.  The exact monad is whichever monad the first
-- argument, the getter and setter of the name cache, requires.
--
readInterfaceFile :: forall m.
                     MonadIO m
                  => NameCacheAccessor m
                  -> FilePath
                  -> Bool  -- ^ Disable version check. Can cause runtime crash.
                  -> m (Either String InterfaceFile)
readInterfaceFile (get_name_cache, set_name_cache) filename bypass_checks = do
  bh0 <- liftIO $ readBinMem filename

  magic   <- liftIO $ get bh0
  version <- liftIO $ get bh0

  case () of
    _ | magic /= binaryInterfaceMagic -> return . Left $
      "Magic number mismatch: couldn't load interface file: " ++ filename
      | not bypass_checks
      , (version `notElem` binaryInterfaceVersionCompatibility) -> return . Left $
      "Interface file is of wrong version: " ++ filename
      | otherwise -> with_name_cache $ \update_nc -> do

      dict  <- get_dictionary bh0

      -- read the symbol table so we are capable of reading the actual data
      bh1 <- do
          let bh1 = setUserData bh0 $ newReadState (error "getSymtabName")
                                                   (getDictFastString dict)
          symtab <- update_nc (get_symbol_table bh1)
          return $ setUserData bh1 $ newReadState (getSymtabName (NCU (\f -> update_nc (return . f))) dict symtab)
                                                  (getDictFastString dict)

      -- load the actual data
      iface <- liftIO $ getInterfaceFile bh1 version
      return (Right iface)
 where
   with_name_cache :: forall a.
                      ((forall n b. MonadIO n
                                => (NameCache -> n (NameCache, b))
                                -> n b)
                       -> m a)
                   -> m a
   with_name_cache act = do
      nc_var <-  get_name_cache >>= (liftIO . newIORef)
      x <- act $ \f -> do
              nc <- liftIO $ readIORef nc_var
              (nc', x) <- f nc
              liftIO $ writeIORef nc_var nc'
              return x
      liftIO (readIORef nc_var) >>= set_name_cache
      return x

   get_dictionary bin_handle = liftIO $ do
      dict_p <- get bin_handle
      data_p <- tellBin bin_handle
      seekBin bin_handle dict_p
      dict <- getDictionary bin_handle
      seekBin bin_handle data_p
      return dict

   get_symbol_table bh1 theNC = liftIO $ do
      symtab_p <- get bh1
      data_p'  <- tellBin bh1
      seekBin bh1 symtab_p
      (nc', symtab) <- getSymbolTable bh1 theNC
      seekBin bh1 data_p'
      return (nc', symtab)


-------------------------------------------------------------------------------
-- * Symbol table
-------------------------------------------------------------------------------


putName :: BinSymbolTable -> BinHandle -> Name -> IO ()
putName BinSymbolTable{
            bin_symtab_map = symtab_map_ref,
            bin_symtab_next = symtab_next }    bh name
  = do
    symtab_map <- readIORef symtab_map_ref
    case lookupUFM symtab_map name of
      Just (off,_) -> put_ bh (fromIntegral off :: Word32)
      Nothing -> do
         off <- readFastMutInt symtab_next
         writeFastMutInt symtab_next (off+1)
         writeIORef symtab_map_ref
             $! addToUFM symtab_map name (off,name)
         put_ bh (fromIntegral off :: Word32)


data BinSymbolTable = BinSymbolTable {
        bin_symtab_next :: !FastMutInt, -- The next index to use
        bin_symtab_map  :: !(IORef (UniqFM Name (Int,Name)))
                                -- indexed by Name
  }


putFastString :: BinDictionary -> BinHandle -> FastString -> IO ()
putFastString BinDictionary { bin_dict_next = j_r,
                              bin_dict_map  = out_r}  bh f
  = do
    out <- readIORef out_r
    let !unique = getUnique f
    case lookupUFM_Directly out unique of
        Just (j, _)  -> put_ bh (fromIntegral j :: Word32)
        Nothing -> do
           j <- readFastMutInt j_r
           put_ bh (fromIntegral j :: Word32)
           writeFastMutInt j_r (j + 1)
           writeIORef out_r $! addToUFM_Directly out unique (j, f)


data BinDictionary = BinDictionary {
        bin_dict_next :: !FastMutInt, -- The next index to use
        bin_dict_map  :: !(IORef (UniqFM FastString (Int,FastString)))
                                -- indexed by FastString
  }


putSymbolTable :: BinHandle -> Int -> UniqFM Name (Int,Name) -> IO ()
putSymbolTable bh next_off symtab = do
  put_ bh next_off
  let names = elems (array (0,next_off-1) (eltsUFM symtab))
  mapM_ (\n -> serialiseName bh n symtab) names


getSymbolTable :: BinHandle -> NameCache -> IO (NameCache, Array Int Name)
getSymbolTable bh namecache = do
  sz <- get bh
  od_names <- replicateM sz (get bh)
  let arr = listArray (0,sz-1) names
      (namecache', names) = mapAccumR (fromOnDiskName arr) namecache od_names
  return (namecache', arr)


type OnDiskName = (Unit, ModuleName, OccName)


fromOnDiskName
   :: Array Int Name
   -> NameCache
   -> OnDiskName
   -> (NameCache, Name)
fromOnDiskName _ nc (pid, mod_name, occ) =
  let
        modu  = mkModule pid mod_name
        cache = nsNames nc
  in
  case lookupOrigNameCache cache modu occ of
     Just name -> (nc, name)
     Nothing   ->
        let
                us        = nsUniqs nc
                u         = uniqFromSupply us
                name      = mkExternalName u modu occ noSrcSpan
                new_cache = extendNameCache cache modu occ name
        in
        case splitUniqSupply us of { (us',_) ->
        ( nc{ nsUniqs = us', nsNames = new_cache }, name )
        }


serialiseName :: BinHandle -> Name -> UniqFM Name (Int,Name) -> IO ()
serialiseName bh name _ = do
  let modu = nameModule name
  put_ bh (moduleUnit modu, moduleName modu, nameOccName name)


-------------------------------------------------------------------------------
-- * GhcBinary instances
-------------------------------------------------------------------------------


instance (Ord k, Binary k, Binary v) => Binary (Map k v) where
  put_ bh m = put_ bh (Map.toList m)
  get bh = fmap (Map.fromList) (get bh)

instance Binary PackageInfo where
  put_ bh PackageInfo { piPackageName, piPackageVersion } = do
    put_ bh (unPackageName piPackageName)
    put_ bh (showVersion piPackageVersion)
  get bh = do
    name <- PackageName <$> get bh
    versionString <- get bh
    let version = case readP_to_S parseVersion versionString of
          [] -> makeVersion []
          vs -> fst (last vs)
    return $ PackageInfo name version

instance Binary InterfaceFile where
  put_ bh (InterfaceFile env info ifaces) = do
    put_ bh env
    put_ bh info
    put_ bh ifaces

  get bh = do
    env    <- get bh
    info   <- get bh
    ifaces <- get bh
    return (InterfaceFile env info ifaces)


putInterfaceFile_ :: BinHandle -> InterfaceFile -> IO ()
putInterfaceFile_ bh (InterfaceFile env info ifaces) = do
  put_ bh env
  put_ bh info
  put_ bh ifaces

getInterfaceFile :: BinHandle -> Word16 -> IO InterfaceFile
getInterfaceFile bh v | v <= 38 = do
  env    <- get bh
  let info = PackageInfo (PackageName mempty) (makeVersion [])
  ifaces <- get bh
  return (InterfaceFile env info ifaces)
getInterfaceFile bh _ = do
  env    <- get bh
  info   <- get bh
  ifaces <- get bh
  return (InterfaceFile env info ifaces)


instance Binary InstalledInterface where
  put_ bh (InstalledInterface modu is_sig info docMap argMap
           exps visExps opts fixMap) = do
    put_ bh modu
    put_ bh is_sig
    put_ bh info
    lazyPut bh (docMap, argMap)
    put_ bh exps
    put_ bh visExps
    put_ bh opts
    put_ bh fixMap

  get bh = do
    modu    <- get bh
    is_sig  <- get bh
    info    <- get bh
    ~(docMap, argMap) <- lazyGet bh
    exps    <- get bh
    visExps <- get bh
    opts    <- get bh
    fixMap  <- get bh
    return (InstalledInterface modu is_sig info docMap argMap
            exps visExps opts fixMap)


instance Binary DocOption where
    put_ bh OptHide = do
            putByte bh 0
    put_ bh OptPrune = do
            putByte bh 1
    put_ bh OptIgnoreExports = do
            putByte bh 2
    put_ bh OptNotHome = do
            putByte bh 3
    put_ bh OptShowExtensions = do
            putByte bh 4
    get bh = do
            h <- getByte bh
            case h of
              0 -> do
                    return OptHide
              1 -> do
                    return OptPrune
              2 -> do
                    return OptIgnoreExports
              3 -> do
                    return OptNotHome
              4 -> do
                    return OptShowExtensions
              _ -> fail "invalid binary data found"


instance Binary Example where
    put_ bh (Example expression result) = do
        put_ bh expression
        put_ bh result
    get bh = do
        expression <- get bh
        result <- get bh
        return (Example expression result)

instance Binary a => Binary (Hyperlink a) where
    put_ bh (Hyperlink url label) = do
        put_ bh url
        put_ bh label
    get bh = do
        url <- get bh
        label <- get bh
        return (Hyperlink url label)

instance Binary a => Binary (ModLink a) where
    put_ bh (ModLink m label) = do
        put_ bh m
        put_ bh label
    get bh = do
        m <- get bh
        label <- get bh
        return (ModLink m label)

instance Binary Picture where
    put_ bh (Picture uri title) = do
        put_ bh uri
        put_ bh title
    get bh = do
        uri <- get bh
        title <- get bh
        return (Picture uri title)

instance Binary a => Binary (Header a) where
    put_ bh (Header l t) = do
        put_ bh l
        put_ bh t
    get bh = do
        l <- get bh
        t <- get bh
        return (Header l t)

instance Binary a => Binary (Table a) where
    put_ bh (Table h b) = do
        put_ bh h
        put_ bh b
    get bh = do
        h <- get bh
        b <- get bh
        return (Table h b)

instance Binary a => Binary (TableRow a) where
    put_ bh (TableRow cs) = put_ bh cs
    get bh = do
        cs <- get bh
        return (TableRow cs)

instance Binary a => Binary (TableCell a) where
    put_ bh (TableCell i j c) = do
        put_ bh i
        put_ bh j
        put_ bh c
    get bh = do
        i <- get bh
        j <- get bh
        c <- get bh
        return (TableCell i j c)

instance Binary Meta where
    put_ bh (Meta v p) = do
        put_ bh v
        put_ bh p
    get bh = do
        v <- get bh
        p <- get bh
        return (Meta v p)

instance (Binary mod, Binary id) => Binary (MetaDoc mod id) where
  put_ bh MetaDoc { _meta = m, _doc = d } = do
    put_ bh m
    put_ bh d
  get bh = do
    m <- get bh
    d <- get bh
    return $ MetaDoc { _meta = m, _doc = d }

instance (Binary mod, Binary id) => Binary (DocH mod id) where
    put_ bh DocEmpty = do
            putByte bh 0
    put_ bh (DocAppend aa ab) = do
            putByte bh 1
            put_ bh aa
            put_ bh ab
    put_ bh (DocString ac) = do
            putByte bh 2
            put_ bh ac
    put_ bh (DocParagraph ad) = do
            putByte bh 3
            put_ bh ad
    put_ bh (DocIdentifier ae) = do
            putByte bh 4
            put_ bh ae
    put_ bh (DocEmphasis ag) = do
            putByte bh 6
            put_ bh ag
    put_ bh (DocMonospaced ah) = do
            putByte bh 7
            put_ bh ah
    put_ bh (DocUnorderedList ai) = do
            putByte bh 8
            put_ bh ai
    put_ bh (DocOrderedList aj) = do
            putByte bh 9
            put_ bh aj
    put_ bh (DocDefList ak) = do
            putByte bh 10
            put_ bh ak
    put_ bh (DocCodeBlock al) = do
            putByte bh 11
            put_ bh al
    put_ bh (DocHyperlink am) = do
            putByte bh 12
            put_ bh am
    put_ bh (DocPic x) = do
            putByte bh 13
            put_ bh x
    put_ bh (DocAName an) = do
            putByte bh 14
            put_ bh an
    put_ bh (DocExamples ao) = do
            putByte bh 15
            put_ bh ao
    put_ bh (DocIdentifierUnchecked x) = do
            putByte bh 16
            put_ bh x
    put_ bh (DocWarning ag) = do
            putByte bh 17
            put_ bh ag
    put_ bh (DocProperty x) = do
            putByte bh 18
            put_ bh x
    put_ bh (DocBold x) = do
            putByte bh 19
            put_ bh x
    put_ bh (DocHeader aa) = do
            putByte bh 20
            put_ bh aa
    put_ bh (DocMathInline x) = do
            putByte bh 21
            put_ bh x
    put_ bh (DocMathDisplay x) = do
            putByte bh 22
            put_ bh x
    put_ bh (DocTable x) = do
            putByte bh 23
            put_ bh x
    -- See note [The DocModule story]
    put_ bh (DocModule af) = do
            putByte bh 24
            put_ bh af

    get bh = do
            h <- getByte bh
            case h of
              0 -> do
                    return DocEmpty
              1 -> do
                    aa <- get bh
                    ab <- get bh
                    return (DocAppend aa ab)
              2 -> do
                    ac <- get bh
                    return (DocString ac)
              3 -> do
                    ad <- get bh
                    return (DocParagraph ad)
              4 -> do
                    ae <- get bh
                    return (DocIdentifier ae)
              -- See note [The DocModule story]
              5 -> do
                    af <- get bh
                    return $ DocModule ModLink
                      { modLinkName  = af
                      , modLinkLabel = Nothing
                      }
              6 -> do
                    ag <- get bh
                    return (DocEmphasis ag)
              7 -> do
                    ah <- get bh
                    return (DocMonospaced ah)
              8 -> do
                    ai <- get bh
                    return (DocUnorderedList ai)
              9 -> do
                    aj <- get bh
                    return (DocOrderedList aj)
              10 -> do
                    ak <- get bh
                    return (DocDefList ak)
              11 -> do
                    al <- get bh
                    return (DocCodeBlock al)
              12 -> do
                    am <- get bh
                    return (DocHyperlink am)
              13 -> do
                    x <- get bh
                    return (DocPic x)
              14 -> do
                    an <- get bh
                    return (DocAName an)
              15 -> do
                    ao <- get bh
                    return (DocExamples ao)
              16 -> do
                    x <- get bh
                    return (DocIdentifierUnchecked x)
              17 -> do
                    ag <- get bh
                    return (DocWarning ag)
              18 -> do
                    x <- get bh
                    return (DocProperty x)
              19 -> do
                    x <- get bh
                    return (DocBold x)
              20 -> do
                    aa <- get bh
                    return (DocHeader aa)
              21 -> do
                    x <- get bh
                    return (DocMathInline x)
              22 -> do
                    x <- get bh
                    return (DocMathDisplay x)
              23 -> do
                    x <- get bh
                    return (DocTable x)
              -- See note [The DocModule story]
              24 -> do
                    af <- get bh
                    return (DocModule af)
              _ -> error "invalid binary data found in the interface file"


instance Binary name => Binary (HaddockModInfo name) where
  put_ bh hmi = do
    put_ bh (hmi_description hmi)
    put_ bh (hmi_copyright   hmi)
    put_ bh (hmi_license     hmi)
    put_ bh (hmi_maintainer  hmi)
    put_ bh (hmi_stability   hmi)
    put_ bh (hmi_portability hmi)
    put_ bh (hmi_safety      hmi)
    put_ bh (fromEnum <$> hmi_language hmi)
    put_ bh (map fromEnum $ hmi_extensions hmi)

  get bh = do
    descr <- get bh
    copyr <- get bh
    licen <- get bh
    maint <- get bh
    stabi <- get bh
    porta <- get bh
    safet <- get bh
    langu <- fmap toEnum <$> get bh
    exten <- map toEnum <$> get bh
    return (HaddockModInfo descr copyr licen maint stabi porta safet langu exten)

instance Binary DocName where
  put_ bh (Documented name modu) = do
    putByte bh 0
    put_ bh name
    put_ bh modu
  put_ bh (Undocumented name) = do
    putByte bh 1
    put_ bh name

  get bh = do
    h <- getByte bh
    case h of
      0 -> do
        name <- get bh
        modu <- get bh
        return (Documented name modu)
      1 -> do
        name <- get bh
        return (Undocumented name)
      _ -> error "get DocName: Bad h"

instance Binary n => Binary (Wrap n) where
  put_ bh (Unadorned n) = do
    putByte bh 0
    put_ bh n
  put_ bh (Parenthesized n) = do
    putByte bh 1
    put_ bh n
  put_ bh (Backticked n) = do
    putByte bh 2
    put_ bh n

  get bh = do
    h <- getByte bh
    case h of
      0 -> do
        name <- get bh
        return (Unadorned name)
      1 -> do
        name <- get bh
        return (Parenthesized name)
      2 -> do
        name <- get bh
        return (Backticked name)
      _ -> error "get Wrap: Bad h"