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{-
Copyright © 2012-2017 John MacFarlane <jgm@berkeley.edu>
2017 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-}
{-# LANGUAGE FlexibleInstances #-}
{- |
Module : Text.Pandoc.Lua.Util
Copyright : © 2012–2017 John MacFarlane,
© 2017 Albert Krewinkel
License : GNU GPL, version 2 or above
Maintainer : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
Stability : alpha
Lua utility functions.
-}
module Text.Pandoc.Lua.Util
( adjustIndexBy
, getTable
, addValue
, addFunction
, getRawInt
, setRawInt
, addRawInt
, raiseError
, OrNil (..)
, PushViaCall
, pushViaCall
, pushViaConstructor
, loadScriptFromDataDir
, dostring'
) where
import Control.Monad (when)
import Data.ByteString.Char8 (unpack)
import Foreign.Lua (FromLuaStack (..), NumResults, Lua, NumArgs, StackIndex,
ToLuaStack (..), ToHaskellFunction, getglobal')
import Foreign.Lua.Api (Status, call, pop, rawget, rawgeti, rawset, rawseti)
import Text.Pandoc.Class (readDataFile, runIOorExplode, setUserDataDir)
import qualified Foreign.Lua as Lua
-- | Adjust the stack index, assuming that @n@ new elements have been pushed on
-- the stack.
adjustIndexBy :: StackIndex -> StackIndex -> StackIndex
adjustIndexBy idx n =
if idx < 0
then idx - n
else idx
-- | Get value behind key from table at given index.
getTable :: (ToLuaStack a, FromLuaStack b) => StackIndex -> a -> Lua b
getTable idx key = do
push key
rawget (idx `adjustIndexBy` 1)
popValue
-- | Add a key-value pair to the table at the top of the stack.
addValue :: (ToLuaStack a, ToLuaStack b) => a -> b -> Lua ()
addValue key value = do
push key
push value
rawset (-3)
-- | Add a function to the table at the top of the stack, using the given name.
addFunction :: ToHaskellFunction a => String -> a -> Lua ()
addFunction name fn = do
Lua.push name
Lua.pushHaskellFunction fn
Lua.wrapHaskellFunction
Lua.rawset (-3)
-- | Get value behind key from table at given index.
getRawInt :: FromLuaStack a => StackIndex -> Int -> Lua a
getRawInt idx key = do
rawgeti idx key
popValue
-- | Set numeric key/value in table at the given index
setRawInt :: ToLuaStack a => StackIndex -> Int -> a -> Lua ()
setRawInt idx key value = do
push value
rawseti (idx `adjustIndexBy` 1) key
-- | Set numeric key/value in table at the top of the stack.
addRawInt :: ToLuaStack a => Int -> a -> Lua ()
addRawInt = setRawInt (-1)
raiseError :: ToLuaStack a => a -> Lua NumResults
raiseError e = do
Lua.push e
fromIntegral <$> Lua.lerror
-- | Get, then pop the value at the top of the stack.
popValue :: FromLuaStack a => Lua a
popValue = do
resOrError <- Lua.peekEither (-1)
pop 1
case resOrError of
Left err -> Lua.throwLuaError err
Right x -> return x
-- | Newtype wrapper intended to be used for optional Lua values. Nesting this
-- type is strongly discouraged and will likely lead to a wrong result.
newtype OrNil a = OrNil { toMaybe :: Maybe a }
instance FromLuaStack a => FromLuaStack (OrNil a) where
peek idx = do
noValue <- Lua.isnoneornil idx
if noValue
then return (OrNil Nothing)
else OrNil . Just <$> Lua.peek idx
instance ToLuaStack a => ToLuaStack (OrNil a) where
push (OrNil Nothing) = Lua.pushnil
push (OrNil (Just x)) = Lua.push x
-- | Helper class for pushing a single value to the stack via a lua function.
-- See @pushViaCall@.
class PushViaCall a where
pushViaCall' :: String -> Lua () -> NumArgs -> a
instance PushViaCall (Lua ()) where
pushViaCall' fn pushArgs num = do
getglobal' fn
pushArgs
call num 1
instance (ToLuaStack a, PushViaCall b) => PushViaCall (a -> b) where
pushViaCall' fn pushArgs num x =
pushViaCall' fn (pushArgs *> push x) (num + 1)
-- | Push an value to the stack via a lua function. The lua function is called
-- with all arguments that are passed to this function and is expected to return
-- a single value.
pushViaCall :: PushViaCall a => String -> a
pushViaCall fn = pushViaCall' fn (return ()) 0
-- | Call a pandoc element constructor within lua, passing all given arguments.
pushViaConstructor :: PushViaCall a => String -> a
pushViaConstructor pandocFn = pushViaCall ("pandoc." ++ pandocFn)
-- | Load a file from pandoc's data directory.
loadScriptFromDataDir :: Maybe FilePath -> FilePath -> Lua ()
loadScriptFromDataDir datadir scriptFile = do
script <- fmap unpack . Lua.liftIO . runIOorExplode $
setUserDataDir datadir >> readDataFile scriptFile
status <- dostring' script
when (status /= Lua.OK) .
Lua.throwTopMessageAsError' $ \msg ->
"Couldn't load '" ++ scriptFile ++ "'.\n" ++ msg
-- | Load a string and immediately perform a full garbage collection. This is
-- important to keep the program from hanging: If the program contained a call
-- to @require@, the a new loader function was created which then become
-- garbage. If that function is collected at an inopportune times, i.e. when the
-- Lua API is called via a function that doesn't allow calling back into Haskell
-- (getraw, setraw, …). The function's finalizer, and the full program, hangs
-- when that happens.
dostring' :: String -> Lua Status
dostring' script = do
loadRes <- Lua.loadstring script
if loadRes == Lua.OK
then Lua.pcall 0 1 Nothing <* Lua.gc Lua.GCCOLLECT 0
else return loadRes
|
