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module GHC.Settings.Utils where
import Prelude -- See Note [Why do we import Prelude here?]
import Data.Char (isSpace)
import Data.Map (Map)
import qualified Data.Map as Map
import GHC.BaseDir
import GHC.Platform.ArchOS
maybeRead :: Read a => String -> Maybe a
maybeRead str = case reads str of
[(x, "")] -> Just x
_ -> Nothing
maybeReadFuzzy :: Read a => String -> Maybe a
maybeReadFuzzy str = case reads str of
[(x, s)] | all isSpace s -> Just x
_ -> Nothing
-- Note [Settings file]
-- ~~~~~~~~~~~~~~~~~~~~
--
-- GHC has a file, `${top_dir}/settings`, which is the main source of run-time
-- configuration. ghc-pkg needs just a little bit of it: the target platform CPU
-- arch and OS. It uses that to figure out what subdirectory of `~/.ghc` is
-- associated with the current version/target platform.
--
-- This module has just enough code to read key value pairs from the settings
-- file, and read the target platform from those pairs.
type RawSettings = Map String String
-- | Read target Arch/OS from the settings
getTargetArchOS
:: FilePath -- ^ Settings filepath (for error messages)
-> RawSettings -- ^ Raw settings file contents
-> Either String ArchOS
getTargetArchOS settingsFile settings =
ArchOS <$> readRawSetting settingsFile settings "target arch"
<*> readRawSetting settingsFile settings "target os"
getRawSetting
:: FilePath -> RawSettings -> String -> Either String String
getRawSetting settingsFile settings key = case Map.lookup key settings of
Just xs -> Right xs
Nothing -> Left $ "No entry for " ++ show key ++ " in " ++ show settingsFile
getRawFilePathSetting
:: FilePath -> FilePath -> RawSettings -> String -> Either String String
getRawFilePathSetting top_dir settingsFile settings key =
expandTopDir top_dir <$> getRawSetting settingsFile settings key
getRawBooleanSetting
:: FilePath -> RawSettings -> String -> Either String Bool
getRawBooleanSetting settingsFile settings key = do
rawValue <- getRawSetting settingsFile settings key
case rawValue of
"YES" -> Right True
"NO" -> Right False
xs -> Left $ "Bad value for " ++ show key ++ ": " ++ show xs
readRawSetting
:: (Show a, Read a) => FilePath -> RawSettings -> String -> Either String a
readRawSetting settingsFile settings key = case Map.lookup key settings of
Just xs -> case maybeRead xs of
Just v -> Right v
Nothing -> Left $ "Failed to read " ++ show key ++ " value " ++ show xs
Nothing -> Left $ "No entry for " ++ show key ++ " in " ++ show settingsFile
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