Add a cSettingOutputDirectory setting for codegen.

If set, this option defines an output destination directory
for generated files.  It will be created if necessary.

Fixes #255

copilot-c99/src/Copilot/Compile/C99/Compile/Internal.hs

@@ -7,6 +7,8 @@ module Copilot.Compile.C99.Compile.Internal
 import Text.PrettyPrint     (render)
 import Data.List            (nub)
 import Data.Maybe           (catMaybes)
+import System.Directory     (createDirectoryIfMissing)
+import System.FilePath      ((</>))
 
 import Language.C99.Pretty  (pretty)
 import qualified Language.C99.Simple as C
@@ -41,8 +43,14 @@ compileWith cSettings prefix spec = do
                         , ""
                         ]
 
-  writeFile (prefix ++ ".c") $ cmacros ++ cfile
-  writeFile (prefix ++ ".h") hfile
+  case cSettingsOutputDirectory cSettings of
+    Nothing ->
+      do writeFile (prefix ++ ".c") $ cmacros ++ cfile
+         writeFile (prefix ++ ".h") hfile
+    Just dir ->
+      do createDirectoryIfMissing True dir
+         writeFile (dir </> prefix ++ ".c") $ cmacros ++ cfile
+         writeFile (dir </> prefix ++ ".h") hfile
 
 -- | Compile a specification to a .h and a .c file.
 --

copilot-c99/src/Copilot/Compile/C99/Settings/Internal.hs

@@ -4,8 +4,9 @@ module Copilot.Compile.C99.Settings.Internal where
 -- | Settings used to customize the code generated.
 data CSettings = CSettings
   { cSettingsStepFunctionName :: String
+  , cSettingsOutputDirectory :: Maybe FilePath
   }
 
 -- | Default settings with a step function called @step@.
 mkDefaultCSettings :: CSettings
-mkDefaultCSettings = CSettings "step"
+mkDefaultCSettings = CSettings "step" Nothing