[Haskell-cafe] System.Win32.Registry... Help?

[Simon Peter Nicholls]

The Registry module has code that will be helpful, as it includes a
helper function for the common use case of setting String values.

regSetStringValue :: HKEY -> String -> String -> IO ()
regSetStringValue hk key val =
  withTString val $ \ v ->
  regSetValueEx hk key rEG_SZ v (length val * sizeOf (undefined::TCHAR))

http://www.haskell.org/ghc/docs/7.4.2/html/libraries/Win32-2.2.2.0/src/System-Win32-Registry.html

On Sun, Jul 22, 2012 at 7:11 AM, Anonymous Void <bitsofchaos at gmail.com> wrote:
> Hi,
>
> I'm working on a project that will require me to create and possibly
> set registry keys.
> I don't have much experience with programming on Windows either,
> but I'm having to learn as you don't get many *nix PCs at a computer
> repair shop, lol.
>
> I found a mailing list post showing how to read registry keys and was
> able to make a function based off of it,
> but I have no idea what to put into some of the arguments for
> regSetValueEx or regCreateKeyEx, so I'm stuck.
> Also, what's the best way to recursively traverse trees in the
> registry, are there any functions for it?
>
> Can someone please help me out with this?
> Thank you.
>
>
> {-# LANGUAGE ForeignFunctionInterface #-}
>
> import System.Win32.Types
> import System.Win32.Registry
> import Foreign.Ptr (castPtr)
> import Foreign.Marshal.Alloc (allocaBytes)
> import Foreign.C.String (peekCWString, withCWString)
> import Control.Exception (bracket, throwIO)
>
> -- // parse a string from a registry value of certain type
> parseRegString :: RegValueType -> LPBYTE -> IO String
> parseRegString ty mem
>   | ty == rEG_SZ        = peekCWString (castPtr mem)
>   | ty == rEG_EXPAND_SZ = peekCWString (castPtr mem) >>=
>                           expandEnvironmentStrings
>   | otherwise           = ioError (userError "Invalid registry value type")
>
> -- // FFI import of the ExpandEnvironmentStrings function needed
> -- // to make use of the registry values
> expandEnvironmentStrings :: String -> IO String
> expandEnvironmentStrings toexpand =
>   withCWString toexpand $ \input ->
>   allocaBytes 512 $ \output ->
>   do c_ExpandEnvironmentStrings input output 256
>      peekCWString output
> foreign import stdcall unsafe "windows.h ExpandEnvironmentStringsW"
>   c_ExpandEnvironmentStrings :: LPCTSTR -> LPTSTR -> DWORD -> IO DWORD
>
> ----
> get_key :: HKEY -> String -> String -> IO String
> get_key cat loc key =
>   bracket op regCloseKey $ \x ->
>   allocaBytes 512 $ \mem ->
>   do ty <- regQueryValueEx x key mem 512
>      parseRegString ty mem
>   where op = regOpenKeyEx cat loc kEY_QUERY_VALUE
>
> set_key :: HKEY -> String -> String -> IO ()
> set_key cat loc key =
>   regSetValueEx cat loc rEG_SZ??? "LPTSTR? What do I put here?"
> magic_win32_number_here?
>   where op = regOpenKeyEx cat loc kEY_SET_VALUE
>
> main = get_key hKEY_CURRENT_USER loc key >>= print
>   where loc = "Software\\7-Zip"
>         key = "Test"
>
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