{-# LINE 1 "libraries/base/System/Environment/ExecutablePath.hsc" #-}
{-# LANGUAGE Safe #-}
{-# LANGUAGE CPP #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  System.Environment.ExecutablePath
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- Function to retrieve the absolute filepath of the current executable.
--
-- @since 4.6.0.0
-----------------------------------------------------------------------------

module System.Environment.ExecutablePath ( getExecutablePath ) where

-- The imports are purposely kept completely disjoint to prevent edits
-- to one OS implementation from breaking another.


{-# LINE 25 "libraries/base/System/Environment/ExecutablePath.hsc" #-}
import Data.Word
import Foreign.C
import Foreign.Marshal.Alloc
import Foreign.Ptr
import Foreign.Storable
import System.Posix.Internals

{-# LINE 51 "libraries/base/System/Environment/ExecutablePath.hsc" #-}

-- The exported function is defined outside any if-guard to make sure
-- every OS implements it with the same type.

-- | Returns the absolute pathname of the current executable.
--
-- Note that for scripts and interactive sessions, this is the path to
-- the interpreter (e.g. ghci.)
--
-- Since base 4.11.0.0, 'getExecutablePath' resolves symlinks on Windows.
-- If an executable is launched through a symlink, 'getExecutablePath'
-- returns the absolute path of the original executable.
--
-- @since 4.6.0.0
getExecutablePath :: IO FilePath

--------------------------------------------------------------------------------
-- Mac OS X


{-# LINE 71 "libraries/base/System/Environment/ExecutablePath.hsc" #-}

type UInt32 = Word32

foreign import ccall unsafe "mach-o/dyld.h _NSGetExecutablePath"
    c__NSGetExecutablePath :: CString -> Ptr UInt32 -> IO CInt

-- | Returns the path of the main executable. The path may be a
-- symbolic link and not the real file.
--
-- See dyld(3)
_NSGetExecutablePath :: IO FilePath
_NSGetExecutablePath =
    allocaBytes 1024 $ \ buf ->  -- PATH_MAX is 1024 on OS X
    alloca $ \ bufsize -> do
        poke bufsize 1024
        status <- c__NSGetExecutablePath buf bufsize
        if status == 0
            then peekFilePath buf
            else do reqBufsize <- fromIntegral `fmap` peek bufsize
                    allocaBytes reqBufsize $ \ newBuf -> do
                        status2 <- c__NSGetExecutablePath newBuf bufsize
                        if status2 == 0
                             then peekFilePath newBuf
                             else errorWithoutStackTrace "_NSGetExecutablePath: buffer too small"

foreign import ccall unsafe "stdlib.h realpath"
    c_realpath :: CString -> CString -> IO CString

-- | Resolves all symbolic links, extra \/ characters, and references
-- to \/.\/ and \/..\/. Returns an absolute pathname.
--
-- See realpath(3)
realpath :: FilePath -> IO FilePath
realpath path =
    withFilePath path $ \ fileName ->
    allocaBytes 1024 $ \ resolvedName -> do
        _ <- throwErrnoIfNull "realpath" $ c_realpath fileName resolvedName
        peekFilePath resolvedName

getExecutablePath = _NSGetExecutablePath >>= realpath

--------------------------------------------------------------------------------
-- Linux


{-# LINE 252 "libraries/base/System/Environment/ExecutablePath.hsc" #-}