[commit: base] encoding: Use correct encoding in Foreign.C.String.charIsRepresentable by improving GHC.Foreign.charIsRepresentable (af1bbde)

[Max Bolingbroke]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : encoding

http://hackage.haskell.org/trac/ghc/changeset/af1bbdee927a56e4b9749a297f827935d5e87cd7

>---------------------------------------------------------------

commit af1bbdee927a56e4b9749a297f827935d5e87cd7
Author: Max Bolingbroke <batterseapower at hotmail.com>
Date:   Mon Apr 11 11:54:34 2011 +0100

    Use correct encoding in Foreign.C.String.charIsRepresentable by improving GHC.Foreign.charIsRepresentable

>---------------------------------------------------------------

 Foreign/C/String.hs |    2 +-
 GHC/Foreign.hs      |    5 +----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/Foreign/C/String.hs b/Foreign/C/String.hs
index cbf8a1e..fdefdc6 100644
--- a/Foreign/C/String.hs
+++ b/Foreign/C/String.hs
@@ -229,7 +229,7 @@ charIsRepresentable c = return (ord c < 256)
 -- -- | Determines whether a character can be accurately encoded in a 'CString'.
 -- -- Unrepresentable characters are converted to '?' or their nearest visual equivalent.
 charIsRepresentable :: Char -> IO Bool
-charIsRepresentable = GHC.charIsRepresentable localeEncoding -- NOT foreignEncoding because that ignores failure
+charIsRepresentable = GHC.charIsRepresentable foreignEncoding
 #endif
 
 -- single byte characters
diff --git a/GHC/Foreign.hs b/GHC/Foreign.hs
index eeac27e..188e190 100644
--- a/GHC/Foreign.hs
+++ b/GHC/Foreign.hs
@@ -138,14 +138,11 @@ withCStringLen enc = withEncodedCString enc False
 
 -- | Determines whether a character can be accurately encoded in a 'CString'.
 --
--- For this to work properly, the supplied 'TextEncoding' must throw an
--- IOException upon encountering an invalid sequence.

>---------------------------------------------------------------

 -- Pretty much anyone who uses this function is in a state of sin because
 -- whether or not a character is encodable will, in general, depend on the
 -- context in which it occurs.
 charIsRepresentable :: TextEncoding -> Char -> IO Bool
-charIsRepresentable enc c = withEncodedCString enc False [c] (\_ -> return True) `catchException` (\e -> let _ = e :: IOException in return False)
+charIsRepresentable enc c = withCString enc [c] (fmap (== [c]) . peekCString enc) `catchException` (\e -> let _ = e :: IOException in return False)
 
 -- auxiliary definitions
 -- ----------------------