[commit: bytestring] ghc-7.6: Add unsafePackMallocCStringLen (c706c00)

[Paolo Capriotti]

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

On branch  : ghc-7.6

http://hackage.haskell.org/trac/ghc/changeset/c706c000f94f044b3042c9a5deaf245372fb0cdd

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

commit c706c000f94f044b3042c9a5deaf245372fb0cdd
Author: Lauri Alanko <la at iki.fi>
Date:   Wed Jun 20 09:22:32 2012 +0000

    Add unsafePackMallocCStringLen

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

 Data/ByteString/Unsafe.hs |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/Data/ByteString/Unsafe.hs b/Data/ByteString/Unsafe.hs
index cf091a6..2aae1a9 100644
--- a/Data/ByteString/Unsafe.hs
+++ b/Data/ByteString/Unsafe.hs
@@ -36,6 +36,7 @@ module Data.ByteString.Unsafe (
         unsafePackCString,      -- :: CString -> IO ByteString
         unsafePackCStringLen,   -- :: CStringLen -> IO ByteString
         unsafePackMallocCString,-- :: CString -> IO ByteString
+        unsafePackMallocCStringLen, -- :: CStringLen -> IO ByteString
 
 #if defined(__GLASGOW_HASKELL__)
         unsafePackAddress,          -- :: Addr# -> IO ByteString
@@ -263,6 +264,22 @@ unsafePackMallocCString cstr = do
     len <- c_strlen cstr
     return $! PS fp 0 (fromIntegral len)
 
+-- | /O(n)/ Build a @ByteString@ from a malloced @CStringLen at . This
+-- value will have a @free(3)@ finalizer associated to it.
+--
+-- This funtion is /unsafe/. If the original @CString@ is later
+-- modified, this change will be reflected in the resulting @ByteString@,
+-- breaking referential transparency.
+--
+-- This function is also unsafe if you call its finalizer twice,
+-- which will result in a /double free/ error, or if you pass it
+-- a CString not allocated with 'malloc'.
+--
+unsafePackMallocCStringLen :: CStringLen -> IO ByteString
+unsafePackMallocCStringLen (cstr, len) = do
+    fp <- newForeignPtr c_free_finalizer (castPtr cstr)
+    return $! PS fp 0 len
+
 -- ---------------------------------------------------------------------
 
 -- | /O(1) construction/ Use a @ByteString@ with a function requiring a