src/Crypt/SHA256.hs

   1 {-# OPTIONS_GHC -fffi -cpp #-}
   2 {-# LANGUAGE CPP, ForeignFunctionInterface #-}
   3
   4 -- |
   5 -- Module:    Data.Digest.SHA256
   6 -- Copyright: Zooko O'Whielacronx
   7 -- License:   GPL
   8 --
   9 -- Stability: experimental
  10
  11 -- ByteString-based, zero-copying binding to Crypto++'s sha interface
  12
  13 -- thanks to Don Stewart <dons@galois.com>, Matthew Sackman
  14 -- <matthew@wellquite.org>, Brian O'Sullivan, lispy, Adam Langley
  15
  16 module Crypt.SHA256 ( sha256sum ) where
  17
  18 import Foreign
  19 import Foreign.C.Types
  20 import Numeric (showHex)
  21 import Foreign.C.String ( withCString )
  22 #if __GLASGOW_HASKELL__ > 606
  23 import Data.ByteString.Unsafe (unsafeUseAsCStringLen)
  24 #else
  25 import Data.ByteString.Base (unsafeUseAsCStringLen)
  26 #endif
  27 import qualified Data.ByteString as B
  28
  29 sha256sum :: B.ByteString -> String
  30 sha256sum p = unsafePerformIO $
  31               withCString (take 64 $ repeat 'x') $ \digestCString ->
  32               unsafeUseAsCStringLen p $ \(ptr,n) ->
  33               do let digest = castPtr digestCString :: Ptr Word8
  34                  c_sha256 ptr (fromIntegral n) digest
  35                  go digest 0 []
  36   where -- print it in 0-padded hex format
  37         go :: Ptr Word8 -> Int -> [String] -> IO String
  38         go q n acc | seq q n >= 32 = return $ concat (reverse acc)
  39                    | otherwise = do w <- peekElemOff q n
  40                                     go q (n+1) (draw w : acc)
  41         draw w = case showHex w [] of
  42                  [x] -> ['0', x]
  43                  x   -> x
  44
  45 -- void sha256sum(const unsigned char *d, size_t n, unsigned char *md);
  46 --
  47 foreign import ccall unsafe "sha2.h sha256" c_sha256
  48     :: Ptr CChar -> CSize -> Ptr Word8 -> IO ()
  49