From 4247520e917c79e37b5894f2a6a17aeca1c67da5 Mon Sep 17 00:00:00 2001
From: Vincent Hanquez <vincent@snarc.org>
Date: Sat, 11 Apr 2015 16:02:31 +0100
Subject: [PATCH] [Internal] add a way to index bytestring

---
 Crypto/Internal/ByteArray.hs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Crypto/Internal/ByteArray.hs b/Crypto/Internal/ByteArray.hs
index eeda4bd..d7b1fbc 100644
--- a/Crypto/Internal/ByteArray.hs
+++ b/Crypto/Internal/ByteArray.hs
@@ -19,6 +19,7 @@ module Crypto.Internal.ByteArray
     , byteArraySplit
     , byteArrayXor
     , byteArrayEq
+    , byteArrayIndex
     , byteArrayConstEq
     , byteArrayConcat
     , byteArrayToBS
@@ -96,6 +97,9 @@ byteArrayXor a b =
         la = byteArrayLength a
         lb = byteArrayLength b
 
+byteArrayIndex :: ByteArrayAccess a => a -> Int -> Word8
+byteArrayIndex b i = unsafeDoIO $ withByteArray b $ \p -> peek (p `plusPtr` i)
+
 byteArraySplit :: ByteArray bs => Int -> bs -> (bs, bs)
 byteArraySplit n bs
     | n <= 0    = (empty, bs)