pbkdf

commit d249a794ca47cb4e3abe494dcde80767d84b8632
parent 15a7fe19cf9759d28e401debfe138a42525e0be9
Author: Jared Tobin <jared@jtobin.io>
Date:   Tue, 25 Feb 2025 08:10:23 +0400

lib: minor bytestring optimization

Diffstat:
M
lib/Crypto/KDF/PBKDF.hs
 | 
10
++++++++--

1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/lib/Crypto/KDF/PBKDF.hs b/lib/Crypto/KDF/PBKDF.hs
@@ -25,6 +25,7 @@ import Data.Bits ((.>>.), (.&.))
 import qualified Data.Bits as B
 import qualified Data.ByteString as BS
 import qualified Data.ByteString.Builder as BSB
+import qualified Data.ByteString.Builder.Extra as BE
 import Data.Word (Word32, Word64)
 
 -- NB following synonym really only exists to make haddocks more
@@ -105,8 +106,13 @@ derive prf p s c dklen
       | i == l =
           let t = f i
               fin = BS.take r t
-          in  BS.toStrict . BSB.toLazyByteString $
-                acc <> BSB.byteString fin
+          in  BS.toStrict $
+                if   dklen <= 128
+                then BE.toLazyByteStringWith
+                       (BE.safeStrategy 128 BE.smallChunkSize) mempty $
+                       acc <> BSB.byteString fin
+                else BSB.toLazyByteString $
+                       acc <> BSB.byteString fin
       | otherwise =
           let t = f i
               nacc = acc <> BSB.byteString t