Incremental.hs

{- Incremental hashing
 -
 - Copyright 2013-2026 Joey Hess <id@joeyh.name>
 -
 - License: BSD-2-clause
 -}

module Utility.Hash.Incremental where

import Utility.Hash.Types

import qualified Data.ByteString as S

data IncrementalHasher = IncrementalHasher
	{ updateIncrementalHasher :: S.ByteString -> IO ()
	-- ^ Called repeatedly on each piece of the content.
	, finalizeIncrementalHasher :: IO (Maybe HashDigest)
	-- ^ Called once the full content has been sent, returns
	-- the hash. (Nothing if unableIncremental was called.)
	, unableIncrementalHasher :: IO ()
	-- ^ Call if the incremental hashing is unable to be done.
	, positionIncrementalHasher :: IO (Maybe Integer)
	-- ^ Returns the number of bytes that have been fed to this
	-- incremental hasher so far. (Nothing if unableIncrementalHasher
	-- was called.)
	}

data IncrementalVerifier = IncrementalVerifier
	{ updateIncrementalVerifier :: S.ByteString -> IO ()
	, finalizeIncrementalVerifier :: IO (Maybe Bool)
	, unableIncrementalVerifier :: IO ()
	, positionIncrementalVerifier :: IO (Maybe Integer)
	, descIncrementalVerifier :: String
	}

mkIncrementalVerifier :: IO IncrementalHasher -> String -> (Hash -> Bool) -> IO IncrementalVerifier
mkIncrementalVerifier mkhasher desc samechecksum = do
	hasher <- mkhasher
	return $ IncrementalVerifier
		{ updateIncrementalVerifier = updateIncrementalHasher hasher
		, finalizeIncrementalVerifier = 
			maybe Nothing (Just . samechecksum . digestToHash)
				<$> finalizeIncrementalHasher hasher
		, unableIncrementalVerifier = unableIncrementalHasher hasher
		, positionIncrementalVerifier = positionIncrementalHasher hasher
		, descIncrementalVerifier = desc
		}