bech32

Pure Haskell bech32, bech32m encodings (docs.ppad.tech/bech32).
git clone git://git.ppad.tech/bech32.git
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Bech32.hs (2072B)

      1 {-# OPTIONS_HADDOCK prune #-}
      2 {-# LANGUAGE ViewPatterns #-}
      3 
      4 -- |
      5 -- Module: Data.ByteString.Bech32
      6 -- Copyright: (c) 2024 Jared Tobin
      7 -- License: MIT
      8 -- Maintainer: Jared Tobin <jared@ppad.tech>
      9 --
     10 -- The
     11 -- [BIP0173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki)
     12 -- bech32 checksummed base32 encoding, with checksum verification.
     13 
     14 module Data.ByteString.Bech32 (
     15     -- * Encoding
     16     encode
     17 
     18     -- * Checksum
     19   , verify
     20   ) where
     21 
     22 import Control.Monad (guard)
     23 import qualified Data.ByteString as BS
     24 import qualified Data.ByteString.Char8 as B8
     25 import qualified Data.ByteString.Base32 as B32
     26 import Data.ByteString.Base32 (Encoding(..))
     27 import qualified Data.ByteString.Builder as BSB
     28 import qualified Data.ByteString.Builder.Extra as BE
     29 import qualified Data.Char as C (toLower)
     30 
     31 -- realization for small builders
     32 toStrict :: BSB.Builder -> BS.ByteString
     33 toStrict = BS.toStrict
     34   . BE.toLazyByteStringWith (BE.safeStrategy 128 BE.smallChunkSize) mempty
     35 {-# INLINE toStrict #-}
     36 
     37 create_checksum :: BS.ByteString -> BS.ByteString -> BS.ByteString
     38 create_checksum = B32.create_checksum Bech32
     39 
     40 -- | Encode a base256 human-readable part and input as bech32.
     41 --
     42 --   >>> let Just bech32 = encode "bc" "my string"
     43 --   >>> bech32
     44 --   "bc1d4ujqum5wf5kuecmu02w2"
     45 encode
     46   :: BS.ByteString        -- ^ base256-encoded human-readable part
     47   -> BS.ByteString        -- ^ base256-encoded data part
     48   -> Maybe BS.ByteString  -- ^ bech32-encoded bytestring
     49 encode hrp (B32.encode -> dat) = do
     50   guard (B32.valid_hrp hrp)
     51   let check = create_checksum hrp (B32.as_word5 dat)
     52       res = toStrict $
     53            BSB.byteString (B8.map C.toLower hrp)
     54         <> BSB.word8 49 -- 1
     55         <> BSB.byteString dat
     56         <> BSB.byteString (B32.as_base32 check)
     57   guard (BS.length res < 91)
     58   pure res
     59 
     60 -- | Verify that a bech32 string has a valid checksum.
     61 --
     62 --   >>> verify "bc1d4ujqum5wf5kuecmu02w2"
     63 --   True
     64 --   >>> verify "bc1d4ujquw5wf5kuecmu02w2" -- s/m/w
     65 --   False
     66 verify
     67   :: BS.ByteString -- ^ bech32-encoded bytestring
     68   -> Bool
     69 verify = B32.verify Bech32
     70