1 files changed, 37 insertions, 0 deletions

diff --git a/Base58.hs b/Base58.hs
new file mode 100644
index 0000000..26f1cb2
--- /dev/null
+++ b/Base58.hs
@@ -0,0 +1,37 @@
+module Base58 where
+
+import qualified Crypto.Hash.SHA256 as SHA256
+import qualified Data.ByteString      as S
+import Data.Maybe
+import Data.List
+import Data.Word ( Word8 )
+import Control.Monad
+
+base58chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
+
+base58digits :: [Char] -> Maybe [Int]
+base58digits str = sequence mbs
+ where
+    mbs = map (flip elemIndex base58chars) str
+    
+-- 5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ
+base58_decode :: [Char] -> Maybe (Word8,[Word8])
+base58_decode str = do
+    ds <- base58digits str
+    let n = foldl' (\a b-> a*58 + b) 0 $ ( map fromIntegral ds :: [Integer] )
+        rbytes = unfoldr getbyte n
+        getbyte d = do
+            guard (d/=0)
+            let (q,b) = d `divMod` 256
+            return (fromIntegral b,q)
+    
+    let (rcksum,rpayload) = splitAt 4 $ rbytes
+        a_payload = reverse rpayload
+        hash_result = S.take 4 . SHA256.hash . SHA256.hash . S.pack $ a_payload
+        expected_hash = S.pack $ reverse rcksum
+        (network_id,payload) = splitAt 1 a_payload
+    
+    network_id <- listToMaybe network_id
+    guard (hash_result==expected_hash)
+    return (network_id,payload)
+