fix hash decoding in abi

Author: Jan Xie

ethereum/abi.py

@@ -371,6 +371,8 @@ def decode_single(typ, data):
     base, sub, _ = typ
     if base == 'address':
         return encode_hex(data[12:])
+    elif base == 'hash':
+        return data[32-int(sub):]
     elif base == 'string' or base == 'bytes' or base == 'hash':
         return data[:int(sub)] if len(sub) else data
     elif base == 'uint':

ethereum/tests/test_abi.py

@@ -30,6 +30,10 @@ def test_abi_encode_single_hash():
     assert abi.encode_single(['hash', '8', []], b'\x00'*8) == b'\x00'*32
     assert abi.encode_single(['hash', '8', []], '00'*8) == b'\x00'*32
 
+def test_abi_decode_single_hash():
+    typ = ['hash', '8', []]
+    assert b'\x01'*8 == abi.decode_single(typ, abi.encode_single(typ, b'\x01'*8))
+
 # SETUP TESTS IN GLOBAL NAME SPACE
 def gen_func(filename, testname, testdata):
     return lambda: do_test_state(filename, testname, testdata)