fix real type decoding in abi

Author: Jan Xie

ethereum/abi.py

@@ -389,7 +389,9 @@ def decode_single(typ, data):
         return big_endian_to_int(data) * 1.0 / 2**low
     elif base == 'real':
         high, low = [int(x) for x in sub.split('x')]
-        return (big_endian_to_int(data) * 1.0 / 2**low) % 2**high
+        o = big_endian_to_int(data)
+        i = (o - 2**(high+low)) if o >= 2**(high+low-1) else o
+        return (i * 1.0 / 2**low)
     elif base == 'bool':
         return bool(int(data.encode('hex'), 16))
 

ethereum/tests/test_abi.py

@@ -45,6 +45,19 @@ def test_abi_encode_single_prefixed_address():
     prefixed_address = '0x' + '0'*40
     assert abi.encode_single(['address', '', []], prefixed_address) == b'\x00' * 32
 
+def test_abi_decode_single_real():
+    real_data = abi.encode_single(['real', '128x128', []], 1)
+    assert abi.decode_single(['real', '128x128', []], real_data) == 1
+
+    real_data = abi.encode_single(['real', '128x128', []], 2**127-1)
+    assert abi.decode_single(['real', '128x128', []], real_data) == (2**127-1)*1.0
+
+    real_data = abi.encode_single(['real', '128x128', []], -1)
+    assert abi.decode_single(['real', '128x128', []], real_data) == -1
+
+    real_data = abi.encode_single(['real', '128x128', []], -2**127)
+    assert abi.decode_single(['real', '128x128', []], real_data) == -2**127
+
 # SETUP TESTS IN GLOBAL NAME SPACE
 def gen_func(filename, testname, testdata):
     return lambda: do_test_state(filename, testname, testdata)