feat: argument decoder (#147)

Author: alexbarnsley

crypto/utils/abi/argument_decoder.py

@@ -0,0 +1,33 @@
+import binascii
+from crypto.utils.abi_decoder import AbiDecoder
+
+class ArgumentDecoder:
+    def __init__(self, hex_string: str):
+        try:
+            self.bytes = binascii.unhexlify(hex_string)
+        except binascii.Error:
+            self.bytes = b''
+
+    def decode_string(self) -> str:
+        value, _ = AbiDecoder.decode_string(self.bytes, 0)
+
+        return value
+
+    def decode_address(self) -> str:
+        value, _ = AbiDecoder.decode_address(self.bytes, 0)
+
+        return value
+
+    def decode_unsigned_int(self) -> int:
+        value, _ = AbiDecoder.decode_number(self.bytes, 0, False)
+
+        return value
+
+    def decode_signed_int(self) -> int:
+        value, _ = AbiDecoder.decode_number(self.bytes, 0, True)
+
+        return value
+
+    def decode_bool(self) -> bool:
+        value, _ = AbiDecoder.decode_bool(self.bytes, 0)
+        return value

crypto/utils/abi_decoder.py

@@ -64,32 +64,36 @@ def decode_parameter(self, bytes_data, offset, param):
         if match:
             signed = match.group(1) == 'int'
             bits = int(match.group(2))
-            return self.decode_number(bytes_data, offset, bits, signed)
+            return self.decode_number(bytes_data, offset, signed)
         if type_ == 'tuple':
             return self.decode_tuple(bytes_data, offset, param)
         raise Exception('Unsupported type: ' + type_)
 
-    def decode_address(self, bytes_data, offset):
+    @staticmethod
+    def decode_address(bytes_data, offset):
         data = bytes_data[offset:offset+32]
         address_bytes = data[12:32]
         address = '0x' + address_bytes.hex()
         address = get_checksum_address(address)
         return address, 32
 
-    def decode_bool(self, bytes_data, offset):
+    @staticmethod
+    def decode_bool(bytes_data, offset):
         data = bytes_data[offset:offset+32]
         value = int.from_bytes(data, byteorder='big') != 0
         return value, 32
 
-    def decode_number(self, bytes_data, offset, bits, signed):
+    @staticmethod
+    def decode_number(bytes_data, offset, signed):
         data = bytes_data[offset:offset+32]
         value = int.from_bytes(data, byteorder='big', signed=signed)
         return value, 32
 
-    def decode_string(self, bytes_data, offset):
-        data_offset = self.read_uint(bytes_data, offset)
+    @classmethod
+    def decode_string(cls, bytes_data, offset):
+        data_offset = cls.read_uint(bytes_data, offset)
         string_offset = offset + data_offset
-        length = self.read_uint(bytes_data, string_offset)
+        length = cls.read_uint(bytes_data, string_offset)
         string_data = bytes_data[string_offset+32:string_offset+32+length]
         value = string_data.decode('utf-8')
         return value, 32
@@ -140,6 +144,7 @@ def decode_tuple(self, bytes_data, offset, param):
             values[name] = value
         return values, 32
 
-    def read_uint(self, bytes_data, offset):
+    @staticmethod
+    def read_uint(bytes_data, offset):
         data = bytes_data[offset:offset+32]
         return int.from_bytes(data, byteorder='big')

tests/utils/abi/test_argument_decoder.py

@@ -0,0 +1,42 @@
+from crypto.utils.abi.argument_decoder import ArgumentDecoder
+
+
+def test_it_should_decode_address():
+    payload  = '000000000000000000000000512F366D524157BcF734546eB29a6d687B762255'
+    expected = '0x512F366D524157BcF734546eB29a6d687B762255'
+
+    decoder = ArgumentDecoder(payload)
+
+    assert decoder.decode_address() == expected
+
+def test_it_should_decode_unsigned_int():
+    payload  = '000000000000000000000000000000000000000000000000016345785d8a0000'
+    expected = 100000000000000000
+
+    decoder = ArgumentDecoder(payload)
+
+    assert decoder.decode_unsigned_int() == expected
+
+def test_it_should_decode_signed_int():
+    payload  = '000000000000000000000000000000000000000000000000016345785d8a0000'
+    expected = 100000000000000000
+
+    decoder = ArgumentDecoder(payload)
+
+    assert decoder.decode_signed_int() == expected
+
+def test_it_should_decode_bool_as_true():
+    payload  = '0000000000000000000000000000000000000000000000000000000000000001'
+    expected = True
+
+    decoder = ArgumentDecoder(payload)
+
+    assert decoder.decode_bool() == expected
+
+def test_it_should_decode_bool_as_false():
+    payload  = '0000000000000000000000000000000000000000000000000000000000000000'
+    expected = False
+
+    decoder = ArgumentDecoder(payload)
+
+    assert decoder.decode_bool() == expected