eth/abi: add a testcase for handling hex and bin strings (#101)

* eth/abi: fix handling of hex values for byte strings

* eth/abi: add a testcase for handling hex and bin strings

* eth/abi: fix handling of hex values for byte strings

* spec: run rufo

lib/eth/abi.rb

@@ -346,11 +346,7 @@ def encode_fixed(arg, type)
     # Properly encodes byte-strings.
     def encode_bytes(arg, type)
       raise EncodingError, "Expecting String: #{arg}" unless arg.instance_of? String
-
-      if Util.is_prefixed? arg
-        arg = Util.remove_hex_prefix arg
-        arg = Util.hex_to_bin arg
-      end
+      arg = handle_hex_string arg, type
 
       if type.sub_type.empty?
         size = Util.zpad_int arg.size
@@ -410,5 +406,23 @@ def encode_address(arg)
         raise EncodingError, "Could not parse address: #{arg}"
       end
     end
+
+    # The ABI encoder needs to be able to determine between a hex `"123"`
+    # and a binary `"123"` string.
+    def handle_hex_string(arg, type)
+      if Util.is_prefixed? arg or
+         (arg.size === type.sub_type.to_i * 2 and Util.is_hex? arg)
+
+        # There is no way telling whether a string is hex or binary with certainty
+        # in Ruby. Therefore, we assume a `0x` prefix to indicate a hex string.
+        # Additionally, if the string size is exactly the double of the expected
+        # binary size, we can assume a hex value.
+        return Util.hex_to_bin arg
+      else
+
+        # Everything else will be assumed binary or raw string.
+        return arg.b
+      end
+    end
   end
 end

spec/eth/abi_spec.rb

@@ -205,6 +205,11 @@
 
     it "can handle hex-strings for bytes types" do
       expect(Abi.encode ["bytes4"], ["0x80ac58cd"]).to eq "\x80\xACX\xCD#{"\x00" * 28}"
+      expect(Abi.encode ["bytes4"], ["80ac58cd"]).to eq "\x80\xACX\xCD#{"\x00" * 28}"
+
+      # But don't break binary strings
+      expect(Abi.encode ["bytes4"], ["\x80\xACX\xCD"]).to eq "\x80\xACX\xCD#{"\x00" * 28}"
+      expect(Util.bin_to_hex Abi.encode ["bytes10"], ["1234567890".b]).to eq "3132333435363738393000000000000000000000000000000000000000000000"
     end
 
     it "can decode types" do