FIX: MOD uses UInt256

Signed-off-by: Thomas Zamojski <thomas.zamojski@quadratic-labs.com>

Author: thomas-quadratic

evm/src/main/java/org/hyperledger/besu/evm/operation/ModOperation.java

@@ -17,12 +17,9 @@
 import org.hyperledger.besu.evm.EVM;
 import org.hyperledger.besu.evm.frame.MessageFrame;
 import org.hyperledger.besu.evm.gascalculator.GasCalculator;
-
-import java.math.BigInteger;
-import java.util.Arrays;
+import org.hyperledger.besu.evm.UInt256;
 
 import org.apache.tuweni.bytes.Bytes;
-import org.apache.tuweni.bytes.Bytes32;
 
 /** The Mod operation. */
 public class ModOperation extends AbstractFixedCostOperation {
@@ -53,24 +50,11 @@ public Operation.OperationResult executeFixedCostOperation(
   public static OperationResult staticOperation(final MessageFrame frame) {
     final Bytes value0 = frame.popStackItem();
     final Bytes value1 = frame.popStackItem();
-    if (value1.isZero()) {
-      frame.pushStackItem(Bytes32.ZERO);
-    } else {
-      BigInteger b1 = new BigInteger(1, value0.toArrayUnsafe());
-      BigInteger b2 = new BigInteger(1, value1.toArrayUnsafe());
-      final BigInteger result = b1.mod(b2);
-
-      Bytes resultBytes = Bytes.wrap(result.toByteArray());
-      if (resultBytes.size() > 32) {
-        resultBytes = resultBytes.slice(resultBytes.size() - 32, 32);
-      }
-
-      final byte[] padding = new byte[32 - resultBytes.size()];
-      Arrays.fill(padding, result.signum() < 0 ? (byte) 0xFF : 0x00);
-
-      frame.pushStackItem(Bytes.concatenate(Bytes.wrap(padding), resultBytes));
-    }
-
+    UInt256 b1 = UInt256.fromBytesBE(value0.toArrayUnsafe());
+    UInt256 b2 = UInt256.fromBytesBE(value1.toArrayUnsafe());
+    final UInt256 result = b1.mod(b2);
+    Bytes resultBytes = Bytes.wrap(result.toBytesBE());
+    frame.pushStackItem(resultBytes);
     return modSuccess;
   }
 }