[ETCM-354] Roundtrip ForkIds

Author: lukasz-golebiewski

src/main/scala/io/iohk/ethereum/forkid/ForkId.scala

@@ -9,6 +9,8 @@ import io.iohk.ethereum.utils.BigIntExtensionMethods._
 import io.iohk.ethereum.utils.ByteUtils._
 import io.iohk.ethereum.rlp._
 
+import RLPImplicitConversions._
+
 case class ForkId(hash: BigInt, next: Option[BigInt])
 
 object ForkId {
@@ -44,7 +46,6 @@ object ForkId {
 
   implicit class ForkIdEnc(forkId: ForkId) extends RLPSerializable {
     import RLPImplicits._
-    import RLPImplicitConversions._
 
     import io.iohk.ethereum.utils.ByteUtils._
     override def toRLPEncodable: RLPEncodeable = {
@@ -55,4 +56,14 @@ object ForkId {
 
   }
 
+  implicit val forkIdEnc = new RLPDecoder[ForkId] {
+
+    def decode(rlp: RLPEncodeable): ForkId = rlp match {
+      case RLPList(hash, next) => {
+        val i = bigIntFromEncodeable(next)
+        ForkId(bigIntFromEncodeable(hash), if (i == 0) None else Some(i))
+      }
+      case _ => throw new RuntimeException("Error when decoding ForkId")
+    }
+  }
 }

src/test/scala/io/iohk/ethereum/forkid/ForkIdSpec.scala

@@ -9,6 +9,10 @@ import org.scalatest.wordspec.AnyWordSpec
 import org.scalatest.matchers.should._
 import org.bouncycastle.util.encoders.Hex
 
+import io.iohk.ethereum.rlp._
+import io.iohk.ethereum.rlp.RLPImplicits._
+
+
 class ForkIdSpec extends AnyWordSpec with Matchers {
 
   val config = blockchains
@@ -79,22 +83,22 @@ class ForkIdSpec extends AnyWordSpec with Matchers {
       create(11700000) shouldBe ForkId(0xB20AFE12L, None)
     }
 
-
     // Here’s a couple of tests to verify the proper RLP encoding (since FORK_HASH is a 4 byte binary but FORK_NEXT is an 8 byte quantity):
     "be correctly encoded via rlp" in {
-      import ForkId._
-      import io.iohk.ethereum.rlp._
-      import io.iohk.ethereum.rlp.RLPImplicits._
-
-      encode(ForkId(0, None).toRLPEncodable) shouldBe Hex.decode("c6840000000080")
-      encode(ForkId(0xdeadbeefL, Some(0xBADDCAFEL)).toRLPEncodable) shouldBe Hex.decode("ca84deadbeef84baddcafe")
+      roundTrip(ForkId(0, None), "c6840000000080")
+      roundTrip(ForkId(0xdeadbeefL, Some(0xBADDCAFEL)), "ca84deadbeef84baddcafe")
 
       val maxUInt64 = (BigInt(0x7FFFFFFFFFFFFFFFL) << 1) + 1
       maxUInt64.toByteArray shouldBe Array(0, -1, -1, -1, -1, -1, -1, -1, -1)
       val maxUInt32 = BigInt(0xFFFFFFFFL)
       maxUInt32.toByteArray shouldBe Array(0, -1, -1, -1, -1)
 
-      encode(ForkId(maxUInt32, Some(maxUInt64)).toRLPEncodable) shouldBe Hex.decode("ce84ffffffff88ffffffffffffffff")
+      roundTrip(ForkId(maxUInt32, Some(maxUInt64)), "ce84ffffffff88ffffffffffffffff")
     }
   }
+
+  private def roundTrip(forkId: ForkId, hex: String) = {
+    encode(forkId.toRLPEncodable) shouldBe Hex.decode(hex)
+    decode[ForkId](Hex.decode(hex)) shouldBe forkId
+  }
 }