eth-abi

jdk 11+ because of http4s-jdk-http-client

eth-abi is currently available for scala 2.12 and scala2.13

Getting Start

to begin using eth-abi, add the following to your build.sbt:

libraryDependencies ++= Seq(
  "com.github.lbqds" %% "ethabi" % "0.3.0",
  "org.typelevel" %% "cats-core" % "2.1.1",
  "org.typelevel" %% "cats-effect" % "2.1.3"
)

Code Generator

eth-abi have a tool which can generate scala code by solidity contract abi and bin code.

download latest version abi-codegen-0.3.0 from the release page, and execute:

$ abi-codegen-0.3.0 --help

use KVStore contract as an example, execute:

$ abi-codegen-0.3.0 gen -a KVStore.abi -b KVStore.bin -p "examples.kvstore" -c "KVStore" -o ./

would generate scala code at the current directory. you can also dive into generated code at here.

now we can call generated scala method instead of execute contract method by eth_sendTransaction or eth_sendRawTransaction:

object Main extends IOApp {

  private def log(str: String): IO[Unit] = IO.delay(println(s"${Thread.currentThread.getName}, $str"))

  override def run(args: List[String]): IO[ExitCode] = {
    val sender = Address("60f7947aef8bbc9bc314a9b8db8096099345fba3")
    val transactionOpt = TransactionOpt(Some(400000), Some(1000), None, None)
    val retryPolicy = retry.RetryPolicies.limitRetries[IO](5).join(RetryPolicies.constantDelay[IO](5 seconds))
    KVStore[IO]("ws://127.0.0.1:8546").use { kvStore =>

      def setAndAwait(key: Uint16, value: DynamicBytes): IO[TransactionReceipt] = {
        for {
          client  <- kvStore.client
          txHash  <- kvStore.set(key, value, sender, transactionOpt).flatMap(_.get)
          receipt <- retryUntil[IO, Option[TransactionReceipt]](
            "wait tx receipt",
            retryPolicy,
            client.getTransactionReceipt(txHash).flatMap(_.get),
            _.isDefined
          ).map(_.get)
        } yield receipt
      }

      val task = for {
        client     <- kvStore.client
        peerCount  <- client.peerCount.flatMap(_.get)
        _          <- log(s"peer count: $peerCount")
        cliVersion <- client.clientVersion.flatMap(_.get)
        _          <- log(s"client version: $cliVersion")
        work       <- client.getWork.flatMap(_.get)
        _          <- log(s"work response: $work")
        protocolV  <- client.protocolVersion.flatMap(_.get)
        _          <- log(s"protocol version: $protocolV")
        coinbase   <- client.coinbase.flatMap(_.get)
        _          <- log(s"coinbase address: $coinbase")
        syncStatus <- client.syncing.flatMap(_.get)
        _          <- log(s"sync status: $syncStatus")
        deployHash <- kvStore.deploy(sender, transactionOpt)
        address    <- retryUntil[IO, Option[Address]]("wait contract deployed", retryPolicy, kvStore.address, _.isDefined).map(_.get)
        _          <- log(s"contract deploy succeed, address: $address")
        contractTx <- deployHash.get.flatMap(client.getTransactionByHash).flatMap(_.get)
        _          <- log(s"contract deploy tx: ${contractTx.get}")
        result     <- kvStore.subscribeRecord
        _          <- log(s"subscription id: ${result.id}")
        fiber      <- result.stream.map(println).compile.drain.start
        receipt1   <- setAndAwait(Uint16(12), DynamicBytes.from("0x010203040506070809"))
        _          <- log(s"tx receipt: $receipt1")
        receipt2   <- setAndAwait(Uint16(13), DynamicBytes.from("0xff001122334455aabbccddee"))
        _          <- log(s"tx receipt: $receipt2")
        result     <- kvStore.get(Uint16(12), sender, transactionOpt)
        _          <- log(s"key: 12, value: $result")
        _          <- fiber.cancel
        _          <- log("quit now")
      } yield ()
      task.handleErrorWith(exp => IO.delay(exp.printStackTrace())) *> IO.delay(ExitCode.Success)
    }
  }
}

NOTE:

• the generated code use websocket client rather than http, because it will subscribe solidity event with ethereum RPC PUB/SUB
• you need to assure the account have been unlocked before deploy and call contract method
• every event will have a generated subscribeEventName method, which return F[Stream[F, Event]]

ABIEncoderV2

eth-abi support experimental ABIEncoderV2 feature, tuple will map to TupleTypeN, the generated exchange use this feature heavily.

JSONRPC

eth-abi can also be used to interact directly with ethereum:

object HttpClientTest extends IOApp {
  override def run(args: List[String]): IO[ExitCode] = {
    import HttpClient._
    import scala.concurrent.duration._

    apply[IO]("http://127.0.0.1:8545").use { client =>
      for {
        cVersion  <- client.clientVersion
        _         <- IO.delay(println(s"client version: $cVersion"))
        nVersion  <- client.netVersion
        _         <- IO.delay(println(s"net version: $nVersion"))
        filterId  <- client.newBlockFilter
        _         <- IO.delay(println(s"filter id: $filterId"))
        changes1  <- IO.sleep(3 seconds) *> client.getFilterChangeHashes(filterId)
        _         <- IO.delay(println(s"changes: $changes1"))
        changes2  <- IO.sleep(3 seconds) *> client.getFilterChangeHashes(filterId)
        _         <- IO.delay(println(s"changes: $changes2"))
      } yield ExitCode.Success
    }
  }
}

all supported JSONRPC api list at here.

Functional Programming

eth-abi use cats and cats-effect, although the above example use cats-effect IO, you can also choose ZIO

and all generated scala code are functional style.

License

Copyright (c) 2020 Lbqds

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.