Title Text

Writing Ewasm in Rust

用 Rust 编写Ewasm 合约

Antonio Yang

yanganto@github

Ewasm Contract

WHAT, HOW & WHY ?

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What

Ewasm  = Ethereum WebAssembly

WebAssembly is an open standard that defines a portable binary-code format for executable programs, and a corresponding textual assembly language.
Ethereum is a decentralized, open-source blockchain with smart contract (web3) functionality.

How

  • A deterministic subset of WebAssembly.

ref :https://ewasm.readthedocs.io/en/mkdocs/

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Why

Any language with HTTP protocol

Web2 Server

API

EVM

Web3 Blockchain

Restricted

Any language compile to EWasm format

WebAssembly

WHY RUST ?

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What is Rust ?

Rust is a multi-paradigm, high-level, general-purpose programming language designed for performance and safety, especially safe concurrency.

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Why Rust ?

  • low-level control and reliable performance.
  • free from the non-deterministic garbage collection
  • no runtime, enabling small binary sizes

Web 3

BLOCKCHAIN

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Web ?

Web3 Blockchain

Talk to contract in Binary over the blockchain network

Web2 Server

API

Talk to API in Hyper Text  Markup Language over the internet

API

API

API

API

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Web 3

Web

Blockchain (Web3)

Handler(s)

Main entry

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Routing

In web2, Uniform Resource Identifier(URI) for routing

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Routing

In web3, functional signature for routing

  • 4 bytes
  • Optional attribute
  • Hash(fn_name(type,))
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Same Backend Idea

Handlers

Main function

(entry point)

Prior Art

CONTRACT IN RUST

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Contract in Rust

ewasm-rust-api

  • Version 0.11.0

  • 2019 Nov 27

.rs

Executor

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ewasm-rust-api

ERC20 in Rust

but ... not really 

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Pain Point

  • Not really Rusty API

    • Result

    • Option

  • Operating in low-level

    • operate on Bytes32

    • Manually handle functional signature
  • Not easy to test with cargo test 
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C vs Rust

 

pub enum CallResult {
    Successful,
    Failure,
    Revert,
    Unknown,
}
pub enum CallError {
    Failure,
    Revert,
    Unknown,
}

fn call() -> CallResult;

fn call() -> Result<(), CallError>;

Please read things behind the wordings!

Current Status

DIFFERENT FROM WEB

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Different in Functions

Constructor

Handlers

Main function

(entry point)

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Constructor

  • Another wasm executable
  • Run once
  • Return main wasm executable
  • Not storage on chain
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Different in Storage

  • File server
  • Key value database
  • Relational database
  • Bytes 32
  • ?
  • ?

Web

Blockchain (Web3)

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Different in Test

  • Local server
  • Hot reload
  • Mock request
  • Free to request
  • Fuzz test
  • Deploy on test net
  • ?
  • ?
  • Request with fee?
  • ?

Web

Blockchain (Web3)

Writing Ewasm In Rust

SEW UP EWASM

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Sew Up

ewasm-rust-api

sewup

.rs

Web3 Blockchain

  • Rusty API
  • high-level operation (kv, rdb, ...)
  • cargo test in local
  • cargo sewup to build & deploy
  • Low-level operation
  • Byte32 operation
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Sew Up

Tests

Create WasmEdge runtime,

Add _compile_constructor_test,

Add _compile_runtime_test

Run each test in runtime

Use macro to add common test utilities,

then just cargo test

SewUp

HAPPY HACKING

THANK YOU

QUESTIONS?

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扫码关注

开源社公众号

Let's meet on github or hackthon,

issue, PR are welcome

second-state/SewUp

Hackthon Oct 16 - Dec 15