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

How

• A deterministic subset of WebAssembly.

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

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Why

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 ?

Talk to contract in Binary over the blockchain network

Talk to API in Hyper Text  Markup Language over the internet

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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

Prior Art

CONTRACT IN RUST

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Contract in Rust

ewasm-rust-api

• Version 0.11.0

• 2019 Nov 27

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ewasm-rust-api

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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

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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

• 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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Let's meet on github or hackthon,

issue, PR are welcome