Smart Contract Cheat Sheet

Collection of code snippets and information bits on smart contract development for Dusk.

Common Data Structures

Because we program for WASM in no-std some data structures are not available. Here is a list of common alternatives:

Example	Explanation
BTreeMap	Alternative to HashMap in a no-std env
BTreeSet	Alternative to HashSet in a no-std env

BTree Information

Data structures based on B-Trees require the Ord trait to be implemented for the values which get inserted. (In the case of a Map, the Ord needs to be implemented on the Key)

Common host functions

Function	Explanation
rusk_abi::emit(“EVENT_NAME”, data)	Emit a contract event

Common Dependencies

• execution-core
• rusk_abi

No-std Crates

• core
• alloc

The alloc crate needs to explicitly be imported in order to use heap-allocated values in a #![no-std] environment. More information on the alloc crate can be found here.

Simple Contract Template

Counter Contract

Example Makefile to compile to WASM

build: ## Build contract
  @RUSTFLAGS="-C link-args=-zstack-size=65536" \
  cargo build \
    --release \
    --manifest-path=Cargo.toml \
    --color=always \
    -Z build-std=core,alloc \
    --target wasm32-unknown-unknown
  @mkdir -p target/stripped
  @find target/wasm32-unknown-unknown/release -maxdepth 1 -name "*.wasm" \
      | xargs -I % basename % \
      | xargs -I % wasm-tools strip -a \
               target/wasm32-unknown-unknown/release/% \
               -o target/stripped/%

# test: contract ## Run all tests
#  @cargo test \
#    --manifest-path=Cargo.toml \
#    --color=always

MAX_COUNTER_CONTRACT_SIZE = 8192

.PHONY: contract test

More references

The Rust Language Cheat Sheet is another great cheat sheet that can be used as a reference for Rust code.

Note: Not all examples apply due to our no-std constraints.