Simple Storage Gas Meter

A simple CosmWasm storage gas meter for estimating gas usage from kv store.

Usage

Unit Test

Use MemoryStorageWithGas instead of MemoryStorage or MockStorage.

// let mut storage = MockStorage::new();
let mut storage = MemoryStorageWithGas::new();
let map = Map::<u64, Vec<u8>>::new("0");

let data = b"hello";
map.save(&mut storage, 0, &data.to_vec())?;

let gas = storage.last_gas_used();
assert_eq!(gas, 2960);

Multi Test

Instantiate cw_multi_test::App with MemoryStorageWithGas instead of MemoryStorage or MockStorage.

Due to the nature of cosmwasm_std::Storage trait, we cannot downcast the dyn Storage back to MemoryStorage directly.

So we pass the pointer to the storage as trait object instead and access the gas log through that pointer.

let storage = MemoryStorageWithGas::new();

AppBuilder::new()
    .with_storage(&storage) // <- ref ptr here
    .build(|r, _, storage| {
        r.bank
            .init_balance(
                storage,
                &Addr::unchecked("admin"),
                vec![Coin::new(100, "uluna")],
            )
            .unwrap();
    });

let gas = storage.last_gas_used();
assert_eq!(gas, 3650);