Supply Functionality

For implementation details on the Asset Library supply functionality please see the Sway Libs Docs.

Importing the Asset Library Supply Functionality

In order to use the Asset Library, Sway Libs and Sway Standards must be added to the Forc.toml file and then imported into your Sway project. To add Sway Libs as a dependency to the Forc.toml file in your project please see the Getting Started. To add Sway Standards as a dependency please see the Sway Standards Book.

To import the Asset Library Supply Functionality and SRC-3 Standard to your Sway Smart Contract, add the following to your Sway file:

use sway_libs::asset::supply::*;
use standards::src3::*;

Integration with the SRC-3 Standard

The SRC-3 definition states that the following abi implementation is required for any Native Asset on Fuel which mints and burns tokens:

abi SRC3 {
    #[storage(read, write)]
    fn mint(recipient: Identity, vault_sub_id: SubId, amount: u64);
    #[payable]
    #[storage(read, write)]
    fn burn(vault_sub_id: SubId, amount: u64);
}

The Asset Library has the following complimentary functions for each function in the SRC3 abi:

_mint()
_burn()

NOTE The _mint() and _burn() functions will mint and burn assets unconditionally. External checks should be applied to restrict the minting and burning of assets.

Setting Up Storage

Once imported, the Asset Library's supply functionality should be available. To use them, be sure to add the storage block bellow to your contract which enables the SRC-3 standard.

storage {
    total_assets: u64 = 0,
    total_supply: StorageMap<AssetId, u64> = StorageMap {},
}

Implementing the SRC-3 Standard with the Asset Library

To use a base function, simply pass the StorageKey from the prescribed storage block. The example below shows the implementation of the SRC-3 standard in combination with the Asset Library with no user defined restrictions or custom functionality. It is recommended that the Ownership Library is used in conjunction with the Asset Library;s supply functionality to ensure only a single user has permissions to mint an Asset.

use sway_libs::asset::supply::{_burn, _mint};
use standards::src3::SRC3;

storage {
    total_assets: u64 = 0,
    total_supply: StorageMap<AssetId, u64> = StorageMap {},
}

// Implement the SRC-3 Standard for this contract
impl SRC3 for Contract {
    #[storage(read, write)]
    fn mint(recipient: Identity, sub_id: SubId, amount: u64) {
        // Pass the StorageKeys to the `_mint()` function from the Asset Library.
        _mint(
            storage
                .total_assets,
            storage
                .total_supply,
            recipient,
            sub_id,
            amount,
        );
    }

    // Pass the StorageKeys to the `_burn_()` function from the Asset Library.
    #[payable]
    #[storage(read, write)]
    fn burn(sub_id: SubId, amount: u64) {
        _burn(storage.total_supply, sub_id, amount);
    }
}