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Precompiles

A precompile means a common functionality for smart contracts which has been compiled, so that Ethereum nodes can run this efficiently. From a contract's perspective, this is just a single command like an opcode. The Frontier EVM used in Astar provides several useful precompiled contracts. These contracts are implemented in our ecosystem as a native implementation. The precompiled contracts 0x01 through 0x08 are the same as those in Ethereum (see list below). Astar additionally implements precompiled contracts start from 0x5001, and support new Astar features.

Ethereum Native Precompiles

PrecompileAddress
ECRecover0x0000000000000000000000000000000000000001
Sha2560x0000000000000000000000000000000000000002
Ripemd1600x0000000000000000000000000000000000000003
Identity0x0000000000000000000000000000000000000004
Modexp0x0000000000000000000000000000000000000005
Bn128Add0x0000000000000000000000000000000000000006
Bn128Mul0x0000000000000000000000000000000000000007
Bn128Pairing0x0000000000000000000000000000000000000008

Astar Specific Precompiles

PrecompileAddress
DappsStaking0x0000000000000000000000000000000000005001
Sr255190x0000000000000000000000000000000000005002
SubstrateEcdsa0x0000000000000000000000000000000000005003
XCM0x0000000000000000000000000000000000005004
assets-erc20ASSET_PRECOMPILE_ADDRESS_PREFIX
XVM0x0000000000000000000000000000000000005005

The interface descriptions for these precompiles can be found in the precompiles folder: astar-frame repo. The Addresses can be checked in the Astar repo for each runtime in precompile.rs files.

Usage example

Here we'll see how to interact with dApp Staking precompile using Remix IDE. Other precompiles can be accessed in a similar manner.

import "./DappsStaking.sol";
contract A {
DappsStaking public constant DAPPS_STAKING = DappsStaking(0x0000000000000000000000000000000000005001);

/// @notice Check current era
function checkCurrentEra() public view {
uint256 currentEra = DAPPS_STAKING.read_current_era();
}
}

Example use: check current era and total staked amount in the pallet-dapps-staking for Shiden Network. For this example we will use Remix.

  1. Copy DappsStaking.sol from astar-frame repo and create new contract in Remix:

  2. Compile the dAppStaking contract:

  3. The precompile does not need to be deployed since it is already on the network, but you need to tell Remix where to find it. After you connect your EVM wallet to Shiden Network (same applies for Astar Network and for Shibuya Testnet) follow these steps:

    1. Go to Deploy tab
    2. Use injected Web3 environment. It should point to Shiden Mainnet with `ChainId 336`
    3. Make sure you have the selected dAppStaking contract
    4. Provide the address of the precompiled contract `0x0000000000000000000000000000000000005001`
    5. The dAppStaking contract will appear under Deployed contracts

  1. Interact with the contract.
    1. Check the current era
    2. Use the current era as input to check total staked amount on the network
    precompile-interact