How to add custom precompiled contract?

Question

I want to implement some features as precompiled contracts in Ethereum. I read some articles and the contract code, but I still don't know how to do this.

Is there's a tutorial from scratch?

Answer 1

This is good reference that do a new pre-compile contract for Ethereum next hardfork named Istanbul

https://github.com/keep-network/go-ethereum/pull/4/files

Basically, you only need to implement two methods of per-compiled contract interface

1. RequiredGas(): to define how many gas user need to pay when calling the per-compiled contract.
2. Run(): write your code to do the thing that you want the per-compiled contract will do.

By the way, the issue for us is official solidity compiler might not support our per-compiled function then the only way that user can use our per-compiled function is use inline assembly code in solidity smart contract.

Hope this will give you some clue to start!