I need all Ethereum smart contracts

Question

The problem

I would like to get all ERC20 token smart contract bytecodes in Ethereum network.

The question

Is there a way to scan the blockchain for ERC20 smart contracts and/or scan an address for a [ERC20] smart contract?

Answer 1

Have a look at EIP165. It allows you some form of introspection wether an address offers a certain interface. Obviously this only works for contracts that at least implement ERC20 and EIP165.

How to detect if a contract implements ERC-165:

1. The source contact makes a STATICCALL to the destination address with input data: 0x01ffc9a701ffc9a700000000000000000000000000000000000000000000000000000000 and gas 30,000. This corresponds to contract.supportsInterface(0x01ffc9a7).
2. If the call fails or return false, the destination contract does not implement ERC-165.

3. If the call returns true, a second call is made with input data 0x01ffc9a7ffffffff00000000000000000000000000000000000000000000000000000000.

4. If the second call fails or returns true, the destination contract does not implement ERC-165. Otherwise it implements ERC-165.

How to detect if a contract implements any given interface:

1. If you are not sure if the contract implements ERC-165, use the above procedure to confirm.
2. If it does not implement ERC-165, then you will have to see what methods it uses the old-fashioned way.
3. If it implements ERC-165 then just call supportsInterface(interfaceID) to determine if it implements an interface you can use.