blockchains-security-toolkit/solidity/abi_encoding.md

ABI encoding

• the solidity built-in function abi.encode encodes solidity types into raw bytes, that can be interpreted directly by the EVM.

contract StringEncoding {
    bytes public encodedString = abi.encode("hacking");
}

• this is what happens:
  1. 1st (32 bytes) word = offset → indicates at which bytes index the string starts. If you count 32 from the beginning (= index 32), you will reach the starting point of where the actual encoded string starts.
  2. 2nd (32 bytes) word = string length → in the case of the string, this indicates how many characters (including whitespaces) are included in the string.
  3. 3rd (32 bytes) word = the actual utf8 encoded string → each individual bytes corresponds to hex notation of a letter / character encoded in utf8.

other ABI Encodings

• address payable -> address
• contract -> address
• enum -> uint8
• struct -> tuple of elementry types