//SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

abstract contract ISignable{
    function recoverSigner(bytes32 message, bytes memory sig)
       internal
       pure
       returns (address)
    {
       uint8 v;
       bytes32 r;
       bytes32 s;
       (v, r, s) = splitSignature(sig);
       return ecrecover(message, v, r, s);
    }
    function splitSignature(bytes memory sig)
       internal
       pure
       returns (uint8, bytes32, bytes32)
    {
       require(sig.length == 65);
       
       bytes32 r;
       bytes32 s;
       uint8 v;
       assembly {
           // first 32 bytes, after the length prefix
           r := mload(add(sig, 32))
           // second 32 bytes
           s := mload(add(sig, 64))
           // final byte (first byte of the next 32 bytes)
           v := byte(0, mload(add(sig, 96)))
       }
       return (v, r, s);
   }
}