合约开发(solidity)进阶2

底层函数解析

1. abi.encode, abi.encodePacked, abi.encodeWithSelector and abi.encodeWithSignature

Example:
bytes  memory  payload  =  abi.encodeWithSignature("register(string)",  "MyName");
(bool  success,  bytes  memory  returnData)  =  address(nameReg).call(payload);
require(success);

It is possible to adjust the supplied gas with the gas modifier:

address(nameReg).call{gas:  1000000}(abi.encodeWithSignature("register(string)",  "MyName"));

Similarly, the supplied Ether value can be controlled too:

address(nameReg).call{value:  1  ether}(abi.encodeWithSignature("register(string)",  "MyName"));

Lastly, these modifiers can be combined. Their order does not matter:

address(nameReg).call{gas:  1000000,  value:  1  ether}(abi.encodeWithSignature("register(string)",  "MyName"));

2. shr,calldataload,sub,calldatasize

EVM Dialect: https://docs.soliditylang.org/en/v0.8.9/yul.html#evm-dialect

assembly {
                ret := shr(96,calldataload(sub(calldatasize(),20)))
            }

• shr(x, y) : logical shift right y by x bits
• calldataload(p) : call data starting from position p (32 bytes)
• sub(x, y) : x - y
• calldatasize() : size of call data in bytes

解答如下:

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