12_String.huff

/* 接口 */
#define function setString(string memory str_) nonpayable returns ()
#define function getString() view returns (string memory)

/* 方法 */
#define macro SET_STRING() = takes (0) returns (0) {
    // 如果string长度<32字节，高阶字节存储string内容，最小一位的字节存储string长度的两倍，即len*2
    0x24 calldataload   // [len]
    0x02 mul            // [len*2]
    0x44 calldataload   // [str, len*2]
    add                 // [str+len*2]
    0x00 sstore // [] storage: [0x00: str+len*2]
    stop
}

#define macro GET_STRING() = takes (0) returns (0) {
    0x20 0x00 mstore    // [] memory: [0x00: 0x20]

    0x00 sload          // [str+len*2] memory: [0x00: 0x20]
    dup1                // [str+len*2, str+len*2] memory: [0x00: 0x20]
    0xFF and 0x01 shr   // [len, str+len*2] memory: [0x00: 0x20]
    0x20 mstore         // [str+len*2] memory: [0x00: 0x20, 0x20: len]

    0xFF not and        // [str] memory: [0x00: 0x20]
    0x40 mstore         // [] memory: [0x00: 0x20, 0x20: len, 0x40: str]   

    0x60 0x00 return
}

#define macro MAIN() = takes (0) returns (0) {
    // 通过selector判断要调用哪个函数
    0x00 calldataload 0xE0 shr
    dup1 __FUNC_SIG(setString) eq set_string jumpi
    dup1 __FUNC_SIG(getString) eq get_string jumpi
    // 如果没有匹配的函数，就revert
    0x00 0x00 revert

    set_string:
        SET_STRING()
    get_string:
        GET_STRING()    
}