代码:funcrlpHash(xinterface{})(hcommon.Hash){hw:=sha3.NewKeccak256()rlp.Encode(hw,x)hw.Sum(h[:0])returnh}如果有用:func(d*state)Sum(in[]byte)[]byte{dup:=d.clone()hash:=make([]byte,dup.outputLen)dup.Read(hash)returnappend(in,hash...)}完整代码上下文参见here.这里的'h'怎么理解？不应该先给h赋值吗？'h[:0]'表示零值字节？“h”到底返回了什么？'hw.Sum(h[