x509的解析为例说明asn1的编码格式的解析逻辑。x509证书的解析实际上是asn1格式的解析，这里着重说的是asn1的ber编码的解析-x509 parsing example asn1 encoding format parsing logic. x509 certificate parsing is actually asn1 format parsing, here focused is the asn1 ber coding in parsing