code: func macSHA1(version uint16, key []byte) macFunction {
  	if version == VersionSSL30 {
  		mac := ssl30MAC{
  			h:   sha1.New(),
  			key: make([]byte, len(key)),
  		}
  		copy(mac.key, key)
  		return mac
  	}
  	return tls10MAC{hmac.New(sha1.New, key)}
  }
docs: // macSHA1 returns a macFunction for the given protocol version.