added DNS_NAME_MAXTEXT and DNS_NAME_FORMATSIZE

lib/dns/include/dns/name.h

@@ -15,7 +15,7 @@
  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: name.h,v 1.79 2000/08/08 23:18:12 gson Exp $ */
+/* $Id: name.h,v 1.80 2000/08/08 23:20:14 gson Exp $ */
 
 #ifndef DNS_NAME_H
 #define DNS_NAME_H 1
@@ -893,6 +893,29 @@ dns_name_totext(dns_name_t *name, isc_boolean_t omit_final_dot,
  *	ISC_R_NOSPACE
  */
 
+#define DNS_NAME_MAXTEXT 1023
+/*
+ * The maximum length of the text representation of a domain
+ * name as generated by dns_name_totext().  This does not
+ * include space for a terminating NULL.
+ *
+ * This definition is conservative - the actual maximum 
+ * is 1004, derived as follows:
+ *
+ *   A backslash-decimal escaped character takes 4 bytes.
+ *   A wire-encoded name can be up to 255 bytes and each
+ *   label is one length byte + at most 63 bytes of data.
+ *   Maximizing the label lengths gives us a name of
+ *   three 63-octet labels, one 61-octet label, and the
+ *   root label:
+ *
+ *      1 + 63 + 1 + 63 + 1 + 63 + 1 + 61 + 1 = 255
+ *
+ *   When printed, this is (3 * 63 + 61) * 4
+ *   bytes for the escaped label data + 4 bytes for the
+ *   dot terminating each label = 1004 bytes total.
+ */
+
 isc_result_t
 dns_name_downcase(dns_name_t *source, dns_name_t *name,
 		  isc_buffer_t *target);
@@ -1185,6 +1208,12 @@ dns_name_format(dns_name_t *name, char *cp, unsigned int size);
  *
  */
 
+#define DNS_NAME_FORMATSIZE (DNS_NAME_MAXTEXT + 1)
+/*
+ * Suggested size of buffer passed to dns_name_format().
+ * Includes space for the terminating NULL.
+ */
+
 ISC_LANG_ENDDECLS
 
 /***