gdt at ir
Jan 13, 2004, 6:23 AM
Post #7 of 16
(519 views)
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> Okay, however lib/prefix.c provides calls to manage the data structure
> 'struct prefix', and not the semantical object "network prefix" (or
> whatever you name it). Clearly, one may use various calls, like
> lib/prefix.c/apply_mask(), to enforce various semantics on specific
> prefixes, but those aren't assumed to be a prerequisite for other calls
> in the library.
Good points.
> Sure, comments are important, but the code and a couple of usage
> examples -- which couldn't be any clearer than in this case -- are an
> immediate evidence to the semantics (at least IMO).
Perhaps, but are the following new comments accurate? If so, I'll
commit them.
Index: lib/prefix.h
===================================================================
RCS file: /var/cvsroot/quagga/lib/prefix.h,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 prefix.h
--- lib/prefix.h 13 Dec 2002 20:15:29 -0000 1.1.1.1
+++ lib/prefix.h 13 Jan 2004 13:21:04 -0000
@@ -23,6 +23,12 @@
#ifndef _ZEBRA_PREFIX_H
#define _ZEBRA_PREFIX_H
+/*
+ * A struct prefix can represent either a true 'network prefix', where
+ * the 'host bits' of the prefix are 0 (e.g. AF_INET:10.0.0.0/8), or
+ * an address and netmask (e.g. AF_INET:10.0.0.9/8).
+ */
+
/* IPv4 and IPv6 unified prefix structure. */
struct prefix
{
Index: lib/prefix.c
===================================================================
RCS file: /var/cvsroot/quagga/lib/prefix.c,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 prefix.c
--- lib/prefix.c 13 Dec 2002 20:15:29 -0000 1.1.1.1
+++ lib/prefix.c 13 Jan 2004 13:21:04 -0000
@@ -118,7 +118,13 @@
}
}
-/* If both prefix structure is same then return 1 else return 0. */
+/*
+ * Return 1 if the address/netmask contained in the prefix structure
+ * is the same, and else return 0. For this routine, 'same' requires
+ * that not only the prefix length and the network part be the same,
+ * but also the host part. Thus, 10.0.0.1/8 and 10.0.0.2/8 are not
+ * the same. This routine has the same return value sense as '=='.
+ */
int
prefix_same (struct prefix *p1, struct prefix *p2)
{
@@ -136,8 +142,16 @@
return 0;
}
-/* When both prefix structure is not same, but will be same after
- applying mask, return 0. otherwise, return 1 */
+/*
+ * Return 0 if the network prefixes represented by the struct prefix
+ * arguments are the same prefix, and 1 otherwise. Network prefixes
+ * are considered the same if the prefix lengths are equal and the
+ * network parts are the same. Host bits (which are considered masked
+ * by the prefix length) are not significant. Thus, 10.0.0.1/8 and
+ * 10.0.0.2/8 are considered equivalent by this routine. Note that
+ * this routine has the same return sense as strcmp (which is different
+ * from prefix_same).
+ */
int
prefix_cmp (struct prefix *p1, struct prefix *p2)
{
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