NNTPC: overview.fmt & Xref:full

[proff@suburbia.net]

> Here's an abbreviated transcript of the *per group* conversation,
> ignoring the beginning and ending parts:
> 
> <- list active newsgroup-name
> -> 215: list:
> -> newsgroup-name <high> <low> <flag>
> 
> This is repeated for each newsgroup in the screen. I suspect it tries
> to avoid a full 'list active' which can be a long operation on a
> loaded server.


Ugh. That is rouge behavior.

The list command should NOT be used for obtaining upto-date singular
group information. The GROUP command is the correct place for that.

nntpcache can locate an individual group data from the sum of
newsgroups very quickly.  It uses a 31337 (prime) entry hash table,
with binary trees for resolving hash collisions.

RFC977 defines the arguments to list as:

	LIST {active,newsgroup,active,times,overview.fmt} [pattern]

Note the optional usage of the pattern keyword. This is typically used for
examples like:

	LIST active alt.*

and not for pulling in information on a specific group in isolation, which is
what your news-reader appears to be doing. When the pattern argument is
specified, nntpcache walks the entire group list, pattern matching every
against every group.

Here is a tiny patch to optimise for the case where the pattern isn't
really a pattern at all, and use the hashing lookup scheme that other
parts of nntpcache rely on - I'd be very surprised if trn4 isn't blindly
fast after the following:

--
Prof. Julian Assange  |If you want to build a ship, don't drum up people
		      |together to collect wood and don't assign them tasks
proff@suburbia.net    |and work, but rather teach them to long for the endless
proff@gnu.ai.mit.edu  |immensity of the sea. -- Antoine de Saint Exupery

Index: list.c
===================================================================
RCS file: /usr/local/cvs/nntpcache/list.c,v
retrieving revision 1.92
diff -u -r1.92 list.c
--- list.c	1997/03/06 10:48:56	1.92
+++ list.c	1997/03/23 19:18:07
@@ -407,6 +456,25 @@
 	}
 	return lo;
 }
+static void print_active(struct newsgroup *n)
+{
+	int hi, lo;
+	if (!n->moderation)
+		return;
+	hi = MAX(n->hi, n->hi_server);
+	if (n->lo>0)
+		lo = n->lo;
+	else
+		lo = 0;
+	if (n->lo_server>0)
+	{
+		if (lo>0)
+			lo = MIN(lo, n->lo_server);
+		else
+			lo = n->lo_server;
+	}
+	emitf ("%s %d %d %c\r\n", n->group, hi, lo, n->moderation);
+}
 
 static bool doList (struct list_s *list, char *group_pat)
 {
@@ -473,6 +541,20 @@
 		emitrn (NNTP_XGTITLE_OK);
 	else
 		emitrn (NNTP_LIST_FOLLOWS);
+	if (group_pat && !strpbrk(group_pat, "*?[]"))
+	{
+		if ((n = newsgroup_find_add(group_pat, NULL, FALSE)))
+#ifdef READ_LOCKS
+			if (newsgroupLockRead(n))
+			{
+				print_active(n);
+				n->read_locks--;
+			}
+#else
+			print_active(n);
+#endif
+		goto end;
+	}
 	for (n=Ni->newsgroup_head; n; n=n->next)
 	{
 #ifdef READ_LOCKS
@@ -489,25 +571,8 @@
 		switch (list->type)
 		{
 		case l_active:
-			{
-			int hi, lo;
-			if (!n->moderation)
-				break;
-			hi = MAX(n->hi, n->hi_server);
-			if (n->lo>0)
-				lo = n->lo;
-			else
-				lo = 0;
-			if (n->lo_server>0)
-			{
-				if (lo>0)
-					lo = MIN(lo, n->lo_server);
-				else
-					lo = n->lo_server;
-			}
-			emitf ("%s %d %d %c\r\n", n->group, hi, lo, n->moderation);
+			print_active(n);
 			break;
-			}
 		case l_active_times:
 			if (n->creation_time && n->creator)
 				emitf ("%s %lu %s\r\n", n->group, n->creation_time, n->creator);
@@ -527,6 +592,7 @@
 		continue;
 #endif
 	}
+end:
 	emitrn (".");
 	return TRUE;
 }