Convert IPX-and-friend dissectors in packet-ipx.c to use

tvbuffs.

In doing so, I realied that my recommendation for using
tvb_new_subset(pi.compat_top_tvb, -1, -1) was incorrect, because
some dissectors (ethernet!) change pi.len and pi.cap_len. So, I have
to take those two variables into account instead of using -1 and -1.

So, I provide a macro called tvb_create_from_top(offset), where
offset is the name of your offset variable. It is a wrapper around
tvb_new_subset().

I converted the lines that followed my suggestion to use
tvb_create_from_top().

In proto.c I added
proto_tree_add_debug_text(proto_tree*, const char*, ...)
It's much like proto_tree_add_text(), except that it takes no offset
or length; it's soley for temporarily putting debug text into the
proto_tree while debugging a dissector. In making sure that its
use is temporary, the funciton also prints the debug string to stdout
to remind the programmer that the debug code needs to be removed
before shipping the code.

svn path=/trunk/; revision=2068

1 files changed, 10 insertions, 6 deletions

diff --git a/doc/README.tvbuff b/doc/README.tvbuff
index 3284e98a73..2fc0b9e494 100644
--- a/doc/README.tvbuff
+++ b/doc/README.tvbuff
@@ -1,4 +1,4 @@
-$Id: README.tvbuff,v 1.3 2000/06/08 03:03:43 gram Exp $
+$Id: README.tvbuff,v 1.4 2000/06/15 03:49:00 gram Exp $
 
 TVBUFFs and Exceptions
 
@@ -168,7 +168,7 @@ not. This code snippet shows how:
 
 	....
 
-	next_tvb = tvb_new_subset(tvb, offset_of_next_protocol, -1);
+	next_tvb = tvb_new_subset(tvb, offset_of_next_protocol, -1, -1);
 	tvb_compat(next_tvb, &next_pd, &next_offset);
 
 That is, next_pd and next_offset will get assigned values relative to
@@ -183,9 +183,13 @@ to use tvbuffs. The dissector can create its own tvbuff by
 using pi.compat_top_tvb, which is the top-level tvbuff created
 in dissect_packet(). "compat_top_tvb" will only be available during
 the conversion process; once all dissector have been converted to use
-tvbuff's, that variable will disappear. Here is an example, from
-packet-cops.c, of how to create your own tvbuff. The use of
-the #if/#endif block is optional.
+tvbuff's, that variable will disappear. 
+
+A macro called tvb_create_from_top() has been provided to ease
+your work. It takes one argument --- the name of the offset variable.
+
+Here is an example, from packet-cops.c, of how to create your own
+tvbuff. The use of the #if/#endif block is optional.
 
 /* Code to actually dissect the packets */
 #if 0
@@ -198,7 +202,7 @@ dissect_cops(const u_char *pd, int offset, frame_data *fd, proto_tree *tree)
 {
         tvbuff_t *tvb;
         packet_info *pinfo = π
-        tvb = tvb_new_subset(pinfo->compat_top_tvb, offset, -1, -1);
+        tvb = tvb_create_from_top(offset);
 #endif
 
 Once we convert all the dissector-table dissectors, the second