Reorganised the code to put more utility functions into virt_top_utils.

Added explicit interfaces for Virt_top_utils & Virt_top modules.
Corrected use of endwin when _not_ in script mode.

8 files changed, 263 insertions, 149 deletions

diff --git a/ChangeLog b/ChangeLog
index a90e6e6..250a8dd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2007-10-19  Richard Jones  <rjones@redhat.com>
+
+	* virt-top/virt_top_utils.mli, virt-top/virt_top.mli: Reorganise
+	  the code and add some interfaces.
+
 2007-10-17  Richard Jones  <rjones@redhat.com>
 
 	* virt-top/virt_top.ml: Added --script option.
diff --git a/virt-top/.depend b/virt-top/.depend
index 12f83ae..4a36b22 100644
--- a/virt-top/.depend
+++ b/virt-top/.depend
@@ -1,10 +1,14 @@
-virt_top_csv.cmo: virt_top.cmo 
+virt_top.cmi: ../libvirt/libvirt.cmi 
+virt_top_utils.cmi: ../libvirt/libvirt.cmi 
+virt_top_csv.cmo: virt_top.cmi 
 virt_top_csv.cmx: virt_top.cmx 
-virt_top_main.cmo: virt_top.cmo ../libvirt/libvirt.cmi 
+virt_top_main.cmo: virt_top.cmi ../libvirt/libvirt.cmi 
 virt_top_main.cmx: virt_top.cmx ../libvirt/libvirt.cmx 
-virt_top.cmo: virt_top_utils.cmo ../libvirt/libvirt_version.cmi \
-    ../libvirt/libvirt.cmi 
+virt_top.cmo: virt_top_utils.cmi ../libvirt/libvirt_version.cmi \
+    ../libvirt/libvirt.cmi virt_top.cmi 
 virt_top.cmx: virt_top_utils.cmx ../libvirt/libvirt_version.cmx \
-    ../libvirt/libvirt.cmx 
-virt_top_xml.cmo: virt_top.cmo ../libvirt/libvirt.cmi 
+    ../libvirt/libvirt.cmx virt_top.cmi 
+virt_top_utils.cmo: ../libvirt/libvirt.cmi virt_top_utils.cmi 
+virt_top_utils.cmx: ../libvirt/libvirt.cmx virt_top_utils.cmi 
+virt_top_xml.cmo: virt_top.cmi ../libvirt/libvirt.cmi 
 virt_top_xml.cmx: virt_top.cmx ../libvirt/libvirt.cmx 
diff --git a/virt-top/README b/virt-top/README
index 86dfd02..f557c9b 100644
--- a/virt-top/README
+++ b/virt-top/README
@@ -1,11 +1,11 @@
 The code is structured into these files:
 
-  virt_top_utils.ml
+  virt_top_utils.mli / virt_top_utils.ml
 
     String functions and other small utility functions.  This is
     included directly into virt_top.ml.
 
-  virt_top.ml
+  virt_top.mli / virt_top.ml
 
     This is the virt-top program.
 
diff --git a/virt-top/virt_top.ml b/virt-top/virt_top.ml
index dc71a71..6047f8e 100644
--- a/virt-top/virt_top.ml
+++ b/virt-top/virt_top.ml
@@ -43,12 +43,6 @@ let csv_write : (string list -> unit) ref =
     fun _ -> ()
   )
 
-(* Int64 operators for convenience. *)
-let (+^) = Int64.add
-let (-^) = Int64.sub
-let ( *^ ) = Int64.mul
-let (/^) = Int64.div
-
 (* Sort order. *)
 type sort_order =
   | DomainID | DomainName | Processor | Memory | Time
@@ -123,6 +117,11 @@ let csv_net = ref true
 let init_file = ref DefaultInitFile
 let script_mode = ref false
 
+(* Tuple of never-changing data returned by start_up function. *)
+type setup =
+    Libvirt.ro C.t * bool * bool * bool * C.node_info * string *
+      (int * int * int)
+
 (* Function to read command line arguments and go into curses mode. *)
 let start_up () =
   (* Read command line arguments. *)
@@ -278,54 +277,6 @@ OPTIONS" in
    node_info, hostname, libvirt_version (* info that doesn't change *)
   )
 
-(* Show a percentage in 4 chars. *)
-let show_percent percent =
-  if percent <= 0. then " 0.0"
-  else if percent <= 9.9 then sprintf " %1.1f" percent
-  else if percent <= 99.9 then sprintf "%2.1f" percent
-  else "100 "
-
-(* Show an int64 option in 4 chars. *)
-let rec show_int64_option = function
-  | None -> "    "
-  | Some n -> show_int64 n
-(* Show an int64 in 4 chars. *)
-and show_int64 = function
-  | n when n < 0L -> "-!!!"
-  | n when n <= 9999L ->
-      sprintf "%4Ld" n
-  | n when n /^ 1024L <= 999L ->
-      sprintf "%3LdK" (n /^ 1024L)
-  | n when n /^ 1_048_576L <= 999L ->
-      sprintf "%3LdM" (n /^ 1_048_576L)
-  | n when n /^ 1_073_741_824L <= 999L ->
-      sprintf "%3LdG" (n /^ 1_073_741_824L)
-  | _ -> ">!!!"
-
-(* Format the total time (may be large!) in 9 chars. *)
-let show_time ns =
-  let secs_in_ns = 1_000_000_000L in
-  let mins_in_ns = 60_000_000_000L in
-  let hours_in_ns = 3_600_000_000_000L in
-
-  let hours = ns /^ hours_in_ns in
-  let ns = ns -^ (hours *^ hours_in_ns) in
-  let mins = ns /^ mins_in_ns in
-  let ns = ns -^ (mins *^ mins_in_ns) in
-  let secs = ns /^ secs_in_ns in
-  let ns = ns -^ (secs *^ secs_in_ns) in
-  let pennies = ns /^ 10_000_000L in
-
-  if hours < 12L then
-    sprintf "%3Ld:%02Ld.%02Ld" (hours *^ 60L +^ mins) secs pennies
-  else if hours <= 999L then
-    sprintf "%3Ld:%02Ld:%02Ld" hours mins secs
-  else (
-    let days = hours /^ 24L in
-    let hours = hours -^ (days *^ 24L) in
-    sprintf "%3Ldd%02Ld:%02Ld" days hours mins
-  )
-
 (* Show a domain state (the 'S' column). *)
 let show_state = function
   | D.InfoNoState -> '?'
@@ -336,65 +287,6 @@ let show_state = function
   | D.InfoShutoff -> 'O'
   | D.InfoCrashed -> 'X'
 
-(* Sum Domain.block_stats structures together.  Missing fields
- * get forced to 0.  Empty list returns all 0.
- *)
-let zero_block_stats =
-  { D.rd_req = 0L; rd_bytes = 0L; wr_req = 0L; wr_bytes = 0L; errs = 0L }
-let add_block_stats bs1 bs2 =
-  let add f1 f2 = if f1 >= 0L && f2 >= 0L then f1 +^ f2 else 0L in
-  { D.rd_req = add bs1.D.rd_req   bs2.D.rd_req;
-    rd_bytes = add bs1.D.rd_bytes bs2.D.rd_bytes;
-    wr_req   = add bs1.D.wr_req   bs2.D.wr_req;
-    wr_bytes = add bs1.D.wr_bytes bs2.D.wr_bytes;
-    errs     = add bs1.D.errs     bs2.D.errs }
-let sum_block_stats =
-  List.fold_left add_block_stats zero_block_stats
-
-(* Get the difference between two block_stats structures.  Missing data
- * forces the difference to -1.
- *)
-let diff_block_stats curr prev =
-  let sub f1 f2 = if f1 >= 0L && f2 >= 0L then f1 -^ f2 else -1L in
-  { D.rd_req = sub curr.D.rd_req   prev.D.rd_req;
-    rd_bytes = sub curr.D.rd_bytes prev.D.rd_bytes;
-    wr_req   = sub curr.D.wr_req   prev.D.wr_req;
-    wr_bytes = sub curr.D.wr_bytes prev.D.wr_bytes;
-    errs     = sub curr.D.errs     prev.D.errs }
-
-(* Sum Domain.interface_stats structures together.  Missing fields
- * get forced to 0.  Empty list returns all 0.
- *)
-let zero_interface_stats =
-  { D.rx_bytes = 0L; rx_packets = 0L; rx_errs = 0L; rx_drop = 0L;
-    tx_bytes = 0L; tx_packets = 0L; tx_errs = 0L; tx_drop = 0L }
-let add_interface_stats is1 is2 =
-  let add f1 f2 = if f1 >= 0L && f2 >= 0L then f1 +^ f2 else 0L in
-  { D.rx_bytes = add is1.D.rx_bytes   is2.D.rx_bytes;
-    rx_packets = add is1.D.rx_packets is2.D.rx_packets;
-    rx_errs    = add is1.D.rx_errs    is2.D.rx_errs;
-    rx_drop    = add is1.D.rx_drop    is2.D.rx_drop;
-    tx_bytes   = add is1.D.tx_bytes   is2.D.tx_bytes;
-    tx_packets = add is1.D.tx_packets is2.D.tx_packets;
-    tx_errs    = add is1.D.tx_errs    is2.D.tx_errs;
-    tx_drop    = add is1.D.tx_drop    is2.D.tx_drop }
-let sum_interface_stats =
-  List.fold_left add_interface_stats zero_interface_stats
-
-(* Get the difference between two interface_stats structures.
- * Missing data forces the difference to -1.
- *)
-let diff_interface_stats curr prev =
-  let sub f1 f2 = if f1 >= 0L && f2 >= 0L then f1 -^ f2 else -1L in
-  { D.rx_bytes = sub curr.D.rx_bytes   prev.D.rx_bytes;
-    rx_packets = sub curr.D.rx_packets prev.D.rx_packets;
-    rx_errs    = sub curr.D.rx_errs    prev.D.rx_errs;
-    rx_drop    = sub curr.D.rx_drop    prev.D.rx_drop;
-    tx_bytes   = sub curr.D.tx_bytes   prev.D.tx_bytes;
-    tx_packets = sub curr.D.tx_packets prev.D.tx_packets;
-    tx_errs    = sub curr.D.tx_errs    prev.D.tx_errs;
-    tx_drop    = sub curr.D.tx_drop    prev.D.tx_drop }
-
 (* Update the display and sleep for given number of seconds. *)
 let sleep n = refresh (); Unix.sleep n
 
@@ -416,13 +308,6 @@ let get_string maxlen =
       Not_found -> str (* it is full maxlen bytes *)
   )
 
-(* Pad a string to the full width with spaces.  If too long, truncate. *)
-let pad width str =
-  let n = String.length str in
-  if n = width then str
-  else if n > width then String.sub str 0 width
-  else (* if n < width then *) str ^ String.make (width-n) ' '
-
 (* Line numbers. *)
 let top_lineno = 0
 let summary_lineno = 1 (* this takes 2 lines *)
@@ -913,16 +798,16 @@ let redraw =
 	   | (name, Active rd) :: doms ->
 	       if lineno < lines then (
 		 let state = show_state rd.rd_info.D.state in
-		 let rd_req = show_int64_option rd.rd_block_rd_reqs in
-		 let wr_req = show_int64_option rd.rd_block_wr_reqs in
-		 let rx_bytes = show_int64_option rd.rd_net_rx_bytes in
-		 let tx_bytes = show_int64_option rd.rd_net_tx_bytes in
-		 let percent_cpu = show_percent rd.rd_percent_cpu in
+		 let rd_req = Show.int64_option rd.rd_block_rd_reqs in
+		 let wr_req = Show.int64_option rd.rd_block_wr_reqs in
+		 let rx_bytes = Show.int64_option rd.rd_net_rx_bytes in
+		 let tx_bytes = Show.int64_option rd.rd_net_tx_bytes in
+		 let percent_cpu = Show.percent rd.rd_percent_cpu in
 		 let percent_mem =
 		   100L *^ rd.rd_info.D.memory /^ node_info.C.memory in
 		 let percent_mem = Int64.to_float percent_mem in
-		 let percent_mem = show_percent percent_mem in
-		 let time = show_time rd.rd_info.D.cpu_time in
+		 let percent_mem = Show.percent percent_mem in
+		 let time = Show.time rd.rd_info.D.cpu_time in
 
 		 let line = sprintf "%5d %c %s %s %s %s %s %s %s %s"
 		   rd.rd_domid state rd_req wr_req rx_bytes tx_bytes
@@ -969,7 +854,7 @@ let redraw =
 	     mvaddstr (p+domains_lineno) 0 (sprintf "%4d   " p);
 	     let cpu_time = pcpus_cpu_time.(p) in (* ns used on this CPU *)
 	     let percent_cpu = 100. *. cpu_time /. total_cpu_per_pcpu in
-	     addstr (show_percent percent_cpu);
+	     addstr (Show.percent percent_cpu);
 	     addch 32;
 
 	     List.iteri (
@@ -982,7 +867,7 @@ let redraw =
 		   else (
 		     let t = Int64.to_float t in
 		     let percent = 100. *. t /. total_cpu_per_pcpu in
-		     sprintf "%s%c%c " (show_percent percent)
+		     sprintf "%s%c%c " (Show.percent percent)
 		       (if is_average then '=' else ' ')
 		       (if is_running then '#' else ' ')
 		   ) in
@@ -1072,19 +957,19 @@ let redraw =
 		 let state = show_state rd.rd_info.D.state in
 		 let rx_bytes =
 		   if stats.D.rx_bytes >= 0L
-		   then show_int64 stats.D.rx_bytes
+		   then Show.int64 stats.D.rx_bytes
 		   else "    " in
 		 let tx_bytes =
 		   if stats.D.tx_bytes >= 0L
-		   then show_int64 stats.D.tx_bytes
+		   then Show.int64 stats.D.tx_bytes
 		   else "    " in
 		 let rx_packets =
 		   if stats.D.rx_packets >= 0L
-		   then show_int64 stats.D.rx_packets
+		   then Show.int64 stats.D.rx_packets
 		   else "    " in
 		 let tx_packets =
 		   if stats.D.tx_packets >= 0L
-		   then show_int64 stats.D.tx_packets
+		   then Show.int64 stats.D.tx_packets
 		   else "    " in
 
 		 let line = sprintf "%5d %c %s %s %s %s %-12s %s"
@@ -1180,19 +1065,19 @@ let redraw =
 		 let state = show_state rd.rd_info.D.state in
 		 let rd_bytes =
 		   if stats.D.rd_bytes >= 0L
-		   then show_int64 stats.D.rd_bytes
+		   then Show.int64 stats.D.rd_bytes
 		   else "    " in
 		 let wr_bytes =
 		   if stats.D.wr_bytes >= 0L
-		   then show_int64 stats.D.wr_bytes
+		   then Show.int64 stats.D.wr_bytes
 		   else "    " in
 		 let rd_req =
 		   if stats.D.rd_req >= 0L
-		   then show_int64 stats.D.rd_req
+		   then Show.int64 stats.D.rd_req
 		   else "    " in
 		 let wr_req =
 		   if stats.D.wr_req >= 0L
-		   then show_int64 stats.D.wr_req
+		   then Show.int64 stats.D.wr_req
 		   else "    " in
 
 		 let line = sprintf "%5d %c %s %s %s %s %-12s %s"
diff --git a/virt-top/virt_top.mli b/virt-top/virt_top.mli
new file mode 100644
index 0000000..7b0ac3b
--- /dev/null
+++ b/virt-top/virt_top.mli
@@ -0,0 +1,36 @@
+(* 'top'-like tool for libvirt domains.
+   (C) Copyright 2007 Richard W.M. Jones, Red Hat Inc.
+   http://libvirt.org/
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*)
+
+(* Hooks for virt_top_xml to override (if present). *)
+val parse_device_xml :
+  (int -> [ `R ] Libvirt.Domain.t -> string list * string list) ref
+
+(* Hooks for virt_top_csv to override (if present). *)
+val csv_start : (string -> unit) ref
+val csv_write : (string list -> unit) ref
+
+type setup =
+    Libvirt.ro Libvirt.Connect.t	(* connection *)
+    * bool * bool * bool		(* batch, script, csv modes *)
+    * Libvirt.Connect.node_info		(* node_info *)
+    * string				(* hostname *)
+    * (int * int * int)			(* libvirt version *)
+
+val start_up : unit -> setup
+val main_loop : setup -> unit
diff --git a/virt-top/virt_top_main.ml b/virt-top/virt_top_main.ml
index cb3486e..ba98e7e 100644
--- a/virt-top/virt_top_main.ml
+++ b/virt-top/virt_top_main.ml
@@ -30,19 +30,19 @@ open Virt_top
  * the program under --debug ...).
  *)
 let error =
-  let setup = start_up () in
+  let ((_, _, script_mode, _, _, _, _) as setup) = start_up () in
 
   try
     main_loop setup;
-    if !script_mode then endwin ();
+    if not script_mode then endwin ();
     false
   with
   | Libvirt.Virterror err ->
-      endwin ();
+      if not script_mode then endwin ();
       prerr_endline (Libvirt.Virterror.to_string err);
       true
   | exn ->
-      endwin ();
+      if not script_mode then endwin ();
       prerr_endline ("Error: " ^ Printexc.to_string exn);
       true
 
diff --git a/virt-top/virt_top_utils.ml b/virt-top/virt_top_utils.ml
index e92d150..53c9bf1 100644
--- a/virt-top/virt_top_utils.ml
+++ b/virt-top/virt_top_utils.ml
@@ -15,10 +15,24 @@
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+   This file contains utility functions.
 *)
 
+open Printf
+
+module C = Libvirt.Connect
+module D = Libvirt.Domain
+module N = Libvirt.Network
+
 let (//) = Filename.concat
 
+(* Int64 operators for convenience. *)
+let (+^) = Int64.add
+let (-^) = Int64.sub
+let ( *^ ) = Int64.mul
+let (/^) = Int64.div
+
 (* Input a whole file as a list of lines. *)
 let input_all_lines chan =
   let lines = ref [] in
@@ -87,3 +101,119 @@ let read_config_file filename =
       let key, value = ExtString.String.split line " " in
       lineno, trim key, trim value
   ) lines
+
+(* Pad a string to the full width with spaces.  If too long, truncate. *)
+let pad width str =
+  let n = String.length str in
+  if n = width then str
+  else if n > width then String.sub str 0 width
+  else (* if n < width then *) str ^ String.make (width-n) ' '
+
+module Show = struct
+  (* Show a percentage in 4 chars. *)
+  let percent percent =
+    if percent <= 0. then " 0.0"
+    else if percent <= 9.9 then sprintf " %1.1f" percent
+    else if percent <= 99.9 then sprintf "%2.1f" percent
+    else "100 "
+
+  (* Show an int64 option in 4 chars. *)
+  let rec int64_option = function
+    | None -> "    "
+    | Some n -> int64 n
+  (* Show an int64 in 4 chars. *)
+  and int64 = function
+    | n when n < 0L -> "-!!!"
+    | n when n <= 9999L ->
+	sprintf "%4Ld" n
+    | n when n /^ 1024L <= 999L ->
+	sprintf "%3LdK" (n /^ 1024L)
+    | n when n /^ 1_048_576L <= 999L ->
+	sprintf "%3LdM" (n /^ 1_048_576L)
+    | n when n /^ 1_073_741_824L <= 999L ->
+	sprintf "%3LdG" (n /^ 1_073_741_824L)
+    | _ -> ">!!!"
+
+  (* Format the total time (may be large!) in 9 chars. *)
+  let time ns =
+    let secs_in_ns = 1_000_000_000L in
+    let mins_in_ns = 60_000_000_000L in
+    let hours_in_ns = 3_600_000_000_000L in
+
+    let hours = ns /^ hours_in_ns in
+    let ns = ns -^ (hours *^ hours_in_ns) in
+    let mins = ns /^ mins_in_ns in
+    let ns = ns -^ (mins *^ mins_in_ns) in
+    let secs = ns /^ secs_in_ns in
+    let ns = ns -^ (secs *^ secs_in_ns) in
+    let pennies = ns /^ 10_000_000L in
+
+    if hours < 12L then
+      sprintf "%3Ld:%02Ld.%02Ld" (hours *^ 60L +^ mins) secs pennies
+    else if hours <= 999L then
+      sprintf "%3Ld:%02Ld:%02Ld" hours mins secs
+    else (
+      let days = hours /^ 24L in
+      let hours = hours -^ (days *^ 24L) in
+      sprintf "%3Ldd%02Ld:%02Ld" days hours mins
+    )
+end
+
+(* Sum Domain.block_stats structures together.  Missing fields
+ * get forced to 0.  Empty list returns all 0.
+ *)
+let zero_block_stats =
+  { D.rd_req = 0L; rd_bytes = 0L; wr_req = 0L; wr_bytes = 0L; errs = 0L }
+let add_block_stats bs1 bs2 =
+  let add f1 f2 = if f1 >= 0L && f2 >= 0L then f1 +^ f2 else 0L in
+  { D.rd_req = add bs1.D.rd_req   bs2.D.rd_req;
+    rd_bytes = add bs1.D.rd_bytes bs2.D.rd_bytes;
+    wr_req   = add bs1.D.wr_req   bs2.D.wr_req;
+    wr_bytes = add bs1.D.wr_bytes bs2.D.wr_bytes;
+    errs     = add bs1.D.errs     bs2.D.errs }
+let sum_block_stats =
+  List.fold_left add_block_stats zero_block_stats
+
+(* Get the difference between two block_stats structures.  Missing data
+ * forces the difference to -1.
+ *)
+let diff_block_stats curr prev =
+  let sub f1 f2 = if f1 >= 0L && f2 >= 0L then f1 -^ f2 else -1L in
+  { D.rd_req = sub curr.D.rd_req   prev.D.rd_req;
+    rd_bytes = sub curr.D.rd_bytes prev.D.rd_bytes;
+    wr_req   = sub curr.D.wr_req   prev.D.wr_req;
+    wr_bytes = sub curr.D.wr_bytes prev.D.wr_bytes;
+    errs     = sub curr.D.errs     prev.D.errs }
+
+(* Sum Domain.interface_stats structures together.  Missing fields
+ * get forced to 0.  Empty list returns all 0.
+ *)
+let zero_interface_stats =
+  { D.rx_bytes = 0L; rx_packets = 0L; rx_errs = 0L; rx_drop = 0L;
+    tx_bytes = 0L; tx_packets = 0L; tx_errs = 0L; tx_drop = 0L }
+let add_interface_stats is1 is2 =
+  let add f1 f2 = if f1 >= 0L && f2 >= 0L then f1 +^ f2 else 0L in
+  { D.rx_bytes = add is1.D.rx_bytes   is2.D.rx_bytes;
+    rx_packets = add is1.D.rx_packets is2.D.rx_packets;
+    rx_errs    = add is1.D.rx_errs    is2.D.rx_errs;
+    rx_drop    = add is1.D.rx_drop    is2.D.rx_drop;
+    tx_bytes   = add is1.D.tx_bytes   is2.D.tx_bytes;
+    tx_packets = add is1.D.tx_packets is2.D.tx_packets;
+    tx_errs    = add is1.D.tx_errs    is2.D.tx_errs;
+    tx_drop    = add is1.D.tx_drop    is2.D.tx_drop }
+let sum_interface_stats =
+  List.fold_left add_interface_stats zero_interface_stats
+
+(* Get the difference between two interface_stats structures.
+ * Missing data forces the difference to -1.
+ *)
+let diff_interface_stats curr prev =
+  let sub f1 f2 = if f1 >= 0L && f2 >= 0L then f1 -^ f2 else -1L in
+  { D.rx_bytes = sub curr.D.rx_bytes   prev.D.rx_bytes;
+    rx_packets = sub curr.D.rx_packets prev.D.rx_packets;
+    rx_errs    = sub curr.D.rx_errs    prev.D.rx_errs;
+    rx_drop    = sub curr.D.rx_drop    prev.D.rx_drop;
+    tx_bytes   = sub curr.D.tx_bytes   prev.D.tx_bytes;
+    tx_packets = sub curr.D.tx_packets prev.D.tx_packets;
+    tx_errs    = sub curr.D.tx_errs    prev.D.tx_errs;
+    tx_drop    = sub curr.D.tx_drop    prev.D.tx_drop }
diff --git a/virt-top/virt_top_utils.mli b/virt-top/virt_top_utils.mli
new file mode 100644
index 0000000..9cce00e
--- /dev/null
+++ b/virt-top/virt_top_utils.mli
@@ -0,0 +1,54 @@
+(* 'top'-like tool for libvirt domains.
+   (C) Copyright 2007 Richard W.M. Jones, Red Hat Inc.
+   http://libvirt.org/
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+   This file contains utility functions.
+*)
+
+(* Filename concatenation. *)
+val (//) : string -> string -> string
+
+(* Read a configuration file as a list of (lineno, key, value) pairs.
+ * If the config file is missing this returns an empty list.
+ *)
+val read_config_file : string -> (int * string * string) list
+
+(* Pad or truncate a string to a fixed width. *)
+val pad : int -> string -> string
+
+(* Int64 operators for convenience. *)
+val (+^) : int64 -> int64 -> int64
+val (-^) : int64 -> int64 -> int64
+val ( *^ ) : int64 -> int64 -> int64
+val (/^) : int64 -> int64 -> int64
+
+(* Utility functions for formating numbers as short strings. *)
+module Show : sig
+  val percent : float -> string
+  val int64_option : int64 option -> string
+  val int64 : int64 -> string
+  val time : int64 -> string
+end
+
+(* Helpers for manipulating block_stats & interface_stats. *)
+open Libvirt.Domain
+
+val sum_block_stats : block_stats list -> block_stats
+val diff_block_stats : block_stats -> block_stats -> block_stats
+
+val sum_interface_stats : interface_stats list -> interface_stats
+val diff_interface_stats : interface_stats -> interface_stats -> interface_stats