Libguestfs - Jan 2022 - [v2v PATCH 7/9] convert/libosinfo_utils: introduce "string_of_osinfo_device_list"

For debugging purposes, we'll want to print the list of devices returned
by the previously introduced "osinfo_os#get_devices" method.

Format the device list as a nice table.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1942325
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---

Notes:
    Log examples will be shown later in this series, in the Notes section(s)
    of other patch(es).

 convert/libosinfo_utils.mli |  3 ++
 convert/libosinfo_utils.ml  | 35 ++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/convert/libosinfo_utils.mli b/convert/libosinfo_utils.mli
index b3714d224ae4..5a703334d9f0 100644
--- a/convert/libosinfo_utils.mli
+++ b/convert/libosinfo_utils.mli
@@ -27,3 +27,6 @@ val get_os_by_short_id : string -> Libosinfo.osinfo_os
 
 val string_of_osinfo_device_driver : Libosinfo.osinfo_device_driver ->
string
 (** Convert a [osinfo_device_driver] to a printable string for debugging. *)
+
+val string_of_osinfo_device_list : Libosinfo.osinfo_device list -> string
+(** Convert an [osinfo_device] list to a printable string for debugging. *)
diff --git a/convert/libosinfo_utils.ml b/convert/libosinfo_utils.ml
index 1fc138cce321..d5eb082b458c 100644
--- a/convert/libosinfo_utils.ml
+++ b/convert/libosinfo_utils.ml
@@ -42,3 +42,38 @@ let string_of_osinfo_device_driver { Libosinfo.architecture;
location;
     (if signed then "signed" else "unsigned")
     priority
     (String.concat " " files)
+
+let string_of_osinfo_device_list dev_list +
+  (* Turn the fields of an "osinfo_device" record into a list. *)
+  let listify { Libosinfo.id; vendor; vendor_id; product; product_id; name;
+                class_; bus_type; subsystem } +    [ id; vendor; vendor_id;
product; product_id; name;
+      class_; bus_type; subsystem ]
+
+  (* Given a list of strings, and a list of previously known maximum widths,
+   * "increase" each width, if necessary, to the length of the
corresponding
+   * string.
+   *)
+  and grow_widths = List.map2 (fun s -> max (String.length s))
+  in
+
+  (* Compute the maximum width for each field in "dev_list". *)
+  let max_widths +    List.fold_right grow_widths (List.map listify dev_list)
+      [ 0; 0; 0; 0; 0; 0; 0; 0; 0 ]
+
+  (* Given a list of strings and a list of field widths, format "string1 |
+   * string2 | ... | stringN" such that each field is right-padded to the
+   * corresponding width.
+   *)
+  and columnate strings widths +    String.concat " | " (List.map2
(Printf.sprintf "%-*s") widths strings)
+  in
+
+  (* Format "dev_list" as a table by (a) printing one
"osinfo_device" record
+   * per line, and (b) right-padding each field of each
"osinfo_device" record
+   * to the maximum width of that field.
+   *)
+  String.concat "\n"
+    (List.map (fun dev -> columnate (listify dev) max_widths) dev_list)
-- 
2.19.1.3.g30247aa5d201

On Thu, Jan 06, 2022 at 03:09:08PM +0100, Laszlo Ersek
wrote:
> For debugging purposes, we'll want to print the list of devices
returned
> by the previously introduced "osinfo_os#get_devices" method.
> 
> Format the device list as a nice table.
> 
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1942325
> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> ---
> 
> Notes:
>     Log examples will be shown later in this series, in the Notes
section(s)
>     of other patch(es).
> 
>  convert/libosinfo_utils.mli |  3 ++
>  convert/libosinfo_utils.ml  | 35 ++++++++++++++++++++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/convert/libosinfo_utils.mli b/convert/libosinfo_utils.mli
> index b3714d224ae4..5a703334d9f0 100644
> --- a/convert/libosinfo_utils.mli
> +++ b/convert/libosinfo_utils.mli
> @@ -27,3 +27,6 @@ val get_os_by_short_id : string -> Libosinfo.osinfo_os
>  
>  val string_of_osinfo_device_driver : Libosinfo.osinfo_device_driver ->
string
>  (** Convert a [osinfo_device_driver] to a printable string for debugging.
*)
> +
> +val string_of_osinfo_device_list : Libosinfo.osinfo_device list ->
string
> +(** Convert an [osinfo_device] list to a printable string for debugging.
*)
> diff --git a/convert/libosinfo_utils.ml b/convert/libosinfo_utils.ml
> index 1fc138cce321..d5eb082b458c 100644
> --- a/convert/libosinfo_utils.ml
> +++ b/convert/libosinfo_utils.ml
> @@ -42,3 +42,38 @@ let string_of_osinfo_device_driver {
Libosinfo.architecture; location;
>      (if signed then "signed" else "unsigned")
>      priority
>      (String.concat " " files)
> +
> +let string_of_osinfo_device_list dev_list > +
> +  (* Turn the fields of an "osinfo_device" record into a list.
*)
> +  let listify { Libosinfo.id; vendor; vendor_id; product; product_id;
name;
> +                class_; bus_type; subsystem } > +    [ id; vendor;
vendor_id; product; product_id; name;
> +      class_; bus_type; subsystem ]
> +
> +  (* Given a list of strings, and a list of previously known maximum
widths,
> +   * "increase" each width, if necessary, to the length of the
corresponding
> +   * string.
> +   *)
> +  and grow_widths = List.map2 (fun s -> max (String.length s))
> +  in
> +
> +  (* Compute the maximum width for each field in "dev_list". *)
> +  let max_widths > +    List.fold_right grow_widths (List.map listify
dev_list)
> +      [ 0; 0; 0; 0; 0; 0; 0; 0; 0 ]
> +
> +  (* Given a list of strings and a list of field widths, format
"string1 |
> +   * string2 | ... | stringN" such that each field is right-padded to
the
> +   * corresponding width.
> +   *)
> +  and columnate strings widths > +    String.concat " | "
(List.map2 (Printf.sprintf "%-*s") widths strings)
> +  in
> +
> +  (* Format "dev_list" as a table by (a) printing one
"osinfo_device" record
> +   * per line, and (b) right-padding each field of each
"osinfo_device" record
> +   * to the maximum width of that field.
> +   *)
> +  String.concat "\n"
> +    (List.map (fun dev -> columnate (listify dev) max_widths) dev_list)
Seems ... complicated, and I guess something that if we think we'll
need to format a lot of tables we should add a generic mechanism to
Std_utils.

I would have done this using printf a fixed maximum width like
this code:

https://gitlab.com/nbdkit/nbdkit/-/blob/d7c69529c453adb1b5b651803881dac2e724f2e9/plugins/vddk/stats.c#L99

But it's encapsulated into a function and only used for debugging so
we could revise it later if we wanted, so sure.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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