Subject: bug#27265: [PATCH] file-systems: Use creation time if modification time is unset for ISO9660.

From: [email-masked] (Ludovic Courtès)
Date: Wed, 07 Jun 2017 01:19:34 +0200

Danny Milosavljevic <[email-masked]> skribis:

> * gnu/build/file-systems.scm (iso9660-superblock-uuid): Modify.
> ---
>  gnu/build/file-systems.scm | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
> index 10be0dc83..7737de3d0 100644
> --- a/gnu/build/file-systems.scm
> +++ b/gnu/build/file-systems.scm
> @@ -268,12 +268,18 @@ as a bytevector, or #f if DEVICE does not contain an iso9660 file system."
>  
>  (define (iso9660-superblock-uuid sblock)
>    "Return the modification time of an iso9660 primary volume descriptor
> -SBLOCK as a bytevector."
> +SBLOCK as a bytevector.  If that's not set, returns the creation time."
>    ;; Drops GMT offset for compatibility with Grub, blkid and /dev/disk/by-uuid.
>    ;; Compare Grub: "2014-12-02-19-30-23-00".
>    ;; Compare blkid result: "2014-12-02-19-30-23-00".
>    ;; Compare /dev/disk/by-uuid entry: "2014-12-02-19-30-23-00".
> -  (sub-bytevector sblock 830 16))
> +  (let* ((creation-time (sub-bytevector sblock 813 17))
> +         (modification-time (sub-bytevector sblock 830 17))
> +         (unset-time (make-bytevector 17 0))
> +         (time (if (bytevector=? unset-time modification-time)
> +                   creation-time
> +                   modification-time)))
> +    (sub-bytevector time 0 16))) ; strips GMT offset.

LGTM.

I suppose this makes those UUIDs a bit more unique, right?

Thank you,
Ludo’.