Re: [PATCH v5 04/13] deb-dl-dir: Make debsrc_download faster

[Henning Schild <henning.schild@siemens.com>]

Am Wed, 22 Apr 2020 03:11:11 -0700 (PDT)
schrieb vijai kumar <vijaikumar.kanagarajan@gmail.com>:

> On Wednesday, April 22, 2020 at 12:45:42 PM UTC+5:30, Henning Schild
> wrote:
> >
> > On Fri, 17 Apr 2020 15:00:31 +0530 
> > Vijai Kumar K <vijaikumar...@gmail.com <javascript:>> wrote: 
> >  
> > > Eventhough apt-get source skips redownloading of files, it is
> > > still slow and takes a lot of time. Instead, lookup if the dsc
> > > file is already present in the cache and skip based on it. 
> > > 
> > > Signed-off-by: Vijai Kumar K <Vijaikumar_...@mentor.com
> > > <javascript:>> --- 
> > >  meta/classes/deb-dl-dir.bbclass | 3 +++ 
> > >  1 file changed, 3 insertions(+) 
> > > 
> > > diff --git a/meta/classes/deb-dl-dir.bbclass 
> > > b/meta/classes/deb-dl-dir.bbclass index 472b9fe..9399741 100644 
> > > --- a/meta/classes/deb-dl-dir.bbclass 
> > > +++ b/meta/classes/deb-dl-dir.bbclass 
> > > @@ -32,6 +32,9 @@ EOSUDO 
> > >          if [ -z "${src}" ];then 
> > >              src="$( dpkg-deb --show --showformat '${Package}' 
> > > "${package}" )" fi 
> > > +        # Strip epoch, if any, from version. 
> > > +        local dscfile=$(find "${DEBSRCDIR}"/"${rootfs_distro}"
> > > -name "${src}_${version#*:}.dsc")   
> >
> > Is that reliable, or might you end up exiting too early. You
> > process that "version" quite a bit, it needs to remain a unique
> > identifier. So you do not skip "foo-1.2.3_r1@deb~42" only because
> > "foo-1.2.3" was there. I made that up but such a version is allowed
> > to have all sorts of funny chars. 
> >  
> 
> As per the Debian policy manual,  version format is 
> [epoch:]upstream_version[-debian_revision].
> While downloading using apt-get source <source pkg>=<version>, I
> observed that epoch is needed
> for downloading the source correctly. However the downloaded dsc file
> does not contain epoch. Hence
> this stripping while checking for the presence of the corresponding
> dsc file.
> 
> Also, Debian policy manual[1] states that . + - ~ (full stop, plus,
> hyphen, tilde) are the valid values
> for use in upstream-version part and + . ~ (plus, full stop, tilde)
> for debian-revision part.
> 
> So, this epoch stripping should be fine.

Thanks for looking into that. I remember running into a very nasty
cornercase once. 

debian-revision
... It is optional; if it isn’t present then the upstream_version may
not contain a hyphen ...

But if you are not cutting the string at hyphens you might be fine.

Henning


> [1] 
> https://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-version
> 
> 
> > > +        [ -z "$dscfile" ] || continue   
> >
> > I personally would say "-n" && continue, might be a matter of
> > taste.   
> 
>  
> >  
> Henning 
> >  
> > >          sudo -E chroot --userspec=$( id -u ):$( id -g )
> > > ${rootfs} \ sh -c ' mkdir -p "/deb-src/${1}/${2}" && cd 
> > > "/deb-src/${1}/${2}" && apt-get -y --download-only --only-source 
> > > source "$2"="$3" ' download-src "${rootfs_distro}" "${src}" 
> > > "${version}"   
> >
> >  
>