[PATCH] base-files: read all 5 bytes in get_magic_fat32() at once

[Adrian Schmutzler]

> -----Original Message-----
> From: openwrt-devel [mailto:openwrt-devel-bounces at lists.openwrt.org]
> On Behalf Of Karl Palsson
> Sent: Montag, 4. Januar 2021 12:58
> To: Adrian Schmutzler <freifunk at adrianschmutzler.de>
> Cc: openwrt-devel <openwrt-devel at lists.openwrt.org>
> Subject: Re: [PATCH] base-files: read all 5 bytes in get_magic_fat32() at once
> 
> The fact that you had to introduce iflags to work around changing IBS/OBS
> which afffected skip size would make me consider this sort of patch to be of
> incredibly marginal utilty, largely even negative value if this isn't some sort of
> hot path.  You've made it more complicated for an _extremely_ small, un
> measured pseudo gain.

Indeed, that's why I initially only touched vfat, until Paul "requested" to update this one as well.

I do not care terribly about this, I just noticed it when looking at the relevant section.
I'd merge the "first" patch for vfat, as there is really no drawback there, but I don't really care what happens to this one.

Best

Adrian

> 
> I'd kinda imagine that the underlying layer already read a bigger block
> anyway...
> 
> Sincerely,
> Karl Palsson
> 
> 
> Adrian Schmutzler <freifunk at adrianschmutzler.de> wrote:
> > While the speed improvement might be negligible, there is still no
> > reason to read individual bytes.
> >
> > Suggested-by: Paul Spooren <mail at aparcar.org>
> > Signed-off-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
> -----
> >
> >  get_magic_fat32() {
> > -	(get_image "$@" | dd bs=1 count=5 skip=82) 2>/dev/null
> > +	(get_image "$@" | dd iflag=skip_bytes bs=5 count=1 skip=82)
> > +2>/dev/null
> >  }
> >
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