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From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: "Torsten Bögershausen" <tboegi@web.de>
Cc: git@vger.kernel.org, larsxschneider@gmail.com,
	Rich Felker <dalias@libc.org>, Junio C Hamano <gitster@pobox.com>,
	Kevin Daudt <me@ikke.info>
Subject: Re: [PATCH] utf8: handle systems that don't write BOM for UTF-16
Date: Sun, 10 Feb 2019 18:55:24 +0000	[thread overview]
Message-ID: <20190210185523.GB28510@genre.crustytoothpaste.net> (raw)
In-Reply-To: <20190210080413.u56vr3fgoejjzjfm@tb-raspi4>

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On Sun, Feb 10, 2019 at 08:04:13AM +0000, Torsten Bögershausen wrote:
> On Sat, Feb 09, 2019 at 08:08:01PM +0000, brian m. carlson wrote:
> > Preserve the existing behavior for systems which do not have this knob
> > enabled, since they may use optimized implementations, including
> > defaulting to the native endianness, to gain improved performance, which
> > can be significant with large checkouts.
> 
> Is the based on measurements on a real system ?

No, I haven't done any performance measurements. However, swapping bytes
is a (IIRC 1-cycle) instruction on x86, which would be executed for each
iteration of the loop. My intuition tells me that will be a significant
expense when there are a lot of files, but I can omit that phrase since
I haven't measured.

> I think we agree that Git will write UTF-16 always as big endian with BOM,
> following the tradition of iconv/libiconv.
> If yes, we can reduce the lines of code/#idefs somewhat, have the knob always on,
> and reduce the maintenance burden a little bit, giving a simpler patch.

No, I don't think it will. libiconv will always write big-endian, but
glibc has a separate iconv implementation which writes the native
endianness. (I believe FreeBSD's does the same thing as glibc's.) I
think it's useful for us to know that we can handle UTF-16 using the
system behavior where possible, since that's what the system is going to
produce.

> What do you think ?

While I like the simplicity of the approach, as I mentioned above, and I
did consider this originally, I'd rather test the behavior of the system
we're operating on, provided it's suitable for our needs.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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  reply	other threads:[~2019-02-10 18:55 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-07 21:59 t0028-working-tree-encoding.sh failing on musl based systems (Alpine Linux) Kevin Daudt
2019-02-08  0:17 ` brian m. carlson
2019-02-08  6:04   ` Rich Felker
2019-02-08 11:45     ` brian m. carlson
2019-02-08 11:55       ` Kevin Daudt
2019-02-08 13:51         ` brian m. carlson
2019-02-08 17:50           ` Junio C Hamano
2019-02-08 20:23             ` Kevin Daudt
2019-02-08 20:42               ` brian m. carlson
2019-02-08 23:12                 ` Junio C Hamano
2019-02-09  0:24                   ` brian m. carlson
2019-02-09 14:57                 ` Kevin Daudt
2019-02-09 20:08                   ` [PATCH] utf8: handle systems that don't write BOM for UTF-16 brian m. carlson
2019-02-10  1:45                     ` Eric Sunshine
2019-02-10 18:14                       ` brian m. carlson
2019-02-10  8:04                     ` Torsten Bögershausen
2019-02-10 18:55                       ` brian m. carlson [this message]
2019-02-11 17:14                         ` Junio C Hamano
2019-02-11  0:23                     ` [PATCH v2] " brian m. carlson
2019-02-11  1:16                       ` Eric Sunshine
2019-02-11  1:20                         ` brian m. carlson
2019-02-11  1:26                     ` [PATCH v3] " brian m. carlson
2019-02-11 21:43                       ` Kevin Daudt
2019-02-11 23:58                         ` brian m. carlson
2019-02-12  0:31                           ` Junio C Hamano
2019-02-12  0:53                             ` brian m. carlson
2019-02-12  2:43                               ` Junio C Hamano
2019-02-12  0:52                     ` [PATCH v4] " brian m. carlson
2019-02-08 16:13         ` t0028-working-tree-encoding.sh failing on musl based systems (Alpine Linux) Rich Felker
2019-02-09  8:09     ` Torsten Bögershausen

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