From: Michael Haggerty <mhagger@alum.mit.edu>
To: Stefan Beller <sbeller@google.com>
Cc: "Junio C Hamano" <gitster@pobox.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Jeff King" <peff@peff.net>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Brandon Williams" <bmwill@google.com>,
"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH v2 02/21] prefix_ref_iterator: break when we leave the prefix
Date: Thu, 21 Sep 2017 09:42:35 +0200 [thread overview]
Message-ID: <32b3d338-6781-a600-2c7e-65dc2818aab5@alum.mit.edu> (raw)
In-Reply-To: <CAGZ79kbwCAidGR3cgukdjckZVYwj+qbOikqN-e934uP1yk9Cuw@mail.gmail.com>
On 09/20/2017 10:25 PM, Stefan Beller wrote:
> On Mon, Sep 18, 2017 at 11:22 PM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
>> [...]
>> +/* Return -1, 0, 1 if refname is before, inside, or after the prefix. */
>> +static int compare_prefix(const char *refname, const char *prefix)
>> +{
>> + while (*prefix) {
>> + if (*refname != *prefix)
>> + return ((unsigned char)*refname < (unsigned char)*prefix) ? -1 : +1;
>
> This looks interesting.
>
> We get a signed char* , cast it to unsigned char* and then
> compare byte by byte.
Not quite. We get a `char *` of unknown signedness (it's
implementation-dependent), dereference it into a `char`, then cast that
value to `unsigned char`. What you described would be
*(const unsigned char *)refname < *(const unsigned char *)prefix
But I assume that these two variants would result in identical assembly
code.
> [...]
Michael
next prev parent reply other threads:[~2017-09-21 7:42 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 6:22 [PATCH v2 00/21] Read `packed-refs` using mmap() Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 01/21] ref_iterator: keep track of whether the iterator output is ordered Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 02/21] prefix_ref_iterator: break when we leave the prefix Michael Haggerty
2017-09-20 20:25 ` Stefan Beller
2017-09-21 4:59 ` Jeff King
2017-09-21 17:29 ` Stefan Beller
2017-09-21 7:42 ` Michael Haggerty [this message]
2017-09-19 6:22 ` [PATCH v2 03/21] packed_ref_cache: add a backlink to the associated `packed_ref_store` Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 04/21] die_unterminated_line(), die_invalid_line(): new functions Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 05/21] read_packed_refs(): use mmap to read the `packed-refs` file Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 06/21] read_packed_refs(): only check for a header at the top of the file Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 07/21] read_packed_refs(): make parsing of the header line more robust Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 08/21] read_packed_refs(): read references with minimal copying Michael Haggerty
2017-09-20 18:27 ` Jeff King
2017-09-21 7:34 ` Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 09/21] packed_ref_cache: remember the file-wide peeling state Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 10/21] mmapped_ref_iterator: add iterator over a packed-refs file Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 11/21] mmapped_ref_iterator_advance(): no peeled value for broken refs Michael Haggerty
2017-09-20 18:29 ` Jeff King
2017-09-19 6:22 ` [PATCH v2 12/21] packed-backend.c: reorder some definitions Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 13/21] packed_ref_cache: keep the `packed-refs` file mmapped if possible Michael Haggerty
2017-09-19 12:44 ` Michael Haggerty
2017-09-24 6:56 ` Junio C Hamano
2017-09-20 18:40 ` Jeff King
2017-09-20 18:51 ` Jeff King
2017-09-21 8:04 ` Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 14/21] read_packed_refs(): ensure that references are ordered when read Michael Haggerty
2017-09-20 18:50 ` Jeff King
2017-09-21 8:27 ` Michael Haggerty
2017-09-25 15:44 ` Johannes Schindelin
2017-09-19 6:22 ` [PATCH v2 15/21] packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator` Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 16/21] packed_read_raw_ref(): read the reference from the mmapped buffer Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 17/21] ref_store: implement `refs_peel_ref()` generically Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 18/21] packed_ref_store: get rid of the `ref_cache` entirely Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 19/21] ref_cache: remove support for storing peeled values Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 20/21] mmapped_ref_iterator: inline into `packed_ref_iterator` Michael Haggerty
2017-09-19 6:22 ` [PATCH v2 21/21] packed-backend.c: rename a bunch of things and update comments Michael Haggerty
2017-09-19 19:53 ` [PATCH v2 00/21] Read `packed-refs` using mmap() Johannes Schindelin
2017-09-20 18:57 ` Jeff King
2017-09-25 15:55 ` Johannes Schindelin
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