From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: "Eric Sunshine" <sunshine@sunshineco.com>,
孟子易 <mengziyi540841@gmail.com>,
git@vger.kernel.org
Subject: Re: [PATCH 3/3] shorten_unambiguous_ref(): avoid sscanf()
Date: Tue, 14 Feb 2023 13:48:57 -0800 [thread overview]
Message-ID: <xmqqmt5f535i.fsf@gitster.g> (raw)
In-Reply-To: <Y+vV8Ifkj1QV7KF0@coredump.intra.peff.net> (Jeff King's message of "Tue, 14 Feb 2023 13:41:52 -0500")
Jeff King <peff@peff.net> writes:
> +/*
> + * Check that the string refname matches a rule of the form
> + * "{prefix}%.*s{suffix}". So "foo/bar/baz" would match the rule
> + * "foo/%.*s/baz", and return the string "bar".
> + */
> +static const char *match_parse_rule(const char *refname, const char *rule,
> + size_t *len)
> +{
> + /*
> + * Check that rule matches refname up to the first percent
> + * in the rule. This is basically skip_prefix(), but
> + * ending at percent in the prefix, rather than end-of-string.
> + */
> + do {
> + if (!*rule)
> + BUG("rev-parse rule did not have percent");
> + if (*rule == '%')
> + break;
> + } while (*refname++ == *rule++);
So, if we have refname="refs/heads/frotz" and rule="refs/%.*s", then
we'll scan refname and rule to skip over their "refs/" prefix, and
the next iteration, where post-increment moved the pointers to point
at 'h' (at the beginning of "heads/frotz") on the refname side and
'%' on the rule side, we iterate once more, notice *rule is '%', and
break out of the loop. We have refname="heads/frotz" and rule="%.*s"
If we have refname="refsXheads/frotz" and rule="refs/%.*s", after
skipping over "refs", refname points at 'X' while rule points at '/'
and the loop needs to break. Both pointers are post-incremented,
and now we have refname="heads/frotz" and rule="%.*s".
Am I reading the loop correctly? I wanted the bogus refname not to
match the rule, but without peeking back refname[-1], I cannot tell
the two cases apart at this point.
> + /*
> + * Check that we matched all the way to the "%" placeholder,
> + * and skip past it within the rule string. If so, "refname" at
> + * this point is the beginning of a potential match.
> + */
> + if (!skip_prefix(rule, "%.*s", &rule))
> + return NULL;
And we now have rule pointing at "" (i.e. "refs/%.*s" has been fully
consumed). refname points at "heads/frotz".
> + /*
> + * And now check that our suffix (if any) matches.
> + */
> + if (!strip_suffix(refname, rule, len))
> + return NULL;
> +
> + return refname; /* len set by strip_suffix() */
> +}
And the suffix "" is stripped and we yield "heads/frotz".
next prev parent reply other threads:[~2023-02-14 21:49 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-13 6:38 bug report: symbolic-ref --short command echos the wrong text while use Chinese language 孟子易
2023-02-13 20:18 ` Jeff King
2023-02-13 22:58 ` Eric Sunshine
2023-02-14 1:39 ` Jeff King
2023-02-14 5:15 ` Eric Sunshine
2023-02-14 5:33 ` Eric Sunshine
2023-02-14 5:40 ` Junio C Hamano
2023-02-14 6:05 ` Eric Sunshine
2023-02-14 6:45 ` Junio C Hamano
2023-02-14 6:55 ` Eric Sunshine
2023-02-14 16:01 ` Jeff King
2023-02-14 16:29 ` Eric Sunshine
2023-02-14 17:07 ` Jeff King
2023-02-14 18:38 ` [PATCH 0/3] get rid of sscanf() when shortening refs Jeff King
2023-02-14 18:39 ` [PATCH 1/3] shorten_unambiguous_ref(): avoid integer truncation Jeff King
2023-02-14 18:40 ` [PATCH 2/3] shorten_unambiguous_ref(): use NUM_REV_PARSE_RULES constant Jeff King
2023-02-14 21:34 ` Junio C Hamano
2023-02-14 22:23 ` Jeff King
2023-02-14 18:41 ` [PATCH 3/3] shorten_unambiguous_ref(): avoid sscanf() Jeff King
2023-02-14 21:48 ` Junio C Hamano [this message]
2023-02-14 22:25 ` Junio C Hamano
2023-02-14 22:30 ` Jeff King
2023-02-14 22:34 ` Junio C Hamano
2023-02-14 22:40 ` Jeff King
2023-02-15 5:10 ` Junio C Hamano
2023-02-15 14:30 ` Jeff King
2023-02-15 16:41 ` Junio C Hamano
2023-02-14 23:20 ` Eric Sunshine
2023-02-15 15:16 ` [PATCH v2 0/3] get rid of sscanf() when shortening refs Jeff King
2023-02-15 15:16 ` [PATCH v2 1/3] shorten_unambiguous_ref(): avoid integer truncation Jeff King
2023-02-15 15:16 ` [PATCH v2 2/3] shorten_unambiguous_ref(): use NUM_REV_PARSE_RULES constant Jeff King
2023-02-15 15:16 ` [PATCH v2 3/3] shorten_unambiguous_ref(): avoid sscanf() Jeff King
2023-02-16 5:56 ` Torsten Bögershausen
2023-02-16 6:16 ` Eric Sunshine
2023-02-16 17:21 ` Junio C Hamano
2023-02-16 17:28 ` Jeff King
2023-02-16 23:36 ` Junio C Hamano
2023-02-16 17:31 ` Jeff King
2023-02-17 6:46 ` Torsten Bögershausen
2023-02-15 18:00 ` [PATCH v2 0/3] get rid of sscanf() when shortening refs Junio C Hamano
2023-02-14 16:40 ` bug report: symbolic-ref --short command echos the wrong text while use Chinese language Junio C Hamano
2023-02-14 17:40 ` Jeff King
2023-02-15 16:26 ` Torsten Bögershausen
2023-02-15 16:37 ` Eric Sunshine
2023-02-15 17:19 ` Torsten Bögershausen
2023-02-16 6:08 ` Eric Sunshine
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