Jeff King <peff@xxxxxxxx> writes:
> In general, parsing subsections accurately involves looking from both
> the start and the end of the string, pulling out the section and key and
> leaving the rest in the middle. But I think we can get away with this
> left-to-right parsing because we're only interested in matching a
> _specific_ subsection name, and a specific key. So there are no cases it
> will handle incorrectly.
In other words, if k were "branch.A.B.mergeoptions", it can only be
the 'branch.*.mergeoptions' variable attached to branch "A.B", but
when checking for branch=="A", the first two skip_prefix() would
pass and the only thing that protects us from misparsing is that
"B.mergeoptions" is not what we are looking for.
> The more general form would be:
>
> const char *subsection, *key;
> int subsection_len;
>
> if (!parse_config_key("branch", &subsection, &subsection_len, &key) &&
> subsection_len == strlen(branch) && !strncmp(subsection, branch) &&
> !strcmp(key, "mergeoptions"))
> ...
>
> but that's a bit more awkward (it would be less so if we had a helper
> function for comparing a NUL-terminated string against a ptr/len pair).
Yes, but even with such a helper, i.e.
if (branch &&
!parse_config_key("branch", &sub, &sublen, &key) &&
!spanstrcmp(sub, sublen, branch) &&
!strcmp(key, "mergeoptions"))
what Martin wrote, especially if it is reflowed to match the above, i.e.
if (branch &&
skip_prefix(key, "branch.", &sub) &&
skip_prefix(sub, branch, &sub) &&
!strcmp(sub, ".mergeoptions")
I find it just as, if not more, easy to read.
Where the parse_config_key() helper shines, I think, is when we do
not have the middle level to compare against, and in that case, we
must work only from the given key, scanning from both ends for dot.
Thanks.
