On Wed, Nov 29, 2023 at 11:15:59AM +1100, patrick.oppenlan...@gmail.com wrote:
> This patch adds support for getting leap second information from the
> leap-seconds.list file included with tzdata and adds a new configuration
> directive leapsecdb to switch on the feature.
Good idea.
I have some comments on the design first. Details can be sorted out
later. Please don't expect this to be ready on first attempt.
> /* ================================================== */
>
> +/* Leap second database */
> +struct leapdb {
> + long long updated;
> + long long expiry;
> + size_t len;
> + struct leap {
> + long long when;
> + int tai_offset;
> + } leap[];
> +};
No need to keep this information in memory. Just read the file for
each request. It's only twice per day.
> + if (leap_db) {
> + /* Check that the leap database has good data for Jun 30 2012 and Dec 31
> 2012 */
> + if (get_db_leap(1341014400, &tai_offset) == LEAP_InsertSecond &&
> tai_offset == 34 &&
> + get_db_leap(1356912000, &tai_offset) == LEAP_Normal && tai_offset ==
> 35) {
> + LOG(LOGS_INFO, "Using leap second database %s", leap_db);
> + } else {
> + LOG(LOGS_WARN, "Leap second database %s failed check, ignoring",
> leap_db);
> + leap_db = NULL;
> + }
> + }
Code like this should not be duplicated. I think there should be a
wrapper around get_tz_leap() and get_db_leap() implementing the
12-hour caching logic and the callers shouldn't care which database is
used.
Also, this is not really relevant to "reference", so it might a good
opportunity to move it out to separate file, e.g. leapdb.c. The API
would be just three functions LDB_Initialise(), LDB_GetLeap(),
LDB_Finalise(). The first commit would refactor the existing code into
that. The second commit would add the leapfile parsing, documentation
and some tests.
--
Miroslav Lichvar
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