struct civil_lookup

A civil_lookup represents the absolute time(s) (time_point) that

correspond to the given civil time (cctz::civil_second) within this

time_zone. Usually the given civil time represents a unique instant

in time, in which case the conversion is unambiguous. However,

within this time zone, the given civil time may be skipped (e.g.,

during a positive UTC offset shift), or repeated (e.g., during a

negative UTC offset shift). To account for these possibilities,

civil_lookup is richer than just a single time_point.

In all cases the civil_lookup::kind enum will indicate the nature

of the given civil-time argument, and the pre, trans, and post

members will give the absolute time answers using the pre-transition

offset, the transition point itself, and the post-transition offset,

respectively (all three times are equal if kind == UNIQUE). If any

of these three absolute times is outside the representable range of a

time_point

<seconds

> the field is set to its maximum/minimum value.

Example:

cctz::time_zone lax;

if (!cctz::load_time_zone("America/Los_Angeles",

&lax

)) { ... }

// A unique civil time.

auto jan01 = lax.lookup(cctz::civil_second(2011, 1, 1, 0, 0, 0));

// jan01.kind == cctz::time_zone::civil_lookup::UNIQUE

// jan01.pre is 2011/01/01 00:00:00 -0800

// jan01.trans is 2011/01/01 00:00:00 -0800

// jan01.post is 2011/01/01 00:00:00 -0800

// A Spring DST transition, when there is a gap in civil time.

auto mar13 = lax.lookup(cctz::civil_second(2011, 3, 13, 2, 15, 0));

// mar13.kind == cctz::time_zone::civil_lookup::SKIPPED

// mar13.pre is 2011/03/13 03:15:00 -0700

// mar13.trans is 2011/03/13 03:00:00 -0700

// mar13.post is 2011/03/13 01:15:00 -0800

// A Fall DST transition, when civil times are repeated.

auto nov06 = lax.lookup(cctz::civil_second(2011, 11, 6, 1, 15, 0));

// nov06.kind == cctz::time_zone::civil_lookup::REPEATED

// nov06.pre is 2011/11/06 01:15:00 -0700

// nov06.trans is 2011/11/06 01:00:00 -0800

// nov06.post is 2011/11/06 01:15:00 -0800