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Export of internal Abseil changes.

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f4e870453d02106c2685e0461816469a4704ad25 by Abseil Team <absl-team@google.com>:

Expose TimeZone::NextTransition() and PrevTransition() now that
we have absl::CivilSecond support in time.h.  Note that these are
for informational purposes only.  General time code should not
care when offset changes occur.

PiperOrigin-RevId: 217177292

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cfadd275c7333f7c27c4d682b9d167010d874e69 by Abseil Team <absl-team@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 217153577

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6ff5b8c61a1239b9c0478a7c62bcd2844b310307 by Jon Cohen <cohenjon@google.com>:

Fix code examples in hash_testing.h.  Includes random clang-format changes.

PiperOrigin-RevId: 216898995

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de124129d27f4627dabe193a10bf106a11783fba by Shaindel Schwartz <shaindel@google.com>:

Add contribution guidelines describing how we decide whether to include an API in Abseil.

PiperOrigin-RevId: 216886943
GitOrigin-RevId: f4e870453d02106c2685e0461816469a4704ad25
Change-Id: Ib9c6706f5bf931b71c0357bf1342053a3bee8ff7
This commit is contained in:
Abseil Team 2018-10-15 11:30:24 -07:00 • committed by Xiaoyi Zhang
parent a00bdd176d
commit 5b70a8910b
6 changed files with 193 additions and 19 deletions
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40
absl/time/time.h
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@ -886,7 +886,7 @@ class TimeZone {
struct TimeInfo {
enum CivilKind {
UNIQUE, // the civil time was singular (pre == trans == post)
SKIPPED, // the civil time did not exist (pre => trans > post)
SKIPPED, // the civil time did not exist (pre >= trans > post)
REPEATED, // the civil time was ambiguous (pre < trans <= post)
} kind;
Time pre; // time calculated using the pre-transition offset
@ -925,6 +925,44 @@ class TimeZone {
// // nov06.post is 2011-11-06 01:15:00 -0800
TimeInfo At(CivilSecond ct) const;
// TimeZone::NextTransition()
// TimeZone::PrevTransition()
//
// Finds the time of the next/previous offset change in this time zone.
//
// By definition, `NextTransition(t, &trans)` returns false when `t` is
// `InfiniteFuture()`, and `PrevTransition(t, &trans)` returns false
// when `t` is `InfinitePast()`. If the zone has no transitions, the
// result will also be false no matter what the argument.
//
// Otherwise, when `t` is `InfinitePast()`, `NextTransition(t, &trans)`
// returns true and sets `trans` to the first recorded transition. Chains
// of calls to `NextTransition()/PrevTransition()` will eventually return
// false, but it is unspecified exactly when `NextTransition(t, &trans)`
// jumps to false, or what time is set by `PrevTransition(t, &trans)` for
// a very distant `t`.
//
// Note: Enumeration of time-zone transitions is for informational purposes
// only. Modern time-related code should not care about when offset changes
// occur.
//
// Example:
// absl::TimeZone nyc;
// if (!absl::LoadTimeZone("America/New_York", &nyc)) { ... }
// const auto now = absl::Now();
// auto t = absl::InfinitePast();
// absl::TimeZone::CivilTransition trans;
// while (t <= now && nyc.NextTransition(t, &trans)) {
// // transition: trans.from -> trans.to
// t = nyc.At(trans.to).trans;
// }
struct CivilTransition {
CivilSecond from; // the civil time we jump from
CivilSecond to; // the civil time we jump to
};
bool NextTransition(Time t, CivilTransition* trans) const;
bool PrevTransition(Time t, CivilTransition* trans) const;
template <typename H>
friend H AbslHashValue(H h, TimeZone tz) {
return H::combine(std::move(h), tz.cz_);