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unix.rs
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unix.rs
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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::{cell::RefCell, env, fs, time::SystemTime};
use super::tz_info::TimeZone;
use super::{DateTime, FixedOffset, Local, NaiveDateTime};
use crate::{Datelike, LocalResult, Utc};
pub(super) fn now() -> DateTime<Local> {
let now = Utc::now().naive_utc();
naive_to_local(&now, false).unwrap()
}
pub(super) fn naive_to_local(d: &NaiveDateTime, local: bool) -> LocalResult<DateTime<Local>> {
TZ_INFO.with(|maybe_cache| {
maybe_cache.borrow_mut().get_or_insert_with(Cache::default).offset(*d, local)
})
}
// we have to store the `Cache` in an option as it can't
// be initalized in a static context.
thread_local! {
static TZ_INFO: RefCell<Option<Cache>> = Default::default();
}
enum Source {
LocalTime { mtime: SystemTime, last_checked: SystemTime },
// we don't bother storing the contents of the environment variable in this case.
// changing the environment while the process is running is generally not reccomended
Environment,
}
impl Default for Source {
fn default() -> Source {
// use of var_os avoids allocating, which is nice
// as we are only going to discard the string anyway
// but we must ensure the contents are valid unicode
// otherwise the behaivour here would be different
// to that in `naive_to_local`
match env::var_os("TZ") {
Some(ref s) if s.to_str().is_some() => Source::Environment,
Some(_) | None => Source::LocalTime {
mtime: fs::symlink_metadata("/etc/localtime")
.expect("localtime should exist")
.modified()
.unwrap(),
last_checked: SystemTime::now(),
},
}
}
}
impl Source {
fn out_of_date(&mut self) -> bool {
let now = SystemTime::now();
let prev = match self {
Source::LocalTime { mtime, last_checked } => match now.duration_since(*last_checked) {
Ok(d) if d.as_secs() < 1 => return false,
Ok(_) | Err(_) => *mtime,
},
Source::Environment => return false,
};
match Source::default() {
Source::LocalTime { mtime, .. } => {
*self = Source::LocalTime { mtime, last_checked: now };
prev != mtime
}
// will only reach here if TZ has been set while
// the process is running
Source::Environment => {
*self = Source::Environment;
true
}
}
}
}
struct Cache {
zone: TimeZone,
source: Source,
}
impl Default for Cache {
fn default() -> Cache {
Cache {
zone: TimeZone::local().expect("unable to parse localtime info"),
source: Source::default(),
}
}
}
impl Cache {
fn offset(&mut self, d: NaiveDateTime, local: bool) -> LocalResult<DateTime<Local>> {
if self.source.out_of_date() {
*self = Cache::default();
}
if !local {
let offset = FixedOffset::east(
self.zone
.find_local_time_type(d.timestamp())
.expect("unable to select local time type")
.offset(),
);
return LocalResult::Single(DateTime::from_utc(d, offset));
}
// we pass through the year as the year of a local point in time must either be valid in that locale, or
// the entire time was skipped in which case we will return LocalResult::None anywa.
match self
.zone
.find_local_time_type_from_local(d.timestamp(), d.year())
.expect("unable to select local time type")
{
LocalResult::None => LocalResult::None,
LocalResult::Ambiguous(early, late) => {
let early_offset = FixedOffset::east(early.offset());
let late_offset = FixedOffset::east(late.offset());
LocalResult::Ambiguous(
DateTime::from_utc(d - early_offset, early_offset),
DateTime::from_utc(d - late_offset, late_offset),
)
}
LocalResult::Single(tt) => {
let offset = FixedOffset::east(tt.offset());
LocalResult::Single(DateTime::from_utc(d - offset, offset))
}
}
}
}