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store hash of environment variable

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Eric Sheppard 2022-10-30 22:50:15 +11:00 committed by Dirkjan Ochtman
parent 57908e918b
commit dc4287a627
1 changed files with 16 additions and 12 deletions
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28
src/offset/local/unix.rs
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@ -8,7 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::{cell::RefCell, env, fs, time::SystemTime};
use std::{cell::RefCell, collections::hash_map, env, fs, hash::Hasher, time::SystemTime};
use super::tz_info::TimeZone;
use super::{DateTime, FixedOffset, Local, NaiveDateTime};
@ -33,20 +33,18 @@ thread_local! {
enum Source {
LocalTime { mtime: 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,
Environment { hash: u64 },
}
impl Source {
fn new(env_tz: Option<&str>) -> 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_tz {
Some(_) => Source::Environment,
Some(tz) => {
let mut hasher = hash_map::DefaultHasher::new();
hasher.write(tz.as_bytes());
let hash = hasher.finish();
Source::Environment { hash }
}
None => match fs::symlink_metadata("/etc/localtime") {
Ok(data) => Source::LocalTime {
// we have to pick a sensible default when the mtime fails
@ -121,14 +119,20 @@ impl Cache {
let out_of_date = match (&self.source, &new_source) {
// change from env to file or file to env, must recreate the zone
(Source::Environment, Source::LocalTime { .. })
| (Source::LocalTime { .. }, Source::Environment) => true,
(Source::Environment { .. }, Source::LocalTime { .. })
| (Source::LocalTime { .. }, Source::Environment { .. }) => true,
// stay as file, but mtime has changed
(Source::LocalTime { mtime: old_mtime }, Source::LocalTime { mtime })
if old_mtime != mtime =>
{
true
}
// stay as env, but hash of variable has changed
(Source::Environment { hash: old_hash }, Source::Environment { hash })
if old_hash != hash =>
{
true
}
// cache can be reused
_ => false,
};