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use std::fs::{read_link, read_to_string};
pub(crate) fn get_timezone_inner() -> Result<String, crate::GetTimezoneError> {
etc_localtime()
.or_else(|_| etc_timezone())
.or_else(|_| openwrt::etc_config_system())
}
fn etc_timezone() -> Result<String, crate::GetTimezoneError> {
// see https://stackoverflow.com/a/12523283
let mut contents = read_to_string("/etc/timezone")?;
// Trim to the correct length without allocating.
contents.truncate(contents.trim_end().len());
Ok(contents)
}
fn etc_localtime() -> Result<String, crate::GetTimezoneError> {
// Per <https://www.man7.org/linux/man-pages/man5/localtime.5.html>:
// “ The /etc/localtime file configures the system-wide timezone of the local system that is
// used by applications for presentation to the user. It should be an absolute or relative
// symbolic link pointing to /usr/share/zoneinfo/, followed by a timezone identifier such as
// "Europe/Berlin" or "Etc/UTC". The resulting link should lead to the corresponding binary
// tzfile(5) timezone data for the configured timezone. ”
// Systemd does not canonicalize the link, but only checks if it is prefixed by
// "/usr/share/zoneinfo/" or "../usr/share/zoneinfo/". So we do the same.
// <https://github.com/systemd/systemd/blob/9102c625a673a3246d7e73d8737f3494446bad4e/src/basic/time-util.c#L1493>
const PREFIXES: &[&str] = &[
"/usr/share/zoneinfo/", // absolute path
"../usr/share/zoneinfo/", // relative path
"/etc/zoneinfo/", // absolute path for NixOS
"../etc/zoneinfo/", // relative path for NixOS
];
let mut s = read_link("/etc/localtime")?
.into_os_string()
.into_string()
.map_err(|_| crate::GetTimezoneError::FailedParsingString)?;
for &prefix in PREFIXES {
if s.starts_with(prefix) {
// Trim to the correct length without allocating.
s.replace_range(..prefix.len(), "");
return Ok(s);
}
}
Err(crate::GetTimezoneError::FailedParsingString)
}
mod openwrt {
use std::io::BufRead;
use std::{fs, io, iter};
pub(crate) fn etc_config_system() -> Result<String, crate::GetTimezoneError> {
let f = fs::OpenOptions::new()
.read(true)
.open("/etc/config/system")?;
let mut f = io::BufReader::new(f);
let mut in_system_section = false;
let mut line = String::with_capacity(80);
// prefer option "zonename" (IANA time zone) over option "timezone" (POSIX time zone)
let mut timezone = None;
loop {
line.clear();
f.read_line(&mut line)?;
if line.is_empty() {
break;
}
let mut iter = IterWords(&line);
let mut next = || iter.next().transpose();
if let Some(keyword) = next()? {
if keyword == "config" {
in_system_section = next()? == Some("system") && next()?.is_none();
} else if in_system_section && keyword == "option" {
if let Some(key) = next()? {
if key == "zonename" {
if let (Some(zonename), None) = (next()?, next()?) {
return Ok(zonename.to_owned());
}
} else if key == "timezone" {
if let (Some(value), None) = (next()?, next()?) {
timezone = Some(value.to_owned());
}
}
}
}
}
}
timezone.ok_or_else(|| crate::GetTimezoneError::OsError)
}
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
struct BrokenQuote;
impl From<BrokenQuote> for crate::GetTimezoneError {
fn from(_: BrokenQuote) -> Self {
crate::GetTimezoneError::FailedParsingString
}
}
/// Iterated over all words in a OpenWRT config line.
struct IterWords<'a>(&'a str);
impl<'a> Iterator for IterWords<'a> {
type Item = Result<&'a str, BrokenQuote>;
fn next(&mut self) -> Option<Self::Item> {
match read_word(self.0) {
Ok(Some((item, tail))) => {
self.0 = tail;
Some(Ok(item))
}
Ok(None) => {
self.0 = "";
None
}
Err(err) => {
self.0 = "";
Some(Err(err))
}
}
}
}
impl iter::FusedIterator for IterWords<'_> {}
/// Read the next word in a OpenWRT config line. Strip any surrounding quotation marks.
///
/// Returns
///
/// * a tuple `Some((word, remaining_line))` if found,
/// * `None` if the line is exhausted, or
/// * `Err(BrokenQuote)` if the line could not be parsed.
#[allow(clippy::manual_strip)] // needs to be compatile to 1.36
fn read_word(s: &str) -> Result<Option<(&str, &str)>, BrokenQuote> {
let s = s.trim_start();
if s.is_empty() || s.starts_with('#') {
Ok(None)
} else if s.starts_with('\'') {
let mut iter = s[1..].splitn(2, '\'');
match (iter.next(), iter.next()) {
(Some(item), Some(tail)) => Ok(Some((item, tail))),
_ => Err(BrokenQuote),
}
} else if s.starts_with('"') {
let mut iter = s[1..].splitn(2, '"');
match (iter.next(), iter.next()) {
(Some(item), Some(tail)) => Ok(Some((item, tail))),
_ => Err(BrokenQuote),
}
} else {
let mut iter = s.splitn(2, |c: char| c.is_whitespace());
match (iter.next(), iter.next()) {
(Some(item), Some(tail)) => Ok(Some((item, tail))),
_ => Ok(Some((s, ""))),
}
}
}
#[cfg(test)]
#[test]
fn test_read_word() {
assert_eq!(
read_word(" option timezone 'CST-8'\n").unwrap(),
Some(("option", "timezone 'CST-8'\n")),
);
assert_eq!(
read_word("timezone 'CST-8'\n").unwrap(),
Some(("timezone", "'CST-8'\n")),
);
assert_eq!(read_word("'CST-8'\n").unwrap(), Some(("CST-8", "\n")));
assert_eq!(read_word("\n").unwrap(), None);
assert_eq!(
read_word(r#""time 'Zone'""#).unwrap(),
Some(("time 'Zone'", "")),
);
assert_eq!(read_word("'CST-8").unwrap_err(), BrokenQuote);
}
}
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