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◆ subrepo-pin-state oxygen / vendor / iana-time-zone / src / tz_linux.rs
6.6 KiB · Rust · last changed Strata: the cloud stores send through ureq, so every release target links 1 month ago source blame history raw
2cd40ea1 Andy McCall ↶ 1 
use std::fs::{read_link, read_to_string};
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pub(crate) fn get_timezone_inner() -> Result<String, crate::GetTimezoneError> {
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    etc_localtime()
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        .or_else(|_| etc_timezone())
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        .or_else(|_| openwrt::etc_config_system())
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}
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fn etc_timezone() -> Result<String, crate::GetTimezoneError> {
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    // see https://stackoverflow.com/a/12523283
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    let mut contents = read_to_string("/etc/timezone")?;
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    // Trim to the correct length without allocating.
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    contents.truncate(contents.trim_end().len());
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    Ok(contents)
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}
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fn etc_localtime() -> Result<String, crate::GetTimezoneError> {
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    // Per <https://www.man7.org/linux/man-pages/man5/localtime.5.html>:
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    // “ The /etc/localtime file configures the system-wide timezone of the local system that is
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    //   used by applications for presentation to the user. It should be an absolute or relative
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    //   symbolic link pointing to /usr/share/zoneinfo/, followed by a timezone identifier such as
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    //   "Europe/Berlin" or "Etc/UTC". The resulting link should lead to the corresponding binary
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    //   tzfile(5) timezone data for the configured timezone. ”
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    // Systemd does not canonicalize the link, but only checks if it is prefixed by
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    // "/usr/share/zoneinfo/" or "../usr/share/zoneinfo/". So we do the same.
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    // <https://github.com/systemd/systemd/blob/9102c625a673a3246d7e73d8737f3494446bad4e/src/basic/time-util.c#L1493>
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    const PREFIXES: &[&str] = &[
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        "/usr/share/zoneinfo/",   // absolute path
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        "../usr/share/zoneinfo/", // relative path
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        "/etc/zoneinfo/",         // absolute path for NixOS
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        "../etc/zoneinfo/",       // relative path for NixOS
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    ];
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    let mut s = read_link("/etc/localtime")?
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        .into_os_string()
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        .into_string()
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        .map_err(|_| crate::GetTimezoneError::FailedParsingString)?;
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    for &prefix in PREFIXES {
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        if s.starts_with(prefix) {
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            // Trim to the correct length without allocating.
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            s.replace_range(..prefix.len(), "");
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            return Ok(s);
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        }
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    }
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    Err(crate::GetTimezoneError::FailedParsingString)
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}
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mod openwrt {
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    use std::io::BufRead;
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    use std::{fs, io, iter};
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    pub(crate) fn etc_config_system() -> Result<String, crate::GetTimezoneError> {
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        let f = fs::OpenOptions::new()
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            .read(true)
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            .open("/etc/config/system")?;
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        let mut f = io::BufReader::new(f);
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        let mut in_system_section = false;
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        let mut line = String::with_capacity(80);
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        // prefer option "zonename" (IANA time zone) over option "timezone" (POSIX time zone)
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        let mut timezone = None;
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        loop {
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            line.clear();
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            f.read_line(&mut line)?;
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            if line.is_empty() {
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                break;
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            }
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            let mut iter = IterWords(&line);
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            let mut next = || iter.next().transpose();
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            if let Some(keyword) = next()? {
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                if keyword == "config" {
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                    in_system_section = next()? == Some("system") && next()?.is_none();
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                } else if in_system_section && keyword == "option" {
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                    if let Some(key) = next()? {
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                        if key == "zonename" {
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                            if let (Some(zonename), None) = (next()?, next()?) {
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                                return Ok(zonename.to_owned());
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                            }
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                        } else if key == "timezone" {
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                            if let (Some(value), None) = (next()?, next()?) {
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                                timezone = Some(value.to_owned());
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                            }
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                        }
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                    }
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                }
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            }
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        }
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        timezone.ok_or(crate::GetTimezoneError::OsError)
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    }
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    #[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
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    struct BrokenQuote;
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    impl From<BrokenQuote> for crate::GetTimezoneError {
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        fn from(_: BrokenQuote) -> Self {
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            crate::GetTimezoneError::FailedParsingString
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        }
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    }
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    /// Iterated over all words in a OpenWRT config line.
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    struct IterWords<'a>(&'a str);
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    impl<'a> Iterator for IterWords<'a> {
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        type Item = Result<&'a str, BrokenQuote>;
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        fn next(&mut self) -> Option<Self::Item> {
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            match read_word(self.0) {
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                Ok(Some((item, tail))) => {
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                    self.0 = tail;
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                    Some(Ok(item))
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                }
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                Ok(None) => {
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                    self.0 = "";
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                    None
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                }
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                Err(err) => {
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                    self.0 = "";
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                    Some(Err(err))
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                }
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            }
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        }
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    }
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    impl iter::FusedIterator for IterWords<'_> {}
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    /// Read the next word in a OpenWRT config line. Strip any surrounding quotation marks.
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    ///
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    /// Returns
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    ///
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    ///  * a tuple `Some((word, remaining_line))` if found,
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    ///  * `None` if the line is exhausted, or
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    ///  * `Err(BrokenQuote)` if the line could not be parsed.
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    #[allow(clippy::manual_strip)] // needs to be compatile to 1.36
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    fn read_word(s: &str) -> Result<Option<(&str, &str)>, BrokenQuote> {
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        let s = s.trim_start();
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        if s.is_empty() || s.starts_with('#') {
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            Ok(None)
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        } else if s.starts_with('\'') {
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            let mut iter = s[1..].splitn(2, '\'');
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            match (iter.next(), iter.next()) {
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                (Some(item), Some(tail)) => Ok(Some((item, tail))),
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                _ => Err(BrokenQuote),
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            }
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        } else if s.starts_with('"') {
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            let mut iter = s[1..].splitn(2, '"');
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            match (iter.next(), iter.next()) {
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                (Some(item), Some(tail)) => Ok(Some((item, tail))),
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                _ => Err(BrokenQuote),
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            }
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        } else {
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            let mut iter = s.splitn(2, |c: char| c.is_whitespace());
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            match (iter.next(), iter.next()) {
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                (Some(item), Some(tail)) => Ok(Some((item, tail))),
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                _ => Ok(Some((s, ""))),
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            }
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        }
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    }
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    #[cfg(test)]
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    #[test]
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    fn test_read_word() {
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        assert_eq!(
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            read_word("       option timezone 'CST-8'\n").unwrap(),
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            Some(("option", "timezone 'CST-8'\n")),
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        );
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        assert_eq!(
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            read_word("timezone 'CST-8'\n").unwrap(),
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            Some(("timezone", "'CST-8'\n")),
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        );
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        assert_eq!(read_word("'CST-8'\n").unwrap(), Some(("CST-8", "\n")));
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        assert_eq!(read_word("\n").unwrap(), None);
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        assert_eq!(
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            read_word(r#""time 'Zone'""#).unwrap(),
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            Some(("time 'Zone'", "")),
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        );
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        assert_eq!(read_word("'CST-8").unwrap_err(), BrokenQuote);
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    }
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}