Rewite caching in local::unix module

src/offset/local/tz_info/timezone.rs

@@ -1,8 +1,5 @@
 //! Types related to a time zone.
 
-use std::fs::{self, File};
-use std::io::{self, Read};
-use std::path::{Path, PathBuf};
 use std::{cmp::Ordering, fmt, str};
 
 use super::rule::{AlternateTime, TransitionRule};
@@ -22,43 +19,8 @@ pub(crate) struct TimeZone {
 }
 
 impl TimeZone {
-    /// Returns local time zone.
-    ///
-    /// This method in not supported on non-UNIX platforms, and returns the UTC time zone instead.
-    pub(crate) fn local(env_tz: Option<&str>) -> Result<Self, Error> {
-        match env_tz {
-            Some(tz) => Self::from_posix_tz(tz),
-            None => Self::from_posix_tz("localtime"),
-        }
-    }
-
     /// Construct a time zone from a POSIX TZ string, as described in [the POSIX documentation of the `TZ` environment variable](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html).
-    fn from_posix_tz(tz_string: &str) -> Result<Self, Error> {
-        if tz_string.is_empty() {
-            return Err(Error::InvalidTzString("empty TZ string"));
-        }
-
-        if tz_string == "localtime" {
-            return Self::from_tz_data(&fs::read("/etc/localtime")?);
-        }
-
-        // attributes are not allowed on if blocks in Rust 1.38
-        #[cfg(target_os = "android")]
-        {
-            if let Ok(bytes) = android_tzdata::find_tz_data(tz_string) {
-                return Self::from_tz_data(&bytes);
-            }
-        }
-
-        let mut chars = tz_string.chars();
-        if chars.next() == Some(':') {
-            return Self::from_file(&mut find_tz_file(chars.as_str())?);
-        }
-
-        if let Ok(mut file) = find_tz_file(tz_string) {
-            return Self::from_file(&mut file);
-        }
-
+    pub(crate) fn from_tz_string(tz_string: &str) -> Result<Self, Error> {
         // TZ string extensions are not allowed
         let tz_string = tz_string.trim_matches(|c: char| c.is_ascii_whitespace());
         let rule = TransitionRule::from_tz_string(tz_string.as_bytes(), false)?;
@@ -85,13 +47,6 @@ impl TimeZone {
         Ok(new)
     }
 
-    /// Construct a time zone from the contents of a time zone file
-    fn from_file(file: &mut File) -> Result<Self, Error> {
-        let mut bytes = Vec::new();
-        file.read_to_end(&mut bytes)?;
-        Self::from_tz_data(&bytes)
-    }
-
     /// Construct a time zone from the contents of a time zone file
     ///
     /// Parse TZif data as described in [RFC 8536](https://datatracker.ietf.org/doc/html/rfc8536).
@@ -606,34 +561,6 @@ impl LocalTimeType {
     pub(super) const UTC: LocalTimeType = Self { ut_offset: 0, is_dst: false, name: None };
 }
 
-/// Open the TZif file corresponding to a TZ string
-fn find_tz_file(path: impl AsRef<Path>) -> Result<File, Error> {
-    // Don't check system timezone directories on non-UNIX platforms
-    #[cfg(not(unix))]
-    return Ok(File::open(path)?);
-
-    #[cfg(unix)]
-    {
-        let path = path.as_ref();
-        if path.is_absolute() {
-            return Ok(File::open(path)?);
-        }
-
-        for folder in &ZONE_INFO_DIRECTORIES {
-            if let Ok(file) = File::open(PathBuf::from(folder).join(path)) {
-                return Ok(file);
-            }
-        }
-
-        Err(Error::Io(io::ErrorKind::NotFound.into()))
-    }
-}
-
-// Possible system timezone directories
-#[cfg(unix)]
-const ZONE_INFO_DIRECTORIES: [&str; 4] =
-    ["/usr/share/zoneinfo", "/share/zoneinfo", "/etc/zoneinfo", "/usr/share/lib/zoneinfo"];
-
 /// Number of seconds in one week
 pub(crate) const SECONDS_PER_WEEK: i64 = SECONDS_PER_DAY * DAYS_PER_WEEK;
 /// Number of seconds in 28 days
@@ -844,34 +771,6 @@ mod tests {
         Ok(())
     }
 
-    #[test]
-    fn test_time_zone_from_posix_tz() -> Result<(), Error> {
-        #[cfg(unix)]
-        {
-            // if the TZ var is set, this essentially _overrides_ the
-            // time set by the localtime symlink
-            // so just ensure that ::local() acts as expected
-            // in this case
-            if let Ok(tz) = std::env::var("TZ") {
-                let time_zone_local = TimeZone::local(Some(tz.as_str()))?;
-                let time_zone_local_1 = TimeZone::from_posix_tz(&tz)?;
-                assert_eq!(time_zone_local, time_zone_local_1);
-            }
-
-            // `TimeZone::from_posix_tz("UTC")` will return `Error` if the environment does not have
-            // a time zone database, like for example some docker containers.
-            // In that case skip the test.
-            if let Ok(time_zone_utc) = TimeZone::from_posix_tz("UTC") {
-                assert_eq!(time_zone_utc.find_local_time_type(0)?.offset(), 0);
-            }
-        }
-
-        assert!(TimeZone::from_posix_tz("EST5EDT,0/0,J365/25").is_err());
-        assert!(TimeZone::from_posix_tz("").is_err());
-
-        Ok(())
-    }
-
     #[test]
     fn test_leap_seconds() -> Result<(), Error> {
         let time_zone = TimeZone::new(