Extract timezone info from tzdata file on Android

Cargo.toml

@@ -49,6 +49,9 @@ winapi = { version = "0.3.0", features = ["std", "minwinbase", "minwindef", "tim
 [target.'cfg(unix)'.dependencies]
 iana-time-zone = { version = "0.1.45", optional = true, features = ["fallback"] }
 
+[target.'cfg(target_os = "android")'.dependencies]
+android-tzdata = "0.1.1"
+
 [dev-dependencies]
 serde_json = { version = "1" }
 serde_derive = { version = "1", default-features = false }

src/offset/local/tz_info/timezone.rs

@@ -8,6 +8,9 @@ use std::{cmp::Ordering, fmt, str};
 use super::rule::{AlternateTime, TransitionRule};
 use super::{parser, Error, DAYS_PER_WEEK, SECONDS_PER_DAY};
 
+#[cfg(target_os = "android")]
+extern crate android_tzdata;
+
 /// Time zone
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub(crate) struct TimeZone {
@@ -52,6 +55,14 @@ impl TimeZone {
             return Self::from_file(&mut file);
         }
 
+        // 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);
+            }
+        }
+
         // 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)?;

src/offset/local/unix.rs

@@ -68,19 +68,18 @@ struct Cache {
     last_checked: SystemTime,
 }
 
-#[cfg(target_os = "android")]
-const TZDB_LOCATION: &str = " /system/usr/share/zoneinfo";
-
 #[cfg(target_os = "aix")]
 const TZDB_LOCATION: &str = "/usr/share/lib/zoneinfo";
 
-#[allow(dead_code)] // keeps the cfg simpler
 #[cfg(not(any(target_os = "android", target_os = "aix")))]
 const TZDB_LOCATION: &str = "/usr/share/zoneinfo";
 
 fn fallback_timezone() -> Option<TimeZone> {
     let tz_name = iana_time_zone::get_timezone().ok()?;
+    #[cfg(not(target_os = "android"))]
     let bytes = fs::read(format!("{}/{}", TZDB_LOCATION, tz_name)).ok()?;
+    #[cfg(target_os = "android")]
+    let bytes = android_tzdata::find_tz_data(&tz_name).ok()?;
     TimeZone::from_tz_data(&bytes).ok()
 }