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Extract timezone info from tzdata file on Android #978

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merged 2 commits into from
May 26, 2023
Merged

Extract timezone info from tzdata file on Android #978

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02ee240
Extract timezone info from tzdata file on Android
RumovZ Mar 4, 2023
53fa3f2
Move up tzdata lookup on Android
RumovZ Apr 6, 2023
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9 changes: 8 additions & 1 deletion .github/workflows/test.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,14 @@ jobs:
strategy:
matrix:
os: [ubuntu-latest]
target: [wasm32-unknown-unknown, wasm32-wasi, wasm32-unknown-emscripten, aarch64-apple-ios, aarch64-linux-android]
target:
[
wasm32-unknown-unknown,
wasm32-wasi,
wasm32-unknown-emscripten,
aarch64-apple-ios,
aarch64-linux-android,
]
runs-on: ${{ matrix.os }}
steps:
- uses: actions/checkout@v2
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3 changes: 3 additions & 0 deletions Cargo.toml
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Expand Up @@ -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 }
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8 changes: 8 additions & 0 deletions src/offset/local/tz_info/timezone.rs
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Expand Up @@ -52,6 +52,14 @@ impl TimeZone {
return Self::from_file(&mut file);
}

// attributes are not allowed on if blocks in Rust 1.38
#[cfg(target_os = "android")]
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should this moved up to above line 46? Also what do we do in the case that the tz_string is "localtime" on android?

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I have yet to find exhaustive documentation on this, but from what I can tell, tzdata doesn't contain a localtime entry, and there is /etc/localtime like on other Unix systems. Moving the tzdata block up sounds good to me.

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I've checked an Android device here, and it does not have an /etc/localtime - perhaps they did away with it in later Android releases, or it varies by manufacturer? Android appears to set TZ to the timezone configured in the settings by default, so presumably users would not hit this unless they explicitly overwrote the default value.

{
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)?;
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7 changes: 3 additions & 4 deletions src/offset/local/unix.rs
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Expand Up @@ -68,19 +68,18 @@ struct Cache {
last_checked: SystemTime,
}

#[cfg(target_os = "android")]
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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()?;
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In PR code for src/offset/local/tz_info/timezone.rs (above) the fn from_posix_tz code attempts do things the "Android Way" but if that doesn't succeed it falls back to the current implementation. Specifically, if android_tzdata::find_tz_data(tz_string) fails it will fall through and use the current general implementation.

Should fn fallback_timezone code allow a similar fallback? e.g.

fn fallback_timezone() -> Option<TimeZone> {
    let tz_name = iana_time_zone::get_timezone().ok()?;
    #[cfg(target_os = "android")]
    if let Ok(bytes) = android_tzdata::find_tz_data(&tz_name).ok() {
        return TimeZone::from_tz_data(&bytes).ok();
    }
    let bytes = fs::read(format!("{}/{}", TZDB_LOCATION, tz_name)).ok()?;
    TimeZone::from_tz_data(&bytes).ok()
}

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In from_posix_tz(), we try to parse the tz string as a transition rule as a fallback, which should or shouldn't work regardless of the OS. On the other hand, trying to find a tz file on Android won't ever work, as far as I know, so I don't think it makes sense as a fallback.

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Okay. 👍

TimeZone::from_tz_data(&bytes).ok()
}

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