1 files changed, 49 insertions, 0 deletions
diff --git a/vendor/iana-time-zone/src/ffi_utils.rs b/vendor/iana-time-zone/src/ffi_utils.rs
new file mode 100644
index 000000000..842b850e8
--- /dev/null
+++ b/vendor/iana-time-zone/src/ffi_utils.rs
@@ -0,0 +1,49 @@
+//! Cross platform FFI helpers.
+
+use std::ffi::CStr;
+
+// The system property named 'persist.sys.timezone' contains the name of the
+// current timezone.
+//
+// From https://android.googlesource.com/platform/bionic/+/gingerbread-release/libc/docs/OVERVIEW.TXT#79:
+//
+// > The name of the current timezone is taken from the TZ environment variable,
+// > if defined. Otherwise, the system property named 'persist.sys.timezone' is
+// > checked instead.
+const ANDROID_TIMEZONE_PROPERTY_NAME: &[u8] = b"persist.sys.timezone\0";
+
+/// Return a [`CStr`] to access the timezone from an Android system properties
+/// environment.
+pub(crate) fn android_timezone_property_name() -> &'static CStr {
+    // In tests or debug mode, opt into extra runtime checks.
+    if cfg!(any(test, debug_assertions)) {
+        return CStr::from_bytes_with_nul(ANDROID_TIMEZONE_PROPERTY_NAME).unwrap();
+    }
+
+    // SAFETY: the key is NUL-terminated and there are no other NULs, this
+    // invariant is checked in tests.
+    unsafe { CStr::from_bytes_with_nul_unchecked(ANDROID_TIMEZONE_PROPERTY_NAME) }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::ffi::CStr;
+
+    use super::{android_timezone_property_name, ANDROID_TIMEZONE_PROPERTY_NAME};
+
+    #[test]
+    fn test_android_timezone_property_name_is_valid_cstr() {
+        CStr::from_bytes_with_nul(ANDROID_TIMEZONE_PROPERTY_NAME).unwrap();
+
+        let mut invalid_property_name = ANDROID_TIMEZONE_PROPERTY_NAME.to_owned();
+        invalid_property_name.push(b'\0');
+        CStr::from_bytes_with_nul(&invalid_property_name).unwrap_err();
+    }
+
+    #[test]
+    fn test_android_timezone_property_name_getter() {
+        let key = android_timezone_property_name().to_bytes_with_nul();
+        assert_eq!(key, ANDROID_TIMEZONE_PROPERTY_NAME);
+        std::str::from_utf8(key).unwrap();
+    }
+}