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use core::ffi::{c_char, CStr};
use core::ptr::NonNull;
use crate::{
tz::{TimeZone, TimeZoneDatabase},
util::constant::unwrapr,
};
extern "C" {
/// <https://emscripten.org/docs/api_reference/emscripten.h.html#c.emscripten_run_script_string>
fn emscripten_run_script_string(script: *const c_char) -> *mut c_char;
}
pub(super) fn get(db: &TimeZoneDatabase) -> Option<TimeZone> {
const SCRIPT: &CStr = unwrapr!(
CStr::from_bytes_with_nul(
"Intl.DateTimeFormat().resolvedOptions().timeZone\0".as_bytes(),
),
"not a valid C string literal"
);
// SAFETY: SCRIPT is a valid pointer to a null-terminated string. The
// result will be a pointer to a null-terminated C string, or null if the
// script failed to run. The returned value is valid until the next call
// to `emscripten_run_script_string` in the same thread, so it is valid
// for the duration of this function. This likely relies on emscripten
// managing its string lifetimes carefully, possibly through TLS or some
// other shenanigans. Either way, this usage seems clearly okay even in a
// multi-threaded environment according to emscripten docs:
//
// > This function can be called from a pthread, and it is executed
// > in the scope of the Web Worker that is hosting the pthread. To
// > evaluate a function in the scope of the main runtime thread,
// > see the function emscripten_sync_run_in_main_runtime_thread().
//
// From: <https://emscripten.org/docs/api_reference/emscripten.h.html#c.emscripten_run_script_string>
let script_result =
unsafe { emscripten_run_script_string(SCRIPT.as_ptr()) };
let script_ptr = match NonNull::new(script_result) {
Some(script_cstr) => script_cstr,
None => {
trace!(
"executing JavaScript to discover IANA time zone \
identifier returned a null pointer",
);
return None;
}
};
// SAFETY: OK because of the contract of `emscripten_run_script_string`.
// We assume that when it returns a non-null pointer (which is checked
// above) that it is a valid C string.
let script_cstr = unsafe { CStr::from_ptr(script_ptr.as_ptr()) };
let name = match script_cstr.to_str().ok() {
Some(name) => name,
None => {
trace!(
"executing JavaScript to discover IANA time zone \
identifier returned invalid UTF-8: {script_cstr}",
script_cstr = escape::Bytes(script_cstr.to_bytes()),
);
return None;
}
};
let tz = match db.get(name) {
Ok(tz) => tz,
Err(_err) => {
trace!(
"got {name:?} as time zone name, \
but failed to find time zone with that name in \
zoneinfo database {db:?}: {_err}",
);
return None;
}
};
Some(tz)
}
pub(super) fn read(_db: &TimeZoneDatabase, path: &str) -> Option<TimeZone> {
match super::read_unnamed_tzif_file(path) {
Ok(tz) => Some(tz),
Err(_err) => {
trace!("failed to read {path} as unnamed time zone: {_err}");
None
}
}
}