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#![macro_use]
use std::sync::{Arc, LockResult, Mutex, MutexGuard};
pub struct SingletonHolder<T> {
inner: Arc<Mutex<T>>,
}
impl<T> SingletonHolder<T> {
pub fn new(mutex: Arc<Mutex<T>>) -> SingletonHolder<T> {
SingletonHolder { inner: mutex }
}
pub fn lock(&self) -> LockResult<MutexGuard<T>> {
self.inner.lock()
}
}
impl<T> Clone for SingletonHolder<T> {
fn clone(&self) -> SingletonHolder<T> {
SingletonHolder {
inner: self.inner.clone(),
}
}
}
#[macro_export]
macro_rules! declare_singleton {
($name:ident, $t:ty, $init:expr) => {
fn $name() -> $crate::singleton::SingletonHolder<$t> {
static mut SINGLETON: *const $crate::singleton::SingletonHolder<$t> =
0 as *const $crate::singleton::SingletonHolder<$t>;
static ONCE: ::std::sync::Once = ::std::sync::ONCE_INIT;
unsafe {
ONCE.call_once(|| {
let singleton = $crate::singleton::SingletonHolder::new(::std::sync::Arc::new(
::std::sync::Mutex::new($init),
));
SINGLETON = ::std::mem::transmute(Box::new(singleton));
});
(*SINGLETON).clone()
}
}
};
}
#[cfg(test)]
mod test {
#[test]
fn smoke_test() {
declare_singleton!(simple_singleton, u32, 0);
let simple = simple_singleton();
match simple.lock() {
Ok(_) => {}
Err(_) => {}
};
}
}