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use std::marker;
use std::mem;
use std::sync::atomic::{AtomicUsize, Ordering};
use libc;
macro_rules! dlsym {
(fn $name:ident($($t:ty),*) -> $ret:ty) => (
#[allow(bad_style)]
static $name: ::sys::unix::dlsym::DlSym<unsafe extern fn($($t),*) -> $ret> =
::sys::unix::dlsym::DlSym {
name: concat!(stringify!($name), "\0"),
addr: ::std::sync::atomic::ATOMIC_USIZE_INIT,
_marker: ::std::marker::PhantomData,
};
)
}
pub struct DlSym<F> {
pub name: &'static str,
pub addr: AtomicUsize,
pub _marker: marker::PhantomData<F>,
}
impl<F> DlSym<F> {
pub fn get(&self) -> Option<&F> {
assert_eq!(mem::size_of::<F>(), mem::size_of::<usize>());
unsafe {
if self.addr.load(Ordering::SeqCst) == 0 {
self.addr.store(fetch(self.name), Ordering::SeqCst);
}
if self.addr.load(Ordering::SeqCst) == 1 {
None
} else {
mem::transmute::<&AtomicUsize, Option<&F>>(&self.addr)
}
}
}
}
unsafe fn fetch(name: &str) -> usize {
assert_eq!(name.as_bytes()[name.len() - 1], 0);
match libc::dlsym(libc::RTLD_DEFAULT, name.as_ptr() as *const _) as usize {
0 => 1,
n => n,
}
}