library/std/src/sys/unsupported/locks/mutex.rs

   1 use crate::cell::Cell;
   2
   3 pub struct Mutex {
   4     // This platform has no threads, so we can use a Cell here.
   5     locked: Cell<bool>,
   6 }
   7
   8 unsafe impl Send for Mutex {}
   9 unsafe impl Sync for Mutex {} // no threads on this platform
  10
  11 impl Mutex {
  12     #[inline]
  13     #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
  14     pub const fn new() -> Mutex {
  15         Mutex { locked: Cell::new(false) }
  16     }
  17
  18     #[inline]
  19     pub fn lock(&self) {
  20         assert_eq!(self.locked.replace(true), false, "cannot recursively acquire mutex");
  21     }
  22
  23     #[inline]
  24     pub unsafe fn unlock(&self) {
  25         self.locked.set(false);
  26     }
  27
  28     #[inline]
  29     pub fn try_lock(&self) -> bool {
  30         self.locked.replace(true) == false
  31     }
  32 }