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 pub type MovableMutex = Mutex;
   9
  10 unsafe impl Send for Mutex {}
  11 unsafe impl Sync for Mutex {} // no threads on this platform
  12
  13 impl Mutex {
  14     #[inline]
  15     pub const fn new() -> Mutex {
  16         Mutex { locked: Cell::new(false) }
  17     }
  18
  19     #[inline]
  20     pub unsafe fn init(&mut self) {}
  21
  22     #[inline]
  23     pub unsafe fn lock(&self) {
  24         assert_eq!(self.locked.replace(true), false, "cannot recursively acquire mutex");
  25     }
  26
  27     #[inline]
  28     pub unsafe fn unlock(&self) {
  29         self.locked.set(false);
  30     }
  31
  32     #[inline]
  33     pub unsafe fn try_lock(&self) -> bool {
  34         self.locked.replace(true) == false
  35     }
  36 }