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     pub const fn new() -> Mutex {
  15         Mutex { locked: Cell::new(false) }
  16     }
  17
  18     #[inline]
  19     pub unsafe fn init(&mut self) {}
  20
  21     #[inline]
  22     pub unsafe fn lock(&self) {
  23         assert_eq!(self.locked.replace(true), false, "cannot recursively acquire mutex");
  24     }
  25
  26     #[inline]
  27     pub unsafe fn unlock(&self) {
  28         self.locked.set(false);
  29     }
  30
  31     #[inline]
  32     pub unsafe fn try_lock(&self) -> bool {
  33         self.locked.replace(true) == false
  34     }
  35
  36     #[inline]
  37     pub unsafe fn destroy(&self) {}
  38 }
  39
  40 // All empty stubs because this platform does not yet support threads, so lock
  41 // acquisition always succeeds.
  42 pub struct ReentrantMutex {}
  43
  44 impl ReentrantMutex {
  45     pub const unsafe fn uninitialized() -> ReentrantMutex {
  46         ReentrantMutex {}
  47     }
  48
  49     pub unsafe fn init(&self) {}
  50
  51     pub unsafe fn lock(&self) {}
  52
  53     #[inline]
  54     pub unsafe fn try_lock(&self) -> bool {
  55         true
  56     }
  57
  58     pub unsafe fn unlock(&self) {}
  59
  60     pub unsafe fn destroy(&self) {}
  61 }