| use crate::cell::Cell; |
| |
| pub struct RwLock { |
| // This platform has no threads, so we can use a Cell here. |
| mode: Cell<isize>, |
| } |
| |
| unsafe impl Send for RwLock {} |
| unsafe impl Sync for RwLock {} // no threads on this platform |
| |
| impl RwLock { |
| #[inline] |
| #[rustc_const_stable(feature = "const_locks", since = "1.63.0")] |
| pub const fn new() -> RwLock { |
| RwLock { mode: Cell::new(0) } |
| } |
| |
| #[inline] |
| pub fn read(&self) { |
| let m = self.mode.get(); |
| if m >= 0 { |
| self.mode.set(m + 1); |
| } else { |
| rtabort!("rwlock locked for writing"); |
| } |
| } |
| |
| #[inline] |
| pub fn try_read(&self) -> bool { |
| let m = self.mode.get(); |
| if m >= 0 { |
| self.mode.set(m + 1); |
| true |
| } else { |
| false |
| } |
| } |
| |
| #[inline] |
| pub fn write(&self) { |
| if self.mode.replace(-1) != 0 { |
| rtabort!("rwlock locked for reading") |
| } |
| } |
| |
| #[inline] |
| pub fn try_write(&self) -> bool { |
| if self.mode.get() == 0 { |
| self.mode.set(-1); |
| true |
| } else { |
| false |
| } |
| } |
| |
| #[inline] |
| pub unsafe fn read_unlock(&self) { |
| self.mode.set(self.mode.get() - 1); |
| } |
| |
| #[inline] |
| pub unsafe fn write_unlock(&self) { |
| assert_eq!(self.mode.replace(0), -1); |
| } |
| } |