use std::{io, ptr};
use winapi::um::synchapi::{CreateSemaphoreW, ReleaseSemaphore};
use crate::{nonnull_handle_result, result, Handle};
/// A [Windows semaphore](https://docs.microsoft.com/en-us/windows/win32/sync/semaphore-objects).
#[derive(Clone, Debug)]
pub struct Semaphore(Handle);
impl Semaphore {
/// Construct a new semaphore.
///
/// This wraps
/// [`CreateSemaphoreW`](https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-createsemaphorew).
pub fn new() -> io::Result<Self> {
let handle = nonnull_handle_result(unsafe {
CreateSemaphoreW(ptr::null_mut(), 0, 1, ptr::null_mut())
})?;
let handle = unsafe { Handle::from_raw(handle) };
Ok(Self(handle))
}
/// Release a permit on the semaphore.
///
/// This wraps
/// [`ReleaseSemaphore`](https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-releasesemaphore).
pub fn release(&self) -> io::Result<()> {
result(unsafe { ReleaseSemaphore(*self.0, 1, ptr::null_mut()) })
}
/// Access the underlying handle to the semaphore.
pub fn handle(&self) -> &Handle {
&self.0
}
}
unsafe impl Send for Semaphore {}
unsafe impl Sync for Semaphore {}