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//! A readers-writer lock implementation backed by the SOLID kernel extension.
use super::{
abi,
itron::{
error::{expect_success, expect_success_aborting, fail, ItronError},
spin::SpinIdOnceCell,
},
};
pub struct RwLock {
/// The ID of the underlying mutex object
rwl: SpinIdOnceCell<()>,
}
// Safety: `num_readers` is protected by `mtx_num_readers`
unsafe impl Send for RwLock {}
unsafe impl Sync for RwLock {}
fn new_rwl() -> Result<abi::ID, ItronError> {
ItronError::err_if_negative(unsafe { abi::rwl_acre_rwl() })
}
impl RwLock {
#[inline]
pub const fn new() -> RwLock {
RwLock { rwl: SpinIdOnceCell::new() }
}
/// Get the inner mutex's ID, which is lazily created.
fn raw(&self) -> abi::ID {
match self.rwl.get_or_try_init(|| new_rwl().map(|id| (id, ()))) {
Ok((id, ())) => id,
Err(e) => fail(e, &"rwl_acre_rwl"),
}
}
#[inline]
pub fn read(&self) {
let rwl = self.raw();
expect_success(unsafe { abi::rwl_loc_rdl(rwl) }, &"rwl_loc_rdl");
}
#[inline]
pub fn try_read(&self) -> bool {
let rwl = self.raw();
match unsafe { abi::rwl_ploc_rdl(rwl) } {
abi::E_TMOUT => false,
er => {
expect_success(er, &"rwl_ploc_rdl");
true
}
}
}
#[inline]
pub fn write(&self) {
let rwl = self.raw();
expect_success(unsafe { abi::rwl_loc_wrl(rwl) }, &"rwl_loc_wrl");
}
#[inline]
pub fn try_write(&self) -> bool {
let rwl = self.raw();
match unsafe { abi::rwl_ploc_wrl(rwl) } {
abi::E_TMOUT => false,
er => {
expect_success(er, &"rwl_ploc_wrl");
true
}
}
}
#[inline]
pub unsafe fn read_unlock(&self) {
let rwl = self.raw();
expect_success_aborting(unsafe { abi::rwl_unl_rwl(rwl) }, &"rwl_unl_rwl");
}
#[inline]
pub unsafe fn write_unlock(&self) {
let rwl = self.raw();
expect_success_aborting(unsafe { abi::rwl_unl_rwl(rwl) }, &"rwl_unl_rwl");
}
}
impl Drop for RwLock {
#[inline]
fn drop(&mut self) {
if let Some(rwl) = self.rwl.get().map(|x| x.0) {
expect_success_aborting(unsafe { abi::rwl_del_rwl(rwl) }, &"rwl_del_rwl");
}
}
}
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