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// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use cell::UnsafeCell;
pub struct RWLock {
mode: UnsafeCell<isize>,
}
unsafe impl Send for RWLock {}
unsafe impl Sync for RWLock {} // no threads on wasm
impl RWLock {
pub const fn new() -> RWLock {
RWLock {
mode: UnsafeCell::new(0),
}
}
#[inline]
pub unsafe fn read(&self) {
let mode = self.mode.get();
if *mode >= 0 {
*mode += 1;
} else {
rtabort!("rwlock locked for writing");
}
}
#[inline]
pub unsafe fn try_read(&self) -> bool {
let mode = self.mode.get();
if *mode >= 0 {
*mode += 1;
true
} else {
false
}
}
#[inline]
pub unsafe fn write(&self) {
let mode = self.mode.get();
if *mode == 0 {
*mode = -1;
} else {
rtabort!("rwlock locked for reading")
}
}
#[inline]
pub unsafe fn try_write(&self) -> bool {
let mode = self.mode.get();
if *mode == 0 {
*mode = -1;
true
} else {
false
}
}
#[inline]
pub unsafe fn read_unlock(&self) {
*self.mode.get() -= 1;
}
#[inline]
pub unsafe fn write_unlock(&self) {
*self.mode.get() += 1;
}
#[inline]
pub unsafe fn destroy(&self) {
}
}
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