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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
//! Supports dynamic assertions about what sort of thread is running and
//! what state it's in.
#![deny(missing_docs)]
use std::cell::Cell;
bitflags! {
/// A thread state flag, used for multiple assertions.
#[derive(Clone, Copy, Default, Debug, Eq, PartialEq)]
pub struct ThreadState: u32 {
/// Whether we're in a script thread.
const SCRIPT = 0x01;
/// Whether we're in a layout thread.
const LAYOUT = 0x02;
/// Whether we're in a script worker thread (actual web workers), or in
/// a layout worker thread.
const IN_WORKER = 0x0100;
/// Whether the current thread is going through a GC.
const IN_GC = 0x0200;
}
}
impl ThreadState {
/// Whether the current thread is a worker thread.
pub fn is_worker(self) -> bool {
self.contains(ThreadState::IN_WORKER)
}
/// Whether the current thread is a script thread.
pub fn is_script(self) -> bool {
self.contains(ThreadState::SCRIPT)
}
/// Whether the current thread is a layout thread.
pub fn is_layout(self) -> bool {
self.contains(ThreadState::LAYOUT)
}
}
thread_local!(static STATE: Cell<Option<ThreadState>> = const { Cell::new(None) });
/// Initializes the current thread state.
pub fn initialize(initialize_to: ThreadState) {
STATE.with(|state| {
if let Some(current_state) = state.get() {
if initialize_to != current_state {
panic!("Thread state already initialized as {:?}", current_state);
}
}
state.set(Some(initialize_to));
});
}
/// Initializes the current thread as a layout worker thread.
pub fn initialize_layout_worker_thread() {
initialize(ThreadState::LAYOUT | ThreadState::IN_WORKER);
}
/// Gets the current thread state.
pub fn get() -> ThreadState {
STATE.with(|state| state.get().unwrap_or_default())
}
/// Enters into a given temporary state. Panics if re-entering.
pub fn enter(additional_flags: ThreadState) {
STATE.with(|state| {
let current_state = state.get().unwrap_or_default();
debug_assert!(!current_state.intersects(additional_flags));
state.set(Some(current_state | additional_flags));
})
}
/// Exits a given temporary state.
pub fn exit(flags_to_remove: ThreadState) {
STATE.with(|state| {
let current_state = state.get().unwrap_or_default();
debug_assert!(current_state.contains(flags_to_remove));
state.set(Some(current_state & !flags_to_remove));
})
}