Move thread_state to style.

1 files changed, 105 insertions, 0 deletions

diff --git a/components/style/thread_state.rs b/components/style/thread_state.rs
new file mode 100644
index 00000000000..25e77ecbb45
--- /dev/null
+++ b/components/style/thread_state.rs
@@ -0,0 +1,105 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+//! Supports dynamic assertions in debug builds about what sort of thread is
+//! running and what state it's in.
+//!
+//! In release builds, `get` returns 0.  All of the other functions inline
+//! away to nothing.
+
+pub use self::imp::{enter, exit, get, initialize};
+
+bitflags! {
+    pub flags ThreadState: u32 {
+        const SCRIPT          = 0x01,
+        const LAYOUT          = 0x02,
+        const PAINT           = 0x04,
+
+        const IN_WORKER       = 0x0100,
+        const IN_GC           = 0x0200,
+        const IN_HTML_PARSER  = 0x0400,
+    }
+}
+
+macro_rules! thread_types ( ( $( $fun:ident = $flag:ident ; )* ) => (
+    impl ThreadState {
+        $(
+            #[cfg(debug_assertions)]
+            pub fn $fun(self) -> bool {
+                self.contains($flag)
+            }
+            #[cfg(not(debug_assertions))]
+            pub fn $fun(self) -> bool {
+                true
+            }
+        )*
+    }
+
+    #[cfg(debug_assertions)]
+    static TYPES: &'static [ThreadState]
+        = &[ $( $flag ),* ];
+));
+
+thread_types! {
+    is_script = SCRIPT;
+    is_layout = LAYOUT;
+    is_paint = PAINT;
+}
+
+#[cfg(debug_assertions)]
+mod imp {
+    use std::cell::RefCell;
+    use super::{TYPES, ThreadState};
+
+    thread_local!(static STATE: RefCell<Option<ThreadState>> = RefCell::new(None));
+
+    pub fn initialize(x: ThreadState) {
+        STATE.with(|ref k| {
+            match *k.borrow() {
+                Some(s) => panic!("Thread state already initialized as {:?}", s),
+                None => ()
+            };
+            *k.borrow_mut() = Some(x);
+        });
+        get(); // check the assertion below
+    }
+
+    pub fn get() -> ThreadState {
+        let state = STATE.with(|ref k| {
+            match *k.borrow() {
+                None => panic!("Thread state not initialized"),
+                Some(s) => s,
+            }
+        });
+
+        // Exactly one of the thread type flags should be set.
+        assert_eq!(1, TYPES.iter().filter(|&&ty| state.contains(ty)).count());
+        state
+    }
+
+    pub fn enter(x: ThreadState) {
+        let state = get();
+        assert!(!state.intersects(x));
+        STATE.with(|ref k| {
+            *k.borrow_mut() = Some(state | x);
+        })
+    }
+
+    pub fn exit(x: ThreadState) {
+        let state = get();
+        assert!(state.contains(x));
+        STATE.with(|ref k| {
+            *k.borrow_mut() = Some(state & !x);
+        })
+    }
+}
+
+#[cfg(not(debug_assertions))]
+mod imp {
+    use super::ThreadState;
+    #[inline(always)] pub fn initialize(_: ThreadState) { }
+    #[inline(always)] pub fn get() -> ThreadState { ThreadState::empty() }
+    #[inline(always)] pub fn enter(_: ThreadState) { }
+    #[inline(always)] pub fn exit(_: ThreadState) { }
+}