зеркало из https://github.com/mozilla/gecko-dev.git
67 строки
2.2 KiB
Rust
67 строки
2.2 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! Reference-counted pointers to flows.
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//!
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//! Eventually, with dynamically sized types in Rust, much of this code will
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//! be superfluous. This design is largely duplicating logic of Arc<T> and
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//! Weak<T>; please see comments there for details.
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use flow::Flow;
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use std::ops::Deref;
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use std::sync::{Arc, Weak};
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#[derive(Clone, Debug)]
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pub struct FlowRef(Arc<Flow>);
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impl Deref for FlowRef {
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type Target = Flow;
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fn deref(&self) -> &Flow {
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self.0.deref()
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}
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}
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impl FlowRef {
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/// `FlowRef`s can only be made available to the traversal code.
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/// See https://github.com/servo/servo/issues/14014 for more details.
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pub fn new(mut r: Arc<Flow>) -> Self {
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// This assertion checks that this `FlowRef` does not alias normal `Arc`s.
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// If that happens, we're in trouble.
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assert!(Arc::get_mut(&mut r).is_some());
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FlowRef(r)
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}
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pub fn get_mut(this: &mut FlowRef) -> Option<&mut Flow> {
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Arc::get_mut(&mut this.0)
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}
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pub fn downgrade(this: &FlowRef) -> WeakFlowRef {
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WeakFlowRef(Arc::downgrade(&this.0))
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}
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pub fn into_arc(mut this: FlowRef) -> Arc<Flow> {
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// This assertion checks that this `FlowRef` does not alias normal `Arc`s.
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// If that happens, we're in trouble.
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assert!(FlowRef::get_mut(&mut this).is_some());
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this.0
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}
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/// WARNING: This should only be used when there is no aliasing:
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/// when the traversal ensures that no other threads accesses the same flow at the same time.
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/// See https://github.com/servo/servo/issues/6503
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/// Use Arc::get_mut instead when possible (e.g. on an Arc that was just created).
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#[allow(unsafe_code)]
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pub fn deref_mut(this: &mut FlowRef) -> &mut Flow {
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let ptr: *const Flow = &*this.0;
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unsafe { &mut *(ptr as *mut Flow) }
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}
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}
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#[derive(Clone, Debug)]
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pub struct WeakFlowRef(Weak<Flow>);
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impl WeakFlowRef {
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pub fn upgrade(&self) -> Option<FlowRef> {
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self.0.upgrade().map(FlowRef)
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}
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}
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