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da3297354f
<!-- Please describe your changes on the following line: --> As discussed in https://bugzilla.mozilla.org/show_bug.cgi?id=1305141 Closes #13176 --- Original PR title: Stop relying on `impl<T: HeapSizeOf> HeapSizeOf for Arc<T>` https://github.com/servo/heapsize/issues/37#issuecomment-249861171 This builds on top of that. --- <!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: --> - [x] `./mach build -d` does not report any errors - [x] `./mach test-tidy` does not report any errors - [ ] These changes fix #__ (github issue number if applicable). <!-- Either: --> - [ ] There are tests for these changes OR - [x] These changes do not require tests because refactor <!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. --> Source-Repo: https://github.com/servo/servo Source-Revision: aea9545e16fd6ea4a6b1234d1b969457313a5fa7 --HG-- rename : servo/components/style/domrefcell.rs => servo/components/script/dom/bindings/cell.rs
648 lines
17 KiB
Rust
648 lines
17 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers.
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// See http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A fork of std::cell::RefCell that makes `as_unsafe_cell` usable on stable Rust.
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//!
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//! FIXME(https://github.com/rust-lang/rust/issues/27708): Remove this
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//! (revert commit f7f81e0ed0b62402db291e28a9bb16f7194ebf78 / PR #11835)
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//! when `std::cell::RefCell::as_unsafe_cell` is in Rust’s stable channel.
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#![allow(unsafe_code)]
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use std::cell::{UnsafeCell, Cell};
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use std::cmp::Ordering;
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use std::fmt::{self, Debug, Display};
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use std::marker::PhantomData;
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use std::ops::{Deref, DerefMut};
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/// A fork of std::cell::RefCell that makes `as_unsafe_cell` usable on stable Rust.
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///
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/// FIXME(https://github.com/rust-lang/rust/issues/27708): Remove this
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/// (revert commit f7f81e0ed0b62402db291e28a9bb16f7194ebf78 / PR #11835)
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/// when `std::cell::RefCell::as_unsafe_cell` is in Rust’s stable channel.
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pub struct RefCell<T: ?Sized> {
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borrow: Cell<BorrowFlag>,
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value: UnsafeCell<T>,
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}
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/// An enumeration of values returned from the `state` method on a `RefCell<T>`.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub enum BorrowState {
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/// The cell is currently being read, there is at least one active `borrow`.
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Reading,
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/// The cell is currently being written to, there is an active `borrow_mut`.
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Writing,
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/// There are no outstanding borrows on this cell.
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Unused,
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}
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/// An error returned by [`RefCell::try_borrow`](struct.RefCell.html#method.try_borrow).
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pub struct BorrowError<'a, T: 'a + ?Sized> {
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marker: PhantomData<&'a RefCell<T>>,
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}
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impl<'a, T: ?Sized> Debug for BorrowError<'a, T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_struct("BorrowError").finish()
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}
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}
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impl<'a, T: ?Sized> Display for BorrowError<'a, T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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Display::fmt("already mutably borrowed", f)
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}
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}
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/// An error returned by [`RefCell::try_borrow_mut`](struct.RefCell.html#method.try_borrow_mut).
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pub struct BorrowMutError<'a, T: 'a + ?Sized> {
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marker: PhantomData<&'a RefCell<T>>,
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}
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impl<'a, T: ?Sized> Debug for BorrowMutError<'a, T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_struct("BorrowMutError").finish()
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}
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}
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impl<'a, T: ?Sized> Display for BorrowMutError<'a, T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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Display::fmt("already borrowed", f)
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}
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}
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// Values [1, MAX-1] represent the number of `Ref` active
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// (will not outgrow its range since `usize` is the size of the address space)
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type BorrowFlag = usize;
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const UNUSED: BorrowFlag = 0;
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const WRITING: BorrowFlag = !0;
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impl<T> RefCell<T> {
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/// Creates a new `RefCell` containing `value`.
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///
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/// # Examples
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///
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/// ```
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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/// ```
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#[inline]
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pub fn new(value: T) -> RefCell<T> {
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RefCell {
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value: UnsafeCell::new(value),
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borrow: Cell::new(UNUSED),
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}
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}
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/// Consumes the `RefCell`, returning the wrapped value.
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///
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/// # Examples
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///
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/// ```
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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///
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/// let five = c.into_inner();
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/// ```
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#[inline]
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pub fn into_inner(self) -> T {
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// Since this function takes `self` (the `RefCell`) by value, the
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// compiler statically verifies that it is not currently borrowed.
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// Therefore the following assertion is just a `debug_assert!`.
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debug_assert!(self.borrow.get() == UNUSED);
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unsafe { self.value.into_inner() }
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}
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}
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impl<T: ?Sized> RefCell<T> {
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/// Query the current state of this `RefCell`
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///
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/// The returned value can be dispatched on to determine if a call to
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/// `borrow` or `borrow_mut` would succeed.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(borrow_state)]
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///
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/// use std::cell::{BorrowState, RefCell};
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///
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/// let c = RefCell::new(5);
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///
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/// match c.borrow_state() {
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/// BorrowState::Writing => println!("Cannot be borrowed"),
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/// BorrowState::Reading => println!("Cannot be borrowed mutably"),
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/// BorrowState::Unused => println!("Can be borrowed (mutably as well)"),
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/// }
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/// ```
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#[inline]
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pub fn borrow_state(&self) -> BorrowState {
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match self.borrow.get() {
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WRITING => BorrowState::Writing,
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UNUSED => BorrowState::Unused,
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_ => BorrowState::Reading,
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}
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}
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/// Immutably borrows the wrapped value.
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///
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/// The borrow lasts until the returned `Ref` exits scope. Multiple
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/// immutable borrows can be taken out at the same time.
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///
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/// # Panics
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///
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/// Panics if the value is currently mutably borrowed. For a non-panicking variant, use
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/// [`try_borrow`](#method.try_borrow).
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///
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/// # Examples
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///
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/// ```
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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///
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/// let borrowed_five = c.borrow();
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/// let borrowed_five2 = c.borrow();
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/// ```
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///
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/// An example of panic:
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///
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/// ```
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/// use std::cell::RefCell;
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/// use std::thread;
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///
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/// let result = thread::spawn(move || {
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/// let c = RefCell::new(5);
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/// let m = c.borrow_mut();
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///
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/// let b = c.borrow(); // this causes a panic
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/// }).join();
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///
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/// assert!(result.is_err());
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/// ```
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#[inline]
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pub fn borrow(&self) -> Ref<T> {
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self.try_borrow().expect("already mutably borrowed")
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}
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/// Immutably borrows the wrapped value, returning an error if the value is currently mutably
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/// borrowed.
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///
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/// The borrow lasts until the returned `Ref` exits scope. Multiple immutable borrows can be
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/// taken out at the same time.
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///
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/// This is the non-panicking variant of [`borrow`](#method.borrow).
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///
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/// # Examples
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///
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/// ```
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/// #![feature(try_borrow)]
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///
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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///
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/// {
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/// let m = c.borrow_mut();
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/// assert!(c.try_borrow().is_err());
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/// }
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///
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/// {
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/// let m = c.borrow();
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/// assert!(c.try_borrow().is_ok());
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/// }
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/// ```
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#[inline]
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pub fn try_borrow(&self) -> Result<Ref<T>, BorrowError<T>> {
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match BorrowRef::new(&self.borrow) {
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Some(b) => Ok(Ref {
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value: unsafe { &*self.value.get() },
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borrow: b,
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}),
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None => Err(BorrowError { marker: PhantomData }),
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}
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}
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/// Mutably borrows the wrapped value.
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///
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/// The borrow lasts until the returned `RefMut` exits scope. The value
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/// cannot be borrowed while this borrow is active.
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///
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/// # Panics
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///
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/// Panics if the value is currently borrowed. For a non-panicking variant, use
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/// [`try_borrow_mut`](#method.try_borrow_mut).
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///
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/// # Examples
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///
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/// ```
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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///
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/// *c.borrow_mut() = 7;
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///
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/// assert_eq!(*c.borrow(), 7);
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/// ```
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///
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/// An example of panic:
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///
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/// ```
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/// use std::cell::RefCell;
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/// use std::thread;
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///
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/// let result = thread::spawn(move || {
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/// let c = RefCell::new(5);
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/// let m = c.borrow();
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///
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/// let b = c.borrow_mut(); // this causes a panic
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/// }).join();
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///
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/// assert!(result.is_err());
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/// ```
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#[inline]
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pub fn borrow_mut(&self) -> RefMut<T> {
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self.try_borrow_mut().expect("already borrowed")
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}
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/// Mutably borrows the wrapped value, returning an error if the value is currently borrowed.
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///
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/// The borrow lasts until the returned `RefMut` exits scope. The value cannot be borrowed
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/// while this borrow is active.
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///
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/// This is the non-panicking variant of [`borrow_mut`](#method.borrow_mut).
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///
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/// # Examples
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///
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/// ```
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/// #![feature(try_borrow)]
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///
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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///
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/// {
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/// let m = c.borrow();
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/// assert!(c.try_borrow_mut().is_err());
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/// }
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///
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/// assert!(c.try_borrow_mut().is_ok());
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/// ```
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#[inline]
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pub fn try_borrow_mut(&self) -> Result<RefMut<T>, BorrowMutError<T>> {
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match BorrowRefMut::new(&self.borrow) {
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Some(b) => Ok(RefMut {
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value: unsafe { &mut *self.value.get() },
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borrow: b,
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}),
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None => Err(BorrowMutError { marker: PhantomData }),
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}
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}
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/// Returns a reference to the underlying `UnsafeCell`.
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///
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/// This can be used to circumvent `RefCell`'s safety checks.
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///
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/// This function is `unsafe` because `UnsafeCell`'s field is public.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(as_unsafe_cell)]
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///
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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/// let c = unsafe { c.as_unsafe_cell() };
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/// ```
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#[inline]
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pub unsafe fn as_unsafe_cell(&self) -> &UnsafeCell<T> {
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&self.value
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}
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/// Returns a raw pointer to the underlying data in this cell.
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///
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/// # Examples
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///
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/// ```
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/// use std::cell::RefCell;
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///
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/// let c = RefCell::new(5);
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///
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/// let ptr = c.as_ptr();
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/// ```
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#[inline]
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pub fn as_ptr(&self) -> *mut T {
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self.value.get()
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}
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/// Returns a mutable reference to the underlying data.
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///
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/// This call borrows `RefCell` mutably (at compile-time) so there is no
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/// need for dynamic checks.
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///
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/// # Examples
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///
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/// ```
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/// use std::cell::RefCell;
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///
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/// let mut c = RefCell::new(5);
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/// *c.get_mut() += 1;
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///
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/// assert_eq!(c, RefCell::new(6));
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/// ```
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#[inline]
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pub fn get_mut(&mut self) -> &mut T {
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unsafe {
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&mut *self.value.get()
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}
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}
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}
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unsafe impl<T: ?Sized> Send for RefCell<T> where T: Send {}
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impl<T: Clone> Clone for RefCell<T> {
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#[inline]
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fn clone(&self) -> RefCell<T> {
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RefCell::new(self.borrow().clone())
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}
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}
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impl<T: Default> Default for RefCell<T> {
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#[inline]
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fn default() -> RefCell<T> {
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RefCell::new(Default::default())
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}
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}
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impl<T: ?Sized + PartialEq> PartialEq for RefCell<T> {
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#[inline]
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fn eq(&self, other: &RefCell<T>) -> bool {
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*self.borrow() == *other.borrow()
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}
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}
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impl<T: ?Sized + Eq> Eq for RefCell<T> {}
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impl<T: ?Sized + PartialOrd> PartialOrd for RefCell<T> {
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#[inline]
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fn partial_cmp(&self, other: &RefCell<T>) -> Option<Ordering> {
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self.borrow().partial_cmp(&*other.borrow())
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}
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#[inline]
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fn lt(&self, other: &RefCell<T>) -> bool {
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*self.borrow() < *other.borrow()
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}
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#[inline]
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fn le(&self, other: &RefCell<T>) -> bool {
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*self.borrow() <= *other.borrow()
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}
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#[inline]
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fn gt(&self, other: &RefCell<T>) -> bool {
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*self.borrow() > *other.borrow()
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}
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#[inline]
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fn ge(&self, other: &RefCell<T>) -> bool {
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*self.borrow() >= *other.borrow()
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}
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}
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impl<T: ?Sized + Ord> Ord for RefCell<T> {
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#[inline]
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fn cmp(&self, other: &RefCell<T>) -> Ordering {
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self.borrow().cmp(&*other.borrow())
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}
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}
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struct BorrowRef<'b> {
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borrow: &'b Cell<BorrowFlag>,
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}
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impl<'b> BorrowRef<'b> {
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#[inline]
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fn new(borrow: &'b Cell<BorrowFlag>) -> Option<BorrowRef<'b>> {
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match borrow.get() {
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WRITING => None,
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b => {
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borrow.set(b + 1);
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Some(BorrowRef { borrow: borrow })
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},
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}
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}
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}
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impl<'b> Drop for BorrowRef<'b> {
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#[inline]
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fn drop(&mut self) {
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let borrow = self.borrow.get();
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debug_assert!(borrow != WRITING && borrow != UNUSED);
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self.borrow.set(borrow - 1);
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}
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}
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impl<'b> Clone for BorrowRef<'b> {
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#[inline]
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fn clone(&self) -> BorrowRef<'b> {
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// Since this Ref exists, we know the borrow flag
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// is not set to WRITING.
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let borrow = self.borrow.get();
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debug_assert!(borrow != UNUSED);
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// Prevent the borrow counter from overflowing.
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assert!(borrow != WRITING);
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self.borrow.set(borrow + 1);
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BorrowRef { borrow: self.borrow }
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}
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}
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/// Wraps a borrowed reference to a value in a `RefCell` box.
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/// A wrapper type for an immutably borrowed value from a `RefCell<T>`.
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///
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/// See the [module-level documentation](index.html) for more.
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pub struct Ref<'b, T: ?Sized + 'b> {
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value: &'b T,
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borrow: BorrowRef<'b>,
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}
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impl<'b, T: ?Sized> Deref for Ref<'b, T> {
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type Target = T;
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#[inline]
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fn deref(&self) -> &T {
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self.value
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}
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}
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impl<'b, T: ?Sized> Ref<'b, T> {
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/// Copies a `Ref`.
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///
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/// The `RefCell` is already immutably borrowed, so this cannot fail.
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///
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/// This is an associated function that needs to be used as
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/// `Ref::clone(...)`. A `Clone` implementation or a method would interfere
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/// with the widespread use of `r.borrow().clone()` to clone the contents of
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/// a `RefCell`.
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#[inline]
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pub fn clone(orig: &Ref<'b, T>) -> Ref<'b, T> {
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Ref {
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value: orig.value,
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borrow: orig.borrow.clone(),
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}
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}
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/// Make a new `Ref` for a component of the borrowed data.
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///
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/// The `RefCell` is already immutably borrowed, so this cannot fail.
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///
|
||
/// This is an associated function that needs to be used as `Ref::map(...)`.
|
||
/// A method would interfere with methods of the same name on the contents
|
||
/// of a `RefCell` used through `Deref`.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// use std::cell::{RefCell, Ref};
|
||
///
|
||
/// let c = RefCell::new((5, 'b'));
|
||
/// let b1: Ref<(u32, char)> = c.borrow();
|
||
/// let b2: Ref<u32> = Ref::map(b1, |t| &t.0);
|
||
/// assert_eq!(*b2, 5)
|
||
/// ```
|
||
#[inline]
|
||
pub fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>
|
||
where F: FnOnce(&T) -> &U
|
||
{
|
||
Ref {
|
||
value: f(orig.value),
|
||
borrow: orig.borrow,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<'b, T: ?Sized> RefMut<'b, T> {
|
||
/// Make a new `RefMut` for a component of the borrowed data, e.g. an enum
|
||
/// variant.
|
||
///
|
||
/// The `RefCell` is already mutably borrowed, so this cannot fail.
|
||
///
|
||
/// This is an associated function that needs to be used as
|
||
/// `RefMut::map(...)`. A method would interfere with methods of the same
|
||
/// name on the contents of a `RefCell` used through `Deref`.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// use std::cell::{RefCell, RefMut};
|
||
///
|
||
/// let c = RefCell::new((5, 'b'));
|
||
/// {
|
||
/// let b1: RefMut<(u32, char)> = c.borrow_mut();
|
||
/// let mut b2: RefMut<u32> = RefMut::map(b1, |t| &mut t.0);
|
||
/// assert_eq!(*b2, 5);
|
||
/// *b2 = 42;
|
||
/// }
|
||
/// assert_eq!(*c.borrow(), (42, 'b'));
|
||
/// ```
|
||
#[inline]
|
||
pub fn map<U: ?Sized, F>(orig: RefMut<'b, T>, f: F) -> RefMut<'b, U>
|
||
where F: FnOnce(&mut T) -> &mut U
|
||
{
|
||
RefMut {
|
||
value: f(orig.value),
|
||
borrow: orig.borrow,
|
||
}
|
||
}
|
||
}
|
||
|
||
struct BorrowRefMut<'b> {
|
||
borrow: &'b Cell<BorrowFlag>,
|
||
}
|
||
|
||
impl<'b> Drop for BorrowRefMut<'b> {
|
||
#[inline]
|
||
fn drop(&mut self) {
|
||
let borrow = self.borrow.get();
|
||
debug_assert!(borrow == WRITING);
|
||
self.borrow.set(UNUSED);
|
||
}
|
||
}
|
||
|
||
impl<'b> BorrowRefMut<'b> {
|
||
#[inline]
|
||
fn new(borrow: &'b Cell<BorrowFlag>) -> Option<BorrowRefMut<'b>> {
|
||
match borrow.get() {
|
||
UNUSED => {
|
||
borrow.set(WRITING);
|
||
Some(BorrowRefMut { borrow: borrow })
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
}
|
||
|
||
/// A wrapper type for a mutably borrowed value from a `RefCell<T>`.
|
||
///
|
||
/// See the [module-level documentation](index.html) for more.
|
||
pub struct RefMut<'b, T: ?Sized + 'b> {
|
||
value: &'b mut T,
|
||
borrow: BorrowRefMut<'b>,
|
||
}
|
||
|
||
impl<'b, T: ?Sized> Deref for RefMut<'b, T> {
|
||
type Target = T;
|
||
|
||
#[inline]
|
||
fn deref(&self) -> &T {
|
||
self.value
|
||
}
|
||
}
|
||
|
||
impl<'b, T: ?Sized> DerefMut for RefMut<'b, T> {
|
||
#[inline]
|
||
fn deref_mut(&mut self) -> &mut T {
|
||
self.value
|
||
}
|
||
}
|
||
|
||
|
||
// Imported from src/libcore/fmt/mod.rs
|
||
|
||
impl<T: ?Sized + Debug> Debug for RefCell<T> {
|
||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||
match self.borrow_state() {
|
||
BorrowState::Unused | BorrowState::Reading => {
|
||
f.debug_struct("RefCell")
|
||
.field("value", &self.borrow())
|
||
.finish()
|
||
}
|
||
BorrowState::Writing => {
|
||
f.debug_struct("RefCell")
|
||
.field("value", &"<borrowed>")
|
||
.finish()
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<'b, T: ?Sized + Debug> Debug for Ref<'b, T> {
|
||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||
Debug::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
impl<'b, T: ?Sized + Debug> Debug for RefMut<'b, T> {
|
||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||
Debug::fmt(&*(self.deref()), f)
|
||
}
|
||
}
|