335e26946e
<!-- Please describe your changes on the following line: --> --- <!-- 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 _____ <!-- 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: b0a8ce5341f5148e36523fee0b0fcbc2684c0a68
56 lines
1.6 KiB
Rust
56 lines
1.6 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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//! Machinery to conditionally expose things.
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use js::jsapi::{HandleObject, JSContext};
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use util::prefs::PREFS;
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/// A container with a condition.
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pub struct Guard<T: Clone + Copy> {
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condition: Condition,
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value: T,
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}
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impl<T: Clone + Copy> Guard<T> {
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/// Construct a new guarded value.
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pub const fn new(condition: Condition, value: T) -> Self {
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Guard {
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condition: condition,
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value: value,
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}
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}
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/// Expose the value if the condition is satisfied.
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///
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/// The passed handle is the object on which the value may be exposed.
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pub unsafe fn expose(&self, cx: *mut JSContext, obj: HandleObject) -> Option<T> {
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if self.condition.is_satisfied(cx, obj) {
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Some(self.value)
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} else {
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None
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}
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}
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}
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/// A condition to expose things.
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pub enum Condition {
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/// The condition is satisfied if the function returns true.
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Func(unsafe fn(*mut JSContext, HandleObject) -> bool),
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/// The condition is satisfied if the preference is set.
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Pref(&'static str),
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/// The condition is always satisfied.
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Satisfied,
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}
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impl Condition {
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unsafe fn is_satisfied(&self, cx: *mut JSContext, obj: HandleObject) -> bool {
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match *self {
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Condition::Pref(name) => PREFS.get(name).as_boolean().unwrap_or(false),
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Condition::Func(f) => f(cx, obj),
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Condition::Satisfied => true,
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}
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}
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}
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