Struct CurrentRealm

Source

pub struct CurrentRealm<'cx> {
    cx: &'cx mut JSContext,
    realm: NonNull<Realm>,
}

Expand description

Represents the current realm of JSContext (top realm on realm stack).

Similarly to AutoRealm, while you can access this type via &mut/&mut we know that this realm is current (on top of realm stack).

use mozjs::context::JSContext;
use mozjs::jsapi::JSObject;
use mozjs::realm::{AutoRealm, CurrentRealm};
use std::ptr::NonNull;

fn f(current_realm: &mut CurrentRealm, target: NonNull<JSObject>) {
    let mut realm = AutoRealm::new(current_realm, target);
    let cx: &mut JSContext = &mut *current_realm; // we cannot use current realm while it's not current
}

Fields§

§cx: &'cx mut JSContext§realm: NonNull<Realm>

Implementations§

Source §

impl<'cx> CurrentRealm<'cx>

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pub fn assert(cx: &'cx mut JSContext) -> CurrentRealm<'cx>

Asserts that the current realm is valid and returns it.

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pub fn global(&self) -> Handle<'_, *mut JSObject>

Obtain the handle to the global object of the this realm. Because the handle is bounded with lifetime to realm, you cannot do this:

use mozjs::context::JSContext;
use mozjs::jsapi::JSObject;
use mozjs::realm::CurrentRealm;
use std::ptr::NonNull;
use mozjs::rust::Handle;

fn g(realm: &'_ mut CurrentRealm, global: Handle<'_, *mut JSObject>) {
}

fn f(realm: &mut CurrentRealm) {
    let global = realm.global();
    g(realm, global);
}

instead use CurrentRealm::global_and_reborrow.

Source

pub fn global_and_reborrow(&mut self) -> (Handle<'_, *mut JSObject>, &mut Self)

Obtain the handle to the global object of this realm and reborrow the realm.

use mozjs::context::JSContext;
use mozjs::jsapi::JSObject;
use mozjs::realm::CurrentRealm;
use std::ptr::NonNull;
use mozjs::rust::Handle;

fn g(realm: &'_ mut CurrentRealm, global: Handle<'_, *mut JSObject>) {
}

fn f(realm: &mut CurrentRealm) {
    let (global, realm) = realm.global_and_reborrow();
    g(realm, global);
}

Source

pub fn realm(&self) -> &NonNull<Realm>

Methods from Deref<Target = JSContext>§

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pub fn no_gc<'cx>(&'cx self) -> &'cx NoGC<'cx>

Returns NoGC token bounded to this JSContext. No function that accepts &mut JSContext (read: triggers GC) can be called while this is alive.

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pub unsafe fn raw_cx(&mut self) -> *mut RawJSContext

Obtain RawJSContext mutable pointer.

§Safety

No NoGC tokens should be constructed while returned pointer is available to user. In practices this means that one should use the result as direct argument to SpiderMonkey function and not store it in variable.

use mozjs::context::*;
use mozjs::jsapi::JSContext as RawJSContext;

fn SM_function_that_can_trigger_gc(_cx: *mut RawJSContext) {}

fn can_trigger_gc(cx: &mut JSContext) {
    unsafe { SM_function_that_can_trigger_gc(cx.raw_cx()) } // returned pointer is immediately used
    cx.no_gc(); // this is ok because no outstanding raw pointer is alive
}

Source

pub unsafe fn raw_cx_no_gc(&self) -> *mut RawJSContext

Obtain RawJSContext mutable pointer, that will not be used for GC.

§Safety

No &mut calls should be done on JSContext while returned pointer is available. In practices this means that one should use the result as direct argument to SpiderMonkey function and not store it in variable.

use mozjs::context::*;
use mozjs::jsapi::JSContext as RawJSContext;

fn SM_function_that_cannot_trigger_gc(_cx: *mut RawJSContext) {}

fn f(cx: &mut JSContext) {
    unsafe { SM_function_that_cannot_trigger_gc(cx.raw_cx_no_gc()) } // returned pointer is immediately used
}