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//! This module implements the `JsObject` structure.
//!
//! The `JsObject` is a garbage collected Object.
use super::{
internal_methods::{InternalMethodContext, InternalObjectMethods, ORDINARY_INTERNAL_METHODS},
shape::RootShape,
JsPrototype, NativeObject, Object, PrivateName, PropertyMap,
};
use crate::{
builtins::{
array::ARRAY_EXOTIC_INTERNAL_METHODS,
array_buffer::{ArrayBuffer, BufferObject, SharedArrayBuffer},
object::OrdinaryObject,
},
context::intrinsics::Intrinsics,
error::JsNativeError,
js_string,
property::{PropertyDescriptor, PropertyKey},
string::utf16,
value::PreferredType,
Context, JsResult, JsString, JsValue,
};
use boa_gc::{self, Finalize, Gc, GcBox, GcRefCell, Trace};
use std::{
cell::RefCell,
collections::HashMap,
error::Error,
fmt::{self, Debug, Display},
hash::Hash,
ptr::NonNull,
result::Result as StdResult,
};
use thin_vec::ThinVec;
/// A wrapper type for an immutably borrowed type T.
pub type Ref<'a, T> = boa_gc::GcRef<'a, T>;
/// A wrapper type for a mutably borrowed type T.
pub type RefMut<'a, T, U> = boa_gc::GcRefMut<'a, T, U>;
/// An `Object` with inner data set to `dyn NativeObject`.
pub type ErasedObject = Object<dyn NativeObject>;
pub(crate) type ErasedVTableObject = VTableObject<dyn NativeObject>;
/// Garbage collected `Object`.
#[derive(Trace, Finalize)]
#[boa_gc(unsafe_no_drop)]
pub struct JsObject<T: NativeObject + ?Sized = dyn NativeObject> {
inner: Gc<VTableObject<T>>,
}
impl<T: NativeObject + ?Sized> Clone for JsObject<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
}
}
}
/// An `Object` that has an additional `vtable` with its internal methods.
// We have to skip implementing `Debug` for this because not using the
// implementation of `Debug` for `JsObject` could easily cause stack overflows,
// so we have to force our users to debug the `JsObject` instead.
#[allow(missing_debug_implementations)]
#[derive(Trace, Finalize)]
pub(crate) struct VTableObject<T: NativeObject + ?Sized> {
#[unsafe_ignore_trace]
vtable: &'static InternalObjectMethods,
object: GcRefCell<Object<T>>,
}
impl Default for JsObject {
fn default() -> Self {
Self::from_proto_and_data(None, OrdinaryObject)
}
}
impl JsObject {
/// Creates a new `JsObject` from its inner object and its vtable.
pub(crate) fn from_object_and_vtable<T: NativeObject>(
object: Object<T>,
vtable: &'static InternalObjectMethods,
) -> Self {
let gc = Gc::new(VTableObject {
object: GcRefCell::new(object),
vtable,
});
Self {
inner: coerce_gc(gc),
}
}
/// Creates a new ordinary object with its prototype set to the `Object` prototype.
///
/// This is equivalent to calling the specification's abstract operation
/// [`OrdinaryObjectCreate(%Object.prototype%)`][call].
///
/// [call]: https://tc39.es/ecma262/#sec-ordinaryobjectcreate
#[inline]
#[must_use]
pub fn with_object_proto(intrinsics: &Intrinsics) -> Self {
Self::from_proto_and_data(
intrinsics.constructors().object().prototype(),
OrdinaryObject,
)
}
/// Creates a new ordinary object, with its prototype set to null.
///
/// This is equivalent to calling the specification's abstract operation
/// [`OrdinaryObjectCreate(null)`][call].
///
/// [call]: https://tc39.es/ecma262/#sec-ordinaryobjectcreate
#[inline]
#[must_use]
pub fn with_null_proto() -> Self {
Self::from_proto_and_data(None, OrdinaryObject)
}
/// Creates a new object with the provided prototype and object data.
///
/// This is equivalent to calling the specification's abstract operation [`OrdinaryObjectCreate`],
/// with the difference that the `additionalInternalSlotsList` parameter is determined by
/// the provided `data`.
///
/// [`OrdinaryObjectCreate`]: https://tc39.es/ecma262/#sec-ordinaryobjectcreate
pub fn from_proto_and_data<O: Into<Option<Self>>, T: NativeObject>(
prototype: O,
data: T,
) -> Self {
let internal_methods = data.internal_methods();
let gc = Gc::new(VTableObject {
object: GcRefCell::new(Object {
data,
properties: PropertyMap::from_prototype_unique_shape(prototype.into()),
extensible: true,
private_elements: ThinVec::new(),
}),
vtable: internal_methods,
});
Self {
inner: coerce_gc(gc),
}
}
/// Creates a new object with the provided prototype and object data.
///
/// This is equivalent to calling the specification's abstract operation [`OrdinaryObjectCreate`],
/// with the difference that the `additionalInternalSlotsList` parameter is determined by
/// the provided `data`.
///
/// [`OrdinaryObjectCreate`]: https://tc39.es/ecma262/#sec-ordinaryobjectcreate
pub(crate) fn from_proto_and_data_with_shared_shape<O: Into<Option<Self>>, T: NativeObject>(
root_shape: &RootShape,
prototype: O,
data: T,
) -> Self {
let internal_methods = data.internal_methods();
let gc = Gc::new(VTableObject {
object: GcRefCell::new(Object {
data,
properties: PropertyMap::from_prototype_with_shared_shape(
root_shape,
prototype.into(),
),
extensible: true,
private_elements: ThinVec::new(),
}),
vtable: internal_methods,
});
Self {
inner: coerce_gc(gc),
}
}
/// Downcasts the object's inner data if the object is of type `T`.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
pub fn downcast<T: NativeObject>(self) -> Result<JsObject<T>, Self> {
if self.borrow().is::<T>() {
let ptr: NonNull<GcBox<VTableObject<dyn NativeObject>>> = Gc::into_raw(self.inner);
// SAFETY: the rooted `Gc` ensures we can read the inner `GcBox` in a sound way.
#[cfg(debug_assertions)]
unsafe {
let erased = ptr.as_ref();
// Some sanity checks to ensure we're doing the correct cast.
assert_eq!(
std::mem::size_of_val(erased),
std::mem::size_of::<GcBox<VTableObject<T>>>()
);
assert_eq!(
std::mem::align_of_val(erased),
std::mem::align_of::<GcBox<VTableObject<T>>>()
);
}
let ptr: NonNull<GcBox<VTableObject<T>>> = ptr.cast();
// SAFETY: The conversion between an `Any` and its downcasted type must be valid.
// The pointer returned by `Gc::into_raw` is the same one that is passed to `Gc::from_raw`,
// just downcasted to the type `T`.
let inner = unsafe { Gc::from_raw(ptr) };
Ok(JsObject { inner })
} else {
Err(self)
}
}
/// Downcasts the object's inner data to `T` without verifying the inner type of `T`.
///
/// # Safety
///
/// For this cast to be sound, `self` must contain an instance of `T` inside its inner data.
#[must_use]
pub unsafe fn downcast_unchecked<T: NativeObject>(self) -> JsObject<T> {
let ptr: NonNull<GcBox<VTableObject<T>>> = Gc::into_raw(self.inner).cast();
// SAFETY: The caller guarantees `T` is the original inner data type of the underlying
// object.
unsafe {
JsObject {
inner: Gc::from_raw(ptr),
}
}
}
/// Downcasts a reference to the object,
/// if the object is of type `T`.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[must_use]
#[track_caller]
pub fn downcast_ref<T: NativeObject>(&self) -> Option<Ref<'_, T>> {
Ref::try_map(self.borrow(), ErasedObject::downcast_ref)
}
/// Downcasts a mutable reference to the object,
/// if the object is type native object type `T`.
///
/// # Panics
///
/// Panics if the object is currently borrowed.
#[must_use]
#[track_caller]
pub fn downcast_mut<T: NativeObject>(&self) -> Option<RefMut<'_, ErasedObject, T>> {
RefMut::try_map(self.borrow_mut(), ErasedObject::downcast_mut)
}
/// Checks if this object is an instance of a certain `NativeObject`.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[must_use]
#[track_caller]
pub fn is<T: NativeObject>(&self) -> bool {
self.borrow().is::<T>()
}
/// Checks if it's an ordinary object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[must_use]
#[track_caller]
pub fn is_ordinary(&self) -> bool {
self.is::<OrdinaryObject>()
}
/// Checks if it's an `Array` object.
#[inline]
#[must_use]
#[track_caller]
pub fn is_array(&self) -> bool {
std::ptr::eq(self.vtable(), &ARRAY_EXOTIC_INTERNAL_METHODS)
}
/// Converts an object to a primitive.
///
/// Diverges from the spec to prevent a stack overflow when the object is recursive.
/// For example,
/// ```javascript
/// let a = [1];
/// a[1] = a;
/// console.log(a.toString()); // We print "1,"
/// ```
/// The spec doesn't mention what to do in this situation, but a naive implementation
/// would overflow the stack recursively calling `toString()`. We follow v8 and SpiderMonkey
/// instead by returning a default value for the given `hint` -- either `0.` or `""`.
/// Example in v8: <https://repl.it/repls/IvoryCircularCertification#index.js>
///
/// More information:
/// - [ECMAScript][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-ordinarytoprimitive
pub(crate) fn ordinary_to_primitive(
&self,
context: &mut Context,
hint: PreferredType,
) -> JsResult<JsValue> {
// 1. Assert: Type(O) is Object.
// Already is JsObject by type.
// 2. Assert: Type(hint) is String and its value is either "string" or "number".
debug_assert!(hint == PreferredType::String || hint == PreferredType::Number);
// Diverge from the spec here to make sure we aren't going to overflow the stack by converting
// a recursive structure
// We can follow v8 & SpiderMonkey's lead and return a default value for the hint in this situation
// (see https://repl.it/repls/IvoryCircularCertification#index.js)
let recursion_limiter = RecursionLimiter::new(self.as_ref());
if recursion_limiter.live {
// we're in a recursive object, bail
return Ok(match hint {
PreferredType::Number => JsValue::new(0),
PreferredType::String => JsValue::new(js_string!()),
PreferredType::Default => unreachable!("checked type hint in step 2"),
});
}
// 3. If hint is "string", then
// a. Let methodNames be « "toString", "valueOf" ».
// 4. Else,
// a. Let methodNames be « "valueOf", "toString" ».
let method_names = if hint == PreferredType::String {
[utf16!("toString"), utf16!("valueOf")]
} else {
[utf16!("valueOf"), utf16!("toString")]
};
// 5. For each name in methodNames in List order, do
for name in method_names {
// a. Let method be ? Get(O, name).
let method = self.get(name, context)?;
// b. If IsCallable(method) is true, then
if let Some(method) = method.as_callable() {
// i. Let result be ? Call(method, O).
let result = method.call(&self.clone().into(), &[], context)?;
// ii. If Type(result) is not Object, return result.
if !result.is_object() {
return Ok(result);
}
}
}
// 6. Throw a TypeError exception.
Err(JsNativeError::typ()
.with_message("cannot convert object to primitive value")
.into())
}
/// The abstract operation `ToPropertyDescriptor`.
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-topropertydescriptor
pub fn to_property_descriptor(&self, context: &mut Context) -> JsResult<PropertyDescriptor> {
// 1 is implemented on the method `to_property_descriptor` of value
// 2. Let desc be a new Property Descriptor that initially has no fields.
let mut desc = PropertyDescriptor::builder();
// 3. Let hasEnumerable be ? HasProperty(Obj, "enumerable").
// 4. If hasEnumerable is true, then ...
if self.has_property(utf16!("enumerable"), context)? {
// a. Let enumerable be ! ToBoolean(? Get(Obj, "enumerable")).
// b. Set desc.[[Enumerable]] to enumerable.
desc = desc.enumerable(self.get(utf16!("enumerable"), context)?.to_boolean());
}
// 5. Let hasConfigurable be ? HasProperty(Obj, "configurable").
// 6. If hasConfigurable is true, then ...
if self.has_property(utf16!("configurable"), context)? {
// a. Let configurable be ! ToBoolean(? Get(Obj, "configurable")).
// b. Set desc.[[Configurable]] to configurable.
desc = desc.configurable(self.get(utf16!("configurable"), context)?.to_boolean());
}
// 7. Let hasValue be ? HasProperty(Obj, "value").
// 8. If hasValue is true, then ...
if self.has_property(utf16!("value"), context)? {
// a. Let value be ? Get(Obj, "value").
// b. Set desc.[[Value]] to value.
desc = desc.value(self.get(utf16!("value"), context)?);
}
// 9. Let hasWritable be ? HasProperty(Obj, ).
// 10. If hasWritable is true, then ...
if self.has_property(utf16!("writable"), context)? {
// a. Let writable be ! ToBoolean(? Get(Obj, "writable")).
// b. Set desc.[[Writable]] to writable.
desc = desc.writable(self.get(utf16!("writable"), context)?.to_boolean());
}
// 11. Let hasGet be ? HasProperty(Obj, "get").
// 12. If hasGet is true, then
let get = if self.has_property(utf16!("get"), context)? {
// a. Let getter be ? Get(Obj, "get").
let getter = self.get(utf16!("get"), context)?;
// b. If IsCallable(getter) is false and getter is not undefined, throw a TypeError exception.
// todo: extract IsCallable to be callable from Value
if !getter.is_undefined() && getter.as_object().map_or(true, |o| !o.is_callable()) {
return Err(JsNativeError::typ()
.with_message("Property descriptor getter must be callable")
.into());
}
// c. Set desc.[[Get]] to getter.
Some(getter)
} else {
None
};
// 13. Let hasSet be ? HasProperty(Obj, "set").
// 14. If hasSet is true, then
let set = if self.has_property(utf16!("set"), context)? {
// 14.a. Let setter be ? Get(Obj, "set").
let setter = self.get(utf16!("set"), context)?;
// 14.b. If IsCallable(setter) is false and setter is not undefined, throw a TypeError exception.
// todo: extract IsCallable to be callable from Value
if !setter.is_undefined() && setter.as_object().map_or(true, |o| !o.is_callable()) {
return Err(JsNativeError::typ()
.with_message("Property descriptor setter must be callable")
.into());
}
// 14.c. Set desc.[[Set]] to setter.
Some(setter)
} else {
None
};
// 15. If desc.[[Get]] is present or desc.[[Set]] is present, then ...
// a. If desc.[[Value]] is present or desc.[[Writable]] is present, throw a TypeError exception.
if get.as_ref().or(set.as_ref()).is_some() && desc.inner().is_data_descriptor() {
return Err(JsNativeError::typ()
.with_message(
"Invalid property descriptor.\
Cannot both specify accessors and a value or writable attribute",
)
.into());
}
desc = desc.maybe_get(get).maybe_set(set);
// 16. Return desc.
Ok(desc.build())
}
/// `7.3.25 CopyDataProperties ( target, source, excludedItems )`
///
/// More information:
/// - [ECMAScript][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-copydataproperties
pub fn copy_data_properties<K>(
&self,
source: &JsValue,
excluded_keys: Vec<K>,
context: &mut Context,
) -> JsResult<()>
where
K: Into<PropertyKey>,
{
let context = &mut InternalMethodContext::new(context);
// 1. Assert: Type(target) is Object.
// 2. Assert: excludedItems is a List of property keys.
// 3. If source is undefined or null, return target.
if source.is_null_or_undefined() {
return Ok(());
}
// 4. Let from be ! ToObject(source).
let from = source
.to_object(context)
.expect("function ToObject should never complete abruptly here");
// 5. Let keys be ? from.[[OwnPropertyKeys]]().
// 6. For each element nextKey of keys, do
let excluded_keys: Vec<PropertyKey> = excluded_keys.into_iter().map(Into::into).collect();
for key in from.__own_property_keys__(context)? {
// a. Let excluded be false.
let mut excluded = false;
// b. For each element e of excludedItems, do
for e in &excluded_keys {
// i. If SameValue(e, nextKey) is true, then
if *e == key {
// 1. Set excluded to true.
excluded = true;
break;
}
}
// c. If excluded is false, then
if !excluded {
// i. Let desc be ? from.[[GetOwnProperty]](nextKey).
let desc = from.__get_own_property__(&key, context)?;
// ii. If desc is not undefined and desc.[[Enumerable]] is true, then
if let Some(desc) = desc {
if let Some(enumerable) = desc.enumerable() {
if enumerable {
// 1. Let propValue be ? Get(from, nextKey).
let prop_value = from.__get__(&key, from.clone().into(), context)?;
// 2. Perform ! CreateDataPropertyOrThrow(target, nextKey, propValue).
self.create_data_property_or_throw(key, prop_value, context)
.expect(
"CreateDataPropertyOrThrow should never complete abruptly here",
);
}
}
}
}
}
// 7. Return target.
Ok(())
}
pub(crate) fn get_property(&self, key: &PropertyKey) -> Option<PropertyDescriptor> {
let mut obj = Some(self.clone());
while let Some(o) = obj {
if let Some(v) = o.borrow().properties.get(key) {
return Some(v);
}
obj = o.borrow().prototype().clone();
}
None
}
/// Casts to a `BufferObject` if the object is an `ArrayBuffer` or a `SharedArrayBuffer`.
#[inline]
pub(crate) fn into_buffer_object(self) -> Result<BufferObject, JsObject> {
let obj = self.borrow();
if obj.is::<ArrayBuffer>() {
drop(obj);
// SAFETY: We have verified that the inner data of `self` is of type `ArrayBuffer`.
return Ok(BufferObject::Buffer(unsafe {
self.downcast_unchecked::<ArrayBuffer>()
}));
}
if obj.is::<SharedArrayBuffer>() {
drop(obj);
// SAFETY: We have verified that the inner data of `self` is of type `SharedArrayBuffer`.
return Ok(BufferObject::SharedBuffer(unsafe {
self.downcast_unchecked::<SharedArrayBuffer>()
}));
}
drop(obj);
Err(self)
}
}
impl<T: NativeObject + ?Sized> JsObject<T> {
/// Creates a new `JsObject` from its root shape, prototype, and data.
///
/// Note that the returned object will not be erased to be convertible to a
/// `JsValue`. To erase the pointer, call [`JsObject::upcast`].
pub fn new<O: Into<Option<JsObject>>>(root_shape: &RootShape, prototype: O, data: T) -> Self
where
T: Sized,
{
let internal_methods = data.internal_methods();
let inner = Gc::new(VTableObject {
object: GcRefCell::new(Object {
data,
properties: PropertyMap::from_prototype_with_shared_shape(
root_shape,
prototype.into(),
),
extensible: true,
private_elements: ThinVec::new(),
}),
vtable: internal_methods,
});
Self { inner }
}
/// Creates a new `JsObject` from prototype, and data.
///
/// Note that the returned object will not be erased to be convertible to a
/// `JsValue`. To erase the pointer, call [`JsObject::upcast`].
pub fn new_unique<O: Into<Option<JsObject>>>(prototype: O, data: T) -> Self
where
T: Sized,
{
let internal_methods = data.internal_methods();
let inner = Gc::new(VTableObject {
object: GcRefCell::new(Object {
data,
properties: PropertyMap::from_prototype_unique_shape(prototype.into()),
extensible: true,
private_elements: ThinVec::new(),
}),
vtable: internal_methods,
});
Self { inner }
}
/// Upcasts this object's inner data from a specific type `T` to an erased type
/// `dyn NativeObject`.
#[must_use]
pub fn upcast(self) -> JsObject
where
T: Sized,
{
JsObject {
inner: coerce_gc(self.inner),
}
}
/// Immutably borrows the `Object`.
///
/// The borrow lasts until the returned `Ref` exits scope.
/// Multiple immutable borrows can be taken out at the same time.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[must_use]
#[track_caller]
pub fn borrow(&self) -> Ref<'_, Object<T>> {
self.try_borrow().expect("Object already mutably borrowed")
}
/// Mutably borrows the Object.
///
/// The borrow lasts until the returned `RefMut` exits scope.
/// The object cannot be borrowed while this borrow is active.
///
/// # Panics
/// Panics if the object is currently borrowed.
#[inline]
#[must_use]
#[track_caller]
pub fn borrow_mut(&self) -> RefMut<'_, Object<T>, Object<T>> {
self.try_borrow_mut().expect("Object already borrowed")
}
/// Immutably borrows the `Object`, returning an error if the value is currently mutably borrowed.
///
/// The borrow lasts until the returned `GcCellRef` exits scope.
/// Multiple immutable borrows can be taken out at the same time.
///
/// This is the non-panicking variant of [`borrow`](#method.borrow).
#[inline]
pub fn try_borrow(&self) -> StdResult<Ref<'_, Object<T>>, BorrowError> {
self.inner.object.try_borrow().map_err(|_| BorrowError)
}
/// Mutably borrows the object, returning an error if the value is currently borrowed.
///
/// The borrow lasts until the returned `GcCellRefMut` exits scope.
/// The object be borrowed while this borrow is active.
///
/// This is the non-panicking variant of [`borrow_mut`](#method.borrow_mut).
#[inline]
pub fn try_borrow_mut(&self) -> StdResult<RefMut<'_, Object<T>, Object<T>>, BorrowMutError> {
self.inner
.object
.try_borrow_mut()
.map_err(|_| BorrowMutError)
}
/// Checks if the garbage collected memory is the same.
#[must_use]
#[inline]
pub fn equals(lhs: &Self, rhs: &Self) -> bool {
Gc::ptr_eq(lhs.inner(), rhs.inner())
}
/// Get the prototype of the object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[must_use]
#[track_caller]
pub fn prototype(&self) -> JsPrototype {
self.borrow().prototype()
}
/// Get the extensibility of the object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
pub(crate) fn extensible(&self) -> bool {
self.borrow().extensible
}
/// Set the prototype of the object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed
#[inline]
#[track_caller]
#[allow(clippy::must_use_candidate)]
pub fn set_prototype(&self, prototype: JsPrototype) -> bool {
self.borrow_mut().set_prototype(prototype)
}
/// Helper function for property insertion.
#[track_caller]
pub(crate) fn insert<K, P>(&self, key: K, property: P) -> bool
where
K: Into<PropertyKey>,
P: Into<PropertyDescriptor>,
{
self.borrow_mut().insert(key, property)
}
/// Inserts a field in the object `properties` without checking if it's writable.
///
/// If a field was already in the object with the same name, than `true` is returned
/// with that field, otherwise `false` is returned.
pub fn insert_property<K, P>(&self, key: K, property: P) -> bool
where
K: Into<PropertyKey>,
P: Into<PropertyDescriptor>,
{
self.insert(key.into(), property)
}
/// It determines if Object is a callable function with a `[[Call]]` internal method.
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iscallable
#[inline]
#[must_use]
pub fn is_callable(&self) -> bool {
self.inner.vtable.__call__ != ORDINARY_INTERNAL_METHODS.__call__
}
/// It determines if Object is a function object with a `[[Construct]]` internal method.
///
/// More information:
/// - [ECMAScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-isconstructor
#[inline]
#[must_use]
pub fn is_constructor(&self) -> bool {
self.inner.vtable.__construct__ != ORDINARY_INTERNAL_METHODS.__construct__
}
pub(crate) fn vtable(&self) -> &'static InternalObjectMethods {
self.inner.vtable
}
pub(crate) const fn inner(&self) -> &Gc<VTableObject<T>> {
&self.inner
}
/// Create a new private name with this object as the unique identifier.
pub(crate) fn private_name(&self, description: JsString) -> PrivateName {
let ptr: *const _ = self.as_ref();
PrivateName::new(description, ptr.cast::<()>() as usize)
}
}
impl<T: NativeObject + ?Sized> AsRef<GcRefCell<Object<T>>> for JsObject<T> {
#[inline]
fn as_ref(&self) -> &GcRefCell<Object<T>> {
&self.inner.object
}
}
impl<T: NativeObject + ?Sized> From<Gc<VTableObject<T>>> for JsObject<T> {
#[inline]
fn from(inner: Gc<VTableObject<T>>) -> Self {
Self { inner }
}
}
impl<T: NativeObject + ?Sized> PartialEq for JsObject<T> {
fn eq(&self, other: &Self) -> bool {
Self::equals(self, other)
}
}
impl<T: NativeObject + ?Sized> Eq for JsObject<T> {}
impl<T: NativeObject + ?Sized> Hash for JsObject<T> {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
std::ptr::hash(self.as_ref(), state);
}
}
/// An error returned by [`JsObject::try_borrow`](struct.JsObject.html#method.try_borrow).
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct BorrowError;
impl Display for BorrowError {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Display::fmt("Object already mutably borrowed", f)
}
}
impl Error for BorrowError {}
/// An error returned by [`JsObject::try_borrow_mut`](struct.JsObject.html#method.try_borrow_mut).
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct BorrowMutError;
impl Display for BorrowMutError {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Display::fmt("Object already borrowed", f)
}
}
impl Error for BorrowMutError {}
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
enum RecursionValueState {
/// This value is "live": there's an active RecursionLimiter that hasn't been dropped.
Live,
/// This value has been seen before, but the recursion limiter has been dropped.
/// For example:
/// ```javascript
/// let b = [];
/// JSON.stringify([ // Create a recursion limiter for the root here
/// b, // state for b's &JsObject here is None
/// b, // state for b's &JsObject here is Visited
/// ]);
/// ```
Visited,
}
/// Prevents infinite recursion during `Debug::fmt`, `JSON.stringify`, and other conversions.
/// This uses a thread local, so is not safe to use where the object graph will be traversed by
/// multiple threads!
#[derive(Debug)]
pub struct RecursionLimiter {
/// If this was the first `JsObject` in the tree.
top_level: bool,
/// The ptr being kept in the HashSet, so we can delete it when we drop.
ptr: usize,
/// If this JsObject has been visited before in the graph, but not in the current branch.
pub visited: bool,
/// If this JsObject has been visited in the current branch of the graph.
pub live: bool,
}
impl Drop for RecursionLimiter {
fn drop(&mut self) {
if self.top_level {
// When the top level of the graph is dropped, we can free the entire map for the next traversal.
SEEN.with(|hm| hm.borrow_mut().clear());
} else if !self.live {
// This was the first RL for this object to become live, so it's no longer live now that it's dropped.
SEEN.with(|hm| {
hm.borrow_mut()
.insert(self.ptr, RecursionValueState::Visited)
});
}
}
}
thread_local! {
/// The map of pointers to `JsObject` that have been visited during the current `Debug::fmt` graph,
/// and the current state of their RecursionLimiter (dropped or live -- see `RecursionValueState`)
static SEEN: RefCell<HashMap<usize, RecursionValueState>> = RefCell::new(HashMap::new());
}
impl RecursionLimiter {
/// Determines if the specified `T` has been visited, and returns a struct that will free it when dropped.
///
/// This is done by maintaining a thread-local hashset containing the pointers of `T` values that have been
/// visited. The first `T` visited will clear the hashset, while any others will check if they are contained
/// by the hashset.
pub fn new<T: ?Sized>(o: &T) -> Self {
let ptr: *const _ = o;
let ptr = ptr.cast::<()>() as usize;
let (top_level, visited, live) = SEEN.with(|hm| {
let mut hm = hm.borrow_mut();
let top_level = hm.is_empty();
let old_state = hm.insert(ptr, RecursionValueState::Live);
(
top_level,
old_state == Some(RecursionValueState::Visited),
old_state == Some(RecursionValueState::Live),
)
});
Self {
top_level,
ptr,
visited,
live,
}
}
}
impl<T: NativeObject + ?Sized> Debug for JsObject<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> std::fmt::Result {
let limiter = RecursionLimiter::new(self.as_ref());
// Typically, using `!limiter.live` would be good enough here.
// However, the JS object hierarchy involves quite a bit of repitition, and the sheer amount of data makes
// understanding the Debug output impossible; limiting the usefulness of it.
//
// Instead, we check if the object has appeared before in the entire graph. This means that objects will appear
// at most once, hopefully making things a bit clearer.
if !limiter.visited && !limiter.live {
let ptr: *const _ = self.as_ref();
let ptr = ptr.cast::<()>();
let obj = self.borrow();
let kind = obj.data.type_name_of_value();
if self.is_callable() {
let name_prop = obj
.properties()
.get(&PropertyKey::String(JsString::from("name")));
let name = match name_prop {
None => JsString::default(),
Some(prop) => prop
.value()
.and_then(JsValue::as_string)
.cloned()
.unwrap_or_default(),
};
return f.write_fmt(format_args!("({:?}) {:?} 0x{:X}", kind, name, ptr as usize));
}
f.write_fmt(format_args!("({:?}) 0x{:X}", kind, ptr as usize))
} else {
f.write_str("{ ... }")
}
}
}
/// Upcasts the reference to an object from a specific type `T` to an erased type `dyn NativeObject`.
fn coerce_gc<T: NativeObject>(ptr: Gc<VTableObject<T>>) -> Gc<VTableObject<dyn NativeObject>> {
// SAFETY: This just makes the casting from sized to unsized. Should eventually be replaced by
// https://github.com/rust-lang/rust/issues/18598
unsafe {
let ptr = Gc::into_raw(ptr);
let ptr: NonNull<GcBox<VTableObject<dyn NativeObject>>> = ptr;
Gc::from_raw(ptr)
}
}