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native.rs
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native.rs
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use std::marker::PhantomData;
use boa_engine::{
builtins::object::Object as GlobalObject,
context::intrinsics::StandardConstructor,
js_string,
object::{
builtins::JsFunction, ConstructorBuilder, FunctionBinding, FunctionObjectBuilder,
JsPrototype, Object, ObjectData, PROTOTYPE,
},
property::{Attribute, PropertyDescriptor, PropertyKey},
Context, JsError, JsNativeError, JsObject, JsResult, JsValue,
};
use boa_gc::{Finalize, GcRef, GcRefMut, Trace};
pub use boa_engine::{object::NativeObject, NativeFunction};
/// This struct permits Rust types to be passed around as JavaScript objects.
#[derive(Trace, Finalize)]
pub struct JsNativeObject<T: NativeObject> {
inner: JsValue,
_phantom: PhantomData<T>,
}
impl<T: NativeObject> Clone for JsNativeObject<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
_phantom: self._phantom.clone(),
}
}
}
impl<T: NativeObject> JsNativeObject<T> {
pub fn is(value: &JsValue) -> bool {
value.as_object().map_or(false, JsObject::is::<T>)
}
fn from_value_unchecked(value: JsValue) -> Self {
Self {
inner: value,
_phantom: PhantomData,
}
}
pub fn new_with_proto<C, P>(
prototype: P,
native_object: T,
context: &mut Context<'_>,
) -> JsResult<Self>
where
C: NativeClass<Instance = T>,
P: Into<Option<JsObject>>,
{
let class = context.global_object().get(js_string!(C::NAME), context)?;
let JsValue::Object(ref class_constructor) = class else {
return Err(JsNativeError::typ()
.with_message(format!(
"invalid constructor for native class `{}` ",
C::NAME
))
.into());
};
let JsValue::Object(class_prototype) = class_constructor.get(PROTOTYPE, context)? else {
return Err(JsNativeError::typ()
.with_message(format!(
"invalid default prototype for native class `{}`",
C::NAME
))
.into());
};
let prototype =
<P as Into<Option<JsObject>>>::into(prototype).unwrap_or(class_prototype);
let obj = JsObject::from_proto_and_data(
prototype,
ObjectData::native_object(native_object),
);
Ok(Self {
inner: obj.into(),
_phantom: PhantomData,
})
}
pub fn new<C>(native_object: T, context: &mut Context<'_>) -> JsResult<Self>
where
C: NativeClass<Instance = T>,
{
Self::new_with_proto::<C, _>(None, native_object, context)
}
pub fn inner(&self) -> &JsValue {
&self.inner
}
pub fn to_inner(&self) -> JsValue {
self.inner.clone()
}
pub fn object(&self) -> &JsObject {
self.inner.as_object().expect("Expected `JsObject`")
}
pub fn to_object(&self) -> JsObject {
self.object().clone()
}
pub fn deref(&self) -> GcRef<'_, T> {
self.object()
.downcast_ref::<T>()
.expect("Type mismatch in `JsNativeObject`")
}
pub fn deref_mut(&self) -> GcRefMut<'_, Object, T> {
self.object()
.downcast_mut::<T>()
.expect("Type mismatch in `JsNativeObject`")
}
}
impl<T: NativeObject> TryFrom<JsValue> for JsNativeObject<T> {
type Error = JsError;
fn try_from(value: JsValue) -> Result<Self, Self::Error> {
if !Self::is(&value) {
return Err(JsNativeError::typ()
.with_message("Type mismatch in `JsNativeObject`")
.into());
}
Ok(Self {
inner: value,
_phantom: PhantomData,
})
}
}
pub struct Accessor {
pub name: &'static str,
pub get: Option<JsFunction>,
pub set: Option<JsFunction>,
}
impl Accessor {
pub fn new(name: &'static str) -> Self {
Self {
name,
get: None,
set: None,
}
}
pub fn get(mut self, function: NativeFunction, context: &mut Context<'_>) -> Self {
let get = FunctionObjectBuilder::new(context.realm(), function)
.name(self.name)
.length(0)
.build();
self.get = Some(get);
self
}
pub fn set(mut self, function: NativeFunction, context: &mut Context<'_>) -> Self {
let set = FunctionObjectBuilder::new(context.realm(), function)
.name(format!("set_{}", self.name))
.length(1)
.build();
self.set = Some(set);
self
}
}
#[macro_export]
macro_rules! accessor {
($context:expr, $instance:ident, $name:expr, get:(($gthis:ident, $gcontext:ident) => $get:expr) $(, set:(($sthis:ident, $sarg:ident : $sarg_ty:ty, $scontext:ident) => $set:expr) )?) => {
$crate::native::Accessor::new($name)
.get(
boa_engine::NativeFunction::from_fn_ptr(|this, _args, $gcontext| {
let $gthis = $instance::try_from_js(this)?;
$get
}),
$context,
)
$(
.set(
boa_engine::NativeFunction::from_fn_ptr(|this, args, $scontext| {
let mut $sthis = $instance::try_from_js(this)?;
let $sarg: $sarg_ty =
args.get_or_undefined(0).try_js_into($scontext)?;
$set;
Ok(boa_engine::JsValue::null())
}),
$context,
)
)?
};
}
/// Class builder which allows adding methods and static methods to the class.
#[derive(Debug)]
pub struct ClassBuilder<'ctx, 'host> {
builder: ConstructorBuilder<'ctx, 'host>,
}
impl<'ctx, 'host> ClassBuilder<'ctx, 'host> {
fn new<T>(context: &'ctx mut Context<'host>) -> Self
where
T: NativeClass,
{
let mut builder = ConstructorBuilder::new(
context,
NativeFunction::from_fn_ptr(raw_constructor::<T>),
);
builder.name(T::NAME);
builder.length(T::LENGTH);
Self { builder }
}
fn build(self) -> StandardConstructor {
self.builder.build()
}
/// Add a method to the class.
///
/// It is added to `prototype`.
pub fn method<N>(
&mut self,
name: N,
length: usize,
function: NativeFunction,
) -> &mut Self
where
N: Into<FunctionBinding>,
{
self.builder.method(function, name, length);
self
}
/// Add a static method to the class.
///
/// It is added to class object itself.
pub fn static_method<N>(
&mut self,
name: N,
length: usize,
function: NativeFunction,
) -> &mut Self
where
N: Into<FunctionBinding>,
{
self.builder.static_method(function, name, length);
self
}
/// Add a data property to the class, with the specified attribute.
///
/// It is added to `prototype`.
pub fn property<K, V>(&mut self, key: K, value: V, attribute: Attribute) -> &mut Self
where
K: Into<PropertyKey>,
V: Into<JsValue>,
{
self.builder.property(key, value, attribute);
self
}
/// Add a static data property to the class, with the specified attribute.
///
/// It is added to class object itself.
pub fn static_property<K, V>(
&mut self,
key: K,
value: V,
attribute: Attribute,
) -> &mut Self
where
K: Into<PropertyKey>,
V: Into<JsValue>,
{
self.builder.static_property(key, value, attribute);
self
}
/// Add an accessor property to the class, with the specified attribute.
///
/// It is added to `prototype`.
pub fn accessor<K>(
&mut self,
key: K,
accessor: Accessor,
attribute: Attribute,
) -> &mut Self
where
K: Into<PropertyKey>,
{
self.builder
.accessor(key, accessor.get, accessor.set, attribute);
self
}
/// Add a static accessor property to the class, with the specified attribute.
///
/// It is added to class object itself.
pub fn static_accessor<K>(
&mut self,
key: K,
accessor: Accessor,
attribute: Attribute,
) -> &mut Self
where
K: Into<PropertyKey>,
{
self.builder
.static_accessor(key, accessor.get, accessor.set, attribute);
self
}
/// Add a property descriptor to the class, with the specified attribute.
///
/// It is added to `prototype`.
pub fn property_descriptor<K, P>(&mut self, key: K, property: P) -> &mut Self
where
K: Into<PropertyKey>,
P: Into<PropertyDescriptor>,
{
self.builder.property_descriptor(key, property);
self
}
/// Add a static property descriptor to the class, with the specified attribute.
///
/// It is added to class object itself.
pub fn static_property_descriptor<K, P>(&mut self, key: K, property: P) -> &mut Self
where
K: Into<PropertyKey>,
P: Into<PropertyDescriptor>,
{
self.builder.static_property_descriptor(key, property);
self
}
/// Specify the parent prototype for the class
pub fn inherit<O: Into<JsPrototype>>(&mut self, prototype: O) -> &mut Self {
self.builder.inherit(prototype);
self
}
/// Return the current context.
#[inline]
pub fn context(&mut self) -> &mut Context<'host> {
self.builder.context()
}
}
fn raw_constructor<T: NativeClass>(
this: &JsValue,
args: &[JsValue],
context: &mut Context<'_>,
) -> JsResult<JsValue> {
if this.is_undefined() {
return Err(JsNativeError::typ()
.with_message(format!(
"cannot call constructor of native class `{}` without new",
T::NAME
))
.into());
}
let prototype = this
.as_object()
.map(|obj| {
obj.get(PROTOTYPE, context)
.map(|val| val.as_object().cloned())
})
.transpose()?
.flatten();
let native_object = T::constructor(
&JsNativeObject::from_value_unchecked(this.clone()),
args,
context,
)?;
let object =
JsNativeObject::new_with_proto::<T, _>(prototype, native_object, context)?;
Ok(object.inner.clone())
}
pub trait JsNativeObjectToString: NativeObject + Sized {
fn to_string(
this: &JsNativeObject<Self>,
context: &mut Context<'_>,
) -> JsResult<JsValue>;
}
pub trait NativeClass {
/// The Rust type of the class's instances.
type Instance: NativeObject + Sized;
/// The binding name of the class.
const NAME: &'static str;
/// The amount of arguments the class `constructor` takes, default is `0`.
const LENGTH: usize = 0usize;
/// The attributes the class will be bound with, default is `writable`, `enumerable`, `configurable`.
const ATTRIBUTES: Attribute = Attribute::all();
/// The constructor of the class.
fn constructor(
this: &JsNativeObject<Self::Instance>,
args: &[JsValue],
context: &mut Context<'_>,
) -> JsResult<Self::Instance>;
/// Initializes the internals and the methods of the class.
fn init(class: &mut ClassBuilder<'_, '_>) -> JsResult<()>;
fn to_string(
this: &JsValue,
_args: &[JsValue],
context: &mut Context<'_>,
) -> JsResult<JsValue>
where
Self::Instance: JsNativeObjectToString,
{
if let Ok(native_obj) = JsNativeObject::<Self::Instance>::try_from(this.clone()) {
Self::Instance::to_string(&native_obj, context)
} else {
GlobalObject::to_string(this, &[], context)
}
}
}
pub fn register_global_class<T: NativeClass>(context: &mut Context<'_>) -> JsResult<()> {
let mut class_builder = ClassBuilder::new::<T>(context);
T::init(&mut class_builder)?;
let class = class_builder.build();
let property = PropertyDescriptor::builder()
.value(class.constructor())
.writable(T::ATTRIBUTES.writable())
.enumerable(T::ATTRIBUTES.enumerable())
.configurable(T::ATTRIBUTES.configurable());
context.global_object().define_property_or_throw(
js_string!(T::NAME),
property,
context,
)?;
Ok(())
}