servo/components/script/dom/bindings/conversions.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

//! Conversions of Rust values to and from `JSVal`.
//!
//! | IDL type                | Argument type   | Return type    |
//! |-------------------------|-----------------|----------------|
//! | any                     | `JSVal`         |                |
//! | boolean                 | `bool`          |                |
//! | byte                    | `i8`            |                |
//! | octet                   | `u8`            |                |
//! | short                   | `i16`           |                |
//! | unsigned short          | `u16`           |                |
//! | long                    | `i32`           |                |
//! | unsigned long           | `u32`           |                |
//! | long long               | `i64`           |                |
//! | unsigned long long      | `u64`           |                |
//! | unrestricted float      | `f32`           |                |
//! | float                   | `Finite<f32>`   |                |
//! | unrestricted double     | `f64`           |                |
//! | double                  | `Finite<f64>`   |                |
//! | DOMString               | `DOMString`     |                |
//! | USVString               | `USVString`     |                |
//! | ByteString              | `ByteString`    |                |
//! | object                  | `*mut JSObject` |                |
//! | interface types         | `&T`            | `DomRoot<T>`   |
//! | dictionary types        | `&T`            | *unsupported*  |
//! | enumeration types       | `T`             |                |
//! | callback function types | `Rc<T>`         |                |
//! | nullable types          | `Option<T>`     |                |
//! | sequences               | `Vec<T>`        |                |
//! | union types             | `T`             |                |

use std::{ffi, ptr};

pub(crate) use js::conversions::{
    ConversionBehavior, ConversionResult, FromJSValConvertible, ToJSValConvertible,
};
use js::error::throw_type_error;
use js::glue::{GetProxyReservedSlot, IsWrapper, JS_GetReservedSlot, UnwrapObjectDynamic};
use js::jsapi::{Heap, IsWindowProxy, JSContext, JSObject, JS_IsExceptionPending};
use js::jsval::UndefinedValue;
use js::rust::wrappers::{IsArrayObject, JS_GetProperty, JS_HasProperty};
use js::rust::{is_dom_object, HandleId, HandleObject, HandleValue, MutableHandleValue};
use num_traits::Float;
pub(crate) use script_bindings::conversions::*;

use crate::dom::bindings::error::{Error, Fallible};
use crate::dom::bindings::num::Finite;
use crate::dom::bindings::reflector::DomObject;
use crate::dom::bindings::root::DomRoot;
use crate::dom::bindings::str::DOMString;
use crate::dom::bindings::trace::{JSTraceable, RootedTraceableBox};
use crate::dom::bindings::utils::DOMClass;
use crate::dom::filelist::FileList;
use crate::dom::htmlcollection::HTMLCollection;
use crate::dom::htmlformcontrolscollection::HTMLFormControlsCollection;
use crate::dom::htmloptionscollection::HTMLOptionsCollection;
use crate::dom::nodelist::NodeList;

impl<T: Float + ToJSValConvertible> ToJSValConvertible for Finite<T> {
    #[inline]
    unsafe fn to_jsval(&self, cx: *mut JSContext, rval: MutableHandleValue) {
        let value = **self;
        value.to_jsval(cx, rval);
    }
}

impl<T: Float + FromJSValConvertible<Config = ()>> FromJSValConvertible for Finite<T> {
    type Config = ();

    unsafe fn from_jsval(
        cx: *mut JSContext,
        value: HandleValue,
        option: (),
    ) -> Result<ConversionResult<Finite<T>>, ()> {
        let result = match FromJSValConvertible::from_jsval(cx, value, option)? {
            ConversionResult::Success(v) => v,
            ConversionResult::Failure(error) => {
                // FIXME(emilio): Why throwing instead of propagating the error?
                throw_type_error(cx, &error);
                return Err(());
            },
        };
        match Finite::new(result) {
            Some(v) => Ok(ConversionResult::Success(v)),
            None => {
                throw_type_error(cx, "this argument is not a finite floating-point value");
                Err(())
            },
        }
    }
}

impl<T: DomObject + IDLInterface> FromJSValConvertible for DomRoot<T> {
    type Config = ();

    unsafe fn from_jsval(
        cx: *mut JSContext,
        value: HandleValue,
        _config: Self::Config,
    ) -> Result<ConversionResult<DomRoot<T>>, ()> {
        Ok(match root_from_handlevalue(value, cx) {
            Ok(result) => ConversionResult::Success(result),
            Err(()) => ConversionResult::Failure("value is not an object".into()),
        })
    }
}

impl<T: ToJSValConvertible + JSTraceable> ToJSValConvertible for RootedTraceableBox<T> {
    #[inline]
    unsafe fn to_jsval(&self, cx: *mut JSContext, rval: MutableHandleValue) {
        let value = &**self;
        value.to_jsval(cx, rval);
    }
}

impl<T> FromJSValConvertible for RootedTraceableBox<Heap<T>>
where
    T: FromJSValConvertible + js::rust::GCMethods + Copy,
    Heap<T>: JSTraceable + Default,
{
    type Config = T::Config;

    unsafe fn from_jsval(
        cx: *mut JSContext,
        value: HandleValue,
        config: Self::Config,
    ) -> Result<ConversionResult<Self>, ()> {
        T::from_jsval(cx, value, config).map(|result| match result {
            ConversionResult::Success(inner) => {
                ConversionResult::Success(RootedTraceableBox::from_box(Heap::boxed(inner)))
            },
            ConversionResult::Failure(msg) => ConversionResult::Failure(msg),
        })
    }
}

/// Convert `id` to a `DOMString`. Returns `None` if `id` is not a string or
/// integer.
///
/// Handling of invalid UTF-16 in strings depends on the relevant option.
pub(crate) unsafe fn jsid_to_string(cx: *mut JSContext, id: HandleId) -> Option<DOMString> {
    let id_raw = *id;
    if id_raw.is_string() {
        let jsstr = std::ptr::NonNull::new(id_raw.to_string()).unwrap();
        return Some(jsstring_to_str(cx, jsstr));
    }

    if id_raw.is_int() {
        return Some(id_raw.to_int().to_string().into());
    }

    None
}

pub(crate) use script_bindings::conversions::is_dom_proxy;

/// The index of the slot wherein a pointer to the reflected DOM object is
/// stored for non-proxy bindings.
// We use slot 0 for holding the raw object.  This is safe for both
// globals and non-globals.
pub(crate) const DOM_OBJECT_SLOT: u32 = 0;

/// Get the private pointer of a DOM object from a given reflector.
pub(crate) unsafe fn private_from_object(obj: *mut JSObject) -> *const libc::c_void {
    let mut value = UndefinedValue();
    if is_dom_object(obj) {
        JS_GetReservedSlot(obj, DOM_OBJECT_SLOT, &mut value);
    } else {
        debug_assert!(is_dom_proxy(obj));
        GetProxyReservedSlot(obj, 0, &mut value);
    };
    if value.is_undefined() {
        ptr::null()
    } else {
        value.to_private()
    }
}

pub(crate) enum PrototypeCheck {
    Derive(fn(&'static DOMClass) -> bool),
    Depth { depth: usize, proto_id: u16 },
}

/// Get a `*const libc::c_void` for the given DOM object, unwrapping any
/// wrapper around it first, and checking if the object is of the correct type.
///
/// Returns Err(()) if `obj` is an opaque security wrapper or if the object is
/// not an object for a DOM object of the given type (as defined by the
/// proto_id and proto_depth).
#[inline]
pub(crate) unsafe fn private_from_proto_check(
    mut obj: *mut JSObject,
    cx: *mut JSContext,
    proto_check: PrototypeCheck,
) -> Result<*const libc::c_void, ()> {
    let dom_class = get_dom_class(obj).or_else(|_| {
        if IsWrapper(obj) {
            trace!("found wrapper");
            obj = UnwrapObjectDynamic(obj, cx, /* stopAtWindowProxy = */ false);
            if obj.is_null() {
                trace!("unwrapping security wrapper failed");
                Err(())
            } else {
                assert!(!IsWrapper(obj));
                trace!("unwrapped successfully");
                get_dom_class(obj)
            }
        } else {
            trace!("not a dom wrapper");
            Err(())
        }
    })?;

    let prototype_matches = match proto_check {
        PrototypeCheck::Derive(f) => (f)(dom_class),
        PrototypeCheck::Depth { depth, proto_id } => {
            dom_class.interface_chain[depth] as u16 == proto_id
        },
    };

    if prototype_matches {
        trace!("good prototype");
        Ok(private_from_object(obj))
    } else {
        trace!("bad prototype");
        Err(())
    }
}

/// Get a `*const libc::c_void` for the given DOM object, unless it is a DOM
/// wrapper, and checking if the object is of the correct type.
///
/// Returns Err(()) if `obj` is a wrapper or if the object is not an object
/// for a DOM object of the given type (as defined by the proto_id and proto_depth).
#[inline]
unsafe fn private_from_proto_check_static(
    obj: *mut JSObject,
    proto_check: fn(&'static DOMClass) -> bool,
) -> Result<*const libc::c_void, ()> {
    let dom_class = get_dom_class(obj).map_err(|_| ())?;
    if proto_check(dom_class) {
        trace!("good prototype");
        Ok(private_from_object(obj))
    } else {
        trace!("bad prototype");
        Err(())
    }
}

/// Get a `*const T` for a DOM object accessible from a `JSObject`.
pub(crate) fn native_from_object<T>(obj: *mut JSObject, cx: *mut JSContext) -> Result<*const T, ()>
where
    T: DomObject + IDLInterface,
{
    unsafe {
        private_from_proto_check(obj, cx, PrototypeCheck::Derive(T::derives))
            .map(|ptr| ptr as *const T)
    }
}

/// Get a `*const T` for a DOM object accessible from a `JSObject`, where the DOM object
/// is guaranteed not to be a wrapper.
pub(crate) fn native_from_object_static<T>(obj: *mut JSObject) -> Result<*const T, ()>
where
    T: DomObject + IDLInterface,
{
    unsafe { private_from_proto_check_static(obj, T::derives).map(|ptr| ptr as *const T) }
}

/// Get a `DomRoot<T>` for the given DOM object, unwrapping any wrapper
/// around it first, and checking if the object is of the correct type.
///
/// Returns Err(()) if `obj` is an opaque security wrapper or if the object is
/// not a reflector for a DOM object of the given type (as defined by the
/// proto_id and proto_depth).
pub(crate) fn root_from_object<T>(obj: *mut JSObject, cx: *mut JSContext) -> Result<DomRoot<T>, ()>
where
    T: DomObject + IDLInterface,
{
    native_from_object(obj, cx).map(|ptr| unsafe { DomRoot::from_ref(&*ptr) })
}

/// Get a `DomRoot<T>` for the given DOM object, unwrapping any wrapper
/// around it first, and checking if the object is of the correct type.
///
/// Returns Err(()) if `obj` is an opaque security wrapper or if the object is
/// not a reflector for a DOM object of the given type (as defined by the
/// proto_id and proto_depth).
pub(crate) fn root_from_object_static<T>(obj: *mut JSObject) -> Result<DomRoot<T>, ()>
where
    T: DomObject + IDLInterface,
{
    native_from_object_static(obj).map(|ptr| unsafe { DomRoot::from_ref(&*ptr) })
}

/// Get a `*const T` for a DOM object accessible from a `HandleValue`.
/// Caller is responsible for throwing a JS exception if needed in case of error.
pub(crate) fn native_from_handlevalue<T>(v: HandleValue, cx: *mut JSContext) -> Result<*const T, ()>
where
    T: DomObject + IDLInterface,
{
    if !v.get().is_object() {
        return Err(());
    }
    native_from_object(v.get().to_object(), cx)
}

/// Get a `DomRoot<T>` for a DOM object accessible from a `HandleValue`.
/// Caller is responsible for throwing a JS exception if needed in case of error.
pub(crate) fn root_from_handlevalue<T>(v: HandleValue, cx: *mut JSContext) -> Result<DomRoot<T>, ()>
where
    T: DomObject + IDLInterface,
{
    if !v.get().is_object() {
        return Err(());
    }
    root_from_object(v.get().to_object(), cx)
}

/// Get a `DomRoot<T>` for a DOM object accessible from a `HandleObject`.
pub(crate) fn root_from_handleobject<T>(
    obj: HandleObject,
    cx: *mut JSContext,
) -> Result<DomRoot<T>, ()>
where
    T: DomObject + IDLInterface,
{
    root_from_object(obj.get(), cx)
}

impl<T: DomObject> ToJSValConvertible for DomRoot<T> {
    unsafe fn to_jsval(&self, cx: *mut JSContext, rval: MutableHandleValue) {
        self.reflector().to_jsval(cx, rval);
    }
}

/// Returns whether `value` is an array-like object (Array, FileList,
/// HTMLCollection, HTMLFormControlsCollection, HTMLOptionsCollection,
/// NodeList).
pub(crate) unsafe fn is_array_like(cx: *mut JSContext, value: HandleValue) -> bool {
    let mut is_array = false;
    assert!(IsArrayObject(cx, value, &mut is_array));
    if is_array {
        return true;
    }

    let object: *mut JSObject = match FromJSValConvertible::from_jsval(cx, value, ()).unwrap() {
        ConversionResult::Success(object) => object,
        _ => return false,
    };

    if root_from_object::<FileList>(object, cx).is_ok() {
        return true;
    }
    if root_from_object::<HTMLCollection>(object, cx).is_ok() {
        return true;
    }
    if root_from_object::<HTMLFormControlsCollection>(object, cx).is_ok() {
        return true;
    }
    if root_from_object::<HTMLOptionsCollection>(object, cx).is_ok() {
        return true;
    }
    if root_from_object::<NodeList>(object, cx).is_ok() {
        return true;
    }

    false
}

/// Get a property from a JS object.
pub(crate) unsafe fn get_property_jsval(
    cx: *mut JSContext,
    object: HandleObject,
    name: &str,
    mut rval: MutableHandleValue,
) -> Fallible<()> {
    rval.set(UndefinedValue());
    let cname = match ffi::CString::new(name) {
        Ok(cname) => cname,
        Err(_) => return Ok(()),
    };
    let mut found = false;
    if JS_HasProperty(cx, object, cname.as_ptr(), &mut found) && found {
        JS_GetProperty(cx, object, cname.as_ptr(), rval);
        if JS_IsExceptionPending(cx) {
            return Err(Error::JSFailed);
        }
        Ok(())
    } else if JS_IsExceptionPending(cx) {
        Err(Error::JSFailed)
    } else {
        Ok(())
    }
}

/// Get a property from a JS object, and convert it to a Rust value.
pub(crate) unsafe fn get_property<T>(
    cx: *mut JSContext,
    object: HandleObject,
    name: &str,
    option: T::Config,
) -> Fallible<Option<T>>
where
    T: FromJSValConvertible,
{
    debug!("Getting property {}.", name);
    rooted!(in(cx) let mut result = UndefinedValue());
    get_property_jsval(cx, object, name, result.handle_mut())?;
    if result.is_undefined() {
        debug!("No property {}.", name);
        return Ok(None);
    }
    debug!("Converting property {}.", name);
    match T::from_jsval(cx, result.handle(), option) {
        Ok(ConversionResult::Success(value)) => Ok(Some(value)),
        Ok(ConversionResult::Failure(_)) => Ok(None),
        Err(()) => Err(Error::JSFailed),
    }
}

/// Get a `DomRoot<T>` for a WindowProxy accessible from a `HandleValue`.
/// Caller is responsible for throwing a JS exception if needed in case of error.
pub(crate) unsafe fn windowproxy_from_handlevalue<D: crate::DomTypes>(
    v: HandleValue,
    _cx: *mut JSContext,
) -> Result<DomRoot<D::WindowProxy>, ()> {
    if !v.get().is_object() {
        return Err(());
    }
    let object = v.get().to_object();
    if !IsWindowProxy(object) {
        return Err(());
    }
    let mut value = UndefinedValue();
    GetProxyReservedSlot(object, 0, &mut value);
    let ptr = value.to_private() as *const D::WindowProxy;
    Ok(DomRoot::from_ref(&*ptr))
}