Transfer ReadableStream (#36181)

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Add transfer support to ReadableStream. Part of
https://github.com/servo/servo/issues/34676

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- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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---------

Signed-off-by: gterzian <2792687+gterzian@users.noreply.github.com>

1 files changed, 83 insertions, 2 deletions

diff --git a/components/script/dom/messageport.rs b/components/script/dom/messageport.rs
index d299ab8156f..3e25602b365 100644
--- a/components/script/dom/messageport.rs
+++ b/components/script/dom/messageport.rs
@@ -5,12 +5,14 @@
 use std::cell::{Cell, RefCell};
 use std::collections::HashMap;
 use std::num::NonZeroU32;
+use std::ptr;
 use std::rc::Rc;
 
 use base::id::{MessagePortId, MessagePortIndex, PipelineNamespaceId};
 use constellation_traits::{MessagePortImpl, PortMessageTask};
 use dom_struct::dom_struct;
-use js::jsapi::{Heap, JSObject};
+use js::jsapi::{Heap, JS_NewObject, JSObject};
+use js::jsval::UndefinedValue;
 use js::rust::{CustomAutoRooter, CustomAutoRooterGuard, HandleValue};
 
 use crate::dom::bindings::codegen::Bindings::EventHandlerBinding::EventHandlerNonNull;
@@ -25,8 +27,10 @@ use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::structuredclone::{self, StructuredData, StructuredDataReader};
 use crate::dom::bindings::trace::RootedTraceableBox;
 use crate::dom::bindings::transferable::{ExtractComponents, IdFromComponents, Transferable};
+use crate::dom::bindings::utils::set_dictionary_property;
 use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
+use crate::js::conversions::ToJSValConvertible;
 use crate::script_runtime::{CanGc, JSContext as SafeJSContext};
 
 #[dom_struct]
@@ -57,7 +61,7 @@ impl MessagePort {
     }
 
     /// Create a new port for an incoming transfer-received one.
-    fn new_transferred(
+    pub(crate) fn new_transferred(
         owner: &GlobalScope,
         transferred_port: MessagePortId,
         entangled_port: Option<MessagePortId>,
@@ -156,6 +160,83 @@ impl MessagePort {
             .post_messageport_msg(*self.message_port_id(), task);
         Ok(())
     }
+
+    /// <https://streams.spec.whatwg.org/#abstract-opdef-crossrealmtransformsenderror>
+    pub(crate) fn cross_realm_transform_send_error(&self, error: HandleValue, can_gc: CanGc) {
+        // Perform PackAndPostMessage(port, "error", error),
+        // discarding the result.
+        let _ = self.pack_and_post_message("error", error, can_gc);
+    }
+
+    /// <https://streams.spec.whatwg.org/#abstract-opdef-packandpostmessagehandlingerror>
+    #[allow(unsafe_code)]
+    pub(crate) fn pack_and_post_message_handling_error(
+        &self,
+        type_: &str,
+        value: HandleValue,
+        can_gc: CanGc,
+    ) -> ErrorResult {
+        // Let result be PackAndPostMessage(port, type, value).
+        let result = self.pack_and_post_message(type_, value, can_gc);
+
+        // If result is an abrupt completion,
+        if result.is_err() {
+            // Perform ! CrossRealmTransformSendError(port, result.[[Value]]).
+            // Note: we send UndefinedValue across,
+            // because somehow sending an error results in another error.
+            // The Error::DataClone, which is the only one that is sent across,
+            // will be created upon receipt.
+            let cx = GlobalScope::get_cx();
+            rooted!(in(*cx) let mut rooted_error = UndefinedValue());
+            self.cross_realm_transform_send_error(rooted_error.handle(), can_gc);
+        }
+
+        result
+    }
+
+    /// <https://streams.spec.whatwg.org/#abstract-opdef-packandpostmessage>
+    #[allow(unsafe_code)]
+    pub(crate) fn pack_and_post_message(
+        &self,
+        type_: &str,
+        value: HandleValue,
+        _can_gc: CanGc,
+    ) -> ErrorResult {
+        let cx = GlobalScope::get_cx();
+
+        // Let message be OrdinaryObjectCreate(null).
+        rooted!(in(*cx) let mut message = unsafe { JS_NewObject(*cx, ptr::null()) });
+        rooted!(in(*cx) let mut type_string = UndefinedValue());
+        unsafe {
+            type_.to_jsval(*cx, type_string.handle_mut());
+        }
+
+        // Perform ! CreateDataProperty(message, "type", type).
+        unsafe {
+            set_dictionary_property(*cx, message.handle(), "type", type_string.handle())
+                .expect("Setting the message type should not fail.");
+        }
+
+        // Perform ! CreateDataProperty(message, "value", value).
+        unsafe {
+            set_dictionary_property(*cx, message.handle(), "value", value)
+                .expect("Setting the message value should not fail.");
+        }
+
+        // Let targetPort be the port with which port is entangled, if any; otherwise let it be null.
+        // Done in `global.post_messageport_msg`.
+
+        // Let options be «[ "transfer" → « » ]».
+        let mut rooted = CustomAutoRooter::new(vec![]);
+        let transfer = CustomAutoRooterGuard::new(*cx, &mut rooted);
+
+        // Run the message port post message steps providing targetPort, message, and options.
+        rooted!(in(*cx) let mut message_val = UndefinedValue());
+        unsafe {
+            message.to_jsval(*cx, message_val.handle_mut());
+        }
+        self.post_message_impl(cx, message_val.handle(), transfer)
+    }
 }
 
 impl Transferable for MessagePort {