Reduce indexing boilerplate for serializable/transferrable objects. (#36624)

Rather than creating unique types for each pipeline-namespaced index
type (eg. MessagePortId, DomExceptionId, etc.), we can create a generic
common type that uses a marker to prevent type confusion. This change
allows us to reduce the boilerplate code required when implementing
serializable/transferable interfaces, since the structured clone
implementation can rely on the common type.

Testing: Existing WPT tests for serialization and transferring provide
coverage.

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/script/dom/bindings/serializable.rs

@@ -6,9 +6,8 @@
 //! (<https://html.spec.whatwg.org/multipage/#serializable-objects>).
 
 use std::collections::HashMap;
-use std::num::NonZeroU32;
 
-use base::id::PipelineNamespaceId;
+use base::id::{Index, NamespaceIndex, PipelineNamespaceId};
 
 use crate::dom::bindings::reflector::DomObject;
 use crate::dom::bindings::root::DomRoot;
@@ -25,9 +24,9 @@ pub(crate) struct StorageKey {
 }
 
 impl StorageKey {
-    pub(crate) fn new(name_space: PipelineNamespaceId, index: NonZeroU32) -> StorageKey {
-        let name_space = name_space.0.to_ne_bytes();
-        let index = index.get().to_ne_bytes();
+    pub(crate) fn new<T>(index: NamespaceIndex<T>) -> StorageKey {
+        let name_space = index.namespace_id.0.to_ne_bytes();
+        let index = index.index.0.get().to_ne_bytes();
         StorageKey {
             index: u32::from_ne_bytes(index),
             name_space: u32::from_ne_bytes(name_space),
@@ -35,11 +34,13 @@ impl StorageKey {
     }
 }
 
-pub(crate) trait IntoStorageKey
-where
-    Self: Sized,
-{
-    fn into_storage_key(self) -> StorageKey;
+impl<T> From<StorageKey> for NamespaceIndex<T> {
+    fn from(key: StorageKey) -> NamespaceIndex<T> {
+        NamespaceIndex {
+            namespace_id: PipelineNamespaceId(key.name_space),
+            index: Index::new(key.index).expect("Index must not be zero"),
+        }
+    }
 }
 
 /// Interface for serializable platform objects.
@@ -48,11 +49,11 @@ pub(crate) trait Serializable: DomObject
 where
     Self: Sized,
 {
-    type Id: Copy + Eq + std::hash::Hash + IntoStorageKey + From<StorageKey>;
+    type Index: Copy + Eq + std::hash::Hash;
     type Data;
 
     /// <https://html.spec.whatwg.org/multipage/#serialization-steps>
-    fn serialize(&self) -> Result<(Self::Id, Self::Data), ()>;
+    fn serialize(&self) -> Result<(NamespaceIndex<Self::Index>, Self::Data), ()>;
     /// <https://html.spec.whatwg.org/multipage/#deserialization-steps>
     fn deserialize(
         owner: &GlobalScope,
@@ -64,7 +65,9 @@ where
 
     /// Returns the field of [StructuredDataReader]/[StructuredDataWriter] that
     /// should be used to read/store serialized instances of this type.
-    fn serialized_storage(data: StructuredData<'_>) -> &mut Option<HashMap<Self::Id, Self::Data>>;
+    fn serialized_storage(
+        data: StructuredData<'_>,
+    ) -> &mut Option<HashMap<NamespaceIndex<Self::Index>, Self::Data>>;
 
     /// Returns the field of [StructuredDataReader] that should be used to store
     /// deserialized instances of this type.

components/script/dom/bindings/structuredclone.rs

@@ -6,11 +6,12 @@
 
 use std::collections::HashMap;
 use std::ffi::CStr;
-use std::num::NonZeroU32;
 use std::os::raw;
 use std::ptr;
 
-use base::id::{BlobId, DomExceptionId, DomPointId, MessagePortId, PipelineNamespaceId};
+use base::id::{
+    BlobId, DomExceptionId, DomPointId, Index, MessagePortId, NamespaceIndex, PipelineNamespaceId,
+};
 use constellation_traits::{
     BlobImpl, DomException, DomPoint, MessagePortImpl, Serializable as SerializableInterface,
     StructuredSerializedData, Transferrable as TransferrableInterface,
@@ -34,8 +35,8 @@ use strum::IntoEnumIterator;
 use crate::dom::bindings::conversions::{ToJSValConvertible, root_from_object};
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::root::DomRoot;
-use crate::dom::bindings::serializable::{IntoStorageKey, Serializable, StorageKey};
-use crate::dom::bindings::transferable::{ExtractComponents, IdFromComponents, Transferable};
+use crate::dom::bindings::serializable::{Serializable, StorageKey};
+use crate::dom::bindings::transferable::Transferable;
 use crate::dom::blob::Blob;
 use crate::dom::dompoint::DOMPoint;
 use crate::dom::dompointreadonly::DOMPointReadOnly;
@@ -120,7 +121,7 @@ unsafe fn read_object<T: Serializable>(
 
     // 1. Re-build the key for the storage location
     // of the serialized object.
-    let id = T::Id::from(storage_key);
+    let id: NamespaceIndex<T::Index> = storage_key.into();
 
     // 2. Get the transferred object from its storage, using the key.
     let objects = T::serialized_storage(StructuredData::Reader(sc_reader));
@@ -155,7 +156,7 @@ unsafe fn write_object<T: Serializable>(
         let objects = T::serialized_storage(StructuredData::Writer(sc_writer))
             .get_or_insert_with(HashMap::new);
         objects.insert(new_id, serialized);
-        let storage_key = new_id.into_storage_key();
+        let storage_key = StorageKey::new(new_id);
 
         assert!(JS_WriteUint32Pair(
             w,
@@ -282,13 +283,13 @@ fn receive_object<T: Transferable>(
             .try_into()
             .expect("name_space to be a slice of four."),
     ));
-    let id = <T::Id as IdFromComponents>::from(
+    let id: NamespaceIndex<T::Index> = NamespaceIndex {
         namespace_id,
-        NonZeroU32::new(u32::from_ne_bytes(
+        index: Index::new(u32::from_ne_bytes(
             index.try_into().expect("index to be a slice of four."),
         ))
         .expect("Index to be non-zero"),
-    );
+    };
 
     // 2. Get the transferred object from its storage, using the key.
     let storage = T::serialized_storage(StructuredData::Reader(sc_reader));
@@ -356,11 +357,10 @@ unsafe fn try_transfer<T: Transferable + IDLInterface>(
                 .get_or_insert_with(HashMap::new);
             objects.insert(id, object);
 
-            let (PipelineNamespaceId(name_space), index) = id.components();
-            let index = index.get();
+            let index = id.index.0.get();
 
             let mut big: [u8; 8] = [0; 8];
-            let name_space = name_space.to_ne_bytes();
+            let name_space = id.namespace_id.0.to_ne_bytes();
             let index = index.to_ne_bytes();
 
             let (left, right) = big.split_at_mut(4);

components/script/dom/bindings/transferable.rs

@@ -6,44 +6,34 @@
 //! (<https://html.spec.whatwg.org/multipage/#transferable-objects>).
 
 use std::collections::HashMap;
-use std::num::NonZeroU32;
+use std::hash::Hash;
 
-use base::id::PipelineNamespaceId;
+use base::id::NamespaceIndex;
 
 use crate::dom::bindings::reflector::DomObject;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::structuredclone::{StructuredData, StructuredDataReader};
 use crate::dom::globalscope::GlobalScope;
-
-pub(crate) trait IdFromComponents
-where
-    Self: Sized,
-{
-    fn from(namespace_id: PipelineNamespaceId, index: NonZeroU32) -> Self;
-}
-
-pub(crate) trait ExtractComponents {
-    fn components(&self) -> (PipelineNamespaceId, NonZeroU32);
-}
-
 pub(crate) trait Transferable: DomObject
 where
     Self: Sized,
 {
-    type Id: Eq + std::hash::Hash + Copy + IdFromComponents + ExtractComponents;
+    type Index: Copy + Eq + Hash;
     type Data;
 
     fn can_transfer(&self) -> bool {
         true
     }
 
-    fn transfer(&self) -> Result<(Self::Id, Self::Data), ()>;
+    fn transfer(&self) -> Result<(NamespaceIndex<Self::Index>, Self::Data), ()>;
     fn transfer_receive(
         owner: &GlobalScope,
-        id: Self::Id,
+        id: NamespaceIndex<Self::Index>,
         serialized: Self::Data,
     ) -> Result<DomRoot<Self>, ()>;
 
-    fn serialized_storage(data: StructuredData<'_>) -> &mut Option<HashMap<Self::Id, Self::Data>>;
+    fn serialized_storage(
+        data: StructuredData<'_>,
+    ) -> &mut Option<HashMap<NamespaceIndex<Self::Index>, Self::Data>>;
     fn deserialized_storage(reader: &mut StructuredDataReader) -> &mut Option<Vec<DomRoot<Self>>>;
 }