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kateinoigakukunkateinoigakukun
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Rename JSObject.Transferring to JSTransferring<T>
This change makes the transferring object to be used with a typed object like `JSDate` or something else in the future.
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3 files changed

+115
-88
lines changed

3 files changed

+115
-88
lines changed

‎Examples/OffscrenCanvas/Sources/MyApp/main.swift‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -11,9 +11,9 @@ protocol CanvasRenderer {
1111
struct BackgroundRenderer: CanvasRenderer {
1212
func render(canvas: JSObject, size: Int) async throws {
1313
let executor = try await WebWorkerTaskExecutor(numberOfThreads: 1)
14-
let transferringCanvas = JSObject.transfer(canvas)
14+
let transfer = JSTransferring(canvas)
1515
let renderingTask = Task(executorPreference: executor) {
16-
let canvas = try await transferringCanvas.receive()
16+
let canvas = try await transfer.receive()
1717
try await renderAnimation(canvas: canvas, size: size)
1818
}
1919
await withTaskCancellationHandler {

‎Sources/JavaScriptEventLoop/JSObject+Transferring.swift‎

Lines changed: 111 additions & 84 deletions
Original file line numberDiff line numberDiff line change
@@ -5,95 +5,109 @@ import _CJavaScriptKit
55
import Synchronization
66
#endif
77

8-
extension JSObject {
8+
/// A temporary object intended to transfer an object from one thread to another.
9+
///
10+
/// ``JSTransferring`` is `Sendable` and it's intended to be shared across threads.
11+
@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
12+
public struct JSTransferring<T>: @unchecked Sendable {
13+
fileprivate struct Storage {
14+
/// The original object that is transferred.
15+
///
16+
/// Retain it here to prevent it from being released before the transfer is complete.
17+
let sourceObject: T
18+
/// A function that constructs an object from a JavaScript object reference.
19+
let construct: (_ id: JavaScriptObjectRef) -> T
20+
/// The JavaScript object reference of the original object.
21+
let idInSource: JavaScriptObjectRef
22+
/// The TID of the thread that owns the original object.
23+
let sourceTid: Int32
924

10-
/// A temporary object intended to transfer a ``JSObject`` from one thread to another.
11-
///
12-
/// ``JSObject`` itself is not `Sendable`, but ``Transferring`` is `Sendable` because it's
13-
/// intended to be shared across threads.
14-
@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
15-
public struct Transferring: @unchecked Sendable {
16-
fileprivate struct CriticalState {
17-
var continuation: CheckedContinuation<JavaScriptObjectRef, Error>?
18-
}
19-
fileprivate class Storage {
20-
/// The original ``JSObject`` that is transferred.
21-
///
22-
/// Retain it here to prevent it from being released before the transfer is complete.
23-
let sourceObject: JSObject
24-
#if compiler(>=6.1) && _runtime(_multithreaded)
25-
let criticalState: Mutex<CriticalState> = .init(CriticalState())
26-
#endif
25+
#if compiler(>=6.1) && _runtime(_multithreaded)
26+
/// A shared context for transferring objects across threads.
27+
let context: _JSTransferringContext = _JSTransferringContext()
28+
#endif
29+
}
2730

28-
var idInSource: JavaScriptObjectRef {
29-
sourceObject.id
30-
}
31+
private let storage: Storage
3132

32-
var sourceTid: Int32 {
33-
#if compiler(>=6.1) && _runtime(_multithreaded)
34-
sourceObject.ownerTid
35-
#else
36-
// On single-threaded runtime, source and destination threads are always the main thread (TID = -1).
37-
-1
38-
#endif
39-
}
33+
fileprivate init(
34+
sourceObject: T,
35+
construct: @escaping (_ id: JavaScriptObjectRef) -> T,
36+
deconstruct: @escaping (_ object: T) -> JavaScriptObjectRef,
37+
getSourceTid: @escaping (_ object: T) -> Int32
38+
) {
39+
self.storage = Storage(
40+
sourceObject: sourceObject,
41+
construct: construct,
42+
idInSource: deconstruct(sourceObject),
43+
sourceTid: getSourceTid(sourceObject)
44+
)
45+
}
4046

41-
init(sourceObject: JSObject) {
42-
self.sourceObject = sourceObject
47+
/// Receives a transferred ``JSObject`` from a thread.
48+
///
49+
/// The original ``JSObject`` is ["Transferred"](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Transferable_objects)
50+
/// to the receiving thread.
51+
///
52+
/// Note that this method should be called only once for each ``Transferring`` instance
53+
/// on the receiving thread.
54+
///
55+
/// ### Example
56+
///
57+
/// ```swift
58+
/// let canvas = JSObject.global.document.createElement("canvas").object!
59+
/// let transferring = JSObject.transfer(canvas.transferControlToOffscreen().object!)
60+
/// let executor = try await WebWorkerTaskExecutor(numberOfThreads: 1)
61+
/// Task(executorPreference: executor) {
62+
/// let canvas = try await transferring.receive()
63+
/// }
64+
/// ```
65+
@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
66+
public func receive(isolation: isolated (any Actor)? = #isolation, file: StaticString = #file, line: UInt = #line) async throws -> T {
67+
#if compiler(>=6.1) && _runtime(_multithreaded)
68+
// The following sequence of events happens when a `JSObject` is transferred from
69+
// the owner thread to the receiver thread:
70+
//
71+
// [Owner Thread] [Receiver Thread]
72+
// <-----requestTransfer------ swjs_request_transferring_object
73+
// ---------transfer---------> swjs_receive_object
74+
let idInDestination = try await withCheckedThrowingContinuation { continuation in
75+
self.storage.context.withLock { context in
76+
guard context.continuation == nil else {
77+
// This is a programming error, `receive` should be called only once.
78+
fatalError("JSObject.Transferring object is already received", file: file, line: line)
79+
}
80+
// The continuation will be resumed by `swjs_receive_object`.
81+
context.continuation = continuation
4382
}
44-
}
45-
46-
private let storage: Storage
47-
48-
fileprivate init(sourceObject: JSObject) {
49-
self.init(storage: Storage(sourceObject: sourceObject))
50-
}
51-
52-
fileprivate init(storage: Storage) {
53-
self.storage = storage
54-
}
55-
56-
/// Receives a transferred ``JSObject`` from a thread.
57-
///
58-
/// The original ``JSObject`` is ["Transferred"](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Transferable_objects)
59-
/// to the receiving thread.
60-
///
61-
/// Note that this method should be called only once for each ``Transferring`` instance
62-
/// on the receiving thread.
63-
///
64-
/// ### Example
65-
///
66-
/// ```swift
67-
/// let canvas = JSObject.global.document.createElement("canvas").object!
68-
/// let transferring = JSObject.transfer(canvas.transferControlToOffscreen().object!)
69-
/// let executor = try await WebWorkerTaskExecutor(numberOfThreads: 1)
70-
/// Task(executorPreference: executor) {
71-
/// let canvas = try await transferring.receive()
72-
/// }
73-
/// ```
74-
@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
75-
public func receive(isolation: isolated (any Actor)? = #isolation, file: StaticString = #file, line: UInt = #line) async throws -> JSObject {
76-
#if compiler(>=6.1) && _runtime(_multithreaded)
7783
swjs_request_transferring_object(
7884
self.storage.idInSource,
7985
self.storage.sourceTid,
80-
Unmanaged.passRetained(self.storage).toOpaque()
86+
Unmanaged.passRetained(self.storage.context).toOpaque()
8187
)
82-
let idInDestination = try await withCheckedThrowingContinuation { continuation in
83-
self.storage.criticalState.withLock { criticalState in
84-
guard criticalState.continuation == nil else {
85-
// This is a programming error, `receive` should be called only once.
86-
fatalError("JSObject.Transferring object is already received", file: file, line: line)
87-
}
88-
criticalState.continuation = continuation
89-
}
90-
}
91-
return JSObject(id: idInDestination)
92-
#else
93-
return JSObject(id: storage.idInSource)
94-
#endif
9588
}
89+
return storage.construct(idInDestination)
90+
#else
91+
return storage.construct(storage.idInSource)
92+
#endif
93+
}
94+
}
95+
96+
fileprivate final class _JSTransferringContext: Sendable {
97+
struct State {
98+
var continuation: CheckedContinuation<JavaScriptObjectRef, Error>?
9699
}
100+
private let state: Mutex<State> = .init(State())
101+
102+
func withLock<R>(_ body: (inout State) -> R) -> R {
103+
return state.withLock { state in
104+
body(&state)
105+
}
106+
}
107+
}
108+
109+
110+
extension JSTransferring where T == JSObject {
97111

98112
/// Transfers the ownership of a `JSObject` to be sent to another thread.
99113
///
@@ -104,8 +118,21 @@ extension JSObject {
104118
/// - Parameter object: The ``JSObject`` to be transferred.
105119
/// - Returns: A ``Transferring`` instance that can be shared across threads.
106120
@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
107-
public static func transfer(_ object: JSObject) -> Transferring {
108-
return Transferring(sourceObject: object)
121+
public init(_ object: JSObject) {
122+
self.init(
123+
sourceObject: object,
124+
construct: { JSObject(id: $0) },
125+
deconstruct: { $0.id },
126+
getSourceTid: {
127+
#if compiler(>=6.1) && _runtime(_multithreaded)
128+
return $0.ownerTid
129+
#else
130+
_ = $0
131+
// On single-threaded runtime, source and destination threads are always the main thread (TID = -1).
132+
return -1
133+
#endif
134+
}
135+
)
109136
}
110137
}
111138

@@ -123,10 +150,10 @@ extension JSObject {
123150
@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
124151
func _swjs_receive_object(_ object: JavaScriptObjectRef, _ transferring: UnsafeRawPointer) {
125152
#if compiler(>=6.1) && _runtime(_multithreaded)
126-
let storage = Unmanaged<JSObject.Transferring.Storage>.fromOpaque(transferring).takeRetainedValue()
127-
storage.criticalState.withLock { criticalState in
128-
assert(criticalState.continuation != nil, "JSObject.Transferring object is not yet received!?")
129-
criticalState.continuation?.resume(returning: object)
153+
let context = Unmanaged<_JSTransferringContext>.fromOpaque(transferring).takeRetainedValue()
154+
context.withLock { state in
155+
assert(state.continuation != nil, "JSObject.Transferring object is not yet received!?")
156+
state.continuation?.resume(returning: object)
130157
}
131158
#endif
132159
}

‎Tests/JavaScriptEventLoopTests/WebWorkerTaskExecutorTests.swift‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -267,7 +267,7 @@ final class WebWorkerTaskExecutorTests: XCTestCase {
267267
func testTransfer() async throws {
268268
let Uint8Array = JSObject.global.Uint8Array.function!
269269
let buffer = Uint8Array.new(100).buffer.object!
270-
let transferring = JSObject.transfer(buffer)
270+
let transferring = JSTransferring(buffer)
271271
let executor = try await WebWorkerTaskExecutor(numberOfThreads: 1)
272272
let task = Task(executorPreference: executor) {
273273
let buffer = try await transferring.receive()
@@ -281,7 +281,7 @@ final class WebWorkerTaskExecutorTests: XCTestCase {
281281

282282
func testTransferNonTransferable() async throws {
283283
let object = JSObject.global.Object.function!.new()
284-
let transferring = JSObject.transfer(object)
284+
let transferring = JSTransferring(object)
285285
let executor = try await WebWorkerTaskExecutor(numberOfThreads: 1)
286286
let task = Task(executorPreference: executor) {
287287
_ = try await transferring.receive()

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