Add swjs_retain and an JSObject(cloning:) initializer

Author: j-f1

Diff for: Runtime/src/index.ts

@@ -177,10 +177,9 @@ export class SwiftRuntime {
         },
 
         swjs_decode_string: (bytes_ptr: pointer, length: number) => {
-            const bytes = this.memory.bytes().subarray(
-                bytes_ptr,
-                bytes_ptr + length
-            );
+            const bytes = this.memory
+                .bytes()
+                .subarray(bytes_ptr, bytes_ptr + length);
             const string = this.textDecoder.decode(bytes);
             return this.memory.retain(string);
         },
@@ -347,6 +346,9 @@ export class SwiftRuntime {
             this.memory.writeBytes(buffer, bytes);
         },
 
+        swjs_retain: (ref: ref) => {
+            this.memory.retain(this.memory.getObject(ref));
+        },
         swjs_release: (ref: ref) => {
             this.memory.release(ref);
         },

Diff for: Runtime/src/types.ts

@@ -84,6 +84,7 @@ export interface ImportedFunctions {
         length: number
     ): number;
     swjs_load_typed_array(ref: ref, buffer: pointer): void;
+    swjs_retain(ref: number): void;
     swjs_release(ref: number): void;
 }
 

Diff for: Sources/JavaScriptKit/FundamentalObjects/JSObject.swift

@@ -21,6 +21,11 @@ public open class JSObject: Equatable {
         self.id = id
     }
 
+    public init(cloning object: JSObject) {
+        _retain(object.id)
+        self.id = object.id
+    }
+
     /// Returns the `name` member method binding this object as `this` context.
     ///
     /// e.g.

Diff for: Sources/JavaScriptKit/XcodeSupport.swift

@@ -86,6 +86,7 @@ import _CJavaScriptKit
         _: JavaScriptObjectRef,
         _: UnsafeMutablePointer<UInt8>!
     ) { fatalError() }
+    func _retain(_: JavaScriptObjectRef) { fatalError() }
     func _release(_: JavaScriptObjectRef) { fatalError() }
 
 #endif

Diff for: Sources/_CJavaScriptKit/include/_CJavaScriptKit.h

@@ -255,6 +255,16 @@ __attribute__((__import_module__("javascript_kit"),
                __import_name__("swjs_load_typed_array")))
 extern void _load_typed_array(const JavaScriptObjectRef ref, unsigned char *buffer);
 
+/// Increments reference count of `ref` retained by `SwiftRuntimeHeap` in JavaScript side.
+///
+/// This is only necessary when copying a JavaScript object to a new JSObject.
+/// All swjs_* APIs return already-retained objects.
+///
+/// @param ref The target JavaScript object.
+__attribute__((__import_module__("javascript_kit"),
+               __import_name__("swjs_retain")))
+extern void _retain(const JavaScriptObjectRef ref);
+
 /// Decrements reference count of `ref` retained by `SwiftRuntimeHeap` in JavaScript side.
 ///
 /// @param ref The target JavaScript object.