Implements JavaScript classes in C++ using JavaScriptCore. Use when creating new JS classes with C++ bindings, prototypes, or constructors.
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For publicly accessible Constructor and Prototype, create 3 classes:
class Foo : public JSC::DestructibleObject - if C++ fields exist; otherwise use JSC::constructEmptyObject with putDirectOffsetclass FooPrototype : public JSC::JSNonFinalObjectclass FooConstructor : public JSC::InternalFunctionNo public constructor? Only Prototype and class needed.
Classes with C++ fields need subspaces in:
src/jsc/bindings/webcore/DOMClientIsoSubspaces.hsrc/jsc/bindings/webcore/DOMIsoSubspaces.htemplate<typename MyClassT, JSC::SubspaceAccess mode>
static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm) {
if constexpr (mode == JSC::SubspaceAccess::Concurrently)
return nullptr;
return WebCore::subspaceForImpl<MyClassT, WebCore::UseCustomHeapCellType::No>(
vm,
[](auto& spaces) { return spaces.m_clientSubspaceForMyClassT.get(); },
[](auto& spaces, auto&& space) { spaces.m_clientSubspaceForMyClassT = std::forward<decltype(space)>(space); },
[](auto& spaces) { return spaces.m_subspaceForMyClassT.get(); },
[](auto& spaces, auto&& space) { spaces.m_subspaceForMyClassT = std::forward<decltype(space)>(space); });
}
static JSC_DECLARE_HOST_FUNCTION(jsFooProtoFuncMethod);
static JSC_DECLARE_CUSTOM_GETTER(jsFooGetter_property);
static const HashTableValue JSFooPrototypeTableValues[] = {
{ "property"_s, static_cast<unsigned>(PropertyAttribute::ReadOnly | PropertyAttribute::CustomAccessor), NoIntrinsic, { HashTableValue::GetterSetterType, jsFooGetter_property, 0 } },
{ "method"_s, static_cast<unsigned>(PropertyAttribute::Function), NoIntrinsic, { HashTableValue::NativeFunctionType, jsFooProtoFuncMethod, 1 } },
};
class JSFooPrototype final : public JSC::JSNonFinalObject {
public:
using Base = JSC::JSNonFinalObject;
static constexpr unsigned StructureFlags = Base::StructureFlags;
static JSFooPrototype* create(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::Structure* structure) {
JSFooPrototype* prototype = new (NotNull, allocateCell<JSFooPrototype>(vm)) JSFooPrototype(vm, structure);
prototype->finishCreation(vm);
return prototype;
}
template<typename, JSC::SubspaceAccess>
static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm) { return &vm.plainObjectSpace(); }
DECLARE_INFO;
static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype) {
auto* structure = JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::ObjectType, StructureFlags), info());
structure->setMayBePrototype(true);
return structure;
}
private:
JSFooPrototype(JSC::VM& vm, JSC::Structure* structure) : Base(vm, structure) {}
void finishCreation(JSC::VM& vm);
};
void JSFooPrototype::finishCreation(VM& vm) {
Base::finishCreation(vm);
reifyStaticProperties(vm, JSFoo::info(), JSFooPrototypeTableValues, *this);
JSC_TO_STRING_TAG_WITHOUT_TRANSITION();
}
// Getter
JSC_DEFINE_CUSTOM_GETTER(jsFooGetter_prop, (JSGlobalObject* globalObject, EncodedJSValue thisValue, PropertyName)) {
VM& vm = globalObject->vm();
auto scope = DECLARE_THROW_SCOPE(vm);
JSFoo* thisObject = jsDynamicCast<JSFoo*>(JSValue::decode(thisValue));
if (UNLIKELY(!thisObject)) {
Bun::throwThisTypeError(*globalObject, scope, "JSFoo"_s, "prop"_s);
return {};
}
return JSValue::encode(jsBoolean(thisObject->value()));
}
// Function
JSC_DEFINE_HOST_FUNCTION(jsFooProtoFuncMethod, (JSGlobalObject* globalObject, CallFrame* callFrame)) {
VM& vm = globalObject->vm();
auto scope = DECLARE_THROW_SCOPE(vm);
auto* thisObject = jsDynamicCast<JSFoo*>(callFrame->thisValue());
if (UNLIKELY(!thisObject)) {
Bun::throwThisTypeError(*globalObject, scope, "Foo"_s, "method"_s);
return {};
}
return JSValue::encode(thisObject->doSomething(vm, globalObject));
}
class JSFooConstructor final : public JSC::InternalFunction {
public:
using Base = JSC::InternalFunction;
static constexpr unsigned StructureFlags = Base::StructureFlags;
static JSFooConstructor* create(JSC::VM& vm, JSC::Structure* structure, JSC::JSObject* prototype) {
JSFooConstructor* constructor = new (NotNull, JSC::allocateCell<JSFooConstructor>(vm)) JSFooConstructor(vm, structure);
constructor->finishCreation(vm, prototype);
return constructor;
}
DECLARE_INFO;
template<typename CellType, JSC::SubspaceAccess>
static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm) { return &vm.internalFunctionSpace(); }
static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype) {
return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::InternalFunctionType, StructureFlags), info());
}
private:
JSFooConstructor(JSC::VM& vm, JSC::Structure* structure) : Base(vm, structure, callFoo, constructFoo) {}
void finishCreation(JSC::VM& vm, JSC::JSObject* prototype) {
Base::finishCreation(vm, 0, "Foo"_s);
putDirectWithoutTransition(vm, vm.propertyNames->prototype, prototype, JSC::PropertyAttribute::DontEnum | JSC::PropertyAttribute::DontDelete | JSC::PropertyAttribute::ReadOnly);
}
};
Add to ZigGlobalObject.h:
JSC::LazyClassStructure m_JSFooClassStructure;
Initialize in ZigGlobalObject.cpp:
m_JSFooClassStructure.initLater([](LazyClassStructure::Initializer& init) {
Bun::initJSFooClassStructure(init);
});
Visit in visitChildrenImpl:
m_JSFooClassStructure.visit(visitor);
extern "C" JSC::EncodedJSValue Bun__JSFooConstructor(Zig::GlobalObject* globalObject) {
return JSValue::encode(globalObject->m_JSFooClassStructure.constructor(globalObject));
}
extern "C" EncodedJSValue Bun__Foo__toJS(Zig::GlobalObject* globalObject, Foo* foo) {
auto* structure = globalObject->m_JSFooClassStructure.get(globalObject);
return JSValue::encode(JSFoo::create(globalObject->vm(), structure, globalObject, WTFMove(foo)));
}
Include #include "root.h" at the top of C++ files.
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