LibJS: Implement Atomics.exchange

Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/655ffce64df
Pull-request: https://github.com/SerenityOS/serenity/pull/8752
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Runtime/AtomicsObject.cpp

@@ -119,6 +119,7 @@ void AtomicsObject::initialize(GlobalObject& global_object)
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(vm.names.add, add, 3, attr);
     define_native_function(vm.names.and_, and_, 3, attr);
+    define_native_function(vm.names.exchange, exchange, 3, attr);
     define_native_function(vm.names.load, load, 2, attr);
     define_native_function(vm.names.or_, or_, 3, attr);
     define_native_function(vm.names.store, store, 3, attr);
@@ -165,6 +166,24 @@ JS_DEFINE_NATIVE_FUNCTION(AtomicsObject::and_)
     VERIFY_NOT_REACHED();
 }
 
+// 25.4.6 Atomics.exchange ( typedArray, index, value ), https://tc39.es/ecma262/#sec-atomics.exchange
+JS_DEFINE_NATIVE_FUNCTION(AtomicsObject::exchange)
+{
+    auto* typed_array = typed_array_from(global_object, vm.argument(0));
+    if (!typed_array)
+        return {};
+
+    auto atomic_exchange = [](auto* storage, auto value) { return AK::atomic_exchange(storage, value); };
+
+#define __JS_ENUMERATE(ClassName, snake_name, PrototypeName, ConstructorName, Type) \
+    if (is<ClassName>(typed_array))                                                 \
+        return perform_atomic_operation<Type>(global_object, *typed_array, move(atomic_exchange));
+    JS_ENUMERATE_TYPED_ARRAYS
+#undef __JS_ENUMERATE
+
+    VERIFY_NOT_REACHED();
+}
+
 // 25.4.8 Atomics.load ( typedArray, index ), https://tc39.es/ecma262/#sec-atomics.load
 JS_DEFINE_NATIVE_FUNCTION(AtomicsObject::load)
 {

Userland/Libraries/LibJS/Runtime/AtomicsObject.h

@@ -21,6 +21,7 @@ public:
 private:
     JS_DECLARE_NATIVE_FUNCTION(add);
     JS_DECLARE_NATIVE_FUNCTION(and_);
+    JS_DECLARE_NATIVE_FUNCTION(exchange);
     JS_DECLARE_NATIVE_FUNCTION(load);
     JS_DECLARE_NATIVE_FUNCTION(or_);
     JS_DECLARE_NATIVE_FUNCTION(store);

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -125,6 +125,7 @@ namespace JS {
     P(escape)                                \
     P(eval)                                  \
     P(every)                                 \
+    P(exchange)                              \
     P(exec)                                  \
     P(exp)                                   \
     P(expm1)                                 \

Userland/Libraries/LibJS/Tests/builtins/Atomics/Atomics.exchange.js

@@ -0,0 +1,74 @@
+test("invariants", () => {
+    expect(Atomics.exchange).toHaveLength(3);
+});
+
+test("error cases", () => {
+    expect(() => {
+        Atomics.exchange("not an array", 0, 0);
+    }).toThrow(TypeError);
+
+    expect(() => {
+        const bad_array_type = new Float32Array(4);
+        Atomics.exchange(bad_array_type, 0, 0);
+    }).toThrow(TypeError);
+
+    expect(() => {
+        const bad_array_type = new Uint8ClampedArray(4);
+        Atomics.exchange(bad_array_type, 0, 0);
+    }).toThrow(TypeError);
+
+    expect(() => {
+        const array = new Int32Array(4);
+        Atomics.exchange(array, 100, 0);
+    }).toThrow(RangeError);
+});
+
+test("basic functionality (non-BigInt)", () => {
+    [Int8Array, Int16Array, Int32Array, Uint8Array, Uint16Array, Uint32Array].forEach(ArrayType => {
+        const array = new ArrayType(4);
+        array[0] = 1;
+        array[1] = 2;
+        array[2] = 3;
+        array[3] = 4;
+
+        expect(Atomics.exchange(array, 0, 5)).toBe(1);
+        expect(array).toEqual([5, 2, 3, 4]);
+
+        expect(Atomics.exchange(array, 0, 6)).toBe(5);
+        expect(array).toEqual([6, 2, 3, 4]);
+
+        expect(Atomics.exchange(array, "1", 7)).toBe(2);
+        expect(array).toEqual([6, 7, 3, 4]);
+
+        expect(Atomics.exchange(array, 2, "8")).toBe(3);
+        expect(array).toEqual([6, 7, 8, 4]);
+
+        expect(Atomics.exchange(array, 3.14, 9)).toBe(4);
+        expect(array).toEqual([6, 7, 8, 9]);
+    });
+});
+
+test("basic functionality (BigInt)", () => {
+    [BigInt64Array, BigUint64Array].forEach(ArrayType => {
+        const array = new ArrayType(4);
+        array[0] = 1n;
+        array[1] = 2n;
+        array[2] = 3n;
+        array[3] = 4n;
+
+        expect(Atomics.exchange(array, 0, 5n)).toBe(1n);
+        expect(array).toEqual([5n, 2n, 3n, 4n]);
+
+        expect(Atomics.exchange(array, 0, 6n)).toBe(5n);
+        expect(array).toEqual([6n, 2n, 3n, 4n]);
+
+        expect(Atomics.exchange(array, 1, 7n)).toBe(2n);
+        expect(array).toEqual([6n, 7n, 3n, 4n]);
+
+        expect(Atomics.exchange(array, 2, 8n)).toBe(3n);
+        expect(array).toEqual([6n, 7n, 8n, 4n]);
+
+        expect(Atomics.exchange(array, 3, 9n)).toBe(4n);
+        expect(array).toEqual([6n, 7n, 8n, 9n]);
+    });
+});