LibJS: Accept ArrayBuffer constructor options argument

Test262 seems to test the changes in the "Resizable ArrayBuffer and
growable SharedArrayBuffer" proposal. Begin implementing this proposal
by accepting the new options object argument to the ArrayBuffer
constructor.

https://tc39.es/proposal-resizablearraybuffer
https://github.com/tc39/test262/blob/main/test/built-ins/ArrayBuffer/options-maxbytelength-diminuitive.js

1 files changed, 47 insertions, 3 deletions

diff --git a/Userland/Libraries/LibJS/Runtime/ArrayBufferConstructor.cpp b/Userland/Libraries/LibJS/Runtime/ArrayBufferConstructor.cpp
index 43318a0328..db1a394e66 100644
--- a/Userland/Libraries/LibJS/Runtime/ArrayBufferConstructor.cpp
+++ b/Userland/Libraries/LibJS/Runtime/ArrayBufferConstructor.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2020, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -46,20 +47,63 @@ ThrowCompletionOr<Value> ArrayBufferConstructor::call()
     return vm.throw_completion<TypeError>(global_object(), ErrorType::ConstructorWithoutNew, vm.names.ArrayBuffer);
 }
 
+// 1.1.6 GetArrayBufferMaxByteLengthOption ( options ), https://tc39.es/proposal-resizablearraybuffer/#sec-getarraybuffermaxbytelengthoption
+static ThrowCompletionOr<Optional<size_t>> get_array_buffer_max_byte_length_option(VM& vm, GlobalObject& global_object, Value options)
+{
+    // 1. If Type(options) is not Object, return empty.
+    if (!options.is_object())
+        return Optional<size_t>();
+
+    // 2. Let maxByteLength be ? Get(options, "maxByteLength").
+    auto max_byte_length = TRY(options.get(global_object, vm.names.maxByteLength));
+
+    // 3. If maxByteLength is undefined, return empty.
+    if (max_byte_length.is_undefined())
+        return Optional<size_t>();
+
+    // 4. Return ? ToIndex(maxByteLength).
+    return TRY(max_byte_length.to_index(global_object));
+}
+
 // 25.1.3.1 ArrayBuffer ( length ), https://tc39.es/ecma262/#sec-arraybuffer-length
+// 1.2.1 ArrayBuffer ( length [, options ] ), https://tc39.es/proposal-resizablearraybuffer/#sec-arraybuffer-constructor
 ThrowCompletionOr<Object*> ArrayBufferConstructor::construct(FunctionObject& new_target)
 {
+    auto& global_object = new_target.realm()->global_object();
     auto& vm = this->vm();
-    auto byte_length_or_error = vm.argument(0).to_index(global_object());
+
+    // 1. If NewTarget is undefined, throw a TypeError exception.
+    // NOTE: See `ArrayBufferConstructor::call()`
+
+    // 2. Let byteLength be ? ToIndex(length).
+    auto byte_length_or_error = vm.argument(0).to_index(global_object);
     if (byte_length_or_error.is_error()) {
         auto error = byte_length_or_error.release_error();
         if (error.value()->is_object() && is<RangeError>(error.value()->as_object())) {
             // Re-throw more specific RangeError
-            return vm.throw_completion<RangeError>(global_object(), ErrorType::InvalidLength, "array buffer");
+            return vm.throw_completion<RangeError>(global_object, ErrorType::InvalidLength, "array buffer");
         }
         return error;
     }
-    return TRY(allocate_array_buffer(global_object(), new_target, byte_length_or_error.release_value()));
+    auto byte_length = byte_length_or_error.release_value();
+
+    // 3. Let requestedMaxByteLength be ? GetArrayBufferMaxByteLengthOption(options).
+    auto options = vm.argument(1);
+    auto requested_max_byte_length_value = TRY(get_array_buffer_max_byte_length_option(vm, global_object, options));
+
+    // 4. If requestedMaxByteLength is empty, then
+    if (!requested_max_byte_length_value.has_value()) {
+        // a. Return ? AllocateArrayBuffer(NewTarget, byteLength).
+        return TRY(allocate_array_buffer(global_object, new_target, byte_length));
+    }
+    auto requested_max_byte_length = requested_max_byte_length_value.release_value();
+
+    // 5. If byteLength > requestedMaxByteLength, throw a RangeError exception.
+    if (byte_length > requested_max_byte_length)
+        return vm.throw_completion<RangeError>(global_object, ErrorType::ByteLengthBeyondRequestedMax);
+
+    // 6. Return ? AllocateArrayBuffer(NewTarget, byteLength, requestedMaxByteLength).
+    return TRY(allocate_array_buffer(global_object, new_target, byte_length, requested_max_byte_length));
 }
 
 // 25.1.4.1 ArrayBuffer.isView ( arg ), https://tc39.es/ecma262/#sec-arraybuffer.isview