LibJS: Define AllocateTypedArrayBuffer AO out of line

Not only is it easier to compare to the spec when defined out of line,
but this AO was implemented inside other AOs twice.

Userland/Libraries/LibJS/Runtime/TypedArray.cpp

@@ -228,19 +228,12 @@ static ThrowCompletionOr<void> initialize_typed_array_from_typed_array(GlobalObj
     return {};
 }
 
-// 23.2.5.1.5 InitializeTypedArrayFromArrayLike, https://tc39.es/ecma262/#sec-initializetypedarrayfromarraylike
+// 23.2.5.1.6 AllocateTypedArrayBuffer ( O, length ), https://tc39.es/ecma262/#sec-allocatetypedarraybuffer
 template<typename T>
-static ThrowCompletionOr<void> initialize_typed_array_from_array_like(GlobalObject& global_object, TypedArray<T>& typed_array, Object const& array_like)
+static ThrowCompletionOr<void> allocate_typed_array_buffer(GlobalObject& global_object, TypedArray<T>& typed_array, size_t length)
 {
     auto& vm = global_object.vm();
 
-    // 1. Let len be ? LengthOfArrayLike(arrayLike).
-    auto length = TRY(length_of_array_like(global_object, array_like));
-
-    // 2. Perform ? AllocateTypedArrayBuffer(O, len).
-
-    // 23.2.5.1.6 AllocateTypedArrayBuffer ( O, length )
-
     // Enforce 2GB "Excessive Length" limit
     if (length > NumericLimits<i32>::max() / sizeof(T))
         return vm.template throw_completion<RangeError>(global_object, ErrorType::InvalidLength, "typed array");
@@ -271,9 +264,21 @@ static ThrowCompletionOr<void> initialize_typed_array_from_array_like(GlobalObje
     // 9. Set O.[[ArrayLength]] to length.
     typed_array.set_array_length(length);
 
-    // 10. Return O.
-    // End of 23.2.5.1.6
+    // 10. Return unused.
+    return {};
+}
+
+// 23.2.5.1.5 InitializeTypedArrayFromArrayLike, https://tc39.es/ecma262/#sec-initializetypedarrayfromarraylike
+template<typename T>
+static ThrowCompletionOr<void> initialize_typed_array_from_array_like(GlobalObject& global_object, TypedArray<T>& typed_array, Object const& array_like)
+{
+    // 1. Let len be ? LengthOfArrayLike(arrayLike).
+    auto length = TRY(length_of_array_like(global_object, array_like));
 
+    // 2. Perform ? AllocateTypedArrayBuffer(O, len).
+    TRY(allocate_typed_array_buffer(global_object, typed_array, length));
+
+    // 3. Let k be 0.
     // 4. Repeat, while k < len,
     for (size_t k = 0; k < length; k++) {
         // a. Let Pk be ! ToString(𝔽(k)).
@@ -286,6 +291,7 @@ static ThrowCompletionOr<void> initialize_typed_array_from_array_like(GlobalObje
         // d. Set k to k + 1.
     }
 
+    // 5. Return unused.
     return {};
 }
 
@@ -293,27 +299,11 @@ static ThrowCompletionOr<void> initialize_typed_array_from_array_like(GlobalObje
 template<typename T>
 static ThrowCompletionOr<void> initialize_typed_array_from_list(GlobalObject& global_object, TypedArray<T>& typed_array, MarkedVector<Value> const& list)
 {
-    auto& vm = global_object.vm();
-
     // 1. Let len be the number of elements in values.
     auto length = list.size();
 
     // 2. Perform ? AllocateTypedArrayBuffer(O, len).
-
-    // Enforce 2GB "Excessive Length" limit
-    if (length > NumericLimits<i32>::max() / sizeof(T))
-        return vm.template throw_completion<RangeError>(global_object, ErrorType::InvalidLength, "typed array");
-
-    auto element_size = typed_array.element_size();
-    if (Checked<size_t>::multiplication_would_overflow(element_size, length))
-        return vm.template throw_completion<RangeError>(global_object, ErrorType::InvalidLength, "typed array");
-    auto byte_length = element_size * length;
-    auto array_buffer = TRY(allocate_array_buffer(global_object, *global_object.array_buffer_constructor(), byte_length));
-
-    typed_array.set_viewed_array_buffer(array_buffer);
-    typed_array.set_byte_length(byte_length);
-    typed_array.set_byte_offset(0);
-    typed_array.set_array_length(length);
+    TRY(allocate_typed_array_buffer(global_object, typed_array, length));
 
     // 3. Let k be 0.
     // 4. Repeat, while k < len,
@@ -328,6 +318,8 @@ static ThrowCompletionOr<void> initialize_typed_array_from_list(GlobalObject& gl
         // d. Set k to k + 1.
     }
 
+    // 5. Assert: values is now an empty List.
+    // 6. Return unused.
     return {};
 }