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ladybird/Libraries/LibJS/Runtime/StringIterator.cpp
Aliaksandr Kalenik 285bc005cb LibJS: Do more comprehensive check if next() fast path is possible
Before this change each built-in iterator object has a boolean
`m_next_method_was_redefined`. If user code later changed the iterator’s
prototype (e.g. `Object.setPrototypeOf()`), we still believed the
built-in fast-path was safe and skipped the user supplied override,
producing wrong results.

With this change
`BuiltinIterator::as_builtin_iterator_if_next_is_not_redefined()` looks
up the current `next` property and verifies that it is still the
built-in native function.
2025-06-02 00:15:36 +02:00

63 lines
1.7 KiB
C++

/*
* Copyright (c) 2020, Matthew Olsson <mattco@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Utf8View.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/StringIterator.h>
namespace JS {
GC_DEFINE_ALLOCATOR(StringIterator);
GC::Ref<StringIterator> StringIterator::create(Realm& realm, String string)
{
return realm.create<StringIterator>(move(string), realm.intrinsics().string_iterator_prototype());
}
StringIterator::StringIterator(String string, Object& prototype)
: Object(ConstructWithPrototypeTag::Tag, prototype)
, m_string(move(string))
, m_iterator(Utf8View(m_string).begin())
{
}
BuiltinIterator* StringIterator::as_builtin_iterator_if_next_is_not_redefined(IteratorRecord const& iterator_record)
{
if (iterator_record.next_method.is_object()) {
auto const& next_function = iterator_record.next_method.as_object();
if (next_function.is_native_function()) {
auto const& native_function = static_cast<NativeFunction const&>(next_function);
if (native_function.is_string_prototype_next_builtin())
return this;
}
}
return nullptr;
}
ThrowCompletionOr<void> StringIterator::next(VM& vm, bool& done, Value& value)
{
if (m_done) {
done = true;
value = js_undefined();
return {};
}
if (m_iterator.done()) {
m_done = true;
done = true;
value = js_undefined();
return {};
}
auto code_point = String::from_code_point(*m_iterator);
++m_iterator;
value = PrimitiveString::create(vm, move(code_point));
return {};
}
}