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/*
* Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/TemporaryChange.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Interpreter.h>
#include <LibJS/Runtime/GeneratorObject.h>
#include <LibJS/Runtime/GeneratorPrototype.h>
#include <LibJS/Runtime/GlobalObject.h>
namespace JS {
ThrowCompletionOr<GeneratorObject*> GeneratorObject::create(Realm& realm, Value initial_value, ECMAScriptFunctionObject* generating_function, ExecutionContext execution_context, Bytecode::RegisterWindow frame)
{
auto& vm = realm.vm();
// This is "g1.prototype" in figure-2 (https://tc39.es/ecma262/img/figure-2.png)
Value generating_function_prototype;
if (generating_function->kind() == FunctionKind::Async) {
// We implement async functions by transforming them to generator function in the bytecode
// interpreter. However an async function does not have a prototype and should not be
// changed thus we hardcode the prototype.
generating_function_prototype = realm.global_object().generator_prototype();
} else {
generating_function_prototype = TRY(generating_function->get(vm.names.prototype));
}
auto* generating_function_prototype_object = TRY(generating_function_prototype.to_object(realm.global_object()));
auto object = realm.heap().allocate<GeneratorObject>(realm, realm, *generating_function_prototype_object, move(execution_context));
object->m_generating_function = generating_function;
object->m_frame = move(frame);
object->m_previous_value = initial_value;
return object;
}
GeneratorObject::GeneratorObject(Realm&, Object& prototype, ExecutionContext context)
: Object(prototype)
, m_execution_context(move(context))
{
}
void GeneratorObject::initialize(Realm&)
{
}
void GeneratorObject::visit_edges(Cell::Visitor& visitor)
{
Base::visit_edges(visitor);
visitor.visit(m_generating_function);
visitor.visit(m_previous_value);
}
ThrowCompletionOr<Value> GeneratorObject::next_impl(VM& vm, GlobalObject& global_object, Optional<Value> next_argument, Optional<Value> value_to_throw)
{
auto& realm = *global_object.associated_realm();
auto bytecode_interpreter = Bytecode::Interpreter::current();
VERIFY(bytecode_interpreter);
auto generated_value = [](Value value) -> ThrowCompletionOr<Value> {
if (value.is_object())
return TRY(value.as_object().get("result"));
return value.is_empty() ? js_undefined() : value;
};
auto generated_continuation = [&](Value value) -> ThrowCompletionOr<Bytecode::BasicBlock const*> {
if (value.is_object()) {
auto number_value = TRY(value.as_object().get("continuation"));
return reinterpret_cast<Bytecode::BasicBlock const*>(static_cast<u64>(TRY(number_value.to_double(global_object))));
}
return nullptr;
};
auto previous_generated_value = TRY(generated_value(m_previous_value));
auto result = Object::create(realm, global_object.object_prototype());
result->define_direct_property("value", previous_generated_value, default_attributes);
if (m_done) {
result->define_direct_property("done", Value(true), default_attributes);
return result;
}
// Extract the continuation
auto next_block = TRY(generated_continuation(m_previous_value));
if (!next_block) {
// The generator has terminated, now we can simply return done=true.
m_done = true;
result->define_direct_property("done", Value(true), default_attributes);
return result;
}
// Make sure it's an actual block
VERIFY(!m_generating_function->bytecode_executable()->basic_blocks.find_if([next_block](auto& block) { return block == next_block; }).is_end());
// Temporarily switch to the captured execution context
TRY(vm.push_execution_context(m_execution_context, global_object));
// Pretend that 'yield' returned the passed value, or threw
if (value_to_throw.has_value()) {
bytecode_interpreter->accumulator() = js_undefined();
return throw_completion(value_to_throw.release_value());
}
Bytecode::RegisterWindow* frame = nullptr;
if (m_frame.has_value())
frame = &m_frame.value();
auto next_value = next_argument.value_or(js_undefined());
if (frame)
frame->registers[0] = next_value;
else
bytecode_interpreter->accumulator() = next_value;
auto next_result = bytecode_interpreter->run_and_return_frame(*m_generating_function->bytecode_executable(), next_block, frame);
vm.pop_execution_context();
if (!m_frame.has_value())
m_frame = move(*next_result.frame);
m_previous_value = TRY(move(next_result.value));
m_done = TRY(generated_continuation(m_previous_value)) == nullptr;
result->define_direct_property("value", TRY(generated_value(m_previous_value)), default_attributes);
result->define_direct_property("done", Value(m_done), default_attributes);
return result;
}
}
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