Checkout with Multiple Addresses and Onepage

Question

Checkout with Multiple Addresses and Onepage. Both save at sales_order table in database. But I don't know what function it call to save at sales_order table. Who can help me?

This is my di.xml

<config>
    <type name="Magento\Multishipping\Model\Checkout\Type\Multishipping">
        <plugin name="logging-checkout-multi" type="TTV\OrderLog\Plugin\Log" sortOrder="1"/>
    </type>
    <type name="Magento\Checkout\Model\PaymentInformationManagement">
        <plugin name="logging-checkout" type="TTV\OrderLog\Plugin\Log" sortOrder="2"/>
    </type>
</config>

function in TTV\OrderLog\Plugin|Log

    public function beforeSavePaymentInformationAndPlaceOrder()
    {
        $this->_log->pushHandler(new \Monolog\Handler\StreamHandler('var/log/information.log'));
        $productList = $this->_sessionCheckout->getQuote()->getAllVisibleItems();
        foreach ($productList as $product) {
            $productName = $product->getName();
            $productQty = $product->getQty();
            $productPrice = $product->getPrice();
            $this->_log->info("Product Name: " . $productName . " - " . "Product Quantity: " . $productQty . " - " . "Product Price: " . $productPrice);
        }
    }

Answer 1

1) For the multishipping:

vendor/magento/module-multishipping/Controller/Checkout/OverviewPost.php

 public function execute()
{
    ......
    $this->_getCheckout()->createOrders();
    ......
}

2) For the onepage checkout, Magento uses API: /V1/carts/mine/payment-information

vendor/magento/module-checkout/Model/PaymentInformationManagement.php

public function savePaymentInformationAndPlaceOrder(
        $cartId,
        \Magento\Quote\Api\Data\PaymentInterface $paymentMethod,
        \Magento\Quote\Api\Data\AddressInterface $billingAddress = null
    ) {
        $this->savePaymentInformation($cartId, $paymentMethod, $billingAddress);
        return $this->cartManagement->placeOrder($cartId);
}