serenity/Libraries/LibCore/CoreIPCClient.h

#pragma once

#include <LibCore/CEvent.h>
#include <LibCore/CEventLoop.h>
#include <LibCore/CLocalSocket.h>
#include <LibCore/CNotifier.h>
#include <LibCore/CSyscallUtils.h>
#include <LibIPC/IMessage.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

//#define CIPC_DEBUG

namespace IPC {
namespace Client {

    template<typename LocalEndpoint, typename PeerEndpoint>
    class ConnectionNG : public CObject {
    public:
        ConnectionNG(LocalEndpoint& local_endpoint, const StringView& address)
            : m_local_endpoint(local_endpoint)
            , m_connection(CLocalSocket::construct(this))
            , m_notifier(CNotifier::construct(m_connection->fd(), CNotifier::Read, this))
        {
            // We want to rate-limit our clients
            m_connection->set_blocking(true);
            m_notifier->on_ready_to_read = [this] {
                drain_messages_from_server();
            };

            int retries = 100000;
            while (retries) {
                if (m_connection->connect(CSocketAddress::local(address))) {
                    break;
                }

                dbgprintf("Client::Connection: connect failed: %d, %s\n", errno, strerror(errno));
                usleep(10000);
                --retries;
            }
            ASSERT(m_connection->is_connected());
        }

        virtual void handshake() = 0;

        void set_server_pid(pid_t pid) { m_server_pid = pid; }
        pid_t server_pid() const { return m_server_pid; }
        void set_my_client_id(int id) { m_my_client_id = id; }
        int my_client_id() const { return m_my_client_id; }

        template<typename MessageType>
        OwnPtr<MessageType> wait_for_specific_message()
        {
            // Double check we don't already have the event waiting for us.
            // Otherwise we might end up blocked for a while for no reason.
            for (ssize_t i = 0; i < m_unprocessed_messages.size(); ++i) {
                if (m_unprocessed_messages[i]->id() == MessageType::static_message_id()) {
                    auto message = move(m_unprocessed_messages[i]);
                    m_unprocessed_messages.remove(i);
                    return message;
                }
            }
            for (;;) {
                fd_set rfds;
                FD_ZERO(&rfds);
                FD_SET(m_connection->fd(), &rfds);
                int rc = CSyscallUtils::safe_syscall(select, m_connection->fd() + 1, &rfds, nullptr, nullptr, nullptr);
                if (rc < 0) {
                    perror("select");
                }
                ASSERT(rc > 0);
                ASSERT(FD_ISSET(m_connection->fd(), &rfds));
                if (!drain_messages_from_server())
                    return nullptr;
                for (ssize_t i = 0; i < m_unprocessed_messages.size(); ++i) {
                    if (m_unprocessed_messages[i]->id() == MessageType::static_message_id()) {
                        auto message = move(m_unprocessed_messages[i]);
                        m_unprocessed_messages.remove(i);
                        return message;
                    }
                }
            }
        }

        bool post_message(const IMessage& message)
        {
            auto buffer = message.encode();
            int nwritten = write(m_connection->fd(), buffer.data(), (size_t)buffer.size());
            if (nwritten < 0) {
                perror("write");
                ASSERT_NOT_REACHED();
                return false;
            }
            ASSERT(nwritten == buffer.size());
            return true;
        }

        template<typename RequestType, typename... Args>
        OwnPtr<typename RequestType::ResponseType> send_sync(Args&&... args)
        {
            bool success = post_message(RequestType(forward<Args>(args)...));
            ASSERT(success);
            auto response = wait_for_specific_message<typename RequestType::ResponseType>();
            ASSERT(response);
            return response;
        }

    private:
        bool drain_messages_from_server()
        {
            Vector<u8> bytes;
            for (;;) {
                u8 buffer[4096];
                ssize_t nread = recv(m_connection->fd(), buffer, sizeof(buffer), MSG_DONTWAIT);
                if (nread < 0) {
                    if (errno == EAGAIN)
                        break;
                    perror("read");
                    exit(1);
                    return false;
                }
                if (nread == 0) {
                    dbg() << "EOF on IPC fd";
                    // FIXME: Dying is definitely not always appropriate!
                    exit(1);
                    return false;
                }
                bytes.append(buffer, nread);
            }

            size_t decoded_bytes = 0;
            for (size_t index = 0; index < (size_t)bytes.size(); index += decoded_bytes) {
                auto remaining_bytes = ByteBuffer::wrap(bytes.data() + index, bytes.size() - index);
                if (auto message = LocalEndpoint::decode_message(remaining_bytes, decoded_bytes)) {
                    m_local_endpoint.handle(*message);
                } else if (auto message = PeerEndpoint::decode_message(remaining_bytes, decoded_bytes)) {
                    m_unprocessed_messages.append(move(message));
                } else {
                    ASSERT_NOT_REACHED();
                }
                ASSERT(decoded_bytes);
            }
            return true;
        }

        LocalEndpoint& m_local_endpoint;
        RefPtr<CLocalSocket> m_connection;
        RefPtr<CNotifier> m_notifier;
        Vector<OwnPtr<IMessage>> m_unprocessed_messages;
        int m_server_pid { -1 };
        int m_my_client_id { -1 };
    };

} // Client
} // IPC