lldb/source/Plugins/Process/gdb-remote/GDBRemoteClientBase.h

//===-- GDBRemoteClientBase.h -----------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef liblldb_GDBRemoteClientBase_h_
#define liblldb_GDBRemoteClientBase_h_

#include "GDBRemoteCommunication.h"

#include <condition_variable>

namespace lldb_private
{
namespace process_gdb_remote
{

class GDBRemoteClientBase : public GDBRemoteCommunication
{
public:
    struct ContinueDelegate
    {
        virtual ~ContinueDelegate();
        virtual void
        HandleAsyncStdout(llvm::StringRef out) = 0;
        virtual void
        HandleAsyncMisc(llvm::StringRef data) = 0;
        virtual void
        HandleStopReply() = 0;

        //
        /// Processes async structured data.
        ///
        /// @return
        ///    true if the data was handled; otherwise, false.
        //
        virtual bool
        HandleAsyncStructuredData(const StructuredData::ObjectSP
                                  &object_sp) = 0;
    };

    GDBRemoteClientBase(const char *comm_name, const char *listener_name);

    bool
    SendAsyncSignal(int signo);

    bool
    Interrupt();

    lldb::StateType
    SendContinuePacketAndWaitForResponse(ContinueDelegate &delegate, const UnixSignals &signals,
                                         llvm::StringRef payload, StringExtractorGDBRemote &response);

    PacketResult
    SendPacketAndWaitForResponse(const char *payload, size_t len, StringExtractorGDBRemote &response, bool send_async)
    {
        return SendPacketAndWaitForResponse(llvm::StringRef(payload, len), response, send_async);
    }

    PacketResult
    SendPacketAndWaitForResponse(llvm::StringRef payload, StringExtractorGDBRemote &response, bool send_async);

    bool
    SendvContPacket(llvm::StringRef payload, StringExtractorGDBRemote &response);

    class Lock
    {
    public:
        Lock(GDBRemoteClientBase &comm, bool interrupt);
        ~Lock();

        explicit operator bool() const { return m_acquired; }

        // Whether we had to interrupt the continue thread to acquire the connection.
        bool
        DidInterrupt() const
        {
            return m_did_interrupt;
        }

    private:
        std::unique_lock<std::mutex> m_async_lock;
        GDBRemoteClientBase &m_comm;
        bool m_acquired;
        bool m_did_interrupt;

        void
        SyncWithContinueThread(bool interrupt);
    };

protected:
    PacketResult
    SendPacketAndWaitForResponse(llvm::StringRef payload, StringExtractorGDBRemote &response, const Lock &lock);

    virtual void
    OnRunPacketSent(bool first);

private:
    // Variables handling synchronization between the Continue thread and any other threads
    // wishing to send packets over the connection. Either the continue thread has control over
    // the connection (m_is_running == true) or the connection is free for an arbitrary number of
    // other senders to take which indicate their interest by incrementing m_async_count.
    // Semantics of individual states:
    // - m_continue_packet == false, m_async_count == 0: connection is free
    // - m_continue_packet == true, m_async_count == 0: only continue thread is present
    // - m_continue_packet == true, m_async_count > 0: continue thread has control, async threads
    //   should interrupt it and wait for it to set m_continue_packet to false
    // - m_continue_packet == false, m_async_count > 0: async threads have control, continue
    //   thread needs to wait for them to finish (m_async_count goes down to 0).
    std::mutex m_mutex;
    std::condition_variable m_cv;
    // Packet with which to resume after an async interrupt. Can be changed by an async thread
    // e.g. to inject a signal.
    std::string m_continue_packet;
    // When was the interrupt packet sent. Used to make sure we time out if the stub does not
    // respond to interrupt requests.
    std::chrono::time_point<std::chrono::steady_clock> m_interrupt_time;
    uint32_t m_async_count;
    bool m_is_running;
    bool m_should_stop; // Whether we should resume after a stop.
    // end of continue thread synchronization block

    // This handles the synchronization between individual async threads. For now they just use a
    // simple mutex.
    std::mutex m_async_mutex;

    bool
    ShouldStop(const UnixSignals &signals, StringExtractorGDBRemote &response);

    class ContinueLock
    {
    public:
        enum class LockResult
        {
            Success,
            Cancelled,
            Failed
        };

        explicit ContinueLock(GDBRemoteClientBase &comm);
        ~ContinueLock();
        explicit operator bool() { return m_acquired; }

        LockResult
        lock();

        void
        unlock();

    private:
        GDBRemoteClientBase &m_comm;
        bool m_acquired;
    };
};

} // namespace process_gdb_remote
} // namespace lldb_private

#endif // liblldb_GDBRemoteCommunicationClient_h_