source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp

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


#include "GDBRemoteCommunication.h"

// C Includes
// C++ Includes
// Other libraries and framework includes
#include "lldb/Core/Log.h"
#include "lldb/Core/StreamString.h"
#include "lldb/Host/TimeValue.h"

// Project includes
#include "ProcessGDBRemoteLog.h"

using namespace lldb;
using namespace lldb_private;

//----------------------------------------------------------------------
// GDBRemoteCommunication constructor
//----------------------------------------------------------------------
GDBRemoteCommunication::GDBRemoteCommunication(const char *comm_name, const char *listener_name) :
    Communication(comm_name),
    m_packet_timeout (1),
    m_rx_packet_listener (listener_name),
    m_sequence_mutex (Mutex::eMutexTypeRecursive),
    m_public_is_running (false),
    m_private_is_running (false)
{
    m_rx_packet_listener.StartListeningForEvents(this,
                                                 Communication::eBroadcastBitPacketAvailable  |
                                                 Communication::eBroadcastBitReadThreadDidExit);
}

//----------------------------------------------------------------------
// Destructor
//----------------------------------------------------------------------
GDBRemoteCommunication::~GDBRemoteCommunication()
{
    m_rx_packet_listener.StopListeningForEvents(this,
                                                Communication::eBroadcastBitPacketAvailable  |
                                                Communication::eBroadcastBitReadThreadDidExit);
    if (IsConnected())
    {
        StopReadThread();
        Disconnect();
    }
}


char
GDBRemoteCommunication::CalculcateChecksum (const char *payload, size_t payload_length)
{
    int checksum = 0;

    // We only need to compute the checksum if we are sending acks
    if (GetSendAcks ())
    {
        for (size_t i = 0; i < payload_length; ++i)
            checksum += payload[i];
    }
    return checksum & 255;
}

size_t
GDBRemoteCommunication::SendAck ()
{
    LogSP log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
    if (log)
        log->Printf ("send packet: +");
    ConnectionStatus status = eConnectionStatusSuccess;
    char ack_char = '+';
    return Write (&ack_char, 1, status, NULL) == 1;
}

size_t
GDBRemoteCommunication::SendNack ()
{
    LogSP log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
    if (log)
        log->Printf ("send packet: -");
    ConnectionStatus status = eConnectionStatusSuccess;
    char nack_char = '-';
    return Write (&nack_char, 1, status, NULL) == 1;
}

size_t
GDBRemoteCommunication::SendPacket (const char *payload)
{
    Mutex::Locker locker(m_sequence_mutex);
    return SendPacketNoLock (payload, ::strlen (payload));
}

size_t
GDBRemoteCommunication::SendPacket (const char *payload, size_t payload_length)
{
    Mutex::Locker locker(m_sequence_mutex);
    return SendPacketNoLock (payload, payload_length);
}

size_t
GDBRemoteCommunication::SendPacketNoLock (const char *payload, size_t payload_length)
{
    if (IsConnected())
    {
        StreamString packet(0, 4, eByteOrderBig);

        packet.PutChar('$');
        packet.Write (payload, payload_length);
        packet.PutChar('#');
        packet.PutHex8(CalculcateChecksum (payload, payload_length));

        LogSP log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
        if (log)
            log->Printf ("send packet: %s", packet.GetData());
        ConnectionStatus status = eConnectionStatusSuccess;
        size_t bytes_written = Write (packet.GetData(), packet.GetSize(), status, NULL);
        if (bytes_written == packet.GetSize())
        {
            if (GetSendAcks ())
            {
                if (GetAck () != '+')
                    return 0;
            }
        }
        else
        {
            LogSP log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
            if (log)
                log->Printf ("error: failed to send packet: %s", packet.GetData());
        }
        return bytes_written;
    }
    return 0;
}

char
GDBRemoteCommunication::GetAck ()
{
    StringExtractorGDBRemote packet;
    if (WaitForPacket (packet, m_packet_timeout) == 1)
        return packet.GetChar();
    return 0;
}

bool
GDBRemoteCommunication::GetSequenceMutex (Mutex::Locker& locker)
{
    return locker.TryLock (m_sequence_mutex.GetMutex());
}


bool
GDBRemoteCommunication::WaitForNotRunningPrivate (const TimeValue *timeout_ptr)
{
    return m_private_is_running.WaitForValueEqualTo (false, timeout_ptr, NULL);
}

size_t
GDBRemoteCommunication::WaitForPacket (StringExtractorGDBRemote &packet, uint32_t timeout_seconds)
{
    Mutex::Locker locker(m_sequence_mutex);
    TimeValue timeout_time;
    timeout_time = TimeValue::Now();
    timeout_time.OffsetWithSeconds (timeout_seconds);
    return WaitForPacketNoLock (packet, &timeout_time);
}

size_t
GDBRemoteCommunication::WaitForPacket (StringExtractorGDBRemote &packet, const TimeValue* timeout_time_ptr)
{
    Mutex::Locker locker(m_sequence_mutex);
    return WaitForPacketNoLock (packet, timeout_time_ptr);
}

size_t
GDBRemoteCommunication::WaitForPacketNoLock (StringExtractorGDBRemote &packet, const TimeValue* timeout_time_ptr)
{
    bool checksum_error = false;
    packet.Clear ();

    EventSP event_sp;

    if (m_rx_packet_listener.WaitForEvent (timeout_time_ptr, event_sp))
    {
        const uint32_t event_type = event_sp->GetType();
        if (event_type | Communication::eBroadcastBitPacketAvailable)
        {
            const EventDataBytes *event_bytes = EventDataBytes::GetEventDataFromEvent(event_sp.get());
            if (event_bytes)
            {
                const char * packet_data =  (const char *)event_bytes->GetBytes();
                LogSP log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
                if (log)
                    log->Printf ("read packet: %s", packet_data);
                const size_t packet_size =  event_bytes->GetByteSize();
                if (packet_data && packet_size > 0)
                {
                    std::string &packet_str = packet.GetStringRef();
                    if (packet_data[0] == '$')
                    {
                        bool success = false;
                        if (packet_size < 4)
                            ::fprintf (stderr, "Packet that starts with $ is too short: '%s'\n", packet_data);
                        else if (packet_data[packet_size-3] != '#' || 
                                 !::isxdigit (packet_data[packet_size-2]) || 
                                 !::isxdigit (packet_data[packet_size-1]))
                            ::fprintf (stderr, "Invalid checksum footer for packet: '%s'\n", packet_data);
                        else
                            success = true;
                        
                        if (success)
                            packet_str.assign (packet_data + 1, packet_size - 4);
                        if (GetSendAcks ())
                        {
                            char packet_checksum = strtol (&packet_data[packet_size-2], NULL, 16);
                            char actual_checksum = CalculcateChecksum (&packet_str[0], packet_str.size());
                            checksum_error = packet_checksum != actual_checksum;
                            // Send the ack or nack if needed
                            if (checksum_error || !success)
                                SendNack();
                            else
                                SendAck();
                        }
                    }
                    else
                    {
                        packet_str.assign (packet_data, packet_size);
                    }
                    return packet_str.size();
                }
            }
        }
        else if (Communication::eBroadcastBitReadThreadDidExit)
        {
            // Our read thread exited on us so just fall through and return zero...
        }
    }
    return 0;
}

void
GDBRemoteCommunication::AppendBytesToCache (const uint8_t *src, size_t src_len, bool broadcast, 
                                            ConnectionStatus status)
{
    // Put the packet data into the buffer in a thread safe fashion
    Mutex::Locker locker(m_bytes_mutex);
    m_bytes.append ((const char *)src, src_len);

    // Parse up the packets into gdb remote packets
    while (!m_bytes.empty())
    {
        // end_idx must be one past the last valid packet byte. Start
        // it off with an invalid value that is the same as the current
        // index.
        size_t end_idx = 0;

        switch (m_bytes[0])
        {
            case '+':       // Look for ack
            case '-':       // Look for cancel
            case '\x03':    // ^C to halt target
                end_idx = 1;  // The command is one byte long...
                break;

            case '$':
                // Look for a standard gdb packet?
                end_idx = m_bytes.find('#');
                if (end_idx != std::string::npos)
                {
                    if (end_idx + 2 < m_bytes.size())
                    {
                        end_idx += 3;
                    }
                    else
                    {
                        // Checksum bytes aren't all here yet
                        end_idx = std::string::npos;
                    }
                }
                break;

            default:
                break;
        }

        if (end_idx == std::string::npos)
        {
            //ProcessGDBRemoteLog::LogIf (GDBR_LOG_PACKETS | GDBR_LOG_VERBOSE, "GDBRemoteCommunication::%s packet not yet complete: '%s'",__FUNCTION__, m_bytes.c_str());
            return;
        }
        else if (end_idx > 0)
        {
            // We have a valid packet...
            assert (end_idx <= m_bytes.size());
            std::auto_ptr<EventDataBytes> event_bytes_ap (new EventDataBytes (&m_bytes[0], end_idx));
            ProcessGDBRemoteLog::LogIf (GDBR_LOG_COMM, "got full packet: %s", event_bytes_ap->GetBytes());
            BroadcastEvent (eBroadcastBitPacketAvailable, event_bytes_ap.release());
            m_bytes.erase(0, end_idx);
        }
        else
        {
            assert (1 <= m_bytes.size());
            ProcessGDBRemoteLog::LogIf (GDBR_LOG_COMM, "GDBRemoteCommunication::%s tossing junk byte at %c",__FUNCTION__, m_bytes[0]);
            m_bytes.erase(0, 1);
        }
    }
}