DCLibraries/src/shared_mem_buffer.cpp

#include "shared_mem_buffer.h"

#include <QDebug>
#include <QFile>
#include <QString>
#include <QTextStream>
#include <QDateTime>
#include <QCoreApplication>
#include <atomic>
#include <algorithm>

#ifdef QT_POSIX_IPC
    // The POSIX backend can be explicitly selected using the -feature-ipc_posix
    // option to the Qt configure script. If it is enabled, the QT_POSIX_IPC
    // macro will be defined. -> we use SystemV shared memory
#error "QT_POSIX_IPC defined"
#else
#ifdef linux
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>    // ftok
#endif
#endif

//static bool shdMemFirstUse;

static QString read1stLineOfFile(QString fileName) { // read for instance /etc/os-release
    QFile f(fileName);
    if (f.exists()) {
        if (f.open(QIODevice::ReadOnly | QIODevice::Text)) {
            QTextStream in(&f);
            in.setCodec("UTF-8");
            while(!in.atEnd()) {
                return in.readLine();
            }
        }
    }
    return "N/A";
}


//QSharedMemory *SharedMemBuffer::getShm(std::size_t size) {
QSharedMemory *SharedMem::getShm(std::size_t size) {
    static QSharedMemory shMem;
    if (size > 0) {
#ifdef linux
        static const long nativeKey = ftok("/etc/os-release", 'H');
        static const QString fkey = std::to_string(nativeKey).c_str();
        //static const QString fkey = "0123456?000=7";
#else
        static const QString fkey = "0123456?000=9";
#endif

        qCritical() << __func__ << ":" << __LINE__ << ": size" << size;

        shMem.setKey(fkey);
        if (!shMem.isAttached()) {
            if (shMem.create(size)) {
                qCritical() << __func__ << ":" << __LINE__ << ": created shared memory";

#ifdef linux
                if ((size != (std::size_t)shMem.size()) || (sizeof(SharedMem) != shMem.size())) {
                    qCritical() << __func__ << ":" << __LINE__
                                << "size=" << size
                                << "shMem.size=" << shMem.size()
                                << "sizeof(SharedMem)=" << sizeof(SharedMem)
                                << "ABOUT TO REBOOT SYSTEM...";
                    if (system("reboot")) {
                        // reboot system -> shared memory re-created
                    }
                }

                struct SharedMem *sh = (SharedMem *)(shMem.data());

                memset(sh->indat_HWversion, 0x00, sizeof(sh->indat_HWversion));
                memset(sh->indat_SWversion, 0x00, sizeof(sh->indat_SWversion));

                memset(sh->os_release, 0x00, sizeof(sh->os_release));
                memset(sh->date_of_creation, 0x00, sizeof(sh->date_of_creation));
                memset(sh->creator, 0x00, sizeof(sh->creator));

                QString const &os_release = read1stLineOfFile("/etc/os-release");
                strncpy(sh->os_release, os_release.toStdString().c_str(),
                        std::min((int)os_release.size(), (int)sizeof(sh->os_release)-1));

                QString const &currentDateTime = QDateTime::currentDateTime().toString(Qt::ISODate);
                char const *current = currentDateTime.toUtf8().constData();
                strncpy(sh->date_of_creation, current,
                        std::min((int)strlen(current), (int)sizeof(sh->date_of_creation)-1));

                QString const &appPid = QString("%1 (%2)").arg(QCoreApplication::applicationName())
                                                          .arg(QCoreApplication::applicationPid());

                strncpy(sh->creator, appPid.toStdString().c_str(),
                        std::min((int)strlen(appPid.toStdString().c_str()),
                                 (int)sizeof(sh->creator)-1));

                qCritical() << "os-release:" << sh->os_release;
                qCritical() << "   creator:" << sh->creator;
                qCritical() << "      date:" << sh->date_of_creation;

#else
                Q_ASSERT_X(size != shMem.size(), "compare sizes", "sizes different");
                Q_ASSERT_X(sizeof(SharedMem) != shMem.size(), "compare sizes", "sizes different");
#endif
                return &shMem;
            } else {
                if (shMem.error() == QSharedMemory::AlreadyExists) {
                    if (shMem.attach()) {
#ifdef linux
                        if ((size != (std::size_t)shMem.size()) || (sizeof(SharedMem) != shMem.size())) {
                            qCritical() << __func__ << ":" << __LINE__
                                        << "size=" << size
                                        << "shMem.size=" << shMem.size()
                                        << "sizeof(SharedMem)=" << sizeof(SharedMem)
                                        << "ABOUT TO REBOOT SYSTEM...";
                            if (system("reboot")) {
                                // reboot system -> shared memory re-created
                            }
                        }
#else
                        Q_ASSERT_X(size != shMem.size(), "compare sizes", "sizes different");
                        Q_ASSERT_X(sizeof(SharedMem) != shMem.size(), "compare sizes", "sizes different");
#endif

                        QString const &appPid = QString("%1 (%2)").arg(QCoreApplication::applicationName())
                                                                  .arg(QCoreApplication::applicationPid());

                        qCritical() << __func__ << ":" << __LINE__ << appPid << "attached shared memory";

                        struct SharedMem const *sh = (SharedMem const *)(shMem.data());
                        qCritical() << "os-release:" << sh->os_release;
                        qCritical() << "   creator:" << sh->creator;
                        qCritical() << "      date:" << sh->date_of_creation;

                        return &shMem;
                    }
                }
            }
            qCritical() << shMem.nativeKey() << shMem.key() << shMem.data()
                        << shMem.error() << shMem.errorString();
            return nullptr;
        } else {
            qCritical() << __func__ << ":" << __LINE__ << "shared memory already attached";

            struct SharedMem const *sh = (SharedMem const *)(shMem.data());
            qCritical() << "os-release:" << sh->os_release;
            qCritical() << "   creator:" << sh->creator;
            qCritical() << "      date:" << sh->date_of_creation;
        }
    }
    return &shMem;
}


// std::atomic_bool SharedMemBuffer::__sharedMemLocked{false};
/*
//QSharedMemory *SharedMemBuffer::getShm(std::size_t size) {
QSharedMemory *SharedMem::getShm(std::size_t size) {

    static QSharedMemory shMem;
    if (size > 0) {
#ifdef __linux__
        static const long nativeKey = ftok("/etc/os-release", 'H');
        static const QString fkey = std::to_string(nativeKey).c_str();
#else
        static const QString fkey = "0123456?000=9";
#endif
        shdMemFirstUse=false;
        shMem.setKey(fkey);
        if (!shMem.isAttached())
        {
            if (shMem.create(size))
            {
                //  sm was created successful, did not exist before
                shdMemFirstUse=true;
                return &shMem;
            } else
            {
                // create was false because mem already existed
                if (shMem.error() == QSharedMemory::AlreadyExists)
                {
                    if (shMem.attach())
                    {
                        return &shMem;
                    }
                }
            }
            qCritical() << shMem.nativeKey() << shMem.key() << shMem.data()
                        << shMem.error() << shMem.errorString();
            return nullptr;
        }
    }
    return &shMem;
}


bool shdMem_firstUse(void)
{
    return shdMemFirstUse;
}
*/