watch.hpp

#pragma once

#include <systemd/sd-event.h>
#include <unistd.h>

namespace openpower
{
namespace software
{
namespace updater
{

/* Need a custom deleter for freeing up sd_event_source */
struct EventSourceDeleter
{
    void operator()(sd_event_source* eventSource) const
    {
        eventSource = sd_event_source_unref(eventSource);
    }
};
using EventSourcePtr = std::unique_ptr<sd_event_source, EventSourceDeleter>;

/** @struct CustomFd
 *
 *  RAII wrapper for file descriptor.
 */
struct CustomFd
{
    public:
        CustomFd() = delete;
        CustomFd(const CustomFd&) = delete;
        CustomFd& operator=(const CustomFd&) = delete;
        CustomFd(CustomFd&&) = delete;
        CustomFd& operator=(CustomFd&&) = delete;

        /** @brief Saves File descriptor and uses it to do file operation
         *
         *  @param[in] fd - File descriptor
         */
        CustomFd(int fd) : fd(fd) {}

        ~CustomFd()
        {
            if (fd >= 0)
            {
                close(fd);
            }
        }

        int operator()() const
        {
            return fd;
        }

    private:
        /** @brief File descriptor */
        int fd = -1;
};

/** @class Watch
 *
 *  @brief Adds inotify watch on PNOR symlinks file to monitor for changes in
 *         "running" PNOR version
 *
 *  The inotify watch is hooked up with sd-event, so that on call back,
 *  appropriate actions related to a change in the "running" PNOR version
 *  can be taken.
 */
class Watch
{
    public:
        /** @brief ctor - hook inotify watch with sd-event
         *
         *  @param[in] loop - sd-event object
         *  @param[in] functionalCallback - The callback function for updating
         *                                  the functional associations.
         */
        Watch(sd_event* loop,
              std::function<void(std::string&)> functionalCallback);

        Watch(const Watch&) = delete;
        Watch& operator=(const Watch&) = delete;
        Watch(Watch&&) = delete;
        Watch& operator=(Watch&&) = delete;

        /** @brief dtor - remove inotify watch
         */
        ~Watch();

    private:
        /** @brief sd-event callback
         *
         *  @param[in] s - event source, floating (unused) in our case
         *  @param[in] fd - inotify fd
         *  @param[in] revents - events that matched for fd
         *  @param[in] userdata - pointer to Watch object
         *  @returns 0 on success, -1 on fail
         */
        static int callback(sd_event_source* s,
                            int fd,
                            uint32_t revents,
                            void* userdata);

        /**  initialize an inotify instance and returns file descriptor */
        int inotifyInit();

        /** @brief PNOR symlink file watch descriptor */
        int wd = -1;

        /** @brief event source */
        EventSourcePtr eventSource;

        /** @brief The callback function for updating the
                   functional associations. */
        std::function<void(std::string&)> functionalCallback;

        /** @brief inotify file descriptor */
        CustomFd fd;
};

} // namespace updater
} // namespace software
} // namespace openpower