FileHelpers.cpp

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#include "utils/FileHelpers.hpp"
 
#include "utils/ErrorHelpers.hpp"
 
#include <format>
#include <iostream>
 
#include <fcntl.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <unistd.h>
 
#include <spdlog/spdlog.h>

constexpr int SLEEP_INTERVAL_MS = 50;
 
void FileMonitor::threadFunc(const std::stop_token &stopToken) const noexcept
{
    while (!stopToken.stop_requested())
    {
        // Buffer for reading events
        unsigned int nBytes = 0;
        if (ioctl(_fDescriptor, FIONREAD, &nBytes) < 0)
        {
            spdlog::error("Failed to get available events for file monitoring: {}", getErrnoString(errno));
        }
 
        auto buffer = std::vector<char>(nBytes + 1, '\0');
        auto nRead = read(_fDescriptor, buffer.data(), nBytes);
        if (nRead < 0 && errno != EAGAIN)
        {
            spdlog::error("Failed to read events for file monitoring: {}", getErrnoString(errno));
        }
        else if (nRead == 0)
        {
            spdlog::debug("No events read for file monitoring");
        }
 
        ssize_t idx = 0;
        while (_notifyCallback && idx < nRead)
        {
            const auto *event = std::bit_cast<inotify_event *>(&buffer[static_cast<size_t>(idx)]);
 
            // Check if file notify type matches
            if ((event->mask & _notifyEvents) != 0)
            {
                _notifyCallback(_userPtr);
                break;
            }
 
            idx += static_cast<ssize_t>(sizeof(inotify_event) + event->len);
        }
 
        std::this_thread::sleep_for(std::chrono::milliseconds(SLEEP_INTERVAL_MS));
    }
}
 
FileMonitor::FileMonitor(std::filesystem::path filePath, uint32_t notifyEvents)
    : _fDescriptor(inotify_init()), _filePath(std::move(filePath)), _notifyEvents(notifyEvents)
{
    if (_fDescriptor < 0)
    {
        throw std::ios_base::failure("Failed to initialize inotify");
    }
 
    _wDescriptor = inotify_add_watch(_fDescriptor, _filePath.c_str(), notifyEvents);
    if (_wDescriptor < 0)
    {
        close(_fDescriptor);
        throw std::ios_base::failure("Failed to add watch descriptor");
    }
 
    if (const int flags = fcntl(_fDescriptor, F_GETFL);
        flags < 0 || fcntl(_fDescriptor, F_SETFL, flags | O_NONBLOCK) < 0)
    {
        close(_fDescriptor);
        throw std::ios_base::failure("Failed to set file descriptor to non-blocking mode");
    }
 
    _thread = std::make_unique<std::jthread>([this](const std::stop_token &sToken) { threadFunc(sToken); });
}
 
FileMonitor::~FileMonitor()
{
    if (_thread)
    {
        _thread.reset();
    }
 
    // Remove watch descriptor first
    if (_wDescriptor >= 0)
    {
        if (inotify_rm_watch(_fDescriptor, _wDescriptor) < 0)
        {
            try
            {
                spdlog::error("Failed to remove watch descriptor: {}", getErrnoString(errno));
            }
            catch (const std::exception &e)
            {
                std::cerr << "Failed to remove watch descriptor and also logger thrown an exception: "
                          << getErrnoString(errno) << " " << e.what() << '\n';
            }
        }
        _wDescriptor = -1;
    }
 
    // Then close the file descriptor
    if (_fDescriptor >= 0)
    {
        if (close(_fDescriptor) < 0)
        {
            try
            {
                spdlog::error("Failed to close file descriptor: {}", getErrnoString(errno));
            }
            catch (const std::exception &e)
            {
                std::cerr << "Failed to close file descriptor and also logger thrown an exception: "
                          << getErrnoString(errno) << " " << e.what() << '\n';
            }
        }
        _fDescriptor = -1;
    }
}