utils: introduce helper class for file descriptors

src/utils/CMakeLists.txt

@@ -3,6 +3,7 @@ target_sources(kwin PRIVATE
     common.cpp
     edid.cpp
     egl_context_attribute_builder.cpp
+    filedescriptor.cpp
     realtime.cpp
     subsurfacemonitor.cpp
     udev.cpp

src/utils/filedescriptor.cpp

@@ -0,0 +1,61 @@
+/*
+    KWin - the KDE window manager
+    This file is part of the KDE project.
+
+    SPDX-FileCopyrightText:: 2022 Xaver Hugl <xaver.hugl@gmail.com>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+#include "filedescriptor.h"
+
+#include <unistd.h>
+#include <utility>
+
+namespace KWin
+{
+
+FileDescriptor::FileDescriptor(int fd)
+    : m_fd(fd)
+{
+}
+
+FileDescriptor::FileDescriptor(FileDescriptor &&other)
+    : m_fd(std::exchange(other.m_fd, -1))
+{
+}
+
+FileDescriptor &FileDescriptor::operator=(FileDescriptor &&other)
+{
+    if (m_fd != -1) {
+        ::close(m_fd);
+    }
+    m_fd = std::exchange(other.m_fd, -1);
+    return *this;
+}
+
+FileDescriptor::~FileDescriptor()
+{
+    if (m_fd != -1) {
+        ::close(m_fd);
+    }
+}
+
+FileDescriptor::operator bool() const
+{
+    return m_fd != -1;
+}
+
+int FileDescriptor::get() const
+{
+    return m_fd;
+}
+
+FileDescriptor FileDescriptor::duplicate() const
+{
+    if (m_fd != -1) {
+        return FileDescriptor{dup(m_fd)};
+    } else {
+        return {};
+    }
+}
+}

src/utils/filedescriptor.h

@@ -0,0 +1,33 @@
+/*
+    KWin - the KDE window manager
+    This file is part of the KDE project.
+
+    SPDX-FileCopyrightText:: 2022 Xaver Hugl <xaver.hugl@gmail.com>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+#pragma once
+
+#include <kwin_export.h>
+
+namespace KWin
+{
+
+class KWIN_EXPORT FileDescriptor
+{
+public:
+    FileDescriptor() = default;
+    explicit FileDescriptor(int fd);
+    FileDescriptor(FileDescriptor &&);
+    FileDescriptor &operator=(FileDescriptor &&);
+    ~FileDescriptor();
+
+    explicit operator bool() const;
+    int get() const;
+    FileDescriptor duplicate() const;
+
+private:
+    int m_fd = -1;
+};
+
+}