libcamera: base: Add MemFd helper class

libcamera creates memfds in two locations already, duplicating some
code. Move the code to a new MemFd helper class.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Milan Zamazal <mzamazal@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>

include/libcamera/base/memfd.h

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas on Board Oy
+ *
+ * Anonymous file creation
+ */
+
+#pragma once
+
+#include <stddef.h>
+
+#include <libcamera/base/flags.h>
+#include <libcamera/base/unique_fd.h>
+
+namespace libcamera {
+
+class MemFd
+{
+public:
+	enum class Seal {
+		None = 0,
+		Shrink = (1 << 0),
+		Grow = (1 << 1),
+	};
+
+	using Seals = Flags<Seal>;
+
+	static UniqueFD create(const char *name, std::size_t size,
+			       Seals seals = Seal::None);
+};
+
+LIBCAMERA_FLAGS_ENABLE_OPERATORS(MemFd::Seal)
+
+} /* namespace libcamera */

include/libcamera/base/meson.build

@@ -21,6 +21,7 @@ libcamera_base_private_headers = files([
     'event_notifier.h',
     'file.h',
     'log.h',
+    'memfd.h',
     'message.h',
     'mutex.h',
     'private.h',