utils: basic helper for creating a file in memory

Needed by the tools for keymap handling.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

meson.build

@@ -24,6 +24,8 @@ lib_util = static_library('util',
     'src/util-logger.h',
     'src/util-logger.c',
     'src/util-macros.h',
+    'src/util-memfile.h',
+    'src/util-memfile.c',
     'src/util-color.h',
     'src/util-object.h',
     'src/util-sources.h',

src/util-memfile.c

@@ -0,0 +1,83 @@
+/*
+ * Copyright © 2020 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <stddef.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+
+#include "util-memfile.h"
+#include "util-mem.h"
+#include "util-io.h"
+
+#include "util-object.h"
+
+struct memfile {
+	struct object object;
+	int fd;
+	size_t size;
+};
+
+static void
+memfile_destroy(struct memfile *memfile)
+{
+	if (memfile->fd != -1)
+		close(memfile->fd);
+}
+
+OBJECT_IMPLEMENT_CREATE(memfile);
+OBJECT_IMPLEMENT_UNREF(memfile);
+OBJECT_IMPLEMENT_REF(memfile);
+OBJECT_IMPLEMENT_GETTER(memfile, fd, int);
+OBJECT_IMPLEMENT_GETTER(memfile, size, size_t);
+
+#define _cleanup_memfile_ _cleanup_(memfile_cleanup)
+
+struct memfile *
+memfile_new(const char *data, size_t sz) {
+	_cleanup_memfile_ struct memfile *memfile = memfile_create(NULL);
+
+	_cleanup_close_ int fd = memfd_create("memfile", MFD_CLOEXEC|MFD_ALLOW_SEALING);
+	if (fd < 0)
+		return NULL;
+
+	fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK);
+	int rc = posix_fallocate(fd, 0, sz);
+	if (rc < 0)
+		return NULL;
+
+	memfile->fd = fd;
+	memfile->size = sz;
+	fd = -1;
+
+	void *map = mmap(NULL, sz, PROT_READ|PROT_WRITE, MAP_SHARED, memfile->fd, 0);
+	if (map == MAP_FAILED)
+		return NULL;
+
+	memcpy(map, data, sz);
+	munmap(map, sz);
+
+	return steal(&memfile);
+}

src/util-memfile.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright © 2020 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "config.h"
+
+struct memfile;
+
+struct memfile *
+memfile_new(const char *data, size_t sz);
+
+struct memfile *
+memfile_ref(struct memfile *memfile);
+
+struct memfile *
+memfile_unref(struct memfile *memfile);
+
+int
+memfile_get_fd(struct memfile *memfile);
+
+size_t
+memfile_get_size(struct memfile *memfile);