cursor: use os_create_anonymous_file()

Copy the implementation of os_create_anonymous_file() here from weston,
so we can use it instead of hardcoding a path to /tmp.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

cursor/os-compatibility.c

@@ -0,0 +1,128 @@
+/*
+ * Copyright © 2012 Collabora, Ltd.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#define _GNU_SOURCE
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "config.h"
+#include "os-compatibility.h"
+
+#ifndef HAVE_MKOSTEMP
+static int
+set_cloexec_or_close(int fd)
+{
+	long flags;
+
+	if (fd == -1)
+		return -1;
+
+	flags = fcntl(fd, F_GETFD);
+	if (flags == -1)
+		goto err;
+
+	if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
+		goto err;
+
+	return fd;
+
+err:
+	close(fd);
+	return -1;
+}
+#endif
+
+static int
+create_tmpfile_cloexec(char *tmpname)
+{
+	int fd;
+
+#ifdef HAVE_MKOSTEMP
+	fd = mkostemp(tmpname, O_CLOEXEC);
+	if (fd >= 0)
+		unlink(tmpname);
+#else
+	fd = mkstemp(tmpname);
+	if (fd >= 0) {
+		fd = set_cloexec_or_close(fd);
+		unlink(tmpname);
+	}
+#endif
+
+	return fd;
+}
+
+/*
+ * Create a new, unique, anonymous file of the given size, and
+ * return the file descriptor for it. The file descriptor is set
+ * CLOEXEC. The file is immediately suitable for mmap()'ing
+ * the given size at offset zero.
+ *
+ * The file should not have a permanent backing store like a disk,
+ * but may have if XDG_RUNTIME_DIR is not properly implemented in OS.
+ *
+ * The file name is deleted from the file system.
+ *
+ * The file is suitable for buffer sharing between processes by
+ * transmitting the file descriptor over Unix sockets using the
+ * SCM_RIGHTS methods.
+ */
+int
+os_create_anonymous_file(off_t size)
+{
+	static const char template[] = "/weston-shared-XXXXXX";
+	const char *path;
+	char *name;
+	int fd;
+
+	path = getenv("XDG_RUNTIME_DIR");
+	if (!path) {
+		errno = ENOENT;
+		return -1;
+	}
+
+	name = malloc(strlen(path) + sizeof(template));
+	if (!name)
+		return -1;
+
+	strcpy(name, path);
+	strcat(name, template);
+
+	fd = create_tmpfile_cloexec(name);
+
+	free(name);
+
+	if (fd < 0)
+		return -1;
+
+	if (ftruncate(fd, size) < 0) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}