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-rw-r--r--lib/util/fopenat.c70
1 files changed, 70 insertions, 0 deletions
diff --git a/lib/util/fopenat.c b/lib/util/fopenat.c
new file mode 100644
index 0000000..6bb9dd8
--- /dev/null
+++ b/lib/util/fopenat.c
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "util.h"
+
+FILE *fopenat(int dirfd, const char *filename, const char *mode)
+{
+ const char *ptr = mode;
+ int fd, flags = 0;
+ FILE *fp;
+
+ switch (*(ptr++)) {
+ case 'r':
+ flags = O_RDONLY;
+ break;
+ case 'w':
+ flags = O_WRONLY | O_CREAT | O_TRUNC;
+ break;
+ case 'a':
+ flags = O_WRONLY | O_CREAT | O_APPEND;
+ break;
+ default:
+ errno = EINVAL;
+ return NULL;
+ }
+
+ if (*ptr == '+') {
+ flags = (flags & ~(O_RDONLY | O_WRONLY)) | O_RDWR;
+ ++ptr;
+ }
+
+ if (*ptr == 'b')
+ ++ptr;
+
+ if (*ptr != '\0') {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ fd = openat(dirfd, filename, flags, 0644);
+ if (fd == -1)
+ return NULL;
+
+ fp = fdopen(fd, mode);
+ if (fp == NULL)
+ close(fd);
+
+ return fp;
+}