Initial Contribution
diff --git a/libc/stdio/flags.c b/libc/stdio/flags.c
new file mode 100644
index 0000000..dde0447
--- /dev/null
+++ b/libc/stdio/flags.c
@@ -0,0 +1,82 @@
+/* $OpenBSD: flags.c,v 1.6 2005/08/08 08:05:36 espie Exp $ */
+/*-
+ * Copyright (c) 1990, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/file.h>
+#include <stdio.h>
+#include <errno.h>
+#include <fcntl.h>
+
+/*
+ * Return the (stdio) flags for a given mode. Store the flags
+ * to be passed to an open() syscall through *optr.
+ * Return 0 on error.
+ */
+int
+__sflags(const char *mode, int *optr)
+{
+ int ret, m, o;
+
+ switch (*mode++) {
+
+ case 'r': /* open for reading */
+ ret = __SRD;
+ m = O_RDONLY;
+ o = 0;
+ break;
+
+ case 'w': /* open for writing */
+ ret = __SWR;
+ m = O_WRONLY;
+ o = O_CREAT | O_TRUNC;
+ break;
+
+ case 'a': /* open for appending */
+ ret = __SWR;
+ m = O_WRONLY;
+ o = O_CREAT | O_APPEND;
+ break;
+
+ default: /* illegal mode */
+ errno = EINVAL;
+ return (0);
+ }
+
+ /* [rwa]\+ or [rwa]b\+ means read and write */
+ if (*mode == '+' || (*mode == 'b' && mode[1] == '+')) {
+ ret = __SRW;
+ m = O_RDWR;
+ }
+ *optr = m | o;
+ return (ret);
+}