auto import from //depot/cupcake/@135843
diff --git a/libc/stdio/fdopen.c b/libc/stdio/fdopen.c
new file mode 100644
index 0000000..1df609c
--- /dev/null
+++ b/libc/stdio/fdopen.c
@@ -0,0 +1,76 @@
+/* $OpenBSD: fdopen.c,v 1.5 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 <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include "local.h"
+
+FILE *
+fdopen(int fd, const char *mode)
+{
+ FILE *fp;
+ int flags, oflags, fdflags, tmp;
+
+ if ((flags = __sflags(mode, &oflags)) == 0)
+ return (NULL);
+
+ /* Make sure the mode the user wants is a subset of the actual mode. */
+ if ((fdflags = fcntl(fd, F_GETFL, 0)) < 0)
+ return (NULL);
+ tmp = fdflags & O_ACCMODE;
+ if (tmp != O_RDWR && (tmp != (oflags & O_ACCMODE))) {
+ errno = EINVAL;
+ return (NULL);
+ }
+
+ if ((fp = __sfp()) == NULL)
+ return (NULL);
+ fp->_flags = flags;
+ /*
+ * If opened for appending, but underlying descriptor does not have
+ * O_APPEND bit set, assert __SAPP so that __swrite() will lseek to
+ * end before each write.
+ */
+ if ((oflags & O_APPEND) && !(fdflags & O_APPEND))
+ fp->_flags |= __SAPP;
+ fp->_file = fd;
+ fp->_cookie = fp;
+ fp->_read = __sread;
+ fp->_write = __swrite;
+ fp->_seek = __sseek;
+ fp->_close = __sclose;
+ return (fp);
+}