diff --git a/libc/stdio/funopen.c b/libc/stdio/funopen.c
new file mode 100644
index 0000000..b85ee96
--- /dev/null
+++ b/libc/stdio/funopen.c
@@ -0,0 +1,68 @@
+/*	$OpenBSD: funopen.c,v 1.8 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 <stdio.h>
+#include <errno.h>
+#include "local.h"
+
+FILE *
+funopen(const void *cookie, int (*readfn)(void *, char *, int),
+	int (*writefn)(void *, const char *, int),
+	fpos_t (*seekfn)(void *, fpos_t, int), int (*closefn)(void *))
+{
+	FILE *fp;
+	int flags;
+
+	if (readfn == NULL) {
+		if (writefn == NULL) {		/* illegal */
+			errno = EINVAL;
+			return (NULL);
+		} else
+			flags = __SWR;		/* write only */
+	} else {
+		if (writefn == NULL)
+			flags = __SRD;		/* read only */
+		else
+			flags = __SRW;		/* read-write */
+	}
+	if ((fp = __sfp()) == NULL)
+		return (NULL);
+	fp->_flags = flags;
+	fp->_file = -1;
+	fp->_cookie = (void *)cookie;		/* SAFE: cookie not modified */
+	fp->_read = readfn;
+	fp->_write = writefn;
+	fp->_seek = seekfn;
+	fp->_close = closefn;
+	return (fp);
+}