auto import from //depot/cupcake/@135843
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);
+}