auto import from //depot/cupcake/@135843
diff --git a/libc/stdio/fileext.h b/libc/stdio/fileext.h
new file mode 100644
index 0000000..2d07043
--- /dev/null
+++ b/libc/stdio/fileext.h
@@ -0,0 +1,54 @@
+/* $OpenBSD: fileext.h,v 1.2 2005/06/17 20:40:32 espie Exp $ */
+/* $NetBSD: fileext.h,v 1.5 2003/07/18 21:46:41 nathanw Exp $ */
+
+/*-
+ * Copyright (c)2001 Citrus Project,
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ *
+ * $Citrus$
+ */
+
+/*
+ * file extension
+ */
+struct __sfileext {
+ struct __sbuf _ub; /* ungetc buffer */
+ struct wchar_io_data _wcio; /* wide char io status */
+};
+
+#define _EXT(fp) ((struct __sfileext *)((fp)->_ext._base))
+#define _UB(fp) _EXT(fp)->_ub
+
+#define _FILEEXT_INIT(fp) \
+do { \
+ _UB(fp)._base = NULL; \
+ _UB(fp)._size = 0; \
+ WCIO_INIT(fp); \
+} while (0)
+
+#define _FILEEXT_SETUP(f, fext) \
+do { \
+ (f)->_ext._base = (unsigned char *)(fext); \
+ _FILEEXT_INIT(f); \
+} while (0)