Initial Contribution
diff --git a/libc/stdio/setvbuf.c b/libc/stdio/setvbuf.c
new file mode 100644
index 0000000..9b92bf0
--- /dev/null
+++ b/libc/stdio/setvbuf.c
@@ -0,0 +1,151 @@
+/* $OpenBSD: setvbuf.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 <stdlib.h>
+#include "local.h"
+
+/*
+ * Set one of the three kinds of buffering, optionally including
+ * a buffer.
+ */
+int
+setvbuf(FILE *fp, char *buf, int mode, size_t size)
+{
+ int ret, flags;
+ size_t iosize;
+ int ttyflag;
+
+ /*
+ * Verify arguments. The `int' limit on `size' is due to this
+ * particular implementation. Note, buf and size are ignored
+ * when setting _IONBF.
+ */
+ if (mode != _IONBF)
+ if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
+ return (EOF);
+
+ /*
+ * Write current buffer, if any. Discard unread input (including
+ * ungetc data), cancel line buffering, and free old buffer if
+ * malloc()ed. We also clear any eof condition, as if this were
+ * a seek.
+ */
+ ret = 0;
+ (void)__sflush(fp);
+ if (HASUB(fp))
+ FREEUB(fp);
+ WCIO_FREE(fp);
+ fp->_r = fp->_lbfsize = 0;
+ flags = fp->_flags;
+ if (flags & __SMBF)
+ free((void *)fp->_bf._base);
+ flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
+
+ /* If setting unbuffered mode, skip all the hard work. */
+ if (mode == _IONBF)
+ goto nbf;
+
+ /*
+ * Find optimal I/O size for seek optimization. This also returns
+ * a `tty flag' to suggest that we check isatty(fd), but we do not
+ * care since our caller told us how to buffer.
+ */
+ flags |= __swhatbuf(fp, &iosize, &ttyflag);
+ if (size == 0) {
+ buf = NULL; /* force local allocation */
+ size = iosize;
+ }
+
+ /* Allocate buffer if needed. */
+ if (buf == NULL) {
+ if ((buf = malloc(size)) == NULL) {
+ /*
+ * Unable to honor user's request. We will return
+ * failure, but try again with file system size.
+ */
+ ret = EOF;
+ if (size != iosize) {
+ size = iosize;
+ buf = malloc(size);
+ }
+ }
+ if (buf == NULL) {
+ /* No luck; switch to unbuffered I/O. */
+nbf:
+ fp->_flags = flags | __SNBF;
+ fp->_w = 0;
+ fp->_bf._base = fp->_p = fp->_nbuf;
+ fp->_bf._size = 1;
+ return (ret);
+ }
+ flags |= __SMBF;
+ }
+
+ /*
+ * Kill any seek optimization if the buffer is not the
+ * right size.
+ *
+ * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
+ */
+ if (size != iosize)
+ flags |= __SNPT;
+
+ /*
+ * Fix up the FILE fields, and set __cleanup for output flush on
+ * exit (since we are buffered in some way).
+ */
+ if (mode == _IOLBF)
+ flags |= __SLBF;
+ fp->_flags = flags;
+ fp->_bf._base = fp->_p = (unsigned char *)buf;
+ fp->_bf._size = size;
+ /* fp->_lbfsize is still 0 */
+ if (flags & __SWR) {
+ /*
+ * Begin or continue writing: see __swsetup(). Note
+ * that __SNBF is impossible (it was handled earlier).
+ */
+ if (flags & __SLBF) {
+ fp->_w = 0;
+ fp->_lbfsize = -fp->_bf._size;
+ } else
+ fp->_w = size;
+ } else {
+ /* begin/continue reading, or stay in intermediate state */
+ fp->_w = 0;
+ }
+ __atexit_register_cleanup(_cleanup);
+
+ return (ret);
+}