auto import from //depot/cupcake/@135843
diff --git a/libc/stdio/fvwrite.c b/libc/stdio/fvwrite.c
new file mode 100644
index 0000000..bbea672
--- /dev/null
+++ b/libc/stdio/fvwrite.c
@@ -0,0 +1,208 @@
+/* $OpenBSD: fvwrite.c,v 1.14 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 <string.h>
+#include <errno.h>
+#include "local.h"
+#include "fvwrite.h"
+
+/*
+ * Write some memory regions. Return zero on success, EOF on error.
+ *
+ * This routine is large and unsightly, but most of the ugliness due
+ * to the three different kinds of output buffering is handled here.
+ */
+int
+__sfvwrite(FILE *fp, struct __suio *uio)
+{
+ size_t len;
+ char *p;
+ struct __siov *iov;
+ int w, s;
+ char *nl;
+ int nlknown, nldist;
+
+ if ((len = uio->uio_resid) == 0)
+ return (0);
+ /* make sure we can write */
+ if (cantwrite(fp)) {
+ errno = EBADF;
+ return (EOF);
+ }
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define COPY(n) (void)memcpy((void *)fp->_p, (void *)p, (size_t)(n))
+
+ iov = uio->uio_iov;
+ p = iov->iov_base;
+ len = iov->iov_len;
+ iov++;
+#define GETIOV(extra_work) \
+ while (len == 0) { \
+ extra_work; \
+ p = iov->iov_base; \
+ len = iov->iov_len; \
+ iov++; \
+ }
+ if (fp->_flags & __SNBF) {
+ /*
+ * Unbuffered: write up to BUFSIZ bytes at a time.
+ */
+ do {
+ GETIOV(;);
+#if 1 /* BIONIC: don't limit to 1KB writes */
+ w = (*fp->_write)(fp->_cookie, p, len);
+#else
+ w = (*fp->_write)(fp->_cookie, p, MIN(len, BUFSIZ2));
+#endif
+ if (w <= 0)
+ goto err;
+ p += w;
+ len -= w;
+ } while ((uio->uio_resid -= w) != 0);
+ } else if ((fp->_flags & __SLBF) == 0) {
+ /*
+ * Fully buffered: fill partially full buffer, if any,
+ * and then flush. If there is no partial buffer, write
+ * one _bf._size byte chunk directly (without copying).
+ *
+ * String output is a special case: write as many bytes
+ * as fit, but pretend we wrote everything. This makes
+ * snprintf() return the number of bytes needed, rather
+ * than the number used, and avoids its write function
+ * (so that the write function can be invalid).
+ */
+ do {
+ GETIOV(;);
+ if ((fp->_flags & (__SALC | __SSTR)) ==
+ (__SALC | __SSTR) && fp->_w < (int)len) {
+ size_t blen = fp->_p - fp->_bf._base;
+ unsigned char *_base;
+ int _size;
+
+ /* Allocate space exponentially. */
+ _size = fp->_bf._size;
+ do {
+ _size = (_size << 1) + 1;
+ } while (_size < (int)(blen + len));
+ _base = realloc(fp->_bf._base, _size + 1);
+ if (_base == NULL)
+ goto err;
+ fp->_w += _size - fp->_bf._size;
+ fp->_bf._base = _base;
+ fp->_bf._size = _size;
+ fp->_p = _base + blen;
+ }
+ w = fp->_w;
+ if (fp->_flags & __SSTR) {
+ if ((int)len < w)
+ w = len;
+ COPY(w); /* copy MIN(fp->_w,len), */
+ fp->_w -= w;
+ fp->_p += w;
+ w = len; /* but pretend copied all */
+ } else if (fp->_p > fp->_bf._base && (int)len > w) {
+ /* fill and flush */
+ COPY(w);
+ /* fp->_w -= w; */ /* unneeded */
+ fp->_p += w;
+ if (fflush(fp))
+ goto err;
+ } else if ((int)len >= (w = fp->_bf._size)) {
+ /* write directly */
+ w = (*fp->_write)(fp->_cookie, p, w);
+ if (w <= 0)
+ goto err;
+ } else {
+ /* fill and done */
+ w = len;
+ COPY(w);
+ fp->_w -= w;
+ fp->_p += w;
+ }
+ p += w;
+ len -= w;
+ } while ((uio->uio_resid -= w) != 0);
+ } else {
+ /*
+ * Line buffered: like fully buffered, but we
+ * must check for newlines. Compute the distance
+ * to the first newline (including the newline),
+ * or `infinity' if there is none, then pretend
+ * that the amount to write is MIN(len,nldist).
+ */
+ nlknown = 0;
+ nldist = 0; /* XXX just to keep gcc happy */
+ do {
+ GETIOV(nlknown = 0);
+ if (!nlknown) {
+ nl = memchr((void *)p, '\n', len);
+ nldist = nl ? nl + 1 - p : (int)len + 1;
+ nlknown = 1;
+ }
+ s = MIN((int)len, nldist);
+ w = fp->_w + fp->_bf._size;
+ if (fp->_p > fp->_bf._base && s > w) {
+ COPY(w);
+ /* fp->_w -= w; */
+ fp->_p += w;
+ if (fflush(fp))
+ goto err;
+ } else if (s >= (w = fp->_bf._size)) {
+ w = (*fp->_write)(fp->_cookie, p, w);
+ if (w <= 0)
+ goto err;
+ } else {
+ w = s;
+ COPY(w);
+ fp->_w -= w;
+ fp->_p += w;
+ }
+ if ((nldist -= w) == 0) {
+ /* copied the newline: flush and forget */
+ if (fflush(fp))
+ goto err;
+ nlknown = 0;
+ }
+ p += w;
+ len -= w;
+ } while ((uio->uio_resid -= w) != 0);
+ }
+ return (0);
+
+err:
+ fp->_flags |= __SERR;
+ return (EOF);
+}