Avoid pathological behavior in OpenBSD's fread.
Bug: https://code.google.com/p/android/issues/detail?id=81155
Bug: 18556607
Change-Id: Idc60976b79610e2202cc42dc393dcb4ca6c42e05
diff --git a/libc/stdio/fread.c b/libc/stdio/fread.c
new file mode 100644
index 0000000..e052128
--- /dev/null
+++ b/libc/stdio/fread.c
@@ -0,0 +1,104 @@
+/* $OpenBSD: fread.c,v 1.12 2014/05/01 16:40:36 deraadt 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 <string.h>
+#include <stdint.h>
+#include <errno.h>
+#include "local.h"
+
+#define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4))
+
+size_t
+fread(void *buf, size_t size, size_t count, FILE *fp)
+{
+ size_t resid;
+ char *p;
+ int r;
+ size_t total;
+
+ /*
+ * Extension: Catch integer overflow
+ */
+ if ((size >= MUL_NO_OVERFLOW || count >= MUL_NO_OVERFLOW) &&
+ size > 0 && SIZE_MAX / size < count) {
+ errno = EOVERFLOW;
+ fp->_flags |= __SERR;
+ return (0);
+ }
+
+ /*
+ * ANSI and SUSv2 require a return value of 0 if size or count are 0.
+ */
+ if ((resid = count * size) == 0)
+ return (0);
+ FLOCKFILE(fp);
+ _SET_ORIENTATION(fp, -1);
+ if (fp->_r < 0)
+ fp->_r = 0;
+ total = resid;
+ p = buf;
+
+ // BEGIN android-added
+ // Avoid pathological behavior on unbuffered files. OpenBSD
+ // will loop reading one byte then memcpying one byte!
+ if ((fp->_flags & __SNBF) != 0) {
+ // We know if we're unbuffered that our buffer is empty, so
+ // we can just read directly.
+ while (resid > 0 && (r = (*fp->_read)(fp->_cookie, p, resid)) > 0) {
+ p += r;
+ resid -= r;
+ }
+ FUNLOCKFILE(fp);
+ return ((total - resid) / size);
+ }
+ // END android-added
+
+ while (resid > (size_t)(r = fp->_r)) {
+ (void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
+ fp->_p += r;
+ /* fp->_r = 0 ... done in __srefill */
+ p += r;
+ resid -= r;
+ if (__srefill(fp)) {
+ /* no more input: return partial result */
+ FUNLOCKFILE(fp);
+ return ((total - resid) / size);
+ }
+ }
+ (void)memcpy((void *)p, (void *)fp->_p, resid);
+ fp->_r -= resid;
+ fp->_p += resid;
+ FUNLOCKFILE(fp);
+ return (count);
+}