upload android base code part3

android/bionic/libc/stdio/fread.c

@@ -0,0 +1,139 @@
+/*	$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 <sys/param.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) __overloadable
+{
+	/*
+	 * 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);
+	}
+
+	const size_t desired_total = count * size;
+	size_t total = desired_total;
+
+	/*
+	 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
+	 */
+	if (total == 0) {
+		return (0);
+	}
+
+	FLOCKFILE(fp);
+	_SET_ORIENTATION(fp, -1);
+
+	// TODO: how can this ever happen?!
+	if (fp->_r < 0)
+		fp->_r = 0;
+
+	/*
+	 * Ensure _bf._size is valid.
+	 */
+	if (fp->_bf._base == NULL) {
+		__smakebuf(fp);
+	}
+
+	char* dst = buf;
+
+	while (total > 0) {
+		/*
+		 * Copy data out of the buffer.
+		 */
+		size_t buffered_bytes = MIN((size_t) fp->_r, total);
+		memcpy(dst, fp->_p, buffered_bytes);
+		fp->_p += buffered_bytes;
+		fp->_r -= buffered_bytes;
+		dst += buffered_bytes;
+		total -= buffered_bytes;
+
+		/*
+		 * Are we done?
+		 */
+		if (total == 0) {
+			goto out;
+		}
+
+		/*
+		 * Do we have so much more to read that we should
+		 * avoid copying it through the buffer?
+		 */
+		if (total > (size_t) fp->_bf._size) {
+			/*
+			 * Make sure that fseek doesn't think it can
+			 * reuse the buffer since we are going to read
+			 * directly from the file descriptor.
+			 */
+			fp->_flags |= __SMOD;
+			break;
+		}
+
+		/*
+		 * Less than a buffer to go, so refill the buffer and
+		 * go around the loop again.
+		 */
+		if (__srefill(fp)) {
+			goto out;
+		}
+	}
+
+	/*
+	 * Read directly into the caller's buffer.
+	 */
+	while (total > 0) {
+		ssize_t bytes_read = (*fp->_read)(fp->_cookie, dst, total);
+		if (bytes_read <= 0) {
+			fp->_flags |= (bytes_read == 0) ? __SEOF : __SERR;
+			break;
+		}
+		dst += bytes_read;
+		total -= bytes_read;
+	}
+
+out:
+	FUNLOCKFILE(fp);
+	return ((desired_total - total) / size);
+}