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https://github.com/ARM-software/arm-trusted-firmware.git
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afc03aebd3
There is no guarantee on the signedness of char. It can be either signed or unsigned. On ARM it is unsigned and hence this memcmp() implementation works as intended. On other machines, char can be signed (x86 for example). In that case (and assuming a 2's complement implementation), interpreting a bit-pattern of 0xFF as signed char can yield -1. If *s1 is 0 and *s2 is 255 then the difference *s1 - *s2 should be negative. The C integer promotion rules guarantee that the unsigned chars will be converted to int before the operation takes place. The current implementation will return a positive value (0 - (-1)) instead, which is wrong. Fix it by changing the signedness to unsigned to avoid surprises for anyone using this code on non-ARM systems. Change-Id: Ie222fcaa7c0c4272d7a521a6f2f51995fd5130cc Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
121 lines
3.2 KiB
C
121 lines
3.2 KiB
C
/*
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* Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of ARM nor the names of its contributors may be used
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* to endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <stddef.h> /* size_t */
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/*
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* Fill @count bytes of memory pointed to by @dst with @val
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*/
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void *memset(void *dst, int val, size_t count)
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{
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char *ptr = dst;
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while (count--)
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*ptr++ = val;
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return dst;
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}
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/*
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* Compare @len bytes of @s1 and @s2
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*/
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int memcmp(const void *s1, const void *s2, size_t len)
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{
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const unsigned char *s = s1;
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const unsigned char *d = s2;
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unsigned char sc;
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unsigned char dc;
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while (len--) {
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sc = *s++;
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dc = *d++;
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if (sc - dc)
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return (sc - dc);
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}
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return 0;
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}
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/*
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* Copy @len bytes from @src to @dst
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*/
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void *memcpy(void *dst, const void *src, size_t len)
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{
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const char *s = src;
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char *d = dst;
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while (len--)
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*d++ = *s++;
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return dst;
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}
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/*
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* Move @len bytes from @src to @dst
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*/
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void *memmove(void *dst, const void *src, size_t len)
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{
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/*
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* The following test makes use of unsigned arithmetic overflow to
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* more efficiently test the condition !(src <= dst && dst < str+len).
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* It also avoids the situation where the more explicit test would give
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* incorrect results were the calculation str+len to overflow (though
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* that issue is probably moot as such usage is probably undefined
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* behaviour and a bug anyway.
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*/
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if ((size_t)dst - (size_t)src >= len) {
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/* destination not in source data, so can safely use memcpy */
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return memcpy(dst, src, len);
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} else {
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/* copy backwards... */
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const char *end = dst;
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const char *s = (const char *)src + len;
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char *d = (char *)dst + len;
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while (d != end)
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*--d = *--s;
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}
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return dst;
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}
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/*
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* Scan @len bytes of @src for value @c
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*/
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void *memchr(const void *src, int c, size_t len)
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{
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const char *s = src;
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while (len--) {
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if (*s == c)
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return (void *) s;
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s++;
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}
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return NULL;
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}
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