1*91f16700Schasinglulu /* 2*91f16700Schasinglulu * Copyright (c) 2013-2018, Arm Limited and Contributors. All rights reserved. 3*91f16700Schasinglulu * 4*91f16700Schasinglulu * SPDX-License-Identifier: BSD-3-Clause 5*91f16700Schasinglulu */ 6*91f16700Schasinglulu 7*91f16700Schasinglulu #include <string.h> 8*91f16700Schasinglulu 9*91f16700Schasinglulu void *memmove(void *dst, const void *src, size_t len) 10*91f16700Schasinglulu { 11*91f16700Schasinglulu /* 12*91f16700Schasinglulu * The following test makes use of unsigned arithmetic overflow to 13*91f16700Schasinglulu * more efficiently test the condition !(src <= dst && dst < str+len). 14*91f16700Schasinglulu * It also avoids the situation where the more explicit test would give 15*91f16700Schasinglulu * incorrect results were the calculation str+len to overflow (though 16*91f16700Schasinglulu * that issue is probably moot as such usage is probably undefined 17*91f16700Schasinglulu * behaviour and a bug anyway. 18*91f16700Schasinglulu */ 19*91f16700Schasinglulu if ((size_t)dst - (size_t)src >= len) { 20*91f16700Schasinglulu /* destination not in source data, so can safely use memcpy */ 21*91f16700Schasinglulu return memcpy(dst, src, len); 22*91f16700Schasinglulu } else { 23*91f16700Schasinglulu /* copy backwards... */ 24*91f16700Schasinglulu const char *end = dst; 25*91f16700Schasinglulu const char *s = (const char *)src + len; 26*91f16700Schasinglulu char *d = (char *)dst + len; 27*91f16700Schasinglulu while (d != end) 28*91f16700Schasinglulu *--d = *--s; 29*91f16700Schasinglulu } 30*91f16700Schasinglulu return dst; 31*91f16700Schasinglulu } 32