| Soby Mathew | b4c6df4 | 2022-11-09 11:13:29 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * SPDX-License-Identifier: BSD-3-Clause |
| 3 | * SPDX-FileCopyrightText: Copyright TF-RMM Contributors. |
| 4 | * SPDX-FileCopyrightText: Copyright Jon Medhurst <tixy@linaro.org> |
| 5 | */ |
| 6 | |
| 7 | #include <stddef.h> |
| 8 | #include <string.h> |
| 9 | |
| 10 | void *memmove(void *dst, const void *src, size_t len) |
| 11 | { |
| 12 | /* |
| 13 | * The following test makes use of unsigned arithmetic overflow to |
| 14 | * more efficiently test the condition !(src <= dst && dst < str+len). |
| 15 | * It also avoids the situation where the more explicit test would give |
| 16 | * incorrect results were the calculation str+len to overflow (though |
| 17 | * that issue is probably moot as such usage is probably undefined |
| 18 | * behaviour and a bug anyway. |
| 19 | */ |
| 20 | if ((size_t)dst - (size_t)src >= len) { |
| 21 | /* destination not in source data, so can safely use memcpy */ |
| 22 | return memcpy(dst, src, len); |
| 23 | } |
| 24 | |
| 25 | /* copy backwards... */ |
| 26 | const char *end = dst; |
| 27 | const char *s = (const char *)src + len; |
| 28 | char *d = (char *)dst + len; |
| 29 | |
| 30 | while (d != end) { |
| 31 | *--d = *--s; |
| 32 | } |
| 33 | return dst; |
| 34 | } |