aml/aml_memmove.c

/*
 * Copyright (c) 2021-2022 Amlogic, Inc. All rights reserved.
 *
 * SPDX-License-Identifier: MIT
 */

#include "aml_memmove.h"
#include <stdint.h>
#include <string.h>

void *memmove(void *dest, const void *src, size_t n)
{
	if ((uintptr_t)dest <= (uintptr_t)src || (uintptr_t)dest >= (uintptr_t)src + n) {
		/* Start of destination doesn't overlap source, so just use memcpy(). */
		return memcpy(dest, src, n);
	}

	/* Need to copy from tail because there is overlap. */
	char *d = (char *)dest + n;
	const char *s = (const char *)src + n;
	uint32_t *dw;
	const uint32_t *sw;
	char *head;
	char *const tail = (char *)dest;
	/* Set 'body' to the last word boundary */
	uint32_t *const body = (uint32_t *)(((uintptr_t)tail + 3) & ~3);

	if (((uintptr_t)dest & 3) != ((uintptr_t)src & 3)) {
		/* Misaligned. no body, no tail. */
		head = tail;
	} else {
		/* Aligned */
		if ((uintptr_t)tail > ((uintptr_t)d & ~3))
			/* Shorter than the first word boundary */
			head = tail;
		else
			/* Set 'head' to the first word boundary */
			head = (char *)((uintptr_t)d & ~3);
	}

	/* Copy head */
	while (d > head)
		*(--d) = *(--s);

	/* Copy body */
	dw = (uint32_t *)d;
	sw = (uint32_t *)s;
	while (dw > body)
		*(--dw) = *(--sw);

	/* Copy tail */
	d = (char *)dw;
	s = (const char *)sw;
	while (d > tail)
		*(--d) = *(--s);

	return dest;
}