#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include  <assert.h>
void *memmove(void *dest, const void *src, size_t count)
{
	assert((dest != NULL) && (src != NULL));     //安全檢查  
	assert(count > 0);

	char *psrc = (char *)src;
	char *pdest = (char *)dest;
	//檢查是否有重疊問題  
	if (pdest < psrc)
	{
		//正向拷貝  
		while (count--)
			*pdest++ = *psrc++;
	}
	else if (psrc < pdest)
	{
		//反向拷貝  
		psrc = psrc + count - 1;
		pdest = pdest + count - 1;
		while (count--)
			*pdest-- = *psrc--;
	}
	return dest;
}

void *memmcpy(void *dest, const void *src, size_t count)
{
	assert((dest != NULL) && (src != NULL));     //安全檢查  
	assert(count > 0);

	char *psrc = (char *)src;
	char *pdest = (char *)dest;
	while (count--)
		*pdest++ = *psrc++;

	return dest;
}

int main()
{
	char str[] = "helloworld!";
	memmove(str + 3, str, 4);
	char str1[] = "helloworld!";
	memmcpy(str1 + 3, str1, 4);

	printf("%s\n", str);
	printf("%s\n", str1);

	getchar();
	return 0;
}