memmove.c

<<c语言接口与实现>>一书源码,此书无疑是一部经典的c语言书籍,只可惜翻译的质量很差

#include <string.h>

/*lint -e613
memmove is defined here because some vendors don't provide it at all
and others do poor job (like calling malloc) 
*/
void *memmove(void *s1, const void *s2, size_t n) {
	unsigned char *cs1;
	const unsigned char *cs2;

	if (n <= 0)
		return s1;
	cs1 = s1;
	cs2 = s2;
	if (cs1 < cs2)
		do
			*cs1++ = *cs2++;
		while (--n);
	else {
		cs1 += n;
		cs2 += n;
		do
			*--cs1 = *--cs2;
		while (--n);
	}
	return s1;
}