代码

void my_memset(char * a, char c, unsigned n) {
	unsigned tc = c;
	unsigned val = tc << 24 | tc << 16 | tc << 8 | tc;
	while (reinterpret_cast<unsigned long> (a) % 4 != 0 && n) {
		*a++ = c;
		--n;
	}
	if (!n) return ;
	char * tar = a + n;
	unsigned blo = n / 4;
	char * be = a + blo * 4;
	unsigned * ed = reinterpret_cast<unsigned*> (be);
	unsigned * st = reinterpret_cast<unsigned*> (a);
	for (; st + 16 < ed; ) {
		*st++ = val; *st++ = val; *st++ = val; *st++ = val;
		*st++ = val; *st++ = val; *st++ = val; *st++ = val;
		*st++ = val; *st++ = val; *st++ = val; *st++ = val;
		*st++ = val; *st++ = val; *st++ = val; *st++ = val;
	}
	while (st != ed) *st++ = val;
	while (be != tar) *be++ = c;
}

评测结果