我的C/C++库理解之memchr

#include <cstdio>
#include <cstring>

//原型
//void *memchr(const void *str, int c, size_t n)
// 搜索参数str指向的字符串的前n个字节中第一次出现的字符c（unsigned char类型）。

void  *Alex_memchr(const void *str, int c, size_t n);
int main()
{
	const char str[] = "Alex is cool!";
	char *ret = NULL;

	//ret = (char*)memchr(str, 'i', strlen(str));
	ret = (char*)Alex_memchr(str, 'i', strlen(str));
	printf("ret: %c\n", *ret);
	printf("ret: %s\n", ret);




	return 0;
}


void  *Alex_memchr(const void *str, int c, size_t n)
{
	while(n && (*((unsigned char*)str) != (unsigned char) c))
	{
		str = (unsigned char*)str + 1;
		--n;
	}

	return n?(void*)str:NULL;
}