继续扩展myprint的功能为操作系统开发加油！

 这段代码虽然不免抄袭大侠们的嫌疑，但是完全是自己重新写过的，没有知识产权的纠纷了，而且更容易看懂，今天真是收获不小。

#include <stdio.h>

char str[0xff];

void str_cpy(const char* s, char* d) {
	while(*s)
		*d++ = *s++;
	*d = '\0';
	return;
}

int str_len(const char* s) {
	int len = 0; 
	while(*s++)
		len++;
	return len;
}

int mydiv(int* x, int y) {
	if(y == 0)
		return -*x;
	int tmp;
	tmp = *x % y;
	*x /= y;
	return tmp;
}

char* myitoa(int x, int d){
	static char mystr[0x20];
	char tmp[0x20];
	const char* c = "0123456789abcdef";
	int y, i = 0, j;
	while(x) {
		y = mydiv(&x, d);
		tmp[i++] = c[y];
	}
	tmp[i] = '\0';
	j = str_len(tmp);
	for(i = 0; i < str_len(tmp); i++){
		mystr[i] = tmp[--j];
	}
	mystr[i] = '\0';
	return mystr;
}

void myprintf(const char* s, ...){
	char* mystr = str;
	char* tmp;
	char** varg = (char**)&s;
	varg++;
	char c;
	int len;
	while(c = *s) {
		if('%' != c) {
			*mystr++ = c;
			s++;
		} else {
			s++;
			switch(c = *s) {
				case '%':
					s++;
					*mystr++ = '%';
					break;
				case 'c':
					s++;
					*mystr++ = *((char*)varg);
					varg++;
					break;
				case 's':
					s++;
					str_cpy(*varg, mystr);
					len = str_len(str);
					mystr = str + len;
					varg++;
					break;
				case 'x':
					s++;
					tmp = myitoa(*((int*)varg), 16);
					*mystr++ = '0';
					*mystr++ = 'x';
					str_cpy(tmp, mystr);
					len = str_len(str);
					mystr = str + len;
					varg++;
					break;
				case 'd':
					s++;
					tmp = myitoa(*((int*)varg), 10);
					str_cpy(tmp, mystr);
					len = str_len(str);
					mystr = str + len;
					varg++;
					break;
				case 'b':
					s++;
					tmp = myitoa(*((int*)varg), 2);
					str_cpy(tmp, mystr);
					len = str_len(str);
					mystr = str + len;
					*mystr++ = 'b';
					*mystr = '\0';
					varg++;
					break;
				default:
					break;
			}
		}
	}
} 

int main(void) {
	myprintf("He%%%llo, %%%%World!\n%s, %c, %b, %s, %d, %s, %x", "How", '@',
	0xff, "YOU", 15, "Wel%come!", 128);
	printf("%s", str);
}

标签：tmp,操作系统,myprint,len,char,++,str,mystr,加油
来源： https://blog.csdn.net/weixin_39410618/article/details/89502252