C语言实现一个简单的环回buffer

#include <stdio.h>
#define  BUF_CNT  10
int in=0;
int out=0;
int cnt=0;
char buf[BUF_CNT]={0};

void data_buff_init()
{
	in = 0;
	out = 0;
	cnt = 0;
}

void data_in(char c)
{
	if(cnt>=BUF_CNT)
	{
		out++;
		if(out==BUF_CNT) out=0;
	}
	else
	{
		cnt++;
	}
	if(in>=BUF_CNT) in=0;
	buf[in] = c;
	in++;
}

char data_out()
{
	char c = 255;
	if(cnt>0)
	{
		if(out>=BUF_CNT) out=0;
		c = buf[out];
		out++;
		cnt--;
	}
	return c;
}

int main()
{
	char i = 0;
    data_buff_init();
	while(1)
	{
		for(i=0;i<20;i++)
			data_in(i);
		for(i=0;i<BUF_CNT;i++)
			printf("%02x\r\n", data_out()&0x00ff);
		break;
	}
}