Serial port circular buffer is simple and initialization free, without heap, pointer and segmented memcpy

#include <stdio.h>
#include <stdlib.h>


#define RINGBUF_LEN 32

typedef struct ringbuf_t
{
	int head;// The head pointer 
	int tail;// Tail pointer 
	int len;// length 
	char buf[RINGBUF_LEN];// Buffer size 
}ringbuf_t;

ringbuf_t t_buf_ring;


// Buffer initialization 
void init_ringbuf(void)
{
	memset(&t_buf_ring, 0, sizeof(t_buf_ring));
}
// The team 
int ringbuf_write(char data)
{
	if(RINGBUF_LEN <= t_buf_ring.len) {
		return -1;
	}
	t_buf_ring.buf[t_buf_ring.tail] = data;
	t_buf_ring.tail = (t_buf_ring.tail + 1) % RINGBUF_LEN;
	t_buf_ring.len++;
	
	return 0;
}
// Out of the team 
int ringbuf_read(char *date)
{
	if(0 >= t_buf_ring.len) {
		return -1;
	}
	*date = t_buf_ring.buf[t_buf_ring.head];
	t_buf_ring.head = (t_buf_ring.head + 1) % RINGBUF_LEN;
	t_buf_ring.len--;
	
	return 0;
}

// Out of the team 
int ringbuf_show()
{
	int i,j;
	for (i = 0, j = t_buf_ring.head; i < t_buf_ring.len; i++, j++) {		
		printf("%d --- %c ", i, t_buf_ring.buf[j]);
	}
	printf("\n");
	return 0;
}




//  The main function 
int main()
{
	char c, c_r;	
	int i, cnt;
	//setvbuf(stdout,NULL,_IONBF,0); //pinrtf、putchar Cannot output immediately , Open this comment 
	//init_ringbuf();

	printf("Please enter a line [blank line to terminate]> ");
	do{
		c=getchar();
		putchar(c);
		switch(c)
		{
			case 'Q':
				goto exit;
			break;
			case 'R':
				printf("----------read----------------\n");
				printf("len - %d \n", t_buf_ring.len);
				cnt = t_buf_ring.len;
				for (i = 0; i < cnt; i++) {
					ringbuf_read(&c_r);
					printf("%d ---- %c ", i, c_r);
				}
				
				//ringbuf_show();
			
			break;
			default :
				printf("----------write-----\n");
				if(c!='\n') 
					ringbuf_write(c);
				printf("%d len\n", t_buf_ring.len);
				ringbuf_show();
			break;
		}
	}while (1);



exit:	
	printf("exit.\n");
    return 0;
}