写一份串口通信，缓冲区为4096大小的c语言代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>

#define BUF_SIZE 4096 // 缓冲区大小

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <serial port device>\n", argv[0]);
        exit(1);
    }

    char *serial_port = argv[1];
    int serial_fd = open(serial_port, O_RDWR | O_NOCTTY | O_NDELAY);
    if (serial_fd == -1) {
        fprintf(stderr, "Error: Cannot open serial port %s\n", serial_port);
        exit(1);
    }

    struct termios options;
    tcgetattr(serial_fd, &options); // 获取当前串口配置
    options.c_cflag = B9600 | CS8 | CLOCAL | CREAD;
    options.c_iflag = IGNPAR | ICRNL;
    options.c_oflag = 0;
    options.c_lflag = ICANON;
    tcflush(serial_fd, TCIFLUSH);
    tcsetattr(serial_fd, TCSANOW, &options); // 配置串口

    char buf[BUF_SIZE];
    int buf_len = 0;
    while (1) {
        // 读取串口数据
        int n = read(serial_fd, buf + buf_len, BUF_SIZE - buf_len);
        if (n == -1) {
            fprintf(stderr, "Error: Cannot read from serial port\n");
            break;
        }
        buf_len += n;

        // 处理缓冲区数据
        char *p = buf;
        while (buf_len >= 6) {
            if (strncmp(p, "START", 5) == 0) { // 如果接收到"START"，回复"ACK"
                write(serial_fd, "ACK", 3);
                p += 5;
                buf_len -= 5;
            } else if (strncmp(p, "STOP", 4) == 0) { // 如果接收到"STOP"，退出程序
                break;
            } else { // 否则跳过一字节
                p++;
                buf_len--;
            }
        }

        // 重置缓冲区
        if (buf_len > 0 && p != buf) {
            memmove(buf, p, buf_len);
        } else {
            buf_len = 0;
        }
    }

    close(serial_fd);
    return 0;
}