帮我找一个C语言完整的HDLC协议代码

这里是一个C语言实现的完整HDLC协议代码示例，仅供参考：

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

#define FLAG 0x7E
#define ESC 0x7D
#define XON 0x11
#define XOFF 0x13

// HDLC frame types
#define FRAME_TYPE_I 0x00
#define FRAME_TYPE_SABM 0x2F
#define FRAME_TYPE_UA 0x63
#define FRAME_TYPE_DISC 0x43

// HDLC frame control fields
#define FRAME_CTRL_RECV_SEQ 0x00
#define FRAME_CTRL_SEND_SEQ 0x40
#define FRAME_CTRL_POLL_FINAL 0x10

// HDLC states
#define STATE_IDLE 0
#define STATE_RECV 1
#define STATE_ESCAPE 2

// HDLC receive state variables
static int state = STATE_IDLE;
static unsigned char recv_buf[1024];
static int recv_index = 0;

// HDLC transmit state variables
static int send_seq = 0;
static int recv_seq = 0;
static unsigned char send_buf[1024];
static int send_index = 0;
static int send_len = 0;
static int send_escaped = 0;

// HDLC CRC calculation
static unsigned short crc16(unsigned char *data, int len) {
    int i, j;
    unsigned short crc = 0xFFFF;
    for (i = 0; i < len; i++) {
        crc ^= (unsigned short)data[i] << 8;
        for (j = 0; j < 8; j++) {
            if (crc & 0x8000) {
                crc = (crc << 1) ^ 0x1021;
            } else {
                crc <<= 1;
            }
        }
    }
    return crc;
}

// HDLC byte stuffing
static void hdlc_send_byte(unsigned char byte) {
    if (byte == FLAG || byte == ESC) {
        send_buf[send_index++] = ESC;
        send_buf[send_index++] = byte ^ 0x20;
    } else {
        send_buf[send_index++] = byte;
    }
}

// HDLC frame transmission
static void hdlc_send_frame(unsigned char frame_type, unsigned char *data, int len) {
    unsigned short crc = crc16(data, len);
    send_index = 0;
    send_buf[send_index++] = FLAG;
    send_buf[send_index++] = frame_type;
    send_buf[send_index++] = FRAME_CTRL_SEND_SEQ | (send_seq << 1);
    if (frame_type == FRAME_TYPE_I) {
        memcpy(&send_buf[send_index], data, len);
        send_index += len;
    }
    send_buf[send_index++] = (unsigned char)(crc >> 8);
    send_buf[send_index++] = (unsigned char)(crc & 0xFF);
    send_buf[send_index++] = FLAG;
    send_len = send_index;
    send_escaped = 0;
}

// HDLC byte unstuffing
static unsigned char hdlc_recv_byte(unsigned char byte) {
    if (state == STATE_ESCAPE) {
        state = STATE_RECV;
        return byte ^ 0x20;
    } else if (byte == FLAG) {
        state = STATE_RECV;
        recv_index = 0;
        return 0;
    } else if (byte == ESC) {
        state = STATE_ESCAPE;
        return 0;
    } else {
        state = STATE_RECV;
        return byte;
    }
}

// HDLC frame reception