void mqtt_publish(uint8_t *data, uint16_t len, MQTT_QoS qos) { static uint16_t pid = 0; uint16_t packet_id = 0; // 默认QoS0的Packet ID为0 if (qos > QoS0) { packet_id = pid++; // 处理pid溢出：跳过正在重传的ID（需辅助函数检查） while (is_packet_id_in_use(pid)) { pid++; } RetransPacket pkt = { .packet_id = packet_id, .send_time = sys_tick, .retry_count = 0, .payload = malloc(len), .payload_len = len, .qos = qos }; memcpy(pkt.payload, data, len); retrans_list_insert(pkt); } // 发送时明确处理QoS0的Packet ID send_mqtt_packet(data, len, qos, (qos > QoS0) ? packet_id : 0); } /* 3、PUBLISH 发布消息 C <=> S */ char MQTT_Publish(int qos, int retain, char *post_topic, unsigned int id, char *message) { const int BUFF_SIZE = 512; char data[BUFF_SIZE] = {0}; int len = 0; int remaining_length; int encoded_remaining_len_bytes = 0; int temp_remaining_length; char remaining_encoded[4]; int encoded_len; /* ------------------------------- 报文检查、配置 ------------------------------------ */ int topic_length = post_topic ? strlen(post_topic) : 0; int message_length = message ? strlen(message) : 0; if (topic_length == 0 || topic_length > 65535) // 主题长度小于65535 return 1; if (!message) // 消息内容不可为空 return 2; if (qos > 0 && id == 0) // QoS>0时必须提供有效id return 3; if (qos < 0 || qos > 2) return 4; /* 剩余长度计算 */ remaining_length = (2 + topic_length) + ((qos > 0) ? 2 : 0) + message_length; /* 缓冲区容量检查 */ temp_remaining_length = remaining_length; do { encoded_remaining_len_bytes++; temp_remaining_length /= 128; } while (temp_remaining_length > 0); /* 确保数据长度不超过缓存大小 */ if ((1 + encoded_remaining_len_bytes + remaining_length) > BUFF_SIZE) { return 5; } /* ------------------------------- 报文检查、配置结束 ------------------------------------ */ /* ------------------------------- 开始构建报文 ------------------------------------ */ /* 固定报头构造 */ data[len++] = 0x30 | (qos << 1) | retain; /* 剩余长度编码 */ encoded_len = encode_remaining_length(remaining_length, remaining_encoded); memcpy(&data[len], remaining_encoded, encoded_len); len += encoded_len; /* 可变报头与有效载荷 */ // 主题名 data[len++] = (topic_length >> 8) & 0xFF; data[len++] = topic_length & 0xFF; memcpy(&data[len], post_topic, topic_length); len += topic_length; /* 报文标识符(QoS > 0) */ if (qos > 0) { data[len++] = (id >> 8) & 0xFF; data[len++] = id & 0xFF; } /* 有效载荷 */ memcpy(&data[len], message, message_length); len += message_length; /* ------------------------------- 构建报文完成 ------------------------------------ */ /* 数据发送 */ MQTT_SendData(data, 4); // 直接发送数据 mqtt_debug(data, len, "\r\n* 3、PUBLISH – 发布消息 *\r\n"); if(qos > 0) { data[0] |= 0x08; // 置位dup重发标志 Write_MQTT_TxDataBuff(data, len); // 将数据保存到缓冲区 mqtt_debug(data, len, "\r\n* 将重发标志dup置1 ，然后将报文保存到缓冲区 *\r\n"); } WIFI_Clean(); return 0; }对比这2个代码，第一个函数能构建publish报文？