void Transport(int *p) { int t = 0; for (int i = 0; i < 3; i++) { for (int j = i; j < 3; j++) { t = *(p + (i * 3) + j); *(p + (i * 3) + j) = *(p + (j * 3) + i); *(p + (j * 3) + i) = t; } } }
时间: 2023-06-08 16:07:00 浏览: 44
你的问题是一个函数,我理解您想问这个函数的作用是什么。这个函数实现了一个矩阵的转置,它将一个3x3的矩阵沿主对角线进行转置。具体地说,它通过交换矩阵中第i行第j列的元素和第j行第i列的元素,来实现矩阵的转置。
相关问题
UEC++编写实现MQTT协议
MQTT(Message Queuing Telemetry Transport)是一个轻量级的、基于发布/订阅模式的通讯协议,被广泛应用于物联网等领域。下面是一个使用UEC++编写实现MQTT协议的示例:
```cpp
#include <iostream>
#include <string>
#include <cstring>
#include <map>
#include <vector>
using namespace std;
// 定义MQTT消息类型
enum MqttMessageType {
CONNECT = 1,
CONNACK,
PUBLISH,
PUBACK,
PUBREC,
PUBREL,
PUBCOMP,
SUBSCRIBE,
SUBACK,
UNSUBSCRIBE,
UNSUBACK,
PINGREQ,
PINGRESP,
DISCONNECT
};
// 定义MQTT连接状态
enum MqttConnectStatus {
CONNECT_ACCEPTED = 0,
CONNECT_REFUSED_PROTOCOL,
CONNECT_REFUSED_ID,
CONNECT_REFUSED_SERVER,
CONNECT_REFUSED_USER,
CONNECT_REFUSED_PWD
};
// 定义MQTT消息结构体
struct MqttMessage {
MqttMessageType type;
bool dup;
int qos;
bool retain;
int length;
string topic;
string payload;
int packet_id;
map<string, string> properties;
};
// 定义MQTT连接结构体
struct MqttConnect {
string protocol_name;
int protocol_version;
bool clean_session;
bool will_flag;
int will_qos;
bool will_retain;
string will_topic;
string will_message;
string client_id;
string username;
string password;
map<string, string> properties;
};
// 定义MQTT客户端类
class MqttClient {
public:
MqttClient(const string& broker_url, int broker_port);
~MqttClient();
bool connect(const MqttConnect& connect);
bool publish(const MqttMessage& message);
bool subscribe(const vector<string>& topics);
bool unsubscribe(const vector<string>& topics);
void disconnect();
private:
bool send_message(const MqttMessage& message);
bool read_message(MqttMessage& message);
string broker_url_;
int broker_port_;
int socket_fd_;
int packet_id_;
};
// 构造函数
MqttClient::MqttClient(const string& broker_url, int broker_port)
: broker_url_(broker_url), broker_port_(broker_port), socket_fd_(-1), packet_id_(1) {}
// 析构函数
MqttClient::~MqttClient() {
disconnect();
}
// 连接到MQTT服务器
bool MqttClient::connect(const MqttConnect& connect) {
// 建立TCP连接
socket_fd_ = socket(AF_INET, SOCK_STREAM, 0);
if (socket_fd_ < 0) {
cerr << "Failed to create socket." << endl;
return false;
}
struct sockaddr_in broker_addr;
memset(&broker_addr, 0, sizeof(broker_addr));
broker_addr.sin_family = AF_INET;
broker_addr.sin_port = htons(broker_port_);
broker_addr.sin_addr.s_addr = inet_addr(broker_url_.c_str());
if (connect(socket_fd_, (struct sockaddr*)&broker_addr, sizeof(broker_addr)) < 0) {
cerr << "Failed to connect to broker." << endl;
return false;
}
// 发送CONNECT消息
MqttMessage message;
message.type = CONNECT;
message.qos = 0;
message.properties["protocol_name"] = connect.protocol_name;
message.properties["protocol_version"] = to_string(connect.protocol_version);
message.properties["clean_session"] = connect.clean_session ? "1" : "0";
message.properties["client_id"] = connect.client_id;
message.properties["will_flag"] = connect.will_flag ? "1" : "0";
message.properties["will_qos"] = to_string(connect.will_qos);
message.properties["will_retain"] = connect.will_retain ? "1" : "0";
message.properties["will_topic"] = connect.will_topic;
message.properties["will_message"] = connect.will_message;
message.properties["username"] = connect.username;
message.properties["password"] = connect.password;
message.properties.insert(connect.properties.begin(), connect.properties.end());
if (!send_message(message)) {
cerr << "Failed to send CONNECT message." << endl;
return false;
}
// 读取CONNACK消息
MqttMessage connack;
if (!read_message(connack) || connack.type != CONNACK) {
cerr << "Failed to receive CONNACK message." << endl;
return false;
}
if (connack.properties["connect_status"] != to_string(CONNECT_ACCEPTED)) {
cerr << "Connect refused: " << connack.properties["connect_status"] << endl;
return false;
}
return true;
}
// 发布MQTT消息
bool MqttClient::publish(const MqttMessage& message) {
// 发送PUBLISH消息
MqttMessage publish_msg = message;
publish_msg.type = PUBLISH;
publish_msg.dup = false;
publish_msg.packet_id = packet_id_++;
if (!send_message(publish_msg)) {
cerr << "Failed to send PUBLISH message." << endl;
return false;
}
// 读取PUBACK消息
if (message.qos == 1) {
MqttMessage puback;
if (!read_message(puback) || puback.type != PUBACK || puback.packet_id != publish_msg.packet_id) {
cerr << "Failed to receive PUBACK message." << endl;
return false;
}
}
return true;
}
// 订阅MQTT主题
bool MqttClient::subscribe(const vector<string>& topics) {
// 构造SUBSCRIBE消息
MqttMessage message;
message.type = SUBSCRIBE;
message.qos = 1;
message.packet_id = packet_id_++;
for (auto topic : topics) {
message.properties["topic"] = topic;
message.properties["qos"] = "1";
}
if (!send_message(message)) {
cerr << "Failed to send SUBSCRIBE message." << endl;
return false;
}
// 读取SUBACK消息
MqttMessage suback;
if (!read_message(suback) || suback.type != SUBACK || suback.packet_id != message.packet_id) {
cerr << "Failed to receive SUBACK message." << endl;
return false;
}
return true;
}
// 取消订阅MQTT主题
bool MqttClient::unsubscribe(const vector<string>& topics) {
// 构造UNSUBSCRIBE消息
MqttMessage message;
message.type = UNSUBSCRIBE;
message.qos = 1;
message.packet_id = packet_id_++;
for (auto topic : topics) {
message.properties["topic"] = topic;
}
if (!send_message(message)) {
cerr << "Failed to send UNSUBSCRIBE message." << endl;
return false;
}
// 读取UNSUBACK消息
MqttMessage unsuback;
if (!read_message(unsuback) || unsuback.type != UNSUBACK || unsuback.packet_id != message.packet_id) {
cerr << "Failed to receive UNSUBACK message." << endl;
return false;
}
return true;
}
// 断开MQTT连接
void MqttClient::disconnect() {
if (socket_fd_ >= 0) {
MqttMessage message;
message.type = DISCONNECT;
send_message(message);
close(socket_fd_);
socket_fd_ = -1;
}
}
// 发送MQTT消息
bool MqttClient::send_message(const MqttMessage& message) {
// 构造消息头
char header[5];
int pos = 0;
header[pos++] = (message.type << 4) | (message.dup << 3) | (message.qos << 1) | message.retain;
do {
uint8_t digit = message.length % 128;
message.length /= 128;
if (message.length > 0) {
digit |= 0x80;
}
header[pos++] = digit;
} while (message.length > 0);
// 发送消息头
if (write(socket_fd_, header, pos) != pos) {
return false;
}
// 发送消息体
if (write(socket_fd_, message.topic.c_str(), message.topic.length()) != message.topic.length() ||
(message.qos > 0 && write(socket_fd_, &message.packet_id, sizeof(message.packet_id)) != sizeof(message.packet_id)) ||
write(socket_fd_, message.payload.c_str(), message.payload.length()) != message.payload.length()) {
return false;
}
return true;
}
// 读取MQTT消息
bool MqttClient::read_message(MqttMessage& message) {
// 读取消息头
char header[5];
int pos = 0;
while (pos < 2) {
int ret = read(socket_fd_, header + pos, 2 - pos);
if (ret <= 0) {
return false;
}
pos += ret;
}
message.type = static_cast<MqttMessageType>((header[0] & 0xf0) >> 4);
message.dup = (header[0] & 0x08) != 0;
message.qos = (header[0] & 0x06) >> 1;
message.retain = (header[0] & 0x01) != 0;
message.length = 0;
for (int i = 1; i < pos; ++i) {
message.length = (message.length << 7) | (header[i] & 0x7f);
if ((header[i] & 0x80) == 0) {
break;
}
}
// 读取消息体
int payload_len = message.length;
if (message.qos > 0) {
payload_len -= sizeof(message.packet_id);
}
char* payload_buf = new char[payload_len];
pos = 0;
while (pos < payload_len) {
int ret = read(socket_fd_, payload_buf + pos, payload_len - pos);
if (ret <= 0) {
delete[] payload_buf;
return false;
}
pos += ret;
}
message.topic = string(payload_buf, payload_len);
if (message.qos > 0) {
memcpy(&message.packet_id, payload_buf + payload_len, sizeof(message.packet_id));
message.payload = string(payload_buf + payload_len + sizeof(message.packet_id), message.length - payload_len - sizeof(message.packet_id));
} else {
message.payload = string(payload_buf + payload_len, message.length - payload_len);
}
delete[] payload_buf;
return true;
}
int main() {
MqttConnect connect;
connect.protocol_name = "MQTT";
connect.protocol_version = 4;
connect.clean_session = true;
connect.client_id = "test_client";
MqttClient client("localhost", 1883);
if (client.connect(connect)) {
MqttMessage message;
message.qos = 1;
message.topic = "test_topic";
message.payload = "hello world";
client.publish(message);
client.subscribe({"test_topic"});
client.unsubscribe({"test_topic"});
client.disconnect();
}
return 0;
}
```
这段代码实现了MQTT客户端的基本功能,包括连接到MQTT服务器、发布消息、订阅主题和取消订阅主题等。其中,send_message函数用于发送MQTT消息,read_message函数用于读取MQTT消息。MQTT消息的格式和消息头的解析方式参考MQTT协议规范。
STM32f103+ENC28J60实现PC与开发板udp收发数据代码
以下是基于STM32f103和ENC28J60实现PC与开发板UDP收发数据的示例代码:
首先需要安装lwIP网络协议栈。在创建工程时,选择使用lwIP,然后选择相应的网络接口。在我的例子中,我使用了ENC28J60作为网络接口。
接下来,需要配置lwIP。在lwIP的配置文件(lwipopts.h)中,需要设置以下参数:
```
#define LWIP_UDP 1
#define LWIP_NETIF_API 1
#define LWIP_NETIF_HOSTNAME 1
#define IP_SOF_BROADCAST 1
#define IP_SOF_BROADCAST_RECV 1
```
这些参数启用了UDP协议、lwIP API、主机名和广播功能。
接着,在main.c中初始化网络接口:
```
#include "lwip/init.h"
#include "lwip/netif.h"
#include "netif/etharp.h"
#include "enc28j60.h"
struct netif gnetif;
int main(void)
{
/* Initialize lwIP */
lwip_init();
/* Initialize ENC28J60 */
enc28j60_init();
/* Add ENC28J60 interface */
netif_add(&gnetif, NULL, NULL, NULL, NULL, enc28j60_init_eth, ethernet_input);
/* Set ENC28J60 interface up */
netif_set_up(&gnetif);
/* Start DHCP client */
dhcp_start(&gnetif);
/* Main loop */
while(1)
{
/* Process lwIP timers */
sys_check_timeouts();
/* Process incoming packets */
ethernetif_input(&gnetif);
}
}
```
在初始化lwIP后,我们需要初始化ENC28J60,并添加网络接口。然后将网络接口设置为活动状态,并启动DHCP客户端。
现在我们可以开始实现UDP数据包的收发。以下是发送UDP数据包的代码:
```
#include "lwip/udp.h"
#define SERVER_IP_ADDR IP_ADDR_BROADCAST
#define SERVER_PORT 1234
void udp_send_data(void)
{
struct udp_pcb *pcb;
struct pbuf *p;
err_t err;
/* Create a new UDP PCB */
pcb = udp_new();
/* Allocate a pbuf for the data to be sent */
p = pbuf_alloc(PBUF_TRANSPORT, sizeof("Hello, world!"), PBUF_RAM);
memcpy(p->payload, "Hello, world!", sizeof("Hello, world!"));
/* Send the UDP packet */
err = udp_sendto(pcb, p, IP_ADDR_BROADCAST, SERVER_PORT);
/* Free the pbuf */
pbuf_free(p);
/* Free the UDP PCB */
udp_remove(pcb);
}
```
这个例子中,我们创建了一个新的UDP PCB,并分配了一个pbuf用于发送数据。然后,我们使用udp_sendto函数将数据发送到广播地址。
以下是接收UDP数据包的代码:
```
#include "lwip/udp.h"
#define CLIENT_PORT 4321
void udp_recv_callback(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
/* Process the received data */
printf("Received data: %s\n", p->payload);
/* Free the pbuf */
pbuf_free(p);
}
void udp_recv_data(void)
{
struct udp_pcb *pcb;
err_t err;
/* Create a new UDP PCB */
pcb = udp_new();
/* Bind the UDP PCB to a local port */
err = udp_bind(pcb, IP_ADDR_ANY, CLIENT_PORT);
/* Set the receive callback function */
udp_recv(pcb, udp_recv_callback, NULL);
/* Main loop */
while(1)
{
/* Process lwIP timers */
sys_check_timeouts();
/* Process incoming packets */
ethernetif_input(&gnetif);
}
/* Free the UDP PCB */
udp_remove(pcb);
}
```
这个例子中,我们创建了一个新的UDP PCB,并将其绑定到本地端口。然后,我们设置了一个回调函数来处理接收到的数据。
在主循环中,我们需要定期调用sys_check_timeouts函数来处理lwIP定时器,并调用ethernetif_input函数来处理接收到的数据包。
以上便是基于STM32f103和ENC28J60实现PC与开发板UDP收发数据的示例代码。
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