am335x Qt SocketCAN Demo hacking

/***********************************************************************************
*                    am335x Qt SocketCAN Demo hacking
*  说明：
*      本源代码来自OK335xS，主要是为分析如何在Qt中使用SocketCAN的这种通信方式。
*
*                                          2015-9-12 晴 深圳 南山平山村 曾剑锋
**********************************************************************************/

cat main.c
#include <QtGui/QApplication>
#include "mainwindow.h"
#include "myinputpanelcontext.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
/**
* 创建软键盘
*/
MyInputPanelContext *ic = new MyInputPanelContext;
/**
* This function replaces the QInputContext instance used by the application with inputContext.
* Qt takes ownership of the given inputContext.
*
* 设置软键盘
*/
a.setInputContext(ic); //将输入上下文与应用程序关联

MainWindow w;
/**
* Qt::WindowMaximizeButtonHint:
*        Adds a maximize button. On some platforms this implies Qt::WindowSystemMenuHint for it to work.
* Qt::WindowMinimizeButtonHint:
*     Adds a minimize button. On some platforms this implies Qt::WindowSystemMenuHint for it to work.
*/
w.setWindowFlags(w.windowFlags()& ~Qt::WindowMaximizeButtonHint& ~Qt::WindowMinimizeButtonHint);
w.showMaximized();
w.show();

return a.exec();
}

cat  mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QProcess>
#include <sys/ioctl.h>
#include <net/if.h>
#include <linux/can.h>
#include "thread.h"
#include <QButtonGroup>

/**
* 引入界面文件生成的UI类
*/
namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
protected:
void moveEvent(QMoveEvent *);        // 界面移动事件
void resizeEvent(QResizeEvent *);    // 界面重绘大小事件
void closeEvent(QCloseEvent *);      // 界面关闭事件
private slots:
void on_send_clicked();              // 发送按钮点击槽
void msg(QString str);               // 信息处理信号槽
void stopcan(int v);                 // 停止can信号槽
void startcan(int v);                // 开始can信号槽
void on_can0_toggled(bool checked);  // can0 被点击翻转信号槽
void on_can1_toggled(bool checked);  // can1 被点击翻转信号槽

private:
Ui::MainWindow *ui;                  // 声明图形界面指针
int socket;                          // can socket 描述符
struct sockaddr_can addr;            // can socket 地址结构体
Thread *t;                           // 线程
QButtonGroup* btg;                   // 按钮
};

#endif // MAINWINDOW_H

cat  mainwindow.c
#include <sys/ioctl.h>
#include <fcntl.h>
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
#include <unistd.h>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),            // 构造函数初始化父类构造函数
ui(new Ui::MainWindow)          // 创建ui实体，并赋值
{
ui->setupUi(this);              // 设置将图形界面放置在哪个对象上

btg = new QButtonGroup;         // 创建分组，多选一
btg->addButton(ui->can0,0);
btg->addButton(ui->can1,1);

startcan(0);
}

MainWindow::~MainWindow()
{
/**
* 这里让人怀疑，都已经删除了ui界面，button group又怎么能够获取到ui里面的checkedId呢？
* 唯一的解释就是button group里面保存了最后一次toggle事件获取的checkedId值，而不是运行
* checkedId()的时候去获取checkedId
*/
delete ui;
stopcan(btg->checkedId());
}

void MainWindow::msg(QString str)
{
/**
* 将获取到的信息放到显示文本框的最后去
*/
ui->label->append(str);
}

void MainWindow::on_send_clicked()
{
/**
* struct can_frame - basic CAN frame structure
* @can_id:  CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition
* @can_dlc: frame payload length in byte (0 .. 8) aka data length code
*           N.B. the DLC field from ISO 11898-1 Chapter 8.4.2.3 has a 1:1
*           mapping of the 'data length code' to the real payload length
* @data:    CAN frame payload (up to 8 byte)
*
* struct can_frame {
*     canid_t can_id;  // 32 bit CAN_ID + EFF/RTR/ERR flags
*     __u8    can_dlc; // frame payload length in byte (0 .. CAN_MAX_DLEN)
*     __u8    data[CAN_MAX_DLEN] __attribute__((aligned(8)));
* };
*/
struct can_frame frame;
/**
* 获取将要发送的文本内容
* Returns a std::string object with the data contained in this QString.
* The Unicode data is converted into 8-bit characters using the toUtf8() function.
*/
std::string  str=ui->edit->text().toStdString();

/**
* 如果文本的长度大于8，那么将给出提示信息，并直接返回，不发送数据
*/
if(str.length() > 8)
{
QMessageBox::about(this,"error","length of send string must less than 8 bytes");
return;
}

/**
* 默认发送的can id是0x123
*
* 扩展格式识别符由 29 位组成。其格式包含两个部分：11 位基本 ID、18 位扩展 ID。
* Controller Area Network Identifier structure:
*
* bit 0-28     : CAN识别符 (11/29 bit)
* bit 29       : 错误帧标志 (0 = data frame, 1 = error frame)
* bit 30       : 远程发送请求标志 (1 = rtr frame)
* bit 31       : 帧格式标志 (0 = standard 11 bit, 1 = extended 29 bit)
*
* typedef __u32 canid_t;
*
* struct can_frame {
*      canid_t can_id;  // 32 bit CAN_ID + EFF/RTR/ERR flags
*       __u8    can_dlc; // 数据长度: 0 .. 8
*       __u8    data[8] __attribute__((aligned(8)));
*  };
*/
frame.can_id = 0x123;
/**
* Returns a pointer to an array that contains a null-terminated sequence of
* characters (i.e., a C-string) representing the current value of the string object.
* This array includes the same sequence of characters that make up the value of
* the string object plus an additional terminating null-character ('\0') at the end.
*/
strcpy((char*)frame.data, str.c_str());
/**
* 目前猜测：dlc --> data length count
* 于是可以很好的解释：can 发送的数据长度，是按字节算的
*/
frame.can_dlc = str.length();

/**
* Send N bytes of BUF on socket FD to peer at address ADDR (which is
* ADDR_LEN bytes long).  Returns the number sent, or -1 for errors.
*
* This function is a cancellation point and therefore not marked with
* __THROW.
*
* extern ssize_t sendto (int __fd, __const void *__buf, size_t __n,
*         int __flags, __CONST_SOCKADDR_ARG __addr,
*         socklen_t __addr_len);
*/
sendto(socket,&frame,sizeof(struct can_frame),0,(struct sockaddr*)&addr,sizeof(addr));
}

void MainWindow::moveEvent(QMoveEvent *)
{
/**
* 让测试窗口不会被移动
*/
this->move(QPoint(0,0));
}

void MainWindow::resizeEvent(QResizeEvent *)
{
/**
* 让窗口最大化显示
*/
this->showMaximized();
}

void MainWindow::closeEvent(QCloseEvent *)
{
/**
* 直接退出，不用关闭can口么？也就是说程序会在真正推出前，先解析掉所有当前生成的类实体？
*/
exit(0);
}

void MainWindow::startcan(int v)
{
/**
* 从提示信息可以看出，使用125000作为默认的波特率
*/
if(v == 0)
{
system("canconfig can0 bitrate 125000 ctrlmode triple-sampling on");
system("canconfig can0 start");
}
else
{
system("canconfig can1 bitrate 125000 ctrlmode triple-sampling on");
system("canconfig can1 start");
}

/**
* Create a new socket of type TYPE in domain DOMAIN, using
* protocol PROTOCOL.  If PROTOCOL is zero, one is chosen automatically.
* Returns a file descriptor for the new socket, or -1 for errors.
*
* extern int socket (int __domain, int __type, int __protocol) __THROW;
*
* #define PF_CAN        29    // Controller Area Network.
*
* SOCK_RAW = 3,               // Raw protocol interface.
* #define SOCK_RAW SOCK_RAW
*
* particular protocols of the protocol family PF_CAN
* #define CAN_RAW        1    // RAW sockets
*
*/
socket =  ::socket(PF_CAN, SOCK_RAW, CAN_RAW);

/**
* struct ifreq
* {
*  # define IFHWADDRLEN    6
*  # define IFNAMSIZ    IF_NAMESIZE
*    union
*    {
*          char ifrn_name[IFNAMSIZ];    // Interface name, e.g. "en0".
*    } ifr_ifrn;
*
*    union
*    {
*          struct sockaddr ifru_addr;
*          struct sockaddr ifru_dstaddr;
*          struct sockaddr ifru_broadaddr;
*          struct sockaddr ifru_netmask;
*          struct sockaddr ifru_hwaddr;
*          short int ifru_flags;
*          int ifru_ivalue;
*          int ifru_mtu;
*          struct ifmap ifru_map;
*          char ifru_slave[IFNAMSIZ];    // Just fits the size
*          char ifru_newname[IFNAMSIZ];
*          __caddr_t ifru_data;
*    } ifr_ifru;
* };
* # define ifr_name    ifr_ifrn.ifrn_name            // interface name
* # define ifr_hwaddr    ifr_ifru.ifru_hwaddr        // MAC address
* # define ifr_addr    ifr_ifru.ifru_addr            // address
* # define ifr_dstaddr    ifr_ifru.ifru_dstaddr      // other end of p-p lnk
* # define ifr_broadaddr    ifr_ifru.ifru_broadaddr  // broadcast address
* # define ifr_netmask    ifr_ifru.ifru_netmask      // interface net mask
* # define ifr_flags    ifr_ifru.ifru_flags          // flags
* # define ifr_metric    ifr_ifru.ifru_ivalue        // metric
* # define ifr_mtu    ifr_ifru.ifru_mtu              // mtu
* # define ifr_map    ifr_ifru.ifru_map              // device map
* # define ifr_slave    ifr_ifru.ifru_slave          // slave device
* # define ifr_data    ifr_ifru.ifru_data            // for use by interface
* # define ifr_ifindex    ifr_ifru.ifru_ivalue       // interface index
* # define ifr_bandwidth    ifr_ifru.ifru_ivalue     // link bandwidth
* # define ifr_qlen    ifr_ifru.ifru_ivalue          // queue length
* # define ifr_newname    ifr_ifru.ifru_newname      // New name
* # define _IOT_ifreq    _IOT(_IOTS(char),IFNAMSIZ,_IOTS(char),16,0,0)
* # define _IOT_ifreq_short _IOT(_IOTS(char),IFNAMSIZ,_IOTS(short),1,0,0)
* # define _IOT_ifreq_int    _IOT(_IOTS(char),IFNAMSIZ,_IOTS(int),1,0,0)
*
* SIOCGIFINDEX:
*     Retrieve the interface index of the interface into ifr_ifindex.
*/
struct ifreq ifr;
strcpy((char *)(ifr.ifr_name),v == 0 ? "can0" : "can1");
ioctl(socket,SIOCGIFINDEX,&ifr);

/**
* 绑定socket
*/
addr.can_family = AF_CAN;
addr.can_ifindex = ifr.ifr_ifindex;
bind(socket,(struct sockaddr*)&addr,sizeof(addr));

/**
* 这里是存在问题，每次线程并没有关闭，而是直接不管，可能导致一些问题
* 从后续的代码可以看出，每次都已经停止了线程，delete了对象实体。
*/
t = NULL;

/**
* 创建线程，并将socket文件描述符作为参数传入线程，主要作为接受数据线程
*/
t = new Thread(socket);

/**
* 用于处理线程发出的信号
*/
connect(t,SIGNAL(msg(QString)),this,SLOT(msg(QString)));

/**
* 开启线程
*/
t->start();
}

void MainWindow::stopcan(int v)
{
/**
* 关闭对应的can之前，先关闭对应socket接受线程
*/
if(t)
{
t->stop();
t->deleteLater();
}

/**
* 关闭socket文件描述符
*/
::close(socket);

/**
* 给出相关的提示信息
*/
if(v == 0)
system("canconfig can0 stop");
else
system("canconfig can1 stop");
}

void MainWindow::on_can0_toggled(bool checked)
{
/**
* 根据对应的情况，打开，或者关闭对应的can设备
*/
if(checked)
{
stopcan(1);
startcan(0);
}
}

void MainWindow::on_can1_toggled(bool checked)
{
/**
* 根据对应的情况，打开，或者关闭对应的can设备
*/
if(checked)
{
stopcan(0);
startcan(1);
}
}