基于tinyXML2的xml文件基本操作

tinyXML2是一款非常轻便的第三方操作xml文件的C++库，现在网络上许多教程都是基于tinyXML2，为此制作了以下的demo。tinyXML2可以从官网去下载，也可以去github下载。本Blog使用的是tinyXML2的6.0.2版本作为讲解。同时，本博客也将附上本demo的下载地址，读者可以自己去测试。

首先，tinyXML2使用起来方便，既可以将其生成dll库，也可以直接将tinyXML2拉到项目中。为了方便起见，本文直接将库的源码拉到项目文件中。
假设，我们在一个视觉项目中使用多个相机，那么每个相机将会有ID、 IP地址、曝光时间、触发模式等属性。所以我们就想有类似下面的配置文件：

<CameraI>
    <DevID>5DevID>
    <IpAddress>178.26.85.83IpAddress>
    <SubnetMask>123.45.67.89SubnetMask>
    <ExposureAuto>falseExposureAuto>
    <ExposureTime>200ExposureTime>
    <TriggerMode>falseTriggerMode>
CameraI>

<CameraII>
    <DevID>5DevID>
    <IpAddress>178.26.85.83IpAddress>
    <SubnetMask>123.45.67.89SubnetMask>
    <ExposureAuto>falseExposureAuto>
    <ExposureTime>200ExposureTime>
    <TriggerMode>falseTriggerMode>
CameraII>

<CameraIII>
    <DevID>5DevID>
    <IpAddress>178.26.85.83IpAddress>
    <SubnetMask>123.45.67.89SubnetMask>
    <ExposureAuto>falseExposureAuto>
    <ExposureTime>200ExposureTime>
    <TriggerMode>falseTriggerMode>
CameraIII>

针对以上情况，我们得写一个怎么去读，怎么去写，怎么去修改属性的代码。下面将附上测试代码，希望读者通过调试来掌握tinyXML2的调用方法。

/**
* 开发环境: VS2015 + TinyXML2 6.0.2 + Windows 10
* 硬件环境: CPU i7-8750H; RAM 8G; Gpu: GTX1050Ti
*
* 建议通过IDE调试来学习
*/
#include 
#include "tinyxml2_6.2.0/tinyxml2.h"

/** @brief 读取每个相机的属性

@param p 相机节点指针
*/
static void ReadOneCameraAttribute(const tinyxml2::XMLElement* p)
{
    int devIdContent = p->FirstChildElement("DevID")->IntText();
    const char* ipAddrContent = p->FirstChildElement("IpAddress")->GetText();
    const char* subnetMaskContent = p->FirstChildElement("SubnetMask")->GetText();
    const char* exposureAutoContent = p->FirstChildElement("ExposureAuto")->GetText();
    int64_t exposureTimeContent = p->FirstChildElement("ExposureTime")->Int64Text();
    bool triggerModeContent = p->FirstChildElement("TriggerMode")->BoolText();

    std::cout << "devIdContent(int):\t" << devIdContent << std::endl;
    std::cout << "ipAddrContent:\t" << ipAddrContent << std::endl;
    std::cout << "subnetMaskContent:\t" << subnetMaskContent << std::endl;
    std::cout << "exposureAutoContent:\t" << exposureAutoContent << std::endl;
    std::cout << "exposureTimeContent(int64_t):\t" << exposureTimeContent << std::endl;
    std::cout << "triggerModeContent(bool):\t" << ((triggerModeContent == true) ? "true" : "false") << std::endl;
}

/** @brief 读取解析某路径的xml文件

@param path xml文件路径
*/
static void ReadParam(const std::string& path)
{
    // 导入文件错误, 退出
    tinyxml2::XMLDocument doc;
    tinyxml2::XMLError error = doc.LoadFile(path.c_str());
    if (error != tinyxml2::XMLError::XML_SUCCESS) return;

    // 三个相机指针
    tinyxml2::XMLElement* pFirst = doc.FirstChildElement("CameraI");
    tinyxml2::XMLElement* pSecond = doc.FirstChildElement("CameraII");
    tinyxml2::XMLElement* pThree = doc.FirstChildElement("CameraIII");

    // 分别读取每个相机的各个属性
    ReadOneCameraAttribute(pFirst); std::cout << "------------------\n";
    ReadOneCameraAttribute(pSecond); std::cout << "------------------\n";
    ReadOneCameraAttribute(pThree); std::cout << "------------------\n";
}


/** @brief 修改相机属性

@param p 相机节点指针
*/
static void ModifyOneCamera(tinyxml2::XMLElement* p)
{
    int devId = 4;
    const char* ipAddr = "139.66.38.13";
    const char* subnetMask = "255.0.0.0";
    bool exposureAuto = false;
    int64_t exposureTime = 80;
    bool triggerMode = false;

    p->FirstChildElement("DevID")->SetText(devId);
    p->FirstChildElement("IpAddress")->SetText(ipAddr);
    p->FirstChildElement("SubnetMask")->SetText(subnetMask);
    p->FirstChildElement("ExposureAuto")->SetText(exposureAuto);
    p->FirstChildElement("ExposureTime")->SetText(exposureTime);
    p->FirstChildElement("TriggerMode")->SetText(triggerMode);
}

/** @brief 修改某xml文件的参数

@param path xml文件路径
*/
static void ModifyParam(const std::string& path)
{
    // 导入文件错误, 退出
    tinyxml2::XMLDocument doc;
    tinyxml2::XMLError error = doc.LoadFile(path.c_str());
    if (error != tinyxml2::XMLError::XML_SUCCESS) return;

    // 三个相机指针
    tinyxml2::XMLElement* pFirst = doc.FirstChildElement("CameraI");
    tinyxml2::XMLElement* pSecond = doc.FirstChildElement("CameraII");
    tinyxml2::XMLElement* pThree = doc.FirstChildElement("CameraIII");

    // 修改
    ModifyOneCamera(pFirst);
    ModifyOneCamera(pSecond);
    ModifyOneCamera(pThree);

    doc.SaveFile(path.c_str());
}



/** @brief 写相机属性. 产生完了之后将所有节点挂在p下面

@param p 某个相机节点
@param doc 所有的元素属性以及值均在doc的下面
*/
static void WriteOneCameraAttibute(tinyxml2::XMLElement* p, tinyxml2::XMLDocument& doc)
{
    const char* ipAddr = "178.26.85.83";
    const char* subnetMask = "123.45.67.89";
    int64_t exposureTime = 200;

    tinyxml2::XMLElement* pDevID = doc.NewElement("DevID");
    tinyxml2::XMLText* pDevIdText = doc.NewText("5");
    pDevID->InsertEndChild(pDevIdText);
    p->InsertEndChild(pDevID);

    tinyxml2::XMLElement* pIpAddr = doc.NewElement("IpAddress");
    tinyxml2::XMLText* pIpAddrText = doc.NewText(ipAddr);
    pIpAddr->InsertEndChild(pIpAddrText);
    p->InsertEndChild(pIpAddr);

    tinyxml2::XMLElement* pSubnetMask = doc.NewElement("SubnetMask");
    tinyxml2::XMLText* pSubnetMaskText = doc.NewText(subnetMask);
    pSubnetMask->InsertEndChild(pSubnetMaskText);
    p->InsertEndChild(pSubnetMask);

    tinyxml2::XMLElement* pExposureAuto = doc.NewElement("ExposureAuto");
    tinyxml2::XMLText* pExposureAutoText = doc.NewText("false");
    pExposureAuto->InsertEndChild(pExposureAutoText);
    p->InsertEndChild(pExposureAuto);

    tinyxml2::XMLElement* pExposureTime = doc.NewElement("ExposureTime");
    tinyxml2::XMLText* pExposureTimeText = doc.NewText("200");
    pExposureTime->InsertEndChild(pExposureTimeText);
    p->InsertEndChild(pExposureTime);

    tinyxml2::XMLElement* pTriggerMode = doc.NewElement("TriggerMode");
    tinyxml2::XMLText* pTriggerModeText = doc.NewText("false");
    pTriggerMode->InsertEndChild(pTriggerModeText);
    p->InsertEndChild(pTriggerMode);
}


/** @brief 将数据写到某个xml文件中

@param path xml文件路径
*/
static void WriteParam(const std::string& path)
{
    tinyxml2::XMLDocument doc;
    const char* declaration = "";
    doc.Parse(declaration);

    tinyxml2::XMLElement* pFirst = doc.NewElement("CameraI");
    WriteOneCameraAttibute(pFirst, doc);
    doc.InsertEndChild(pFirst);

    tinyxml2::XMLElement* pSecond = doc.NewElement("CameraII");
    WriteOneCameraAttibute(pSecond, doc);
    doc.InsertEndChild(pSecond);

    tinyxml2::XMLElement* pThree = doc.NewElement("CameraIII");
    WriteOneCameraAttibute(pThree, doc);
    doc.InsertEndChild(pThree);

    doc.SaveFile(path.c_str());
}

void test_CameraXML()
{
    std::string path = "../Resources/camera_info.xml";
    std::cout << "---------------生成一个xml文件------------------" << std::endl;
    WriteParam(path);

    std::cout << "--------------写文件结束，读取生成的xml文件------------------" << std::endl;
    ReadParam(path);

    std::cout << "--------------读文件结束，修改文件开始------------------" << std::endl;
    ModifyParam(path);
}