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openfoam文件读取

来源：博客园

对于openfoam或其他c++程序而言，文件的读取是尤为重要的

我们最开始学习C++时，会学到类的初始化，或者是变量定义为某个值，再对某个值进行遍历，，，类似如下：

点击查看代码
#include          // 包含头文件。using namespace std;        // 指定缺省的命名空间。int main(){    int a = 10;    int b = (10);    int c(10);    int e = {10};    int f{ 10 };    cout << "a=" << a << endl;    cout << "b=" << b << endl;    cout << "c=" << c << endl;    cout << "e=" << e << endl;    cout << "f=" << f << endl;}

尤其c++，初学时候内心非常感慨，怎么这么多初始化方式，我该用哪个现在回头看，其实能熟悉一个，其他看懂就行，看不懂都没关系，毕竟我们还有gdb或者typeid()帮忙，可以看看这个变量类型具体是什么说到底我们要问题导向目标导向，我们学习C++是为了类似openfoam这样的大工程服务的那学这么多初始化赋值，有必要吗如果是个大工程或者大程序是完全没必要的，因为大工程的数据都是从文件或者数据库中获得的你想想，要计算一个流体问题，如果有一万个网格，手打一万个三维位置就已经非常让人头疼了，更不要说上百个组分和压力等参数了，不现实所以又回到了问题的起点，读取文件很重要，那么如何从文件中初始化程序，如何读取文件


(资料图片)

在看of源码之前，不妨复习下C++是怎么读取文件的，进行下知识巩固

C++多使用fstream类或ifstream类

点击查看代码
#include #include   // ifstream类需要包含的头文件。#include      // getline()函数需要包含的头文件。using  namespace std;int main(){    string filename = R"(./test.txt)";    //ifstream fin(filename, ios::in);    ifstream fin;    fin.open(filename , ios::in);    // 判断打开文件是否成功。    // 失败的原因主要有：1）目录不存在；2）文件不存在；3）没有权限，Linux平台下很常见。    if (fin.is_open() == false)    {        cout << "打开文件" << filename << "失败。\n";  return 0;    }    string buffer;    while (fin >> buffer)    {        cout << buffer << endl;    }    fin.close();   // 关闭文件，fin对象失效前会自动调用close()。    cout << "操作文件完成。\n";}

OPENFOAM的文件读写，主要是用IOdictionary类

打开IOdictionary类的头文件，并不复杂

点击查看代码
class IOdictionary:    public baseIOdictionary{public:    // Constructors        //- Construct given an IOobject        IOdictionary(const IOobject&);        //- Construct given an IOobject and dictionary        IOdictionary(const IOobject&, const dictionary&);        //- Construct given an IOobject and Istream        IOdictionary(const IOobject&, Istream&);        //- Copy constructor        IOdictionary(const IOdictionary&);        //- Move constructor        IOdictionary(IOdictionary&&);    //- Destructor    virtual ~IOdictionary();    // Member Functions        //- Is object global        virtual bool global() const        {            return true;        }        //- Return complete path + object name if the file exists        //  either in the case/processor or case otherwise null        virtual fileName filePath() const        {            return globalFilePath(type());        }    // Member Operators        //- Move assignment        void operator=(IOdictionary&&);};

继承于baseIOdictionary类，借助于IOobject接口有五个构造函数，这五个中一个移动构造一个拷贝构造，其他类继承可以创建自己成员函数global()和filePath()，头文件还对移动构造创建了等号赋值运算符我们再看IOdictionary类的关键先生IOobject

IOobjectIOobject就稍显复杂了，我们先看openfoam对其的描述：

IOobject defines the attributes of an object for which implicit objectRegistry management is supported, and provides the infrastructure for performing stream I/O.An IOobject is constructed with an object name, a class name, an instance path, a reference to a objectRegistry, and parameters determining its storage status.

下面这张图是openfoam与该接口有关的类谱图打开regIOobject类，这是个抽象类，openfoam对regIOobject的描述为：

regIOobject is an abstract class derived from IOobject to handle automatic object registration with the objectRegistry.

刨根问底，那么再继续看IOobject类，openfoam对IOobject类的描述为：

IOobject defines the attributes of an object for which implicit objectRegistry management is supported, and provides the infrastructure for performing stream I/O.An IOobject is constructed with an object name, a class name, an instance path, a reference to a objectRegistry, and parameters determining its storage status.

看到这里，可能你都忍不住要吐槽一句，这么溯源什么时候是头

刨根问底刨个稀烂，知道结果明年再见

是的，openfoam征程就是这么快乐，快乐的我现在看起来略显迷茫这里不赘述了，最后查了好半天，大概是哈希表来的，方便查询读取。openfoam中/0，/constant以及/system文件夹中那种奇怪的文件格式肯定有适合自己的读取方法。

那我们看看IOobject类相关源码，IOobject类有四个枚举控制读取权限以及文件检查

点击查看代码
//- Enumeration defining the valid states of an IOobject        enum objectState        {            GOOD,            BAD        };        //- Enumeration defining the read options        enum readOption        {            MUST_READ,            MUST_READ_IF_MODIFIED,            READ_IF_PRESENT,            NO_READ        };        //- Enumeration defining the write options        enum writeOption        {            AUTO_WRITE = 0,            NO_WRITE = 1        };        //- Enumeration defining the file checking options        enum fileCheckTypes        {            timeStamp,            timeStampMaster,            inotify,            inotifyMaster        };

内共有六个构造函数，其中一个拷贝构造

点击查看代码
// Constructors        //- Construct from name, instance, registry, io options        IOobject        (            const word& name,            const fileName& instance,            const objectRegistry& registry,            readOption r=NO_READ,            writeOption w=NO_WRITE,            bool registerObject=true        );        //- Construct from name, instance, local, registry, io options        IOobject        (            const word& name,            const fileName& instance,            const fileName& local,            const objectRegistry& registry,            readOption r=NO_READ,            writeOption w=NO_WRITE,            bool registerObject=true        );        //- Construct from path, registry, io options        //  Uses fileNameComponents() to split path into components.        IOobject        (            const fileName& path,            const objectRegistry& registry,            readOption r=NO_READ,            writeOption w=NO_WRITE,            bool registerObject=true        );        //- Construct from copy resetting registry        IOobject        (            const IOobject& io,            const objectRegistry& registry        );        //- Construct from copy resetting name        IOobject        (            const IOobject& io,            const word& name        );        //- Copy constructor        IOobject(const IOobject& io) = default;

我们举个例子，基于这些构造函数可以这样写类似这样的读取端口：

点击查看代码
IOobject dicName(    "dicName",    runTime.timeName(),    //runTime.constant(),    mesh,    IOobject::MUST_READ,    IOobject::AUTO_WRITE) ;

再回到IOdictionary类，

通过查看IOdictionary类的构造函数，我们了解到可以在创建好的IOobject端口基础上构建，也可以直接构建IOobject端口

点击查看代码
IOdictionary dicName(        IOobject (            "dicName",            //runTime.constant(),            runTime.system(),            mesh,            IOobject::MUST_READ,            IOobject::AUTO_WRITE        )    ) ;

那么我们如何通过IOdictionary类读取openfoam内文件呢，以openfoam内置icoFoam为例$ ls cavity/0 constant system$ tree cavity/cavity/├── 0│ ├── U│ └── p├── constant│ ├── polyMesh│ │ ├── boundary│ │ ├── faces│ │ ├── neighbour│ │ ├── owner│ │ └── points│ └── transportProperties└── system├── blockMeshDict├── controlDict├── fvSchemes└── fvSolution$ head cavity/0/* -n15

  • cavity/0/U */--------------------------------- C++ -----------------------------------========= |\ / F ield | OpenFOAM: The Open Source CFD Toolbox\ / O peration | Website: https://openfoam.org\ / A nd | Version: 8\/ M anipulation |*---------------------------------------------------------------------------*/FoamFile{version 2.0;format ascii;class ** volVectorField;**object U;}// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

  • cavity/0/p */--------------------------------- C++ -----------------------------------========= |\ / F ield | OpenFOAM: The Open Source CFD Toolbox\ / O peration | Website: https://openfoam.org\ / A nd | Version: 8\/ M anipulation |*---------------------------------------------------------------------------*/FoamFile{version 2.0;format ascii;class ** volScalarField;**object p;}// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //从以上内容可以看到，U和v分别属于volVectorField类以及volScalarField类，那么就利用IOobject接口分别创建相关类如下所示：

点击查看代码
volVectorField U(        IOobject(            "U" ,            runTime.timeName() ,            mesh ,            IOobject::MUST_READ ,            IOobject::AUTO_WRITE        ) ,        mesh    );    volScalarField p(        IOobject(            "p" ,            runTime.timeName() ,            mesh ,            IOobject::MUST_READ ,            IOobject::AUTO_WRITE        ) ,        mesh    );

再看其他两个文件夹$ grep -rn "dicti" ../cavity/constant/transportProperties:12: class dictionary;./cavity/system/controlDict:12: class dictionary;./cavity/system/fvSolution:12: class dictionary;./cavity/system/blockMeshDict:12: class dictionary;./cavity/system/fvSchemes:12: class dictionary;./constant/transportProperties:12: class dictionary;./system/controlDict:12: class dictionary;./system/fvSolution:12: class dictionary;./system/blockMeshDict:12: class dictionary;./system/fvSchemes:12: class dictionary;都是dictionary类，那创建起来更方便了，比如说contorlDict文件

点击查看代码
IOdictionary controlDict(        IOobject (            "controlDict",            runTime.constant(),            //runTime.system(),            mesh,            IOobject::MUST_READ,            IOobject::AUTO_WRITE        )    ) ;

有了dictionary这个字典类，顾名思义，字典当然是很方便查找啊，而且本身也是在链表以及哈希列表基础上建立的，能用的函数就很丰富了，如lookup()等。

综上，openfoam创建了一个读取方便查找容易的类支持of进行数据处理，寻根溯源很麻烦，但是用起来还是很简单的。

正因为文件读取占用很大的比重，这篇文章写了三个多小时，我们也是借此机会对openfoam内部略窥一二，这样我们就知道我们的程序在写什么，知道其所能为与不能为。

最后奉上自己编写的openfoam codesnip ，节约大家时间

点击查看代码
//***********************************************////openfoam"Foam_IOobject": {"prefix": "IOobject_Foam_","body": ["IOobject ${1|U,p,T,dicName|}(",// "\t${2|\"U\",\"p\",\"T\"|}","\t\"${1}\",","\t//runTime.timeName(),","\t//runTime.constant(),","\tmesh,","\tIOobject::MUST_READ,","\tIOobject::AUTO_WRITE",") ;"],"description": "FOAM::IOobject"},"Foam::IOdictionary": {"prefix": "IOdictionary_Foam_","body": ["IOdictionary ${1:dicName}(","\tIOobject (",// "\t${2|\"U\",\"p\",\"T\"|}","\t\t\"${1}\",","\t\t//runTime.constant(),","\t\t//runTime.system(),","\t\tmesh,","\t\tIOobject::MUST_READ,","\t\tIOobject::AUTO_WRITE","\t)",") ;"],"description": "Foam::IOdictionary"},"Foam::volVectorField": {"prefix": "volVectorField_Foam_","body": ["volVectorField ${U}(","\tIOobject (","\t\t\"${U}\",","\t\trunTime.timeName(),","\t\tmesh,","\t\tIOobject::MUST_READ,","\t\tIOobject::AUTO_WRITE","\t),","\tmesh",") ;"],"description": "Foam::volVectorField"},"Foam::volScalarField": {"prefix": "volScalarField_Foam_","body": ["volScalarField ${p}(","\tIOobject (","\t\t\"${p}\",","\t\trunTime.timeName(),","\t\tmesh,","\t\tIOobject::MUST_READ,","\t\tIOobject::AUTO_WRITE","\t),","\tmesh",") ;"],"description": "Foam::volScalarField"},"Foam::scalar": {"prefix": "scalar","body": ["scalar "],"description": "Foam::scalar"},//***********************************************//

创作不易，如若喜欢，不胜感激，欢迎支持，欢迎指正

关键词： 点击查看 构造函数 刨根问底