在MATLAB mex文件中正确重载一个stringbuf来替换cout [英] Correctly over-loading a stringbuf to replace cout in a MATLAB mex file

问题描述

MathWorks目前不允许您在MATLAB桌面打开时使用来自mex文件的cout，因为它们已重定向stdout。他们目前的解决方法是提供 mexPrintf，他们要求您改用的功能。在googling一点后，我认为可以扩展std :: stringbuf类来做我需要的。这是我到目前为止。这是足够健壮，还是有其他方法我需要重载或更好的方法来做到这一点？ （在普通UNIX环境中寻找可移植性，并且如果这个代码没有链接到一个mex可执行文件，那么可以正常使用std :: cout）

MathWorks currently doesn't allow you to use cout from a mex file when the MATLAB desktop is open because they have redirected stdout. Their current workaround is providing a function, mexPrintf, that they request you use instead. After googling around a bit, I think that it's possible to extend the std::stringbuf class to do what I need. Here's what I have so far. Is this robust enough, or are there other methods I need to overload or a better way to do this? (Looking for portability in a general UNIX environment and the ability to use std::cout as normal if this code is not linked against a mex executable)

class mstream : public stringbuf {
public:
  virtual streamsize xsputn(const char *s, std::streamsize n) 
  {
mexPrintf("*s",s,n);
return basic_streambuf<char, std::char_traits<char>>::xsputn(s,n);
  }
}; 

mstream mout;
outbuf = cout.rdbuf(mout.rdbuf());

推荐答案

你真的不想重载std :: stringbuf，你想重载std :: streambuf或std :: basic_streambuf（如果你想支持多个字符类型），你也需要重写溢出方法。

You don't really want to overload std::stringbuf, you want to overload std::streambuf or std::basic_streambuf (if you want to support multiple character types), also you need to override the overflow method as well.

但我也认为你需要重新思考你的解决方案你的问题。

But I also think you need to rethink your solution to your problem.

cout只是一个ostream，所以如果所有的类/函数都需要一个ostream，那么你可以传递在任何你喜欢的。例如cout，ofstream等等

cout is just a ostream, so if all classes / functions takes a ostream then you can pass in anything you like. e.g. cout, ofstream, etc

如果这太难了，我会创建自己的cout版本，也许叫mycout，可以在编译器时间或运行时间定义

If that's too hard then I would create my own version of cout, maybe called mycout that can be defined at either compiler time or runtime time (depending on what you want to do).

一个简单的解决方案可能是：

A simple solution may be:

#include <streambuf>
#include <ostream>

class mystream : public std::streambuf
{
public:
    mystream() {}

protected:
    virtual int_type overflow(int_type c)
    {
        if(c != EOF)
        {
            char z = c;
            mexPrintf("%c",c);
            return EOF;
        }
        return c;
    }

    virtual std::streamsize xsputn(const char* s, std::streamsize num)
    {
        mexPrintf("*s",s,n);
        return num;
    }
};

class myostream : public std::ostream
{
protected:
    mystream buf;

public:
    myostream() : std::ostream(&buf) {}
};

myostream mycout;

cout版本可以是：

And the cout version could just be:

typedef std::cout mycout;

运行时版本有点多，但很容易做。

A runtime version is a bit more work but easily doable.

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