Redirect printf to QTextEdit?

[cwomeijer]

I seem to have a similar request for my project.
In my huge C code base we printed:
Informational messages,
Warning messages,
Error messages.

All of the obviously doen with printf().
So we created our own version that sended out signals
with the corresponding ascii line as an argument.
I was lucky that we had our own routines for printing
but I guess some nifty #define can do the trick/ or a big grep.

Anyway the signal solution is realy neat. It's thread safe and does
not add a lot of overhead. I tested it with several million of messages
and there was not a big impact on the performance.

You do need to take care of the C -> C++ wrappers though.

[Randulf]

So we created our own version that sended out signals
with the corresponding ascii line as an argument.

But then you had to implement a signal in every class?
Or how did you do it?

Perhaps there is a non-blocking version of _read() that you can call?

Exactly, been looking for that or the possibility to set fcntl O_NONBLOCK but I cant find how to that in windows. For now problem was solved by adding a \n before I do fflush.

Now I think it's working with some cheating.

#ifndef STDOUTREDIRECTOR_H
#define STDOUTREDIRECTOR_H
#include <QString>
#include <iostream>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
#include <QTextEdit>
 
class StdOutRedirector : public QObject
{
	Q_OBJECT
public:
	StdOutRedirector()
	{
		// Redirect
		if(_pipe(fdguistd, 4096, _O_BINARY) == -1) 
			printf("failed!");
		//int tr = fcntl(fdguistd, O_NONBLOCK);
		// Duplicate stdout file descriptor (next line will close original)
		fdStdOut = _dup(_fileno(stdout));
		// Duplicate write end of pipe to stdout file descriptor
		if(_dup2(fdguistd[1], _fileno(stdout)) != 0)
			printf("failed!");
		// Close original 
		close(1);
		// Duplicate write end of original
		dup2(fdguistd[1], 1);
 
	}
	void setOutputTF(QTextEdit *_output)
	{
		output = _output;
	}
public slots:
	void readOutsToTF()
	{
		int n_out;
		char *buffer = new char [4096];
		QString str;
		//char buffer[512];
		printf("\n");
		fflush(stdout);
 
		n_out = _read(fdguistd[0], buffer, 4096);
 
		if(n_out <= 0)
			return;
		if(n_out > 1) {
			str.append(QString(buffer));
			int con = str.lastIndexOf('\n');
			int remv = str.at(con-1) == '/n' ? 1 : 0;
			if(con) {
				str = str.remove(con-remv, str.length());
				output->append(str);
			}
		}
 
	}
private:
	QTextEdit *output;
	int fdStdOut;
	int fdguistd[2];
};
#endif

#ifndef STDOUTREDIRECTOR_H
#define STDOUTREDIRECTOR_H
#include <QString>
#include <iostream>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
#include <QTextEdit>

class StdOutRedirector : public QObject
{
	Q_OBJECT
public:
	StdOutRedirector()
	{
		// Redirect
		if(_pipe(fdguistd, 4096, _O_BINARY) == -1) 
			printf("failed!");
		//int tr = fcntl(fdguistd, O_NONBLOCK);
		// Duplicate stdout file descriptor (next line will close original)
		fdStdOut = _dup(_fileno(stdout));
		// Duplicate write end of pipe to stdout file descriptor
		if(_dup2(fdguistd[1], _fileno(stdout)) != 0)
			printf("failed!");
		// Close original 
		close(1);
		// Duplicate write end of original
		dup2(fdguistd[1], 1);

	}
	void setOutputTF(QTextEdit *_output)
	{
		output = _output;
	}
public slots:
	void readOutsToTF()
	{
		int n_out;
		char *buffer = new char [4096];
		QString str;
		//char buffer[512];
		printf("\n");
		fflush(stdout);

		n_out = _read(fdguistd[0], buffer, 4096);
		
		if(n_out <= 0)
			return;
		if(n_out > 1) {
			str.append(QString(buffer));
			int con = str.lastIndexOf('\n');
			int remv = str.at(con-1) == '/n' ? 1 : 0;
			if(con) {
				str = str.remove(con-remv, str.length());
				output->append(str);
			}
		}

	}
private:
	QTextEdit *output;
	int fdStdOut;
	int fdguistd[2];
};
#endif

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