TGRedirectOutputGuard.cxx

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// @(#)root/gui:$Id$
// Author: G. Ganis   10/10/2005
 
/*************************************************************************
 * Copyright (C) 1995-2005, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
 
/** \class TGRedirectOutputGuard
    \ingroup guiwidgets
 
This class provides output redirection to a TGTextView in guaranteed
exception safe way. Use like this:
 
```
{
   TGRedirectOutputGuard guard(textview);
   ... // do something
   guard.Update();
   ... // do something else
}
```
 
when guard goes out of scope, Update() is called to flush what left
on the screed and the output is automatically redirected again to
the standard units.
The exception mechanism takes care of calling the dtors
of local objects so it is exception safe.
Optionally the output can also be saved into a file:
 
```
{
   TGRedirectOutputGuard guard(textview, file, mode);
   ... // do something
}
```
 
*/
 
 
#include <cerrno>
#include <sys/types.h>
#ifdef WIN32
#   include <io.h>
#else
#   include <unistd.h>
#endif
 
#include "TError.h"
#include "TGRedirectOutputGuard.h"
#include "TGTextView.h"
#include "TSystem.h"
 
////////////////////////////////////////////////////////////////////////////////
/// Create output redirection guard.
/// The TGTextView instance should be initialized outside.
/// Text is added to the existing text in the frame.
/// If defined, 'flog' is interpreted as the path of a file
/// where to save the output; in such a case 'mode' if the
/// opening mode of the file (either "w" or "a").
/// By default a temporary file is used.
 
TGRedirectOutputGuard::TGRedirectOutputGuard(TGTextView *tv,
                                             const char *flog,
                                             const char *mode)
{
   fTextView = tv;
   fLogFile = flog;
   fTmpFile = kFALSE;
   fLogFileRead = 0;
   if (!flog) {
      // Create temporary file
      fLogFile = "RedirOutputGuard_";
      fLogFileRead = gSystem->TempFileName(fLogFile);
      if (!fLogFileRead) {
         Error("TGRedirectOutputGuard", "could create temp file");
         return;
      }
      fTmpFile = kTRUE;
 
      // We need it in read mode
      fclose(fLogFileRead);
   } else {
      // Check permissions, if existing
      if (!gSystem->AccessPathName(flog, kFileExists)) {
         if (gSystem->AccessPathName(flog,
               (EAccessMode)(kWritePermission | kReadPermission))) {
            Error("TGRedirectOutputGuard",
                  "no write or read permission on file: %s", flog);
            return;
         }
      }
   }
 
   // Redirect
   const char *m = (mode[0] != 'a' && mode[0] != 'w') ? "a" : mode;
   if (gSystem->RedirectOutput(fLogFile.Data(), m) == -1) {
      Error("TGRedirectOutputGuard","could not redirect output");
      return;
   }
 
   // Open file in read mode
   if ((fLogFileRead = fopen(fLogFile.Data(),"r"))) {
      // Start reading from the present end
      lseek(fileno(fLogFileRead),(off_t)0, SEEK_END);
   } else {
      Error("TGRedirectOutputGuard","could not open file in read mode");
      return;
   }
 
   return;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Destructor.
 
TGRedirectOutputGuard::~TGRedirectOutputGuard()
{
   // Display last info
   Update();
 
   // Close the file
   if (fLogFileRead)
      fclose(fLogFileRead);
 
   // Unlink the file if we are the owners
   if (fTmpFile && fLogFile.Length() > 0)
      gSystem->Unlink(fLogFile);
 
   // Restore standard output
   gSystem->RedirectOutput(0);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Send to text frame the undisplayed content of the file.
 
void TGRedirectOutputGuard::Update()
{
   if (!fTextView) {
      Warning("Update","no TGTextView defined");
      return;
   }
 
   if (!fLogFileRead) {
      Warning("Update","no file open for reading");
      return;
   }
 
   // Make sure you get anything
   fflush(stdout);
 
   char line[4096];
   while (fgets(line,sizeof(line),fLogFileRead)) {
 
      // Get read of carriage return
      if (line[strlen(line)-1] == '\n')
         line[strlen(line)-1] = 0;
 
      // Send line to the TGTextView
      fTextView->AddLine(line);
   }
}