cwd_resource.h

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/*
    Copyright (C) 2011 Laszlo Kajan, Technical University of Munich, Germany
 
    This file is part of librostlab.
 
    librostlab is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.
 
    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef ROSTLAB_CWD_RESOURCE
#define ROSTLAB_CWD_RESOURCE
 
#include <errno.h>
#include <stdexcept>
#include <unistd.h>
#include <string.h>
 
namespace rostlab {
 
class cwd_resource
{
  private:
    string        _olddir;
    // this is a resource - disable copy contructor and copy assignment
                  cwd_resource( const cwd_resource& ){};
    cwd_resource&
                  operator=(const cwd_resource&){return *this;};
  public:
                  cwd_resource() : _olddir("") {};
 
                  cwd_resource( const string& __dirname ) : _olddir("")
    {
      acquire( __dirname );
    }
 
    inline void   acquire( const string& __dirname ) throw (runtime_error)
    {
      release();
      //
      char *buf = NULL;
      if( ( buf = getcwd( NULL, 0 ) ) == NULL ) throw runtime_error( string("failed to get working directory: ") + strerror( errno ) );
      string cwd = buf; free( buf ); buf = NULL;
 
      if( chdir( __dirname.c_str() ) ) throw runtime_error( "failed to chdir to '" + __dirname + "': " + strerror( errno ) );
      _olddir = cwd;
    }
 
    inline void   release() throw (runtime_error)
    {
      if( _olddir != "" )
      {
        if( chdir( _olddir.c_str() ) ) throw runtime_error( "failed to chdir to '" + _olddir + "': " + strerror( errno ) );
        _olddir = "";
      }
    }
 
    virtual       ~cwd_resource()
    {
      release();
    }
};
 
};
 
#endif // ROSTLAB_CWD_RESOURCE
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