Power-Programmierung/CD2.mdf/c/library/dos/diverses/tctnt/cincoutd.cpp

C/C++ Source or Header | 1991-08-27 | 4.4 KB | 168 lines

/* CINCOUTD.CPP: Redirecting CIN or COUT.

         In the following program, the input with CIN can be redirected
         to gather the data from a file, or the output with COUT can be
         redirected to a file or stdprn depending on the program's
         command line arguments.
*/

#include <fstream.h>
#include <iostream.h>
#include <io.h>
#include <fcntl.h>
#include <process.h>
#include <string.h>
#include <sys\stat.h>

#define  PRNHANDLE  4
#define  ARRAYSIZE  80

void OutputUsage( void );
int  OpenOutFile( char * );
int  OpenInFile( char * );

int main( int argc, char *argv[] )
{
        char      io = 0;             //Keeps track if CIN or COUT redirection
        filebuf   *fBuf;              //Filebuf created with stdprn filehandle
        streambuf *oldBuf;            //Used to hold the old streambuf while CIN
                                                                    //  or COUT is being redirected
        unsigned  fhndl = -1;         //File handle of redirected file
        char      a[ARRAYSIZE + 1];   //Used for the sample I/O

        if ( argc != 2 ) {
            switch( argv[1][0] ) {      //Check the second command argument

            // Redirect CIN to gather from file specified at
            // command line
                case 'I':
                case 'i':

                    // Capture CIN's current streambuf before it is reassigned
                    oldBuf = cin.rdbuf();
                    io = 'i';

                    // Opens file specified at command line and redirects
                    // CIN to extract from it
                    fhndl = OpenInFile( argv[2] );
                    break;

                // Redirect COUT to output to file specified
                // at the command line
                case 'O':
                case 'o':

                    // Capture COUT's streambuf before new
                    // streambuf * is assigned.
                    oldBuf = cout.rdbuf();
                    io = 'o';

                    // Opens file specified at command line and
                    // redirects output via COUT to file
                    fhndl = OpenOutFile( argv[2] );
                    break;

                // Redirect COUT to stdprn
                case 'P':
                case 'p':

                    // Create a new filebuf with the file handle to stdprn
                    fBuf = new filebuf( PRNHANDLE );

                    // Use overloaded assignment operator to assign
                    // new filebuf to COUT
                    cout = fBuf;
                    break;
                default:

                    // If no command line arguments specified, use
                    // default settings for CIN and COUT
                    if ( argc == 1 ) {
                        break;
                    }
                    // Output command line usage if 2nd command
                    // line argument incorrect
                    OutputUsage();
                }
        }

        // NOW NORMAL USE OF CIN AND COUT WILL HONOR ANY
        // REDIRECTION DONE ABOVE

        // Simple demonstration of CIN inserting characters
        // into array 'a'
        cin.getline( a, ARRAYSIZE );

        // Check to make sure the previous function call did
        // not produce errors
        if( cin.fail() ) {
            return 1;
        }

        // Simple demonstration of COUT outputting contents
        // of 'a' to output stream
        cout << a << endl;

        // If a file was opened for redirection, close that file
        if ( fhndl != -1 ) {
                close( fhndl );

            // Reassign the old streambuf * to either CIN or COUT
            if ( io == 'i' ) {
                cin = oldBuf;
            }
            else
                if ( io == 'o' ) {
                    cout = oldBuf;
                }
            // NOW CIN AND COUT HAVE BEEN SET TO ORIGINAL STATE
        }
        return 0;
}

int OpenOutFile( char *filename ) {
    filebuf *tmpFBuf;
    int fhndl;
    fhndl = open( filename, O_CREAT|O_TEXT|O_RDWR, S_IREAD|S_IWRITE );
    if ( fhndl == -1 ) {
        cout << "Error opening file " << filename << ", program terminated.";
        cout << endl;
        exit(1);
    }

    // Create new filebuf with file handle of file specified
    // at command line
    tmpFBuf = new filebuf( fhndl );

    // Use overloaded assignment operator to assign new
    // filebuf to COUT
    cout = tmpFBuf;
    return fhndl;
}

int OpenInFile( char *filename ) {
    filebuf *tmpFBuf;
    int fhndl;
    fhndl = open( filename, O_CREAT|O_TEXT|O_RDONLY, S_IREAD|S_IWRITE );
    if ( fhndl == -1 ) {
        cout << "Error opening file " << filename << ", program terminated.";
        cout << endl;
        exit(1);
    }

    // Create new filebuf with file handle of file specified at command line
    tmpFBuf = new filebuf( fhndl );

    // Use overloaded assignment operator to assign new filebuf to CIN
    cin = tmpFBuf;
    return fhndl;
}

void OutputUsage( void ) {
    cout << endl << "Usage: <exe filename> [I, O, ?, h] <filename>" << endl;
    cout << "I - cin will be redirected to input from  <filename>." << endl;
    cout << "O - cout will be redirected to output to <filename>." << endl;
    cout << "P - cout will be redirected to output to stdprn." << endl;
    cout << "? or h - Outputs this screen." << endl;
}