Q43975: QuickC: Increasing Maximum Number of Open Files and Streams

Article: Q43975
Product(s): See article
Version(s): 2.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 2-MAY-1989

Question:

Is it possible to increase the maximum number of open files and
maximum number of streams under QuickC Version 2.00?

Response:

QuickC 2.00 does not come with start-up code; therefore, you MUST have
the Microsoft C 5.10 Optimizing Compiler to increase the maximum
number of open files and streams. CRT0DAT.ASM and _FILE.C should be
modified as described in the README.DOC included in the C 5.10
package.

Limited testing has been performed with QuickC 2.00 after altering
the start-up code in this manner; however, Microsoft cannot guarantee
that it will work properly in all cases.

After successfully assembling CRT0DAT.ASM (use the /MX switch) and
successfully compiling _FILE.C, you must do one of the following:

1. Explicitly link your program with the new CRT0DAT.OBJ and/or
   _FILE.OBJ by compiling and linking on the command line using QuickC
   2.00. One possible command might be as follows:

      QCL TEST.C CRT0DAT /LINK /NOE

2. You can also link with the modified start-up code by creating a
   program list in QuickC 2.00, which should include TEST.C,
   CRT0DAT.OBJ, and/or _FILE.OBJ. Do not forget to turn the extended
   dictionary flag OFF under the linker flags.

3. Replace the CRT0DAT.OBJ and/or _FILE.OBJ in the appropriate model
   of the QuickC 2.00 run-time library. You can use the library
   manager and the Replace command symbol (-+) in the "commands" field
   to replace a module in the library.

Note: Remember that the number of low-level files must be greater than
or equal to the number of stream-level files. Therefore, if you
increase the value of _NFILE_ in _FILE.C, you must also increase the
value of _NFILE_ in CRT0DAT.ASM.

The following program will open up to 64 files, write to them, close
them, open the files again, and read from them:

#include <stdio.h>
#include <string.h>

#define MAX_FILES  64
#define MAX_BUFFER 128
#define FILE_BASE  "MAX"
#define FILE_EXT   ".TXT"
#define TO_WRITE   "This is a bunch of text!"

void main( void )
{
    FILE *streams[MAX_FILES];
    char  buffer[MAX_BUFFER];
    int   i;
    int   max;
    int   cmp;

    /*  Open as many files as possible. */
    for( i = 0; i < MAX_FILES; i++ )
    {
        sprintf( buffer, FILE_BASE "%2.2d" FILE_EXT, i + 1 );
        streams[i] = fopen( buffer, "w" );
        if( streams[i] == NULL )
        {
            fprintf( stderr, "Open #%2.2d failed.\n", i + 1 );
            break;
        }
    }
    max = i;

    /*  Write to all open files. */
    for( i = 0; i < max; i++ )
        fputs( TO_WRITE, streams[i] );

    /*  Close all open files. */
    for( i = 0; i < max; i++ )
        fclose( streams[i] );

    /*  Open all of our files. */
    for( i = 0; i < max; i++ )
    {
        sprintf( buffer, FILE_BASE "%2.2d" FILE_EXT, i + 1 );
        streams[i] = fopen( buffer, "r" );
        if( streams[i] == NULL )
            fprintf( stderr, "Unable to re-open file #%2.2d\n", i + 1 );
    }

    /*  Read from all open files. */
    for( i = 0; i < max; i++ )
    {
        fgets( buffer, MAX_BUFFER, streams[i] );
        cmp = strcmp( buffer, TO_WRITE );
        if( cmp != 0 )
            fprintf( stderr, "Bad data in file #%2.2d\n", i + 1 );
    }

    /*  Close all open files. */
    for( i = 0; i < max; i++ )
        fclose( streams[i] );

    fputs( "All done!\n", stdout );
}

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