Q112339: BUG: Opening More Than 61 Files in a FORTRAN Windows NT App

Article: Q112339
Product(s): Microsoft Fortran Compiler
Version(s): 1.0,4.0
Operating System(s): 
Keyword(s): kbcode kbFortranPS kbLangFortran
Last Modified: 05-NOV-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Fortran Powerstation 32 for Windows NT, versions 1.0, 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

A FORTRAN PowerStation application on Windows NT can have only 61 files open at
a time. Attempting to OPEN the file number 62 will produce the run- time error:

  error F6417: too many open files

Page 806 of the FORTRAN PowerStation "Programmer's Guide" incorrectly states that
the fix for this problem is to change the FILES= setting in CONFIG.SYS.

CAUSE
=====

The 64-file limit of the PowerStation for MS-DOS has been carried over to
Powerstation for Windows NT. Three of these files are reserved for system use,
leaving 61 files for the program to use.

RESOLUTION
==========

Use WIN32 application programming interface (API) functions to perform some or
all of your file I/O.

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products listed at
the beginning of this article. We are researching this problem and will post new
information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

The following sample keeps 100 files open at the same time:

Sample Code #1
--------------

  c Compile options needed: none
  c

        include 'IO.FI'
        program OPEN_TEST
        character*9 fname/'FILE.000 '/ 
        integer*4 j
        fname(9:9) = CHAR(0)  ! Append null character
        do j = 1,100
           write(*,*) fname
           call open(fname)
           write(fname(6:8),'(i3.3)') j ! Write file extension
        enddo
        end

  c

        subroutine open(name)
        character*(*) name, buffer*16
        integer lcreat, handle, len
        data buffer/'Open many files.'/ 

        handle = lcreat(name, 0)         ! Create a new file
        len = lwrite(handle, buffer, 16) ! Write to file
        len = llseek(handle, 0, 0)       ! Seek to the beginning
        len = lread(handle, buffer, 16)  ! Read data back from file
        end

The following interface file, IO.FI, is used by the program above:

Sample Code #2
--------------

  C Open an existing file

        interface to integer function lopen
       +  [stdcall, alias:'__lopen@8'](filename, mode)
        character*1 filename[reference] ! null terminated file name
        integer mode[value] ! 0 = read-only, 1 = write-only
                            ! 2 = read-write
        end

  C Create a file (erase the old file if one exists)

        interface to integer function lcreat
       +  [stdcall, alias:'__lcreat@8'](filename, mode)
        character*1 filename [reference] ! null terminated file name
        integer mode[value] ! 0 = read-write, 1 = read-only
                            ! 2 = hidden, 3 = system
        end
  C Close a file (use with files opened by lcreat or lopen)

        interface to integer function lclose
       +  [stdcall, alias:'__lclose@4'](handle)
        integer handle[value]
        end
  C Move the file pointer to a specific offset in a file

        interface to integer function llseek
       +  [stdcall, alias:'__llseek@12'](handle,offset,origin)
        integer handle[value]
        integer offset[value] ! number of bytes to move pointer
        integer origin[value] ! 0 = beginning, 1 = current position
                              ! 2 = end of the file
        end
  C Read a specified number of bytes from a file

        interface to integer function lread
       +  [stdcall, alias:'__lread@12'](handle,buffer,length)
        integer handle[value]
        character*1 buffer
        integer length[value]  ! number of bytes
        end
  C Write a specified number of bytes to a file

        interface to integer function lwrite
       +  [stdcall, alias:'__lwrite@12'](handle,buffer,length)
        integer handle[value]
        character*1 buffer
        integer length[value]
        end

Additional query words: 1.00 4.00

======================================================================
Keywords          : kbcode kbFortranPS kbLangFortran 
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword2 kbFORTRANPower32100NT kbFORTRANPower32400NT
Version           : :1.0,4.0

=============================================================================

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