Fortran Fortran: how do you read from a memory-mapped file?

[Franzy]

Hello everyone!

I have some binary data (list of integer and float values) stored in a memory-mapped file. I need to read this data. I know how to do this in Delphi and C, but Fortran completely stalled me. So far I managed to open my virtual file (OpenFileMapping) and create a mapview (MapViewOfFile). I believe I have a pointer to the starting byte :) But how do I read, say, first 4 bytes and turn them into an integer value? And then next 8 bytes and turn them into double float? In Delphi, I use move procedure for this. You just give it a pointer to the source, a pointer to the destination and a number of bytes to read - works like a charm.
So, 1) how to read bytes and write them into variables? 2) how to perform pointer arithmetics in Fortran (for example, to move pointer X bytes forward in address space)?

Here is the listing of my subroutine (it's a dll, btw):

function FSReadGridData
 ! Func returns error code, 0 for success
 
 !DEC$ ATTRIBUTES DLLEXPORT::FSReadGridData

 USE sizeconstants 
 USE Kernel32, ONLY: OpenFileMapping, MapViewOfFile   

 ! Variables

  Implicit NONE
 !---------------------------------
  Integer(4)      :: FSReadGridData 
 !---------------------------------
   
  Character(LEN=63)           :: MapName 
  Byte, Pointer                   :: GM_start, GM_caret
  Integer(SHANDLE)            :: GeometryMH   ! SHANDLE =4 for Win32
  
  Integer(4), Dimension(1:10) ::  test1 ! arrays to store test data from memory file
  Real(8), Dimension(1:10) ::  test2 


 !=============================

  MapName = 'PKSigma_Grid_Map'//CHAR(0) ! We need a null-terminated string

  GeometryMH = OpenFileMapping(FILE_MAP_READ,.FALSE.,MapName)

  if (GeometryMH.EQ.0) then
    FSReadGridData =2001
    return
    ! return error code if could not open mapped file
  end if

  GM_start = MapViewOfFile(GeometryMH,FILE_MAP_READ,0,0,0);
  GM_caret = GM_start;
  
    ! GM_start holds pointer to starting byte, we 'll need it later to unmap view
    ! Using GM_caret for current location 

   ! ...NOW I need to read 40 bytes from GM_caret and write them to test1 array, how do I do that?!

end function FSReadGridData

 

[Franzy]

I think I got it. I just have to use WinApi function CopyMemory and fortran loc function in pointer arithmetics.