v4.0/src/MAPPER/CLOSE.ASM

   1 ;\ f\e0
   2 page 80,132
   3
   4 title CP/DOS  DosClose  mapper   * * *
   5
   6 dosxxx  segment byte public 'dos'
   7         assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
   8 ;
   9 ; ************************************************************************* *
  10 ; *
  11 ; *      MODULE: DosClose
  12 ; *
  13 ; *      FUNCTION: This module will close a file or a device.
  14 ; *
  15 ; *      CALLING SEQUENCE:
  16 ; *
  17 ; *                PUSH  WORD  FileHandle ;  File Handle or device handle
  18 ; *                CALL  DosClose
  19 ; *
  20 ; *      RETURN SEQUENCE:
  21 ; *
  22 ; *                IF ERROR (AX not = 0)
  23 ; *
  24 ; *                   AX = Error Code:
  25 ; *
  26 ; *                   o   Invalid file handle
  27 ; *
  28 ; *
  29 ; *      MODULES CALLED:  DOS int 21H function 3EH
  30 ; *
  31 ; *
  32 ; *************************************************************************
  33
  34         public  DosClose
  35         .sall
  36         .xlist
  37         include macros.inc
  38         .list
  39
  40 str     struc
  41 old_bp     dw     ?
  42 return     dd     ?
  43 FileHandle dw     ?          ; file or device handle
  44 str     ends
  45
  46
  47 DosClose  proc   far
  48         Enter   DosClose               ; push registers
  49
  50 ; Only files are closed.  Devices are not closed, since OPEN creates
  51 ; a dummy device handle without actually openning the device.
  52
  53         mov     bx,[bp].FileHandle     ; load the handle
  54         mov     ax,bx                  ; check for device handle
  55         neg     ax                     ; if device handle, return
  56         jns     GoodExit               ; do not close the device
  57
  58 FileCloseRequest:
  59         mov     ax,03e00h              ; load opcode
  60         int     21h                    ; close the file
  61         jc      ErrorExit              ; return if error
  62
  63 GoodExit:
  64         sub     ax,ax                  ; else, set good return code
  65
  66 ErrorExit:
  67         mexit                          ; pop registers
  68         ret     size str - 6           ; return
  69
  70 DosClose  endp
  71
  72 dosxxx  ends
  73
  74         end