v4.0/src/MAPPER/FREESEG.ASM

   1 ;
   2 page 60,132
   3 ;
   4 title CP/DOS  DosFreeSeg  mapper
   5 ;
   6 dosxxx  segment byte public 'dos'
   7         assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
   8 ;
   9 ; ************************************************************************* *
  10 ; *
  11 ; *      MODULE: DosFreeSeg
  12 ; *
  13 ; *      FILE NAME: dos023.asm
  14 ; *
  15 ; *      FUNCTION: This module deallocates a segment
  16 ; *
  17 ; *
  18 ; *      CALLING SEQUENCE:
  19 ; *
  20 ; *             push    selector        ; selector of the segment
  21 ; *             call    dosfreeseg
  22 ; *
  23 ; *      RETURN SEQUENCE:
  24 ; *
  25 ; *      MODULES CALLED:  DOS int 21h, ah=49h
  26 ; *
  27 ; *************************************************************************
  28
  29         public  dosfreeseg
  30         .sall
  31         .xlist
  32         include macros.inc
  33         .list
  34
  35 invalid_selector equ 0006h
  36
  37
  38 str     struc
  39 Old_bp   dw      ?
  40 Return   dd      ?
  41 Selector dw      ?         ; selector of the segment to be freed
  42 str     ends
  43
  44 dosfreeseg proc   far
  45         Enter   dosfreeseg              ; push registers
  46
  47         mov     es,[bp].selector        ; get selector in es
  48
  49         mov     ah,49h
  50         int     21h                     ; free memory segment
  51         jc      error                   ; jump if error
  52
  53         sub     ax,ax                   ; zero return code
  54         jmp     exit                    ; go to exit
  55
  56 error:  mov     ax,invalid_selector     ; put in error code
  57
  58 exit:   Mexit                           ; pop registers
  59         ret     size str - 6            ; return
  60
  61 dosfreeseg endp
  62
  63 dosxxx  ends
  64
  65         end