v4.0/src/MAPPER/REALLSEG.ASM

   1 ;
   2 page 60,132
   3 ;
   4 title CP/DOS  DosReallocSeg  mapper
   5 ;
   6 dosxxx  segment byte public 'dos'
   7         assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
   8 ;
   9 ; ************************************************************************* *
  10 ; *
  11 ; *      MODULE: DosReallocSeg
  12 ; *
  13 ; *      FILE NAME: dos043.asm
  14 ; *
  15 ; *      FUNCTION: This module changes the size of a segment already
  16 ; *             allocated
  17 ; *
  18 ; *      CALLING SEQUENCE:
  19 ; *
  20 ; *             push    size            ; new segment size requested in bytes
  21 ; *             push    selector        ; selector
  22 ; *             call    dosreallocseg
  23 ; *
  24 ; *      RETURN SEQUENCE:
  25 ; *
  26 ; *
  27 ; *
  28 ; *      MODULES CALLED:  DOS Int 21, AH=4A
  29 ; *
  30 ; *
  31 ; *
  32 ; *************************************************************************
  33 ;
  34         public  dosreallocseg
  35         .sall
  36         .xlist
  37         include macros.inc
  38         .list
  39
  40 str     struc
  41 old_bp  dw      ?
  42 return  dd      ?
  43 Selector        dw      ?       ; segment selector
  44 SegmentSize     dw      ?       ; new segment size in bytes
  45 str     ends
  46
  47 dosreallocseg proc   far
  48         Enter   dosreallocseg           ; save registers
  49
  50         mov     bx,[bp].SegmentSize     ; Get new segment size
  51         cmp     bx,0                    ; check for 0
  52         je      AllocateMax             ; jmp to full seg
  53
  54         shr     bx,1                    ; else convert segment in bytes
  55         shr     bx,1                    ; paragraph
  56         shr     bx,1
  57         shr     bx,1
  58         jmp     HaveSize
  59
  60 AllocateMax:
  61         mov     bx,4096                 ; default segment size in paragraph
  62
  63 HaveSize:
  64         mov     es,[bp].Selector        ; set up segment for new size
  65
  66         mov     ah,4ah                  ; set up for DOS realloc call
  67         int     21h                     ; realloc segment
  68         jc      ErrorExit               ; jump if error
  69
  70         sub     ax,ax                   ; else set good return code
  71
  72 ErrorExit:
  73         Mexit                           ; restore registers
  74
  75         ret     size str - 6            ; return
  76
  77 dosreallocseg  endp
  78
  79 dosxxx  ends
  80
  81         end