v4.0/src/MAPPER/ALLOCSEG.ASM

   1 ;\ f\e0
   2 page 80,132
   3 ;
   4 title CP/DOS  DosAllocSeg  mapper
   5 ;
   6 dosxxx  segment byte public 'dos'
   7         assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
   8 ;
   9 ; ************************************************************************* *
  10 ; *
  11 ; *      MODULE: DosAllocSeg
  12 ; *
  13 ; *      FUNCTION: This module allocates a segment of memory to the
  14 ; *             requesting process
  15 ; *
  16 ; *      CALLING SEQUENCE:
  17 ; *
  18 ; *             push    size            ; number of bytes requested
  19 ; *             push@   selector        ; selector allocated (returned)
  20 ; *             push    shareind        ; whether segment will be shared
  21 ; *             call    dosallocseg
  22 ; *
  23 ; *      RETURN SEQUENCE:
  24 ; *
  25 ; *             AX = error      , 0 = no error
  26 ; *
  27 ; *      MODULES CALLED:  DOS int 21h
  28 ; *
  29 ; *************************************************************************
  30 ;
  31         public  dosallocseg
  32         .sall
  33         .xlist
  34         include macros.inc
  35         .list
  36 ;
  37 str     struc
  38 old_bp   dw      ?
  39 return   dd      ?
  40 ShareIndicator  dw      ?       ; whether segment will be shared
  41 SelectorPtr     dd      ?       ; selector allocated
  42 SegmentSize     dw      ?       ; number of bytes requested
  43 str     ends
  44
  45 dosallocseg proc   far
  46         Enter   dosallocseg              ; push registers
  47
  48         mov     bx,[bp].SegmentSize      ; Get segment size
  49
  50         test    bx,0000fh                ; check segment size
  51         jz      NoRoundRequired
  52
  53         and     bx,not 0000fh
  54         add     bx,00010h
  55
  56 NoRoundRequired:
  57         cmp     bx,0                     ; check for 0 (full seg)
  58         je      AllocateMax              ; jmp to full seg
  59
  60         shr     bx,1                     ; convert segment in bytes to
  61         shr     bx,1                     ; paragraph
  62         shr     bx,1
  63         shr     bx,1
  64         jmp     HaveSize
  65
  66 AllocateMax:
  67         mov     bx,4096                  ; setup default paragraph size
  68
  69 HaveSize:
  70         mov     ah,48h                   ; set up for dos allocate call
  71         int     21h                      ; allocate segment
  72         jc      ErrorExit                ; jump if error
  73
  74         lds     si,[bp].SelectorPtr      ; get selector address
  75         mov     ds:[si],ax               ; save allocated memory block
  76
  77 AllocDone:
  78         sub     ax,ax                    ; set good return code
  79 ErrorExit:
  80         mexit                            ; pop registers
  81         ret     size str - 6             ; return
  82
  83 dosallocseg endp
  84
  85 dosxxx  ends
  86
  87         end