v4.0/src/MAPPER/LSEEK.ASM

   1 ;
   2 page 80,132
   3 ;\e0\ f
   4 title CP/DOS DosChgFilePtr mapper           * * *
   5 ;
   6 dosxxx  segment byte public 'dos'
   7         assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
   8
   9 ;**********************************************************************
  10 ;*
  11 ;*   MODULE:   doschgfileptr
  12 ;*
  13 ;*   FILE NAME: dos007.asm
  14 ;*
  15 ;*   CALLING SEQUENCE:
  16 ;*
  17 ;*       push      word    file handle
  18 ;*       push      dword   distance
  19 ;*       push      word    move type
  20 ;*       push@     dword   new pointer
  21 ;*       call      doschgfileptr
  22 ;*
  23 ;*   MODULES CALLED:  PC-DOS Int 21h, ah=42h, move file pointer
  24 ;*
  25 ;*********************************************************************
  26
  27             public   doschgfileptr
  28             .sall
  29             .xlist
  30             include  macros.inc
  31             .list
  32
  33 str         struc
  34 old_bp      dw       ?
  35 return      dd       ?
  36 newptr      dd       ?       ; new file pointer
  37 movtyp      dw       ?       ; move type
  38 dstnce      dd       ?       ; distance to be moved
  39 handle      dw       ?       ; file handle
  40 str         ends
  41
  42 doschgfileptr  proc  far
  43             Enter    doschgfileptr       ; push registers
  44
  45             push     es
  46             les      dx,[bp].dstnce
  47             mov      cx,es               ; set distance
  48             pop      es
  49             mov      ax,[bp].movtyp      ; get move type
  50             mov      bx,[bp].handle      ; get handle
  51
  52             mov      ah,42h
  53             int      21h                 ; move file pointer
  54             jc       exit                ; return if error
  55
  56             lds      si,[bp].newptr        ; set pointer
  57             mov      word ptr [si],ax      ; save the new pointer
  58             mov      word ptr [si]+2,dx    ;
  59             sub      ax,ax                 ; set godd return code
  60
  61 exit:       mexit                      ;pop registers
  62             ret      size str - 6      ;return
  63
  64 doschgfileptr endp
  65
  66 dosxxx      ends
  67
  68             end