QB/PDS/VBDOS INT Handlers

Area:    Quik_Bas
  Msg:    #288
 Date:    11-23-92 19:08 (Public) 
 From:    Steve Gartrell           
 To:      Robert Church            
 Subject: QB/PDS/VBDOS INT Handlers

      .model medium, basic

      .code

handle  PROC
IntEntry:

  push    bp                      ; push everything
  mov     bp, sp                  ; stack frame
  pushf
  push    ds
  push    es
  push    di
  push    si
  push    dx
  push    cx
  push    bx
  push    ax


  mov     di, ss                  ;cuz the damned data seg
  mov     ds, di                  ; can get lost

BusyOff:
  mov     bx, 9090h
  mov     ax, [bx]
  and     ax, ax
  jnz     SHORT TooBusy

  mov     es, di                  ;point dest seg at DGROUP
  mov     si, sp                  ;stack address for regs to si
  cld

RegsOff:
  mov     di, 9090h               ;QB/PDS reg TYPE offset to di

  mov     cx, 0Ah
  rep     movsw

  sub     di, 14h
  push    di
  sub     si, 14h
  push    si
  sti

HandSeg:
  mov     ax, 9090h               ;Here the QB sub segment
  push    ax                      ; is placed on the stack for the
          ; RETF
HandOff:
  mov     ax, 9090h               ;Here the QB sub offset
  push    ax                      ; is placed on the stack for the
  retf                            ; RETF

AllDone:

  add     sp, 0Eh                 ;roll the stack ptr back past the
          ; last CALL Absolute far return
          ; address and the five dummy
          ; variables on the stack.  Then
          ; pop everything

  mov     di, ss                  ;cuz the damned data seg
  mov     ds, di                  ; can get lost
  mov     es, di

  pop     di                      ;popped in reverse dest/source
  pop     si

  cld
  mov     cx, 0Ah
  rep     movsw

TooBusy:
  pop     ax
  pop     bx
  pop     cx
  pop     dx
  pop     si
  pop     di
  pop     es
  pop     ds
  popf
  pop     bp
  jmp     cs:OldInt

JmpAddr:

OldInt  DD      90909090h

Start:
  assume  ds:seg IntEntry
  push    bp                      ; set up stack frame ptr
  mov     bp, sp
  push    ax
  push    bx
  push    dx
  push    si
  mov     bx, [bp + 6]            ;get ptr to start of this handler
          ; (stored in DGROUP)
  mov     bx, [bx]
  sub     bx, Start - IntEntry

  mov     ax, [bp + 2]            ; get QB sub return offset
  add     ax, 03h                 ; add 3 to compensate for JMP
          ;  opcode/disp and store in code

  mov     WORD PTR [bx + HandOff + 1], ax

  mov     ax, [bp + 4]            ; get QB sub return seg
          ;  and store in code

  mov     WORD PTR [bx + HandSeg + 1], ax

  mov     si, bx                  ;preserve start of code ptr

  mov     bx, [bp + 8]            ;original int offset ptr to DX
  mov     dx, WORD PTR [bx]       ; and moved to code storage
  mov     WORD PTR [si + JmpAddr], dx

  mov     bx, [bp + 0Ah]          ;original int segment ptr to DX
  mov     dx, WORD PTR [bx]       ; and moved to code storage
  mov     WORD PTR [si + JmpAddr + 2], dx

  mov     bx, [bp + 0Ch]          ;busy flag ptr offset to DX
          ; and moved to code storage
  mov     WORD PTR [si + BusyOff + 1], bx

  mov     bx, [bp + 0Eh]          ;SKGregs ptr to DX, adj to end,
  mov     dx, WORD PTR [bx]       ; and moved to code storage
  mov     WORD PTR [si + RegsOff + 1], dx

  mov     ax, si                  ;start of code ptr in AX
  add     ax, JmpAddr - IntEntry  ;add distance to offset of OldInt
          ; and move to actual JMP opcode
  mov     [si + (JmpAddr - IntEntry) - 2], ax

  pop     si
  pop     dx
  pop     bx
  pop     ax
  pop     bp
  retf    0Ah                     ;return clearing stack
          ; of five ptr words

handle  ENDP

  END     ;this is the end, my FIDO friend, the end...


--- D'Bridge 1.30/071082
 * Origin: RadioLink! Columbus, OH (614)766-2162 HST/DS (1:226/140)