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Assembly Source File  |  1992-06-10  |  1.9 KB  |  62 lines
  1. ;[]-----------------------------------------------------------------[]
  2. ;|      H_PSBP.ASM -- long pointer routines                          |
  3. ;[]-----------------------------------------------------------------[]
  4.  
  5. ;
  6. ;       C/C++ Run Time Library - Version 5.0
  7. ; 
  8. ;       Copyright (c) 1987, 1992 by Borland International
  9. ;       All Rights Reserved.
  10. ; 
  11.  
  12.                 INCLUDE RULES.ASI
  13.  
  14. ; calls to these routines are generated by the compiler to perform
  15. ; arithmetic operations on long pointers.
  16.  
  17. _TEXT           SEGMENT BYTE PUBLIC 'CODE'
  18.                 ASSUME  CS:_TEXT
  19. ;
  20. ;       ax:dx   left hand pointer
  21. ;       bx:cx   right hand pointer
  22. ;
  23. ;               To subtract, first convert both pointers to longs.
  24. ;               then do a simple signed long subtraction.  Actually
  25. ;               we only store 24 bit ints until the subtraction is
  26. ;               done.
  27. ;
  28.                 public  PSBP@
  29.                 public  F_PSBP@
  30.                 public  N_PSBP@
  31.  
  32. N_PSBP@:
  33.                 pop     es              ;fix up far return
  34.                 push    cs
  35.                 push    es
  36. PSBP@:
  37. F_PSBP@:
  38.                 push    di
  39.                 mov     di,cx
  40.                 mov     ch,dh
  41.                 mov     cl,4
  42.                 shl     dx,cl
  43.                 shr     ch,cl           ; dx:ch has the left hand long
  44.                 add     dx,ax
  45.                 adc     ch,0
  46.                 mov     ax,di
  47.                 shl     di,cl
  48.                 shr     ah,cl
  49.                 add     bx,di
  50.                 adc     ah,0            ; bx:ah has the right hand long
  51.                 sub     dx,bx
  52.                 sbb     ch,ah
  53.                 mov     al,ch
  54.                 cbw                     ; sign extend the upper part
  55.                 xchg    ax,dx
  56.                 pop     di
  57.                 retf
  58.  
  59. _TEXT           ENDS
  60.                 END
  61.  
  62.