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Assembly Source File  |  1992-06-10  |  1.6 KB  |  51 lines
  1. ;[]-----------------------------------------------------------------[]
  2. ;|      H_LRSH.ASM -- long shift right                               |
  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. _TEXT   segment public byte 'CODE'
  15.         assume  cs:_TEXT
  16.         public  LXRSH@
  17.         public  F_LXRSH@
  18.         public  N_LXRSH@
  19.  
  20. N_LXRSH@:
  21.         pop     bx                      ;fix up for far return
  22.         push    cs
  23.         push    bx
  24. LXRSH@:
  25. F_LXRSH@:
  26.         cmp     cl,16
  27.         jae     lsh@small
  28.         mov     bx,dx                   ; save the high bits
  29.         shr     ax,cl                   ; now shift each half
  30.         sar     dx,cl
  31. ;
  32. ;                       We now have a hole in AX where the lower bits of
  33. ;                       DX should have been shifted.  So we must take our
  34. ;                       copy of DX and do a reverse shift to get the proper
  35. ;                       bits to be or'ed into AX.
  36. ;
  37.         neg     cl
  38.         add     cl,16
  39.         shl     bx,cl
  40.         or      ax,bx
  41.         retf
  42. lsh@small:
  43.         sub     cl,16                   ; for shifts more than 15, do this
  44.                                         ; short sequence.
  45.         xchg    ax,dx                   ;
  46.         cwd                             ; We have now done a shift by 16.
  47.         sar     ax,cl                   ; Now shift the remainder.
  48.         retf
  49. _TEXT   ends
  50.         end
  51.