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Assembly Source File  |  1984-05-09  |  4KB  |  71 lines
  1. PAGE 50,132
  2. TITLE GETSEC5   -PASCAL FUNCTION TO GET DISK SECTORS
  3. ;GETSEC --  Pascal Function to get sectors from disk using DOS's INT 25H.
  4. ;                       Interfaces to IBM PC Pascal v1.00 Compiler (Microsoft).
  5. ;                       see DOS Manual, page D-25; and Tech Ref Manual, page A-32.
  6. ;***********  (c) Copyright 1982 by Walter H. Rauser   5-16-82   ***********
  7. ;{sample of Pascal declarations to use GETSEC}
  8. ;function GETSEC(drive  :integer;       {A is 0, B is 1, C is 2, D is 3}
  9. ;                                first  :integer;       {first sector # in 0-origin}
  10. ;                                numof  :integer;       {number of sectors to get}
  11. ;                        var buffer :dirtype;   {buffer to hold all fetched sectors}
  12. ;                        var errorc :integer    {DOS error code}
  13. ;                                          ):boolean; EXTERN;
  14. ;{sample of buffer type for directory sectors, DOS 1.10}
  15. ;type dirtype = array[1..112] of record         {112 for DS Drives, 64 for SS}
  16. ;                                       name    [0]:string(8);
  17. ;                                       ext             [8]:string(3);
  18. ;                                       attr   [11]:byte;
  19. ;                                       resvd  [12]:array[1..10] of byte;
  20. ;                                       time   [22]:word;
  21. ;                                       date   [24]:word;
  22. ;                                cluster1  [26]:word;
  23. ;                                sizelow   [28]:word;
  24. ;                                sizehigh  [30]:word;
  25. ;                               end;
  26. ; frame contents for call from Pascal
  27. ; offset len  variable     attributes
  28. ; [BP]+14  2  drive                     int value parameter
  29. ; [BP]+12  2  firstsector       int value parameter
  30. ; [BP]+10  2  numofsectors      int value param
  31. ; [BP]+ 8  2  buffer                    var param
  32. ; [BP]+ 6  2  errorcode         int var param
  33. ; [BP]+ 4  2  CS:               return address long call
  34. ; [BP]+ 2  2  offset    return address
  35. ; [BP]+ 0  2  old frame pointer storage
  36. ;
  37. ;
  38. MYSEG   SEGMENT PARA    PUBLIC  'CODE'
  39.                 ASSUME CS:MYSEG
  40.                 PUBLIC GETSEC
  41. ;
  42. GETSEC  PROC    FAR
  43.                 PUSH    BP                              ;save old frame pointer
  44.                 MOV             BP,SP                   ;set new frame pointer
  45.                 MOV             AX,[BP].14              ;put drive num into AL
  46.                 XOR             AH,AH
  47.                 MOV             CX,[BP].10              ;num of sectors to fetch
  48.                 MOV             DX,[BP]+12              ;logical record # of first sec, 0-orgin
  49.                 PUSH    DS                              ;restore before ret
  50.                 PUSH    SS                              ;buffer is in stack segment
  51.                 POP             DS                              ;DS: of buffer (transfer address)
  52. ;
  53.                 MOV             BX,[BP]+8               ;offset of buffer
  54.                 INT             25H                             ;absolute disk read, DOS function.
  55.                 JC              ERROR                   ;error if carry flag set
  56.                 MOV             AL,01H                  ; okay, set AL to return GETSEC=true
  57.                 JMP             DONE
  58. ;
  59. ERROR:  MOV             BP,[BP].6               ;adr of errorc
  60.                 MOV     [BP],AX                 ;dos error code
  61.                 MOV             AL,00H                  ; error, set AL to return GETSEC=false
  62. ;
  63. DONE:   XOR             AH,AH
  64.                 POPF                                    ;int 25H left Flags on stack
  65.                 POP             DS                              ;restore DS
  66.                 POP             BP                              ;restore frame pointer
  67.                 RET             10                              ;clear parameters from stack
  68. GETSEC  ENDP
  69. MYSEG   ENDS
  70.                 END
  71.