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Text File  |  1990-07-09  |  5KB  |  114 lines
  1. /*
  2. **  Figure 1 - Validate, determine, or change disk drives
  3. */
  4.  
  5. #include <dos.h>
  6. #include <stdlib.h>
  7.  
  8. typedef enum {ERROR = -1, FALSE, TRUE} LOGICAL;
  9. #define SUCCESS 0
  10.  
  11. #ifdef __ZTC__
  12.  #define readisk(d,n,s,b) dos_abs_disk_read(d,n,s,b)
  13. #elif defined(__TURBOC__)
  14.  #define readisk(d,n,s,b) absread(d,n,s,b)
  15. #else /* MSC or others */
  16. int readisk(int drv, int num, int start, char *buf)
  17. {
  18.         union REGS regs;
  19.         struct SREGS sregs;
  20.  
  21.         regs.h.al = (char)drv;
  22.         regs.x.cx = num;
  23.         regs.x.dx = start;
  24.         segread(&sregs);              /* To work in any memory model */
  25.         sregs.ds  = FP_SEG((char far *)buf);
  26.         regs.x.bx = FP_OFF((char far *)buf);
  27.         intdosx(®s, ®s, &sregs);
  28.         if (regs.x.cflag)
  29.                 return ERROR;
  30.         else    return SUCCESS;
  31. }
  32. #endif
  33.  
  34. /*********************************************************************/
  35. /*                                                                   */
  36. /*  drvalid()                                                        */
  37. /*                                                                   */
  38. /*  Verifies whether a disk drive is mounted in the system without   */
  39. /*  triggering the DOS critical error handler.                       */
  40. /*                                                                   */
  41. /*  Arguments: 1 - target drive (0 = A;, 1 = B:, etc.)               */
  42. /*                                                                   */
  43. /*  Returns:   TRUE  - drive is valid                                */
  44. /*             FALSE - drive is invalid                              */
  45. /*             ERROR - no buffer space availabl                      */
  46. /*                                                                   */
  47. /*  Side effects: none                                               */
  48. /*                                                                   */
  49. /*********************************************************************/
  50.  
  51. int drvalid(int drive)
  52. {
  53.         int status;
  54.         char *buf;
  55.  
  56.         buf = (char *)malloc(4096);    /* Since we really don't know */
  57.         if (!buf)
  58.                 return ERROR;
  59.         status = readisk(drive, 1, 0, buf);
  60.         free(buf);
  61.         return(!status);
  62. }
  63.  
  64. /*********************************************************************/
  65. /*                                                                   */
  66. /*  getdrv()                                                         */
  67. /*                                                                   */
  68. /*  Just as getcwd() returns the default directory, getdrv() returns */
  69. /*  the drive letter of the current drive.                           */
  70. /*                                                                   */
  71. /*  Arguments: None.                                                 */
  72. /*                                                                   */
  73. /*  Returns:   Current drive (0 = A:, 1 = B:, etc.)                  */
  74. /*                                                                   */
  75. /*  Side effects: none                                               */
  76. /*                                                                   */
  77. /*********************************************************************/
  78.  
  79. int getdrv(void)
  80. {
  81.         union REGS regs;
  82.  
  83.         regs.h.ah = 0x19;
  84.         intdos(®s, ®s);
  85.         return (regs.h.al);
  86. }
  87.  
  88. /*********************************************************************/
  89. /*                                                                   */
  90. /*  chdrv()                                                          */
  91. /*                                                                   */
  92. /*  Like chdir(), except changes drives rather than directories.     */
  93. /*                                                                   */
  94. /*  Arguments: 1 - target drive (0 = A:, 1 = B:, etc.)               */
  95. /*                                                                   */
  96. /*  Returns: SUCCESS or ERROR                                        */
  97. /*                                                                   */
  98. /*  Side effects: none                                               */
  99. /*                                                                   */
  100. /*********************************************************************/
  101.  
  102. int chdrv(int drive)
  103. {
  104.         union REGS regs;
  105.  
  106.         if (!drvalid(drive))
  107.                 return ERROR;
  108.         regs.h.ah = 0x0e;
  109.         regs.h.dl = (char)drive;
  110.         intdos(®s, ®s);
  111.         return SUCCESS;
  112. }
  113.  
  114.