systable.c

C语言常用的程序900例

#include <stdio.h>
#include <dos.h>
#include <stdlib.h>

void main (void)
  {
     union REGS inregs, outregs;
     struct SREGS segs;

     int i, j;

     int structure_size;

     struct SystemTableEntry {
      struct SystemTableEntry far *next; // Next SFT entry
      unsigned file_count;    // Files in table 
      unsigned handle_count;  // Handles to this file
      unsigned open_mode;     // File open mode
      char file_attribute;    // Attribute byte
      unsigned local_remote;  // Bit 15 set means remote
      unsigned far *DPD;      // Drive parameter block
      unsigned starting_cluster;
      unsigned time_stamp;
      unsigned date_stamp;
      long file_size;
      long current_offset;
      unsigned relative_cluster;  
      long directory_sector_number;
      char directory_entry_offset;
      char filename_ext[11];   // No period, space padded
      // Ignore SHARE fields for example 
     } far *table_ptr, far *file;   

     long far *system_table; 

     // Get DOS version 
     inregs.x.ax = 0x3001;
     intdos (&inregs, &outregs);
     if (outregs.h.al < 3)
       {
	 printf ("This program requires DOS version 3 or later\n");
	 exit (1);
       }
     else if (outregs.h.al == 3)
       structure_size = 0x35;
     else if (outregs.h.al >= 4)
       structure_size = 0x3B;    
	
     // Get the list of lists pointer
     inregs.h.ah = 0x52;
     intdosx (&inregs, &outregs, &segs);

     // The pointer to the system file table is at offset 4
     system_table = MK_FP(segs.es, outregs.x.bx + 4);  
     table_ptr = (struct SystemTableEntry far *) *system_table;

     do {
       printf ("%d entries in table\n", table_ptr->file_count);
       for (i = 0; i < table_ptr->file_count; i++)
	{
	  file = MK_FP(FP_SEG(table_ptr), FP_OFF(table_ptr) +
	    (i * structure_size));

	  if (file->handle_count)
	    {   
	       for (j = 0; j < 8; j++)
		 if (file->filename_ext[j] != ' ')
		   putchar(file->filename_ext[j]);
		 else 
		   break;  
       
	       if (file->filename_ext[8] != ' ')
		 putchar('.');
 
	       for (j = 8; j < 11; j++)
		 if (file->filename_ext[j] != ' ')
		   putchar(file->filename_ext[j]);
   
	       printf ("  %ld bytes %x attribute %d references\n",
		 file->file_size, file->file_attribute,
		 file->handle_count); 
	   }
	}
      table_ptr = table_ptr->next;
    } while (FP_OFF(table_ptr) != 0xFFFF);
  }