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/*
** FILES.C: A program to determine the number of file handles
**
** Released in to the Public Domian by Matthew Hunt @ 1:129/135, in the
** hopes that no "programmer" will be so lazy that he|she simple reads
** the CONFIG.SYS file ever again.
**
** Any improvements and modifications are welcome, but I ask that all
** modified versions also be placed into the Public Domain.
**
** Information on the List of Lists and SFT format was provided by
** PC Magazine November 26, 1991, and PC Interrupts by Ralf Brown
** and Jim Kyle. FILES.C was originally written for Power C.
**
** Modifcations for other compiler support by Bob Stout @ 1:106/2000.6
*/
#include <dos.h>
#ifdef __TURBOC__
#define FAR far
#else
#define FAR _far
#endif
#ifndef MK_FP
#define MK_FP(seg,offset) \
((void FAR *)(((unsigned long)(seg)<<16) | (unsigned)(offset)))
#endif
/*
** This is the format for a System File Table header. SFT's are a linked
** list in which the header points to the next SFT, is followed by the
** number of FILES in this SFT, and ends with the FILES themselves, which
** are not important here.
*/
struct SFT_HEADER {
struct SFT_HEADER (FAR *next);
unsigned number;
};
/*
** Walk the SFT linked list, counting file handles as we go
*/
int files(void)
{
struct SFT_HEADER (FAR *sft);
unsigned int segment, offset;
int count=0;
union REGS regs;
struct SREGS sregs;
/* Get ptr to List of Lists in ES:DX */
regs.x.ax = 0x5200;
segread(&sregs);
intdosx(®s, ®s, &sregs);
/* Get ssss:oooo to first SFT */
segment = *((unsigned FAR *)(MK_FP(sregs.es, regs.x.bx + 6)));
offset = *((unsigned FAR *)(MK_FP(sregs.es, regs.x.bx + 4)));
/* Point our structure to it. */
sft = MK_FP(segment, offset);
do
{
count += sft->number; /* Add the number of FILES */
sft = sft->next; /* Point to next one */
} while(FP_OFF(sft->next) != 0x0FFFF); /* Last one in the chain */
/* Add the FILES for the last entry */
count += sft->number;
return count;
}
#ifdef TEST
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
printf("Number of FILES entries: %d", files());
return EXIT_SUCCESS;
}
#endif /* TEST */
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