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/*
** ADDHNDLS.C
**
** A compilation of public domain sources originally written by
** Doug Burger and Bob Jarvis
**
** Collected and modified for Zortech, Microsoft, and Borland by Bob Stout
**
** Demonstrates relocating the file handle table under DOS 3.x
** for having more than the usual 20 files open in a single
** program
*/
#include <stdio.h>
#include <dos.h>
#include <io.h>
#include <fcntl.h>
#define TABLE_SIZE 255 /* NOTE: *Must* be <= FILES in CONFIG.SYS */
#ifdef TEST
#if !defined(__ZTC__) && !defined(__TURBOC__) /* i.e. #if MSC/QC */
#include <stdlib.h>
#define MK_FP(seg,offset) \
((void far *)(((unsigned long)(seg)<<16) | (unsigned)(offset)))
/* MSC's open() is funny - this code only works with _dos_open() */
int open(const char *name, int mode, ...)
{
int hdl;
if (0 == _dos_open(name, mode, &hdl))
return hdl;
else return -1;
}
#endif /* MSC */
#endif /* TEST */
unsigned char handle_table[TABLE_SIZE]; /* table of file DOS handles */
unsigned char far * far * handle_ptr; /* ptr to DOS's ptr to hand. */
unsigned int far *handle_count; /* ptr to handle count */
int relocate(void)
{
switch (_osmajor)
{
case 2:
return -1;
case 3:
if (3 > _osminor)
{ /* by Doug Burger */
unsigned int i;
handle_count = MK_FP(_psp, 0x32); /* handle count at PSP:32h */
handle_ptr = MK_FP(_psp, 0x34); /* table ptr at PSP:34h */
for (i = 0; i < *handle_count; i++) /* relocate exiting table */
handle_table[i] = (*handle_ptr)[i];
for (i = *handle_count; i < TABLE_SIZE; i++) /* init. rest */
handle_table[i] = 255;
*handle_ptr = handle_table; /* set pointer to new table */
*handle_count = TABLE_SIZE; /* set new table size */
return 0;
}
else
default: /* DOS 4+ */
{ /* by Bob Jarvis */
union REGS regs;
regs.h.ah = 0x67;
regs.x.bx = TABLE_SIZE | 1; /* has to be an odd number */
intdos(®s, ®s);
if(regs.x.cflag) /* error */
return -1;
else
return 0;
}
}
} /* relocate() */
/*
** Test code
*/
#ifdef TEST
void main(void)
{
int c, h;
relocate();
c = 0;
while ((h = open("CON", O_RDONLY)) >= 0) /* DOS closes files */
{
c++; /* on exit, so I */
printf("handle = %d\n", h); /* don't bother */
} /* saving handles */
printf("total opened files = %d\n", c);
} /* ADDHNDLS.C */
#endif /* TEST */
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