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/*
** DRVALID.C - validate disk drives
**
** Original Copyright 1988-1991 by Bob Stout as part of
** the MicroFirm Function Library (MFL)
**
** This subset version is functionally identical to the
** version originally published by the author in Tech Specialist
** magazine and is hereby donated to the public domain.
**
** Uses ABSDISKC.C and ABSDISK.ASM in SNIPPETS.
*/
#include <dos.h>
#include <stdlib.h>
typedef enum {ERROR = -1, SUCCESS, FALSE = 0, TRUE} LOGICAL;
/*
** Function to read an absolute disk sector
*/
int AbsDiskRead(unsigned short, size_t, size_t, void *);
/*
** getdrv()
**
** Just as getcwd() returns the default directory, getdrv() returns
** the current drive.
**
** Arguments: None.
**
** Returns: Current drive (0 = A:, 1 = B:, etc.)
**
** Side effects: none
*/
int getdrv(void)
{
union REGS regs;
regs.h.ah = 0x19;
intdos(®s, ®s);
return (regs.h.al);
}
/*
** chdrv()
**
** Like chdir(), except changes drives rather than directories.
**
** Arguments: 1 - target drive (0 = A:, 1 = B:, etc.)
**
** Returns: SUCCESS or ERROR
**
** Side effects: none
*/
LOGICAL chdrv(int drive)
{
union REGS regs;
regs.h.ah = 0x0e;
regs.h.dl = (char)drive;
intdos(®s, ®s);
if (drive != getdrv())
return ERROR;
else return SUCCESS;
}
/*
** drvalid()
**
** Verifies whether a logical disk drive is available without
** triggering the DOS critical error handler.
**
** Arguments: 1 - target drive (0 = A;, 1 = B:, etc.)
**
** Returns: TRUE - drive is valid
** FALSE - drive is invalid
**
** Side effects: none
*/
LOGICAL drvalid(int drive)
{
int original, result;
original = getdrv();
result = (SUCCESS == chdrv(drive));
chdrv(original);
return result;
}
/*
** drvrdy()
**
** Checks whether a drive with removable media is ready.
**
** Arguments: 1 - target drive (0 = A;, 1 = B:, etc.)
**
** Returns: TRUE - drive is ready
** FALSE - drive is not ready
** ERROR - other read error
**
** Side effects: none
*/
LOGICAL drvrdy(int drive)
{
int status;
char buf[2048]; /* nice & roomy */
status = AbsDiskRead(drive, 1, 0, buf);
if (0 == status)
return TRUE;
status &= 0xff;
if (2 == status)
return FALSE;
else return ERROR;
}
#ifdef TEST
#include <stdio.h>
#include <ctype.h>
int main(int argc, char *argv[])
{
int drive;
if (2 > argc)
{
puts("Usage: DRVALID drive[:]");
return EXIT_FAILURE;
}
drive = toupper(*argv[1]);
if (!isalpha(drive))
{
puts("Error: Invalid drive name");
return EXIT_FAILURE;
}
printf("Drive %c: is %svalid\n", drive,
drvalid(drive - 'A') ? "" : "not ");
if (2 < _osmajor)
{
union REGS regs;
regs.x.ax = 0x4408;
regs.h.bl = (unsigned char)(drive - '@');
intdos(®s, ®s);
printf("ioctl returned Cflag=%s\n",
regs.x.cflag ? "TRUE" : "FALSE");
printf("ioctl returned AX=0x%X\n", regs.x.ax);
printf("Drive %c is%s removable\n", drive,
regs.x.ax ? " not" : "");
if (0 == regs.x.ax)
{
printf("Drive %c is %sready\n", drive,
drvrdy(drive - 'A') ? "" : "not ");
}
}
return EXIT_SUCCESS;
}
#endif /* TEST */
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