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#ifdef __ELKS__
#include <stdio.h>
#endif
#include <dos.h>
#include "readfs.h"
#define HEADER_SIZE 512
#define NAME_SIZE 100
#define BLOCK_BOUNDARY 20
typedef union {
char hdr_block[HEADER_SIZE];
struct m {
char m_name[NAME_SIZE];
char m_mode[8];
char m_uid[8];
char m_gid[8];
char m_size[12];
char m_time[12];
char m_checksum[8];
char m_linked;
char m_link[NAME_SIZE];
} member;
} HEADER;
#ifdef __STANDALONE__
extern union REGS __argr;
#endif
tar_open_file(fname)
char * fname;
{
HEADER * sptr;
#ifdef __STANDALONE__
if( disk_drive != __argr.h.dl ) return -1; /* Only the one booted off */
if( __argr.x.si < 9 || __argr.x.si > 63 ) return -1; /* SPT good */
#endif
sptr = read_sector(0);
/* Boot sector a volume label ? */
if( sptr->member.m_linked != 'V' ) return -1;
if( !valid_tar_checksum(sptr) ) return -1;
#ifdef __STANDALONE__
disk_spt = __argr.x.si;
#else
disk_spt = 18; /* Testing only */
#endif
#ifdef __ELKS__
fprintf(stderr, "Got vaild tar header\n");
#endif
return -1;
}
tar_rewind_file()
{
return -1;
}
tar_close_file()
{
return -1;
}
long
tar_file_length()
{
return -1;
}
tar_read_block(buffer)
char * buffer;
{
return -1;
}
long
tar_convert(str, type)
char str[];
int type;
{
register long ac = 0L;
register int i;
for (i = 0; i < type; i++)
{
if (str[i] >= '0' && str[i] <= '7')
{
ac <<= 3;
ac += (long) (str[i] - '0');
}
}
return ac;
}
valid_tar_checksum(sptr)
HEADER * sptr;
{
register char *ptr;
register int ac = 0;
ptr = sptr->hdr_block;
while (ptr < sptr->hdr_block+sizeof(sptr->hdr_block))
if( ptr < sptr->member.m_checksum ||
ptr >= sptr->member.m_checksum+sizeof(sptr->member.m_checksum))
ac += (*ptr++ & 0xFF);
else
ptr++, (ac += ' ');
ac -= tar_convert(sptr->member.m_checksum, sizeof(sptr->member.m_checksum));
return ac == 0;
}
#if 0
#asm
!-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
!
! These are the number of sectors per track that will be scanned for.
! For 3.5 inch floppies 36 is 2.88 Mb, 18 is 1.44Mb, 21 is 1.68Mb on
! a 1.44Mb floppy drive. 15 and 9 are for 5.25 inch floppies.
disksizes: .byte 36,21,18,15,9
! It seems that there is no BIOS call to get the number of sectors. Guess
! 36 sectors if sector 36 can be read, 18 sectors if sector 18 can be read,
! 15 if sector 15 can be read. Otherwise guess 9.
export _probe_sectors
_probe_sectors:
mov si,#disksizes ! table of sizes to try
probe_loop:
lodsb
cbw ! extend to word
mov _disk_spt, ax
cmp al,#9
je got_sectors ! if all else fails, try 9
xchg ax, cx ! cx = track and sector
xor dx, dx ! drive 0, head 0
mov bx,#probe_buf ! address after setup (es = cs)
mov ax,#0x0201 ! service 2, 1 sector
int 0x13
jc probe_loop ! try next value
got_sectors:
ret
#endasm
#endif
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