/*----------------------------------------------------------------------------
40-line Turbo C program to display root directory of a FAT12 floppy disk
without using DOS.
Chris Giese	<ChrisGiese@SisAndHappy.com>
http://SisAndHappy.com/ChrisGiese/

This code is public domain (no copyright).
You can do whatever you want with it.
----------------------------------------------------------------------------*/
#include <stdio.h>
#include <bios.h>
#define	read_le16(X)	*(unsigned short *)(X)
static unsigned g_drive_num = 0, g_heads = 1, g_sectors = 1;
static int read_sector(void *buf, unsigned lba) {
	unsigned sector, head;

	sector = (lba % g_sectors) + 1;
	lba /= g_sectors;
	head = lba % g_heads;
	lba /= g_heads;
	return biosdisk(/*_DISK_READ=*/2, g_drive_num, head,
		/*cylinder=*/lba, sector, /* num_sects=*/1, buf); }

int main(void) {
	unsigned first_root_sector, num_root_sectors, s;
	unsigned char buf[512], *e;

/* should test for error here; and validate boot sector */
	(void)read_sector(buf, 0);
	g_heads = read_le16(&buf[26]);	/* number of heads */
	g_sectors = read_le16(&buf[24]); /* sectors per track */
	first_root_sector =
		read_le16(&buf[14]) +	/* start of FATs */
		buf[16] *		/* number of FATs */
		read_le16(&buf[22]);	/* sectors per FAT */
	num_root_sectors = read_le16(&buf[17]) *
		32 /	/* bytes per directory entry */
		512;	/* bytes per sector */
	for(s = 0; s < num_root_sectors; s++) {
		(void)read_sector(buf, first_root_sector + s);
		for(e = buf; e < &buf[512]; e = &e[32]) {
			if(e[0] == '\0' /* unused directory entry */
				|| e[0] == 0xE5 /* deleted entry */
				|| (e[11] & 0x08)) /* volume label or LFN */
					continue;
			printf("%-11.11s     ", e); }}
	printf("\n");
	return 0; }