/*

	This program reads/writes MS-DOS formatted disks,
using the CPM bios routines.  The data is converted to/from
C (non-ascii) files.  The code is written so that it can
be compiled with Small-C, but uses K&R standard I/O
whenever possible.

Author:	Bob Alverson
	8717 Empire Ct.
	Cincinnati, OH  45231
	513-729-1676

1.1	 9 DEC 83	Add ability to read all four IBM formats
1.0	27 NOV 83	First working version.

*/


#include <stdio.h>

/* Define the disk bios calls */

#define	SELDSK	9			/* Select disk drive */
#define	SETTRK	10			/* Select track */
#define	SETSEC	11			/* Select sector */
#define	SETDMA	12			/* Set DMA address */
#define	RDSEC	13			/* Read sector */
#define	WRSEC	14			/* Write sector */
#define SECTRAN	16			/* Translate sector # */

#define CURDSK	25			/* bdos selected disk */

/* disk parameters */

#define ALLMAX	1024			/* maximum alloc table size */
#define DIRMAX	7*512			/* maximum directory size */

/* misc data */

#define DATSIZ	0x4000			/* size of data buffer */

/* global data */

char	spttbl[4] = {32, 32, 36, 36};	/* sectors per track (logical) */
int	spt;

char	alltbl[4] = {8, 4, 8, 4};	/* size of alloc table / 128 */
int	allsiz;

char	dirtbl[4] = {28, 16, 28, 16};	/* size of directory / 128 */
int	dirsiz;

int	blktbl[4] = {8, 4, 8, 4};	/* size of block / 128 */
int	blksiz;
int	blklen;				/* block size in bytes */

int	secofs;
char	allmap[ALLMAX];			/* allocation map */
char	dirbuf[DIRMAX];			/* directory data */
char	datbuf[DATSIZ];			/* data transfer buffer */
char	*datptr;
int	cpmdsk;				/* cpm default disk */
char	xfile[20];			/* filename to transfer */
int	drive;				/* drive of MSDOS disk */
int	blk;				/* MSDOS block number */ 
int	xtra, blks;			/* file length */
FILE	*cfile;				/* output file stream */

main()
{
	fputs("\nRead MS-DOS disks, Version 1.1\nDec  9, 1983\n", stdout);
	do {
		fputs("Drive of MSDOS disk: ",stdout);
		fgets(xfile, 20, stdin);
		drive = toupper(*xfile) - 'A';
		if (drive < 0 || drive >= 16) {
			fputs("\n\7Drive spec error!\n", stderr);
			drive = -1;		/* flag bad drive */
		}
	} /* do */
	while (drive < 0);

	cpmdsk = bdos(CURDSK, 0);

	bios(SELDSK, drive, 0);			/* select disk drive */
	dettype();

	readdsk(4, allsiz, allmap);		/* read allocation map in */
	readdsk(allsiz*2+4, dirsiz, dirbuf);	/* read dir into memory */

	bios(SELDSK, cpmdsk, 1);

	while (getnam()) {
		if (find()) {
			cfile = fopen(xfile, "w");
			bios(SELDSK, drive, 1);
			datptr = datbuf;
			do {
				readblk(blk, datptr);
				if (blks) {	/* complete sector */
					--blks;
					datptr += blklen;
				}
				else {		/* partial sector */
					datptr += xtra;
					xtra = 0;
				}
				if (datptr > datbuf+DATSIZ-blklen) {
					bios(SELDSK, cpmdsk, 1);
					fwrite(datbuf, 1, datptr-datbuf, cfile);
					bios(SELDSK, drive, 1);
					datptr = datbuf;
				} /* if */
				nxtblk();
			} /* do */
			while (blks || xtra);
			bios(SELDSK, cpmdsk, 1);
			fwrite(datbuf, 1, datptr-datbuf, cfile);
			fclose(cfile);
		} /* if */
		else fputs("\nFile not found\n",stdout);
	} /* while */
} /* main */


dettype()		/* determine disk type */
{
	char	secbuf[128];
	int	dsktyp;

	readsec(0, 5, secbuf);
	dsktyp = (~ *secbuf) & 3;

	spt = spttbl[dsktyp];
	allsiz = alltbl[dsktyp];
	dirsiz = dirtbl[dsktyp];
	blksiz = blktbl[dsktyp];

	blklen = blksiz*128;
	secofs = ((allsiz - blksiz) << 1) + dirsiz + 4;
} /* dettype */


getnam()
{
	char *str, *ptr;

	fputs("\nEnter filename: ", stdout);
	str = fgets(xfile, 20, stdin);
	if (ptr=strchr(xfile, '\n')) *ptr = '\0';
	return str;
}


/* read MSDOS block */

readblk(blkno, bufptr)
int	blkno;
char	*bufptr;
{
	readdsk((blkno * blksiz) + secofs, blksiz, bufptr);
}


readdsk(dsksec, numsec, bufptr)
int	dsksec,
	numsec;
char	*bufptr;
{
	do {
		readsec(dsksec/spt, (dsksec%spt)+1, bufptr);
		bufptr += 128;
		++dsksec;
	} /* do */
 	while (--numsec);	/* do all sectors requested */
} /* readdsk */


readsec(trk, sec, buf)
int	trk, sec;
char	*buf;
{
	int retcode;

	bios(SETTRK, trk, 0);
	bios(SETSEC, sec, 0);
	bios(SETDMA, buf, 0);
	do {
		if (retcode = bios(RDSEC, 0, 0)) {
			char ask[3];
			fputs("\nDisk read error\nIgnore or Retry? ", stdout);
			fgets(ask, 3, stdin);
			if (toupper(*ask) == 'I') retcode = 0;
		} /* if */
	} /* do */
	while (retcode);
} /* readsec */


/* find next block (cluster) in chain */

nxtblk()
{
	int nblk;
	int *blkptr;

	blkptr = allmap + ((blk*3) >> 1);
	nblk = *blkptr;
	if (blk & 1) nblk >>= 4;
	blk = nblk & 0x0fff;
}

/* find file name in directory buffer */

find()
{
	char	name[12];
	char	*dirptr;
	int	*blkptr;

	fmtfn(xfile, name);
	dirptr = dirbuf;
	while (strncmp(dirptr, name, 11) && *dirptr) dirptr += 32;
	if (*dirptr) {
		blk = *(blkptr = dirptr+26);
		xtra = *(++blkptr);
		blks = (xtra/blklen) + *(++blkptr)*(512/blksiz);
		xtra %= blklen;
		return 1;
	}
	return 0;	/* not found */
}

/* format filename for directory search */

fmtfn(text, buf)
char	*text, *buf;
{
	if (text[1] == ':') text += 2;	/* skip over drive */

	fmtbit(&text, buf, 8);
	fmtbit(&text, buf+8, 3);

	buf[11] = 0;
}

fmtbit(tptr, dest, cnt)
int	*tptr;		/* should be char **text */
char	*dest;
int	cnt;
{
	char	*text;

	text = *tptr;
	while (--cnt >= 0) {
		if (*text && *text != '.')
			*dest = toupper(*text++);	/* no macro allowed */
		else
			*dest = ' ';
		++dest;
	}
	while (*text && *text != '.') ++text;
	if (*text == '.') ++text;	/* scan past . */
	*tptr = text;
}