#include	"u.h"#include	"lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"dosfs.h" extern char *premature; /* *  predeclared */static void	bootdump(Dosboot*);static void	setname(Dosfile*, char*);long		dosreadseg(Dosfile*, long, long); /* *  debugging */#define chatty	1#define chat	if(chatty)print /* *  block io buffers */enum{	Nbio=	16,};typedef struct	Clustbuf	Clustbuf;struct Clustbuf{	int	age;	long	sector;	uchar	*iobuf;	Dos	*dos;	int	size;};Clustbuf	bio[Nbio]; /* *  get an io block from an io buffer */Clustbuf*getclust(Dos *dos, long sector){	Clustbuf *p, *oldest;	int size; 	chat("getclust @ %d\n", sector); 	/*	 *  if we have it, just return it	 */	for(p = bio; p < &bio[Nbio]; p++){		if(sector == p->sector && dos == p->dos){			p->age = m->ticks;			chat("getclust %d in cache\n", sector);			return p;		}	} 	/*	 *  otherwise, reuse the oldest entry	 */	oldest = bio;	for(p = &bio[1]; p < &bio[Nbio]; p++){		if(p->age <= oldest->age)			oldest = p;	}	p = oldest; 	/*	 *  make sure the buffer is big enough	 */	size = dos->clustsize*dos->sectsize;	if(p->iobuf==0 || p->size < size)		p->iobuf = ialloc(size, 0);	p->size = size; 	/*	 *  read in the cluster	 */	chat("getclust addr %d\n", (sector+dos->start)*dos->sectsize);	if((*dos->seek)(dos->dev, (sector+dos->start)*dos->sectsize) < 0){		chat("can't seek block\n");		return 0;	}	if((*dos->read)(dos->dev, p->iobuf, size) != size){		chat("can't read block\n");		return 0;	} 	p->age = m->ticks;	p->dos = dos;	p->sector = sector;	chat("getclust %d read\n", sector);	return p;} /* *  walk the fat one level ( n is a current cluster number ). *  return the new cluster number or -1 if no more. */static longfatwalk(Dos *dos, int n){	ulong k, sect;	Clustbuf *p;	int o; 	chat("fatwalk %d\n", n); 	if(n < 2 || n >= dos->fatclusters)		return -1; 	switch(dos->fatbits){	case 12:		k = (3*n)/2; break;	case 16:		k = 2*n; break;	default:		return -1;	}	if(k >= dos->fatsize*dos->sectsize)		panic("getfat"); 	sect = (k/(dos->sectsize*dos->clustsize))*dos->clustsize + dos->fataddr;	o = k%(dos->sectsize*dos->clustsize);	p = getclust(dos, sect);	k = p->iobuf[o++];	if(o >= dos->sectsize*dos->clustsize){		p = getclust(dos, sect+dos->clustsize);		o = 0;	}	k |= p->iobuf[o]<<8;	if(dos->fatbits == 12){		if(n&1)			k >>= 4;		else			k &= 0xfff;		if(k >= 0xff8)			k |= 0xf000;	}	k = k < 0xfff8 ? k : -1;	chat("fatwalk %d -> %d\n", n, k);	return k;} /* *  map a file's logical cluster address to a physical sector address */static longfileaddr(Dosfile *fp, long ltarget){	Dos *dos = fp->dos;	long l;	long p; 	chat("fileaddr %8.8s %d\n", fp->name, ltarget);	/*	 *  root directory is contiguous and easy	 */	if(fp->pstart == 0){		if(ltarget*dos->sectsize*dos->clustsize >= dos->rootsize*sizeof(Dosdir))			return -1;		l = dos->rootaddr + ltarget*dos->clustsize;		chat("fileaddr %d -> %d\n", ltarget, l);		return l;	} 	/*	 *  anything else requires a walk through the fat	 */	if(ltarget >= fp->lcurrent && fp->pcurrent){		/* start at the currrent point */		l = fp->lcurrent;		p = fp->pcurrent;	} else {		/* go back to the beginning */		l = 0;		p = fp->pstart;	}	while(l != ltarget){		/* walk the fat */		p = fatwalk(dos, p);		if(p < 0)			return -1;		l++;	}	fp->lcurrent = l;	fp->pcurrent = p; 	/*	 *  clusters start at 2 instead of 0 (why? - presotto)	 */	l =  dos->dataaddr + (p-2)*dos->clustsize;	chat("fileaddr %d -> %d\n", ltarget, l);	return l;} /* *  read from a dos file */longdosread(Dosfile *fp, void *a, long n){	long addr;	long rv;	int i;	int off;	Clustbuf *p;	uchar *from, *to; 	if((fp->attr & DDIR) == 0){		if(fp->offset >= fp->length)			return 0;		if(fp->offset+n > fp->length)			n = fp->length - fp->offset;	} 	to = a;	for(rv = 0; rv < n; rv+=i){		/*		 *  read the cluster		 */		addr = fileaddr(fp, fp->offset/fp->dos->clustbytes);		if(addr < 0)			return -1;		p = getclust(fp->dos, addr);		if(p == 0)			return -1; 		/*		 *  copy the bytes we need		 */		off = fp->offset % fp->dos->clustbytes;		from = &p->iobuf[off];		i = n - rv;		if(i > fp->dos->clustbytes - off)			i = fp->dos->clustbytes - off;		memmove(to, from, i);		to += i;		fp->offset += i;	} 	return rv;} /* *  walk a directory returns * 	-1 if something went wrong *	 0 if not found *	 1 if found */intdoswalk(Dosfile *file, char *name){	Dosdir d;	long n; 	if((file->attr & DDIR) == 0){		chat("walking non-directory!\n");		return -1;	} 	setname(file, name); 	file->offset = 0;	/* start at the beginning */	while((n = dosread(file, &d, sizeof(d))) == sizeof(d)){		chat("comparing to %8.8s.%3.3s\n", d.name, d.ext);		if(memcmp(file->name, d.name, sizeof(d.name)) != 0)			continue;		if(memcmp(file->ext, d.ext, sizeof(d.ext)) != 0)			continue;		if(d.attr & DVLABEL){			chat("%8.8s.%3.3s is a LABEL\n", d.name, d.ext);			continue;		}		file->attr = d.attr;		file->pstart = GSHORT(d.start);		file->length = GLONG(d.length);		file->pcurrent = 0;		file->lcurrent = 0;		file->offset = 0;		return 1;	}	return n >= 0 ? 0 : -1;}  /* *  instructions that boot blocks can start with */#define	JMPSHORT	0xeb#define JMPNEAR		0xe9 /* *  read dos file system properties */intdosinit(Dos *dos, int start, int ishard){	Dosboot *b;	int i;	Clustbuf *p;	Dospart *dp;	ulong mbroffset, offset; 	/* defaults till we know better */	dos->start = start;	dos->sectsize = 512;	dos->clustsize = 1;	mbroffset = 0; dmddo:	/* get first sector */	p = getclust(dos, mbroffset);	if(p == 0){		chat("can't read boot block\n");		return -1;	} 	/*	 * If it's a hard disc then look for an MBR and pick either an	 * active partition or the FAT with the lowest starting LBA.	 * Things are tricky because we could be pointing to, amongst others:	 *	1) a floppy BPB;	 *	2) a hard disc MBR;	 *	3) a hard disc extended partition table;	 *	4) a logical drive on a hard disc;	 *	5) a disc-manager boot block.	 * They all have the same magic at the end of the block.	 */	if(p->iobuf[0x1FE] != 0x55 || p->iobuf[0x1FF] != 0xAA) {		chat("not DOS\n");		return -1;	}	p->dos = 0;	b = (Dosboot *)p->iobuf;	if(ishard && b->mediadesc != 0xF8){		dp = (Dospart*)&p->iobuf[0x1BE];		offset = 0xFFFFFFFF;		for(i = 0; i < 4; i++, dp++){			if(dp->type == DMDDO){				mbroffset = 63;				goto dmddo;			}			if(dp->type != FAT12 && dp->type != FAT16 && dp->type != FATHUGE)				continue;			if(dp->flag & 0x80){				offset = GLONG(dp->start);				break;			}			if(GLONG(dp->start) < offset)				offset = GLONG(dp->start);		}		if(i != 4 || offset != 0xFFFFFFFF){			dos->start = mbroffset+offset;			p = getclust(dos, 0);			if(p == 0 || p->iobuf[0x1FE] != 0x55 || p->iobuf[0x1FF] != 0xAA)				return -1;		}		p->dos = 0;	} 	b = (Dosboot *)p->iobuf;	if(b->magic[0] != JMPNEAR && (b->magic[0] != JMPSHORT || b->magic[2] != 0x90)){		chat("no dos file system\n");		return -1;	} 	if(chatty)		bootdump(b); 	/*	 *  determine the systems' wondersous properties	 */	dos->sectsize = GSHORT(b->sectsize);	dos->clustsize = b->clustsize;	dos->clustbytes = dos->sectsize*dos->clustsize;	dos->nresrv = GSHORT(b->nresrv);	dos->nfats = b->nfats;	dos->rootsize = GSHORT(b->rootsize);	dos->volsize = GSHORT(b->volsize);	if(dos->volsize == 0)		dos->volsize = GLONG(b->bigvolsize);	dos->mediadesc = b->mediadesc;	dos->fatsize = GSHORT(b->fatsize);	dos->fataddr = dos->nresrv;	dos->rootaddr = dos->fataddr + dos->nfats*dos->fatsize;	i = dos->rootsize*sizeof(Dosdir) + dos->sectsize - 1;	i = i/dos->sectsize;	dos->dataaddr = dos->rootaddr + i;	dos->fatclusters = 2+(dos->volsize - dos->dataaddr)/dos->clustsize;	if(dos->fatclusters < 4087)		dos->fatbits = 12;	else		dos->fatbits = 16;	dos->freeptr = 2; 	/*	 *  set up the root	 */	dos->root.dos = dos;	dos->root.pstart = 0;	dos->root.pcurrent = dos->root.lcurrent = 0;	dos->root.offset = 0;	dos->root.attr = DDIR;	dos->root.length = dos->rootsize*sizeof(Dosdir); 	return 0;} static voidbootdump(Dosboot *b){	if(chatty == 0)		return;	print("magic: 0x%2.2x 0x%2.2x 0x%2.2x\n",		b->magic[0], b->magic[1], b->magic[2]);	print("version: \"%8.8s\"\n", b->version);	print("sectsize: %d\n", GSHORT(b->sectsize));	print("allocsize: %d\n", b->clustsize);	print("nresrv: %d\n", GSHORT(b->nresrv));	print("nfats: %d\n", b->nfats);	print("rootsize: %d\n", GSHORT(b->rootsize));	print("volsize: %d\n", GSHORT(b->volsize));	print("mediadesc: 0x%2.2x\n", b->mediadesc);	print("fatsize: %d\n", GSHORT(b->fatsize));	print("trksize: %d\n", GSHORT(b->trksize));	print("nheads: %d\n", GSHORT(b->nheads));	print("nhidden: %d\n", GLONG(b->nhidden));	print("bigvolsize: %d\n", GLONG(b->bigvolsize));	print("driveno: %d\n", b->driveno);	print("reserved0: 0x%2.2x\n", b->reserved0);	print("bootsig: 0x%2.2x\n", b->bootsig);	print("volid: 0x%8.8x\n", GLONG(b->volid));	print("label: \"%11.11s\"\n", b->label);} /* *  grab next element from a path, return the pointer to unprocessed portion of *  path. */static char *nextelem(char *path, char *elem){	int i; 	while(*path == '/')		path++;	if(*path==0 || *path==' ')		return 0;	for(i=0; *path!='\0' && *path!='/' && *path!=' '; i++){		if(i==28){			print("name component too long\n");			return 0;		}		*elem++ = *path++;	}	*elem = '\0';	return path;} intdosstat(Dos *dos, char *path, Dosfile *f){	char element[NAMELEN]; 	*f = dos->root;	while(path = nextelem(path, element)){		switch(doswalk(f, element)){		case -1:			return -1;		case 0:			return 0;		}	}	return 1;} /* *  boot */intdosboot(Dos *dos, char *path){	Dosfile file;	long n;	long addr;	Exec *ep;	void (*b)(void); 	switch(dosstat(dos, path, &file)){ 	case -1:		print("error walking to %s\n", path);		return -1;	case 0:

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