#include	"u.h"#include	"lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"fs.h" struct Dosboot{	uchar	magic[3];	uchar	version[8];	uchar	sectsize[2];	uchar	clustsize;	uchar	nresrv[2];	uchar	nfats;	uchar	rootsize[2];	uchar	volsize[2];	uchar	mediadesc;	uchar	fatsize[2];	uchar	trksize[2];	uchar	nheads[2];	uchar	nhidden[4];	uchar	bigvolsize[4];/* fat 32 */	uchar	bigfatsize[4];	uchar	extflags[2];	uchar	fsversion[2];	uchar	rootdirstartclust[4];	uchar	fsinfosect[2];	uchar	backupbootsect[2];/* ???	uchar	driveno;	uchar	reserved0;	uchar	bootsig;	uchar	volid[4];	uchar	label[11];	uchar	reserved1[8];*/}; struct Dosdir{	uchar	name[8];	uchar	ext[3];	uchar	attr;	uchar	lowercase;	uchar	hundredth;	uchar	ctime[2];	uchar	cdate[2];	uchar	adate[2];	uchar	highstart[2];	uchar	mtime[2];	uchar	mdate[2];	uchar	start[2];	uchar	length[4];}; #define	DOSRONLY	0x01#define	DOSHIDDEN	0x02#define	DOSSYSTEM	0x04#define	DOSVLABEL	0x08#define	DOSDIR	0x10#define	DOSARCH	0x20 /* *  predeclared */static void	bootdump(Dosboot*);static void	setname(Dosfile*, char*); /* *  debugging */#define chatty	0#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){	Fs *fs;	Clustbuf *p, *oldest;	int size; 	chat("getclust @ %ld\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 %ld 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	 */	fs = (Fs*)dos;	chat("getclust addr %lud %p %p %p\n", (ulong)((sector+dos->start)*(vlong)dos->sectsize),		fs, fs->diskseek, fs->diskread);	if(fs->diskseek(fs, (sector+dos->start)*(vlong)dos->sectsize) < 0){		chat("can't seek block\n");		return 0;	}	if(fs->diskread(fs, p->iobuf, size) != size){		chat("can't read block\n");		return 0;	} 	p->age = m->ticks;	p->dos = dos;	p->sector = sector;	chat("getclust %ld 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;	case 32:		k = 4*n; break;	default:		return -1;	}	if(k >= dos->fatsize*dos->sectsize)		panic("getfat"); 	if (dos->sectsize == 0 || dos->clustsize == 0)		panic("fatwalk: zero sector or cluster size");	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 = -1;	}	else if (dos->fatbits == 32){		if(o >= dos->sectsize*dos->clustsize){			p = getclust(dos, sect+dos->clustsize);			o = 0;		}		k |= p->iobuf[o++]<<16;		k |= p->iobuf[o]<<24;		if (k >= 0xfffffff8)			k = -1;	}	else		k = k < 0xfff8 ? k : -1;	chat("fatwalk %d -> %lud\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 %ld\n", fp->name, ltarget);	/*	 *  root directory is contiguous and easy (unless FAT32)	 */	if(fp->pstart == 0 && dos->rootsize != 0) {		if(ltarget*dos->sectsize*dos->clustsize >= dos->rootsize*sizeof(Dosdir))			return -1;		l = dos->rootaddr + ltarget*dos->clustsize;		chat("fileaddr %ld -> %ld\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 %ld -> %ld\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 & DOSDIR) == 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(File *f, char *name){	Dosdir d;	long n;	Dosfile *file; 	chat("doswalk %s\n", name); 	file = &f->dos; 	if((file->attr & DOSDIR) == 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", (char*)d.name, (char*)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 & DOSVLABEL){			chat("%8.8s.%3.3s is a LABEL\n", (char*)d.name, (char*)d.ext);			continue;		}		file->attr = d.attr;		file->pstart = GSHORT(d.start);		if (file->dos->fatbits == 32)			file->pstart |= GSHORT(d.highstart) << 16;		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 in a segment */longdosreadseg(File *f, void *va, long len){	char *a;	long n, sofar;	Dosfile *fp; 	fp = &f->dos;	a = va;	for(sofar = 0; sofar < len; sofar += n){		n = 8*1024;		if(len - sofar < n)			n = len - sofar;		n = dosread(fp, a + sofar, n);		if(n <= 0)			break;		print(".");	}	return sofar;} intdosinit(Fs *fs){	Clustbuf *p;	Dosboot *b;	int i;	Dos *dos;	Dosfile *root; chat("dosinit0 %p %p %p\n", fs, fs->diskseek, fs->diskread); 	dos = &fs->dos;	/* defaults till we know better */	dos->sectsize = 512;	dos->clustsize = 1; 	/* get first sector */	p = getclust(dos, 0);	if(p == 0){		chat("can't read boot block\n");		return -1;	} chat("dosinit0a\n"); 	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 %x %x %x %x\n",			b->magic[0], b->magic[1], b->magic[2], b->magic[3]);		return -1;	} 	if(chatty)		bootdump(b); 	if(b->clustsize == 0) {unreasonable:		if(chatty){			print("unreasonable FAT BPB: ");			for(i=0; i<3+8+2+1; i++)				print(" %.2ux", p->iobuf[i]);			print("\n");		}		return -1;	} chat("dosinit1\n"); 	/*	 * Determine the systems' wondrous properties.	 * There are heuristics here, but there's no real way	 * of knowing if this is a reasonable FAT.	 */	dos->fatbits = 0;	dos->sectsize = GSHORT(b->sectsize);	if(dos->sectsize & 0xFF)		goto unreasonable;	dos->clustsize = b->clustsize;	dos->clustbytes = dos->sectsize*dos->clustsize;	dos->nresrv = GSHORT(b->nresrv);	dos->nfats = b->nfats;	dos->fatsize = GSHORT(b->fatsize);	dos->rootsize = GSHORT(b->rootsize);	dos->volsize = GSHORT(b->volsize);	if(dos->volsize == 0)		dos->volsize = GLONG(b->bigvolsize);	dos->mediadesc = b->mediadesc;	if(dos->fatsize == 0) {		chat("fat32\n");		dos->rootsize = 0;		dos->fatsize = GLONG(b->bigfatsize);		dos->fatbits = 32;	}	dos->fataddr = dos->nresrv;	if (dos->rootsize == 0) {		dos->rootaddr = 0;		dos->rootclust = GLONG(b->rootdirstartclust);		dos->dataaddr = dos->fataddr + dos->nfats*dos->fatsize;	} else {		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->fatbits != 32) {		if(dos->fatclusters < 4087)			dos->fatbits = 12;		else			dos->fatbits = 16;	}	dos->freeptr = 2; 	if(dos->clustbytes < 512 || dos->clustbytes > 64*1024)		goto unreasonable; chat("dosinit2\n"); 	/*	 *  set up the root	 */ 

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