implement Gettar; include "sys.m";	sys: Sys;	print, sprint, fprint: import sys;	stdin, stderr: ref sys->FD; include "draw.m"; include "arg.m"; TBLOCK: con 512;	# tar logical blocksize Header: adt{	name: string;	size: int;	mode: int;	mtime: int;	skip: int;}; Gettar: module{	init:   fn(nil: ref Draw->Context, nil: list of string);}; error(mess: string){	fprint(stderr,"gettar: %s\n",mess);	raise "fail:error";} verbose := 0;NBLOCK: con 20;		# traditional blocking factor for efficient readtarbuf := array[NBLOCK*TBLOCK] of byte;	# static buffernblock := NBLOCK;			# how many blocks of data are in tarbufrecno := NBLOCK;			# how many blocks in tarbuf have been consumed getblock(): array of byte{	if(recno>=nblock){		i := sys->read(stdin,tarbuf,TBLOCK*NBLOCK);		if(i==0)			return nil;		if(i<0)			error(sys->sprint("read error: %r"));		if(i%TBLOCK!=0)			error("blocksize error");		nblock = i/TBLOCK;		recno = 0;	}	recno++;	return tarbuf[(recno-1)*TBLOCK:recno*TBLOCK];}  octal(b:array of byte): int{	sum := 0;	for(i:=0; i<len b; i++){		bi := int b[i];		if(bi==' ') continue;		if(bi==0) break;		sum = 8*sum + bi-'0';	}	return sum;} nullterm(b:array of byte): string{	for(i:=0; i<len b; i++)		if(b[i]==byte 0) break;	return string b[0:i];} getdir(): ref Header{	dblock := getblock();	if(len dblock==0)		return nil;	if(dblock[0]==byte 0)		return nil; 	name := nullterm(dblock[0:100]);	if(int dblock[345]!=0)		name = nullterm(dblock[345:500])+"/"+name;	if(!absolute){		if(name[0] == '#')			name = "./"+name;		else if(name[0] == '/')			name = "."+name;	} 	magic := string(dblock[257:262]);	if(magic[0]!=0 && magic!="ustar")		error("bad magic "+name);	chksum := octal(dblock[148:156]);	for(ci:=148; ci<156; ci++)		dblock[ci] = byte ' ';	for(i:=0; i<TBLOCK; i++)		chksum -= int dblock[i];	if(chksum!=0)		error("directory checksum error "+name); 	skip := 1;	size := 0;	mode := 0;	mtime := 0;	case int dblock[156]{	'0' or '7' or 0 =>		skip = 0;		size = octal(dblock[124:136]);		mode = 8r777 & octal(dblock[100: 108]);		mtime = octal(dblock[136:148]);	'1' =>		fprint(stderr,"gettar: skipping link %s -> %s\n",name,string(dblock[157:257]));	'2' or 's' =>		fprint(stderr,"gettar: skipping symlink %s\n",name);	'3' or '4' or '6' =>		fprint(stderr,"gettar: skipping special file %s\n",name);	'5' =>		if(name[(len name)-1]=='/')			checkdir(name+".");		else			checkdir(name+"/.");	* =>		error(sprint("unrecognized typeflag %d for %s",int dblock[156],name));	}	return ref Header(name, size, mode, mtime, skip);} keep := 0;absolute := 0; init(nil: ref Draw->Context, args: list of string){	sys = load Sys Sys->PATH;	stdin = sys->fildes(0);	stderr = sys->fildes(2);	ofile: ref sys->FD; 	arg := load Arg Arg->PATH;	arg->init(args);	arg->setusage("gettar [-kTRv] [file ...]");	while((o := arg->opt()) != 0)		case o {		'k' =>	keep = 1;		'v' =>	verbose = 1;		'R' =>	absolute = 1;		* =>	arg->usage();		}	args = arg->argv();	arg = nil; 	while((file := getdir())!=nil){		if(!file.skip){			if((args == nil || matched(file.name, args)) && !(keep && exists(file.name))){				if(verbose)					sys->fprint(stderr, "%s\n", file.name);				checkdir(file.name);				ofile = sys->create(file.name, Sys->OWRITE, 8r666);				if(ofile==nil){					fprint(stderr, "gettar: cannot create %s: %r\n",file.name);					file.skip = 1;				}			}else				file.skip = 1;		}		bytes := file.size;		blocks := (bytes+TBLOCK-1)/TBLOCK;		if(file.skip){			for(; blocks>0; blocks--)				getblock();			continue;		} 		for(; blocks>0; blocks--){			buf := getblock();			nwrite := bytes;			if(nwrite>TBLOCK)				nwrite = TBLOCK;			if(sys->write(ofile,buf,nwrite)!=nwrite)				error(sprint("write error for %s: %r",file.name));			bytes -= nwrite;		}		ofile = nil;		stat := sys->nulldir;		stat.mode = file.mode;		stat.mtime = file.mtime;		rc := sys->wstat(file.name,stat);		if(rc<0){			# try just the mode			stat.mtime = ~0;			rc = sys->wstat(file.name, stat);			if(rc < 0)				fprint(stderr,"gettar: cannot set mode/mtime %s %#o %ud: %r\n",file.name, file.mode, file.mtime);		}	}} checkdir(name: string){	(nc,compl) := sys->tokenize(name,"/");	path := "";	while(compl!=nil){		comp := hd compl;		if(comp=="..")			error(".. pathnames forbidden");		if(nc>1){			if(path=="")				path = comp;			else				path += "/"+comp;			(rc,stat) := sys->stat(path);			if(rc<0){				fd := sys->create(path,Sys->OREAD,Sys->DMDIR+8r777);				if(fd==nil)					error(sprint("cannot mkdir %s: %r",path));				fd = nil;			}else if(stat.mode&Sys->DMDIR==0)				error(sprint("found non-directory at %s",path));		}		nc--; compl = tl compl;	}} exists(path: string): int{	return sys->stat(path).t0 >= 0;} matched(n: string, names: list of string): int{	for(; names != nil; names = tl names){		p := hd names;		if(prefix(p, n))			return 1;	}	return 0;} prefix(p: string, s: string): int{	l := len p;	if(l > len s)		return 0;	return p == s[0:l] && (l == len s || s[l] == '/');}