implement lstar; include "sys.m";	sys: Sys;	print, sprint, fprint: import sys;	stdin, stderr: ref sys->FD;include "draw.m"; TBLOCK: con 512;	# tar logical blocksizeHeader: adt{	name: string;	size: int;	mtime: int;	skip: int;}; lstar: module{	init:   fn(nil: ref Draw->Context, nil: list of string);}; Error(mess: string){	fprint(stderr,"lstar: %s: %r\n",mess);	exit;}  NBLOCK: con 20;		# 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 consumedgetblock():array of byte{	if(recno>=nblock){		i := sys->read(stdin,tarbuf,TBLOCK*NBLOCK);		if(i==0)			return tarbuf[0:0];		if(i<0)			Error("read error");		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; 	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;	mtime := 0;	case int dblock[156]{	'0' or '5' or '7' or 0 =>		skip = 0;		size = octal(dblock[124:136]);		mtime = octal(dblock[136:148]);	'1' =>		fprint(stderr,"skipping link %s -> %s\n",name,string(dblock[157:257]));	'2' or 's' =>		fprint(stderr,"skipping symlink %s\n",name);	'3' or '4' or '6' =>		fprint(stderr,"skipping special file %s\n",name);	* =>		Error(sprint("unrecognized typeflag %d for %s",int dblock[156],name));	}	return ref Header(name,size,mtime,skip);}  init(nil: ref Draw->Context, nil: list of string){	sys = load Sys Sys->PATH;	stdin = sys->fildes(0);	stderr = sys->fildes(2);	ofile: ref sys->FD; 	while((file := getdir())!=nil){		bytes := file.size;		blocks := (bytes+TBLOCK-1)/TBLOCK;		for(; blocks>0; blocks--)			getblock();		print("%s %d %d 0\n",file.name,file.mtime,file.size);		ofile = nil;	}}