src/cmd/vac/vac.c - plan9 - Git at Google

 #include "stdinc.h"
 #include "vac.h"
 #include "dat.h"
 #include "fns.h"

 // TODO: qids

 void
 usage(void)
 {
 	fprint(2, "vac [-imqsv] [-a archive.vac] [-b bsize] [-d old.vac] [-f new.vac] [-e exclude]... [-h host] file...\n");
 	threadexitsall("usage");
 }

 enum
 {
 	BlockSize = 8*1024,
 	CacheSize = 4<<20,
 };

 struct
 {
 	int nfile;
 	int ndir;
 	vlong data;
 	vlong skipdata;
 	int skipfiles;
 } stats;

 int qdiff;
 int merge;
 int verbose;
 char *host;
 VtConn *z;
 VacFs *fs;
 char *archivefile;
 char *vacfile;

 int vacmerge(VacFile*, char*);
 void vac(VacFile*, VacFile*, char*, Dir*);
 void vacstdin(VacFile*, char*);
 VacFile *recentarchive(VacFs*, char*);

 static u64int unittoull(char*);
 static void warn(char *fmt, ...);
 static void removevacfile(void);

 #ifdef PLAN9PORT
 /*
  * We're between a rock and a hard place here.
  * The pw library (getpwnam, etc.) reads the
  * password and group files into an on-stack buffer,
  * so if you have some huge groups, you overflow
  * the stack.  Because of this, the thread library turns
  * it off by default, so that dirstat returns "14571" instead of "rsc".
  * But for vac we want names.  So cautiously turn the pwlibrary
  * back on (see threadmain) and make the main thread stack huge.
  */
 extern int _p9usepwlibrary;
 int mainstacksize = 4*1024*1024;

 #endif
 void
 threadmain(int argc, char **argv)
 {
 	int i, j, fd, n, printstats;
 	Dir *d;
 	char *s;
 	uvlong u;
 	VacFile *f, *fdiff;
 	VacFs *fsdiff;
 	int blocksize;
 	int outfd;
 	char *stdinname;
 	char *diffvac;
 	uvlong qid;

 #ifdef PLAN9PORT
 	/* see comment above */
 	_p9usepwlibrary = 1;
 #endif

 	fmtinstall('F', vtfcallfmt);
 	fmtinstall('H', encodefmt);
 	fmtinstall('V', vtscorefmt);

 	blocksize = BlockSize;
 	stdinname = nil;
 	printstats = 0;
 	fsdiff = nil;
 	diffvac = nil;

 	ARGBEGIN{
 	case 'V':
 		chattyventi++;
 		break;
 	case 'a':
 		archivefile = EARGF(usage());
 		break;
 	case 'b':
 		u = unittoull(EARGF(usage()));
 		if(u < 512)
 			u = 512;
 		blocksize = u;
 		break;
 	case 'd':
 		diffvac = EARGF(usage());
 		break;
 	case 'e':
 		excludepattern(EARGF(usage()));
 		break;
 	case 'f':
 		vacfile = EARGF(usage());
 		break;
 	case 'h':
 		host = EARGF(usage());
 		break;
 	case 'i':
 		stdinname = EARGF(usage());
 		break;
 	case 'm':
 		merge++;
 		break;
 	case 'q':
 		qdiff++;
 		break;
 	case 's':
 		printstats++;
 		break;
 	case 'v':
 		verbose++;
 		break;
 	case 'x':
 		loadexcludefile(EARGF(usage()));
 		break;
 	default:
 		usage();
 	}ARGEND

 	if(argc == 0 && !stdinname)
 		usage();

 	if(archivefile && (vacfile || diffvac)){
 		fprint(2, "cannot use -a with -f, -d\n");
 		usage();
 	}

 	z = vtdial(host);
 	if(z == nil)
 		sysfatal("could not connect to server: %r");
 	if(vtconnect(z) < 0)
 		sysfatal("vtconnect: %r");

 	// Setup:
 	//	fs is the output vac file system
 	//	f is directory in output vac to write new files
 	//	fdiff is corresponding directory in existing vac
 	if(archivefile){
 		VacFile *fp;
 		char yyyy[5];
 		char mmdd[10];
 		char oldpath[40];
 		Tm tm;

 		fdiff = nil;
 		if((outfd = open(archivefile, ORDWR)) < 0){
 			if(access(archivefile, 0) >= 0)
 				sysfatal("open %s: %r", archivefile);
 			if((outfd = create(archivefile, OWRITE, 0666)) < 0)
 				sysfatal("create %s: %r", archivefile);
 			atexit(removevacfile);	// because it is new
 			if((fs = vacfscreate(z, blocksize, CacheSize)) == nil)
 				sysfatal("vacfscreate: %r");
 		}else{
 			if((fs = vacfsopen(z, archivefile, VtORDWR, CacheSize)) == nil)
 				sysfatal("vacfsopen %s: %r", archivefile);
 			if((fdiff = recentarchive(fs, oldpath)) != nil){
 				if(verbose)
 					fprint(2, "diff %s\n", oldpath);
 			}else
 				if(verbose)
 					fprint(2, "no recent archive to diff against\n");
 		}

 		// Create yyyy/mmdd.
 		tm = *localtime(time(0));
 		snprint(yyyy, sizeof yyyy, "%04d", tm.year+1900);
 		fp = vacfsgetroot(fs);
 		if((f = vacfilewalk(fp, yyyy)) == nil
 		&& (f = vacfilecreate(fp, yyyy, ModeDir|0555)) == nil)
 			sysfatal("vacfscreate %s: %r", yyyy);
 		vacfiledecref(fp);
 		fp = f;

 		snprint(mmdd, sizeof mmdd, "%02d%02d", tm.mon+1, tm.mday);
 		n = 0;
 		while((f = vacfilewalk(fp, mmdd)) != nil){
 			vacfiledecref(f);
 			n++;
 			snprint(mmdd+4, sizeof mmdd-4, ".%d", n);
 		}
 		f = vacfilecreate(fp, mmdd, ModeDir|0555);
 		if(f == nil)
 			sysfatal("vacfscreate %s/%s: %r", yyyy, mmdd);
 		vacfiledecref(fp);

 		if(verbose)
 			fprint(2, "archive %s/%s\n", yyyy, mmdd);
 	}else{
 		if(vacfile == nil)
 			outfd = 1;
 		else if((outfd = create(vacfile, OWRITE, 0666)) < 0)
 			sysfatal("create %s: %r", vacfile);
 		atexit(removevacfile);
 		if((fs = vacfscreate(z, blocksize, CacheSize)) == nil)
 			sysfatal("vacfscreate: %r");
 		f = vacfsgetroot(fs);

 		fdiff = nil;
 		if(diffvac){
 			if((fsdiff = vacfsopen(z, diffvac, VtOREAD, CacheSize)) == nil)
 				warn("vacfsopen %s: %r", diffvac);
 			else
 				fdiff = vacfsgetroot(fsdiff);
 		}
 	}

 	if(stdinname)
 		vacstdin(f, stdinname);
 	for(i=0; i<argc; i++){
 		// We can't use / and . and .. and ../.. as valid archive
 		// names, so expand to the list of files in the directory.
 		if(argv[i][0] == 0){
 			warn("empty string given as command-line argument");
 			continue;
 		}
 		cleanname(argv[i]);
 		if(strcmp(argv[i], "/") == 0
 		|| strcmp(argv[i], ".") == 0
 		|| strcmp(argv[i], "..") == 0
 		|| (strlen(argv[i]) > 3 && strcmp(argv[i]+strlen(argv[i])-3, "/..") == 0)){
 			if((fd = open(argv[i], OREAD)) < 0){
 				warn("open %s: %r", argv[i]);
 				continue;
 			}
 			while((n = dirread(fd, &d)) > 0){
 				for(j=0; j<n; j++){
 					s = vtmalloc(strlen(argv[i])+1+strlen(d[j].name)+1);
 					strcpy(s, argv[i]);
 					strcat(s, "/");
 					strcat(s, d[j].name);
 					cleanname(s);
 					vac(f, fdiff, s, &d[j]);
 				}
 				free(d);
 			}
 			close(fd);
 			continue;
 		}
 		if((d = dirstat(argv[i])) == nil){
 			warn("stat %s: %r", argv[i]);
 			continue;
 		}
 		vac(f, fdiff, argv[i], d);
 		free(d);
 	}
 	if(fdiff)
 		vacfiledecref(fdiff);

 	/*
 	 * Record the maximum qid so that vacs can be merged
 	 * without introducing overlapping qids.  Older versions
 	 * of vac arranged that the root would have the largest
 	 * qid in the file system, but we can't do that anymore
 	 * (the root gets created first!).
 	 */
 	if(_vacfsnextqid(fs, &qid) >= 0)
 		vacfilesetqidspace(f, 0, qid);
 	vacfiledecref(f);

 	/*
 	 * Copy fsdiff's root block score into fs's slot for that,
 	 * so that vacfssync will copy it into root.prev for us.
 	 * Just nice documentation, no effect.
 	 */
 	if(fsdiff)
 		memmove(fs->score, fsdiff->score, VtScoreSize);
 	if(vacfssync(fs) < 0)
 		fprint(2, "vacfssync: %r\n");

 	fprint(outfd, "vac:%V\n", fs->score);
 	atexitdont(removevacfile);
 	vacfsclose(fs);
 	vthangup(z);

 	if(printstats){
 		fprint(2,
 			"%d files, %d files skipped, %d directories\n"
 			"%lld data bytes written, %lld data bytes skipped\n",
 			stats.nfile, stats.skipfiles, stats.ndir, stats.data, stats.skipdata);
 		dup(2, 1);
 		packetstats();
 	}
 	threadexitsall(0);
 }

 VacFile*
 recentarchive(VacFs *fs, char *path)
 {
 	VacFile *fp, *f;
 	VacDirEnum *de;
 	VacDir vd;
 	char buf[10];
 	int year, mmdd, nn, n, n1;
 	char *p;

 	fp = vacfsgetroot(fs);
 	de = vdeopen(fp);
 	year = 0;
 	if(de){
 		for(; vderead(de, &vd) > 0; vdcleanup(&vd)){
 			if(strlen(vd.elem) != 4)
 				continue;
 			if((n = strtol(vd.elem, &p, 10)) < 1900 || *p != 0)
 				continue;
 			if(year < n)
 				year = n;
 		}
 	}
 	vdeclose(de);
 	if(year == 0){
 		vacfiledecref(fp);
 		return nil;
 	}
 	snprint(buf, sizeof buf, "%04d", year);
 	if((f = vacfilewalk(fp, buf)) == nil){
 		fprint(2, "warning: dirread %s but cannot walk", buf);
 		vacfiledecref(fp);
 		return nil;
 	}
 	fp = f;

 	de = vdeopen(fp);
 	mmdd = 0;
 	nn = 0;
 	if(de){
 		for(; vderead(de, &vd) > 0; vdcleanup(&vd)){
 			if(strlen(vd.elem) < 4)
 				continue;
 			if((n = strtol(vd.elem, &p, 10)) < 100 || n > 1231 || p != vd.elem+4)
 				continue;
 			if(*p == '.'){
 				if(p[1] == '0' || (n1 = strtol(p+1, &p, 10)) == 0 || *p != 0)
 					continue;
 			}else{
 				if(*p != 0)
 					continue;
 				n1 = 0;
 			}
 			if(n < mmdd || (n == mmdd && n1 < nn))
 				continue;
 			mmdd = n;
 			nn = n1;
 		}
 	}
 	vdeclose(de);
 	if(mmdd == 0){
 		vacfiledecref(fp);
 		return nil;
 	}
 	if(nn == 0)
 		snprint(buf, sizeof buf, "%04d", mmdd);
 	else
 		snprint(buf, sizeof buf, "%04d.%d", mmdd, nn);
 	if((f = vacfilewalk(fp, buf)) == nil){
 		fprint(2, "warning: dirread %s but cannot walk", buf);
 		vacfiledecref(fp);
 		return nil;
 	}
 	vacfiledecref(fp);

 	sprint(path, "%04d/%s", year, buf);
 	return f;
 }

 static void
 removevacfile(void)
 {
 	if(vacfile)
 		remove(vacfile);
 }

 void
 plan9tovacdir(VacDir *vd, Dir *dir)
 {
 	memset(vd, 0, sizeof *vd);

 	vd->elem = dir->name;
 	vd->uid = dir->uid;
 	vd->gid = dir->gid;
 	vd->mid = dir->muid;
 	if(vd->mid == nil)
 		vd->mid = "";
 	vd->mtime = dir->mtime;
 	vd->mcount = 0;
 	vd->ctime = dir->mtime;		/* ctime: not available on plan 9 */
 	vd->atime = dir->atime;
 	vd->size = dir->length;

 	vd->mode = dir->mode & 0777;
 	if(dir->mode & DMDIR)
 		vd->mode |= ModeDir;
 	if(dir->mode & DMAPPEND)
 		vd->mode |= ModeAppend;
 	if(dir->mode & DMEXCL)
 		vd->mode |= ModeExclusive;
 #ifdef PLAN9PORT
 	if(dir->mode & DMDEVICE)
 		vd->mode |= ModeDevice;
 	if(dir->mode & DMNAMEDPIPE)
 		vd->mode |= ModeNamedPipe;
 	if(dir->mode & DMSYMLINK)
 		vd->mode |= ModeLink;
 #endif

 	vd->plan9 = 1;
 	vd->p9path = dir->qid.path;
 	vd->p9version = dir->qid.vers;
 }

 #ifdef PLAN9PORT
 enum {
 	Special =
 		DMSOCKET |
 		DMSYMLINK |
 		DMNAMEDPIPE |
 		DMDEVICE
 };
 #endif

 /*
  * Archive the file named name, which has stat info d,
  * into the vac directory fp (p = parent).
  *
  * If we're doing a vac -d against another archive, the
  * equivalent directory to fp in that archive is diffp.
  */
 void
 vac(VacFile *fp, VacFile *diffp, char *name, Dir *d)
 {
 	char *elem, *s;
 	static char *buf;
 	int fd, i, n, bsize;
 	vlong off;
 	Dir *dk;	// kids
 	VacDir vd, vddiff;
 	VacFile *f, *fdiff;
 	VtEntry e;

 	if(!includefile(name)){
 		warn("excluding %s%s", name, (d->mode&DMDIR) ? "/" : "");
 		return;
 	}

 	if(d->mode&DMDIR)
 		stats.ndir++;
 	else
 		stats.nfile++;

 	if(merge && vacmerge(fp, name) >= 0)
 		return;

 	if(verbose)
 		fprint(2, "%s%s\n", name, (d->mode&DMDIR) ? "/" : "");

 #ifdef PLAN9PORT
 	if(d->mode&Special)
 		fd = -1;
 	else
 #endif
 	if((fd = open(name, OREAD)) < 0){
 		warn("open %s: %r", name);
 		return;
 	}

 	elem = strrchr(name, '/');
 	if(elem)
 		elem++;
 	else
 		elem = name;

 	plan9tovacdir(&vd, d);
 	if((f = vacfilecreate(fp, elem, vd.mode)) == nil){
 		warn("vacfilecreate %s: %r", name);
 		return;
 	}
 	if(diffp)
 		fdiff = vacfilewalk(diffp, elem);
 	else
 		fdiff = nil;

 	if(vacfilesetdir(f, &vd) < 0)
 		warn("vacfilesetdir %s: %r", name);

 	bsize = fs->bsize;
 	if(buf == nil)
 		buf = vtmallocz(bsize);

 #ifdef PLAN9PORT
 	if(d->mode&(DMSOCKET|DMNAMEDPIPE)){
 		/* don't write anything */
 	}
 	else if(d->mode&DMSYMLINK){
 		n = readlink(name, buf, sizeof buf);
 		if(n > 0 && vacfilewrite(f, buf, n, 0) < 0){
 			warn("venti write %s: %r", name);
 			goto Out;
 		}
 		stats.data += n;
 	}else if(d->mode&DMDEVICE){
 		snprint(buf, sizeof buf, "%c %d %d",
 			(char)((d->qid.path >> 16) & 0xFF),
 			(int)(d->qid.path & 0xFF),
 			(int)((d->qid.path >> 8) & 0xFF));
 		if(vacfilewrite(f, buf, strlen(buf), 0) < 0){
 			warn("venti write %s: %r", name);
 			goto Out;
 		}
 		stats.data += strlen(buf);
 	}else
 #endif
 	if(d->mode&DMDIR){
 		while((n = dirread(fd, &dk)) > 0){
 			for(i=0; i<n; i++){
 				s = vtmalloc(strlen(name)+1+strlen(dk[i].name)+1);
 				strcpy(s, name);
 				strcat(s, "/");
 				strcat(s, dk[i].name);
 				vac(f, fdiff, s, &dk[i]);
 				free(s);
 			}
 			free(dk);
 		}
 	}else{
 		off = 0;
 		if(fdiff){
 			/*
 			 * Copy fdiff's contents into f by moving the score.
 			 * We'll diff and update below.
 			 */
 			if(vacfilegetentries(fdiff, &e, nil) >= 0)
 			if(vacfilesetentries(f, &e, nil) >= 0){
 				bsize = e.dsize;

 				/*
 				 * Or if -q is set, and the metadata looks the same,
 				 * don't even bother reading the file.
 				 */
 				if(qdiff && vacfilegetdir(fdiff, &vddiff) >= 0){
 					if(vddiff.mtime == vd.mtime)
 					if(vddiff.size == vd.size)
 					if(!vddiff.plan9 || (/* vddiff.p9path == vd.p9path && */ vddiff.p9version == vd.p9version)){
 						stats.skipfiles++;
 						stats.nfile--;
 						vdcleanup(&vddiff);
 						goto Out;
 					}

 					/*
 					 * Skip over presumably-unchanged prefix
 					 * of an append-only file.
 					 */
 					if(vd.mode&ModeAppend)
 					if(vddiff.size < vd.size)
 					if(vddiff.plan9 && vd.plan9)
 					if(vddiff.p9path == vd.p9path){
 						off = vd.size/bsize*bsize;
 						if(seek(fd, off, 0) >= 0)
 							stats.skipdata += off;
 						else{
 							seek(fd, 0, 0);	// paranoia
 							off = 0;
 						}
 					}

 					vdcleanup(&vddiff);
 					// XXX different verbose chatty prints for kaminsky?
 				}
 			}
 		}
 		if(qdiff && verbose)
 			fprint(2, "+%s\n", name);
 		while((n = readn(fd, buf, bsize)) > 0){
 			if(fdiff && sha1matches(f, off/bsize, (uchar*)buf, n)){
 				off += n;
 				stats.skipdata += n;
 				continue;
 			}
 			if(vacfilewrite(f, buf, n, off) < 0){
 				warn("venti write %s: %r", name);
 				goto Out;
 			}
 			stats.data += n;
 			off += n;
 		}
 		/*
 		 * Since we started with fdiff's contents,
 		 * set the size in case fdiff was bigger.
 		 */
 		if(fdiff && vacfilesetsize(f, off) < 0)
 			warn("vtfilesetsize %s: %r", name);
 	}

 Out:
 	vacfileflush(f, 1);
 	vacfiledecref(f);
 	if(fdiff)
 		vacfiledecref(fdiff);
 	close(fd);
 }

 void
 vacstdin(VacFile *fp, char *name)
 {
 	vlong off;
 	VacFile *f;
 	static char buf[8192];
 	int n;

 	if((f = vacfilecreate(fp, name, 0666)) == nil){
 		warn("vacfilecreate %s: %r", name);
 		return;
 	}

 	off = 0;
 	while((n = read(0, buf, sizeof buf)) > 0){
 		if(vacfilewrite(f, buf, n, off) < 0){
 			warn("venti write %s: %r", name);
 			vacfiledecref(f);
 			return;
 		}
 		off += n;
 	}
 	vacfileflush(f, 1);
 	vacfiledecref(f);
 }

 /*
  * fp is the directory we're writing.
  * mp is the directory whose contents we're merging in.
  * d is the directory entry of the file from mp that we want to add to fp.
  * vacfile is the name of the .vac file, for error messages.
  * offset is the qid that qid==0 in mp should correspond to.
  * max is the maximum qid we expect to see (not really needed).
  */
 int
 vacmergefile(VacFile *fp, VacFile *mp, VacDir *d, char *vacfile,
 	vlong offset, vlong max)
 {
 	VtEntry ed, em;
 	VacFile *mf;
 	VacFile *f;

 	mf = vacfilewalk(mp, d->elem);
 	if(mf == nil){
 		warn("could not walk %s in %s", d->elem, vacfile);
 		return -1;
 	}
 	if(vacfilegetentries(mf, &ed, &em) < 0){
 		warn("could not get entries for %s in %s", d->elem, vacfile);
 		vacfiledecref(mf);
 		return -1;
 	}

 	if((f = vacfilecreate(fp, d->elem, d->mode)) == nil){
 		warn("vacfilecreate %s: %r", d->elem);
 		vacfiledecref(mf);
 		return -1;
 	}
 	if(d->qidspace){
 		d->qidoffset += offset;
 		d->qidmax += offset;
 	}else{
 		d->qidspace = 1;
 		d->qidoffset = offset;
 		d->qidmax = max;
 	}
 	if(vacfilesetdir(f, d) < 0
 	|| vacfilesetentries(f, &ed, &em) < 0
 	|| vacfilesetqidspace(f, d->qidoffset, d->qidmax) < 0){
 		warn("vacmergefile %s: %r", d->elem);
 		vacfiledecref(mf);
 		vacfiledecref(f);
 		return -1;
 	}

 	vacfiledecref(mf);
 	vacfiledecref(f);
 	return 0;
 }

 int
 vacmerge(VacFile *fp, char *name)
 {
 	VacFs *mfs;
 	VacDir vd;
 	VacDirEnum *de;
 	VacFile *mp;
 	uvlong maxqid, offset;

 	if(strlen(name) < 4 || strcmp(name+strlen(name)-4, ".vac") != 0)
 		return -1;
 	if((mfs = vacfsopen(z, name, VtOREAD, CacheSize)) == nil)
 		return -1;
 	if(verbose)
 		fprint(2, "merging %s\n", name);

 	mp = vacfsgetroot(mfs);
 	de = vdeopen(mp);
 	if(de){
 		offset = 0;
 		if(vacfsgetmaxqid(mfs, &maxqid) >= 0){
 			_vacfsnextqid(fs, &offset);
 			vacfsjumpqid(fs, maxqid+1);
 		}
 		while(vderead(de, &vd) > 0){
 			if(vd.qid > maxqid){
 				warn("vacmerge %s: maxqid=%lld but %s has %lld",
 					name, maxqid, vd.elem, vd.qid);
 				vacfsjumpqid(fs, vd.qid - maxqid);
 				maxqid = vd.qid;
 			}
 			vacmergefile(fp, mp, &vd, name,
 				offset, maxqid);
 			vdcleanup(&vd);
 		}
 		vdeclose(de);
 	}
 	vacfiledecref(mp);
 	vacfsclose(mfs);
 	return 0;
 }

 #define TWID64	((u64int)~(u64int)0)

 static u64int
 unittoull(char *s)
 {
 	char *es;
 	u64int n;

 	if(s == nil)
 		return TWID64;
 	n = strtoul(s, &es, 0);
 	if(*es == 'k' || *es == 'K'){
 		n *= 1024;
 		es++;
 	}else if(*es == 'm' || *es == 'M'){
 		n *= 1024*1024;
 		es++;
 	}else if(*es == 'g' || *es == 'G'){
 		n *= 1024*1024*1024;
 		es++;
 	}
 	if(*es != '\0')
 		return TWID64;
 	return n;
 }

 static void
 warn(char *fmt, ...)
 {
 	va_list arg;

 	va_start(arg, fmt);
 	fprint(2, "vac: ");
 	vfprint(2, fmt, arg);
 	fprint(2, "\n");
 	va_end(arg);
 }
	#include "stdinc.h"
	#include "vac.h"
	#include "dat.h"
	#include "fns.h"

	// TODO: qids

	void
	usage(void)
	{
	fprint(2, "vac [-imqsv] [-a archive.vac] [-b bsize] [-d old.vac] [-f new.vac] [-e exclude]... [-h host] file...\n");
	threadexitsall("usage");
	}

	enum
	{
	BlockSize = 8*1024,
	CacheSize = 4<<20,
	};

	struct
	{
	int nfile;
	int ndir;
	vlong data;
	vlong skipdata;
	int skipfiles;
	} stats;

	int qdiff;
	int merge;
	int verbose;
	char *host;
	VtConn *z;
	VacFs *fs;
	char *archivefile;
	char *vacfile;

	int vacmerge(VacFile, char);
	void vac(VacFile, VacFile, char, Dir);
	void vacstdin(VacFile, char);
	VacFile recentarchive(VacFs, char*);

	static u64int unittoull(char*);
	static void warn(char *fmt, ...);
	static void removevacfile(void);

	#ifdef PLAN9PORT
	/*
	* We're between a rock and a hard place here.
	* The pw library (getpwnam, etc.) reads the
	* password and group files into an on-stack buffer,
	* so if you have some huge groups, you overflow
	* the stack. Because of this, the thread library turns
	* it off by default, so that dirstat returns "14571" instead of "rsc".
	* But for vac we want names. So cautiously turn the pwlibrary
	* back on (see threadmain) and make the main thread stack huge.
	*/
	extern int _p9usepwlibrary;
	int mainstacksize = 410241024;

	#endif
	void
	threadmain(int argc, char **argv)
	{
	int i, j, fd, n, printstats;
	Dir *d;
	char *s;
	uvlong u;
	VacFile f, fdiff;
	VacFs *fsdiff;
	int blocksize;
	int outfd;
	char *stdinname;
	char *diffvac;
	uvlong qid;

	#ifdef PLAN9PORT
	/* see comment above */
	_p9usepwlibrary = 1;
	#endif

	fmtinstall('F', vtfcallfmt);
	fmtinstall('H', encodefmt);
	fmtinstall('V', vtscorefmt);

	blocksize = BlockSize;
	stdinname = nil;
	printstats = 0;
	fsdiff = nil;
	diffvac = nil;

	ARGBEGIN{
	case 'V':
	chattyventi++;
	break;
	case 'a':
	archivefile = EARGF(usage());
	break;
	case 'b':
	u = unittoull(EARGF(usage()));
	if(u < 512)
	u = 512;
	blocksize = u;
	break;
	case 'd':
	diffvac = EARGF(usage());
	break;
	case 'e':
	excludepattern(EARGF(usage()));
	break;
	case 'f':
	vacfile = EARGF(usage());
	break;
	case 'h':
	host = EARGF(usage());
	break;
	case 'i':
	stdinname = EARGF(usage());
	break;
	case 'm':
	merge++;
	break;
	case 'q':
	qdiff++;
	break;
	case 's':
	printstats++;
	break;
	case 'v':
	verbose++;
	break;
	case 'x':
	loadexcludefile(EARGF(usage()));
	break;
	default:
	usage();
	}ARGEND

	if(argc == 0 && !stdinname)
	usage();

	if(archivefile && (vacfile \|\| diffvac)){
	fprint(2, "cannot use -a with -f, -d\n");
	usage();
	}

	z = vtdial(host);
	if(z == nil)
	sysfatal("could not connect to server: %r");
	if(vtconnect(z) < 0)
	sysfatal("vtconnect: %r");

	// Setup:
	// fs is the output vac file system
	// f is directory in output vac to write new files
	// fdiff is corresponding directory in existing vac
	if(archivefile){
	VacFile *fp;
	char yyyy[5];
	char mmdd[10];
	char oldpath[40];
	Tm tm;

	fdiff = nil;
	if((outfd = open(archivefile, ORDWR)) < 0){
	if(access(archivefile, 0) >= 0)
	sysfatal("open %s: %r", archivefile);
	if((outfd = create(archivefile, OWRITE, 0666)) < 0)
	sysfatal("create %s: %r", archivefile);
	atexit(removevacfile); // because it is new
	if((fs = vacfscreate(z, blocksize, CacheSize)) == nil)
	sysfatal("vacfscreate: %r");
	}else{
	if((fs = vacfsopen(z, archivefile, VtORDWR, CacheSize)) == nil)
	sysfatal("vacfsopen %s: %r", archivefile);
	if((fdiff = recentarchive(fs, oldpath)) != nil){
	if(verbose)
	fprint(2, "diff %s\n", oldpath);
	}else
	if(verbose)
	fprint(2, "no recent archive to diff against\n");
	}

	// Create yyyy/mmdd.
	tm = *localtime(time(0));
	snprint(yyyy, sizeof yyyy, "%04d", tm.year+1900);
	fp = vacfsgetroot(fs);
	if((f = vacfilewalk(fp, yyyy)) == nil
	&& (f = vacfilecreate(fp, yyyy, ModeDir\|0555)) == nil)
	sysfatal("vacfscreate %s: %r", yyyy);
	vacfiledecref(fp);
	fp = f;

	snprint(mmdd, sizeof mmdd, "%02d%02d", tm.mon+1, tm.mday);
	n = 0;
	while((f = vacfilewalk(fp, mmdd)) != nil){
	vacfiledecref(f);
	n++;
	snprint(mmdd+4, sizeof mmdd-4, ".%d", n);
	}
	f = vacfilecreate(fp, mmdd, ModeDir\|0555);
	if(f == nil)
	sysfatal("vacfscreate %s/%s: %r", yyyy, mmdd);
	vacfiledecref(fp);

	if(verbose)
	fprint(2, "archive %s/%s\n", yyyy, mmdd);
	}else{
	if(vacfile == nil)
	outfd = 1;
	else if((outfd = create(vacfile, OWRITE, 0666)) < 0)
	sysfatal("create %s: %r", vacfile);
	atexit(removevacfile);
	if((fs = vacfscreate(z, blocksize, CacheSize)) == nil)
	sysfatal("vacfscreate: %r");
	f = vacfsgetroot(fs);

	fdiff = nil;
	if(diffvac){
	if((fsdiff = vacfsopen(z, diffvac, VtOREAD, CacheSize)) == nil)
	warn("vacfsopen %s: %r", diffvac);
	else
	fdiff = vacfsgetroot(fsdiff);
	}
	}

	if(stdinname)
	vacstdin(f, stdinname);
	for(i=0; i<argc; i++){
	// We can't use / and . and .. and ../.. as valid archive
	// names, so expand to the list of files in the directory.
	if(argv[i][0] == 0){
	warn("empty string given as command-line argument");
	continue;
	}
	cleanname(argv[i]);
	if(strcmp(argv[i], "/") == 0
	\|\| strcmp(argv[i], ".") == 0
	\|\| strcmp(argv[i], "..") == 0
	\|\| (strlen(argv[i]) > 3 && strcmp(argv[i]+strlen(argv[i])-3, "/..") == 0)){
	if((fd = open(argv[i], OREAD)) < 0){
	warn("open %s: %r", argv[i]);
	continue;
	}
	while((n = dirread(fd, &d)) > 0){
	for(j=0; j<n; j++){
	s = vtmalloc(strlen(argv[i])+1+strlen(d[j].name)+1);
	strcpy(s, argv[i]);
	strcat(s, "/");
	strcat(s, d[j].name);
	cleanname(s);
	vac(f, fdiff, s, &d[j]);
	}
	free(d);
	}
	close(fd);
	continue;
	}
	if((d = dirstat(argv[i])) == nil){
	warn("stat %s: %r", argv[i]);
	continue;
	}
	vac(f, fdiff, argv[i], d);
	free(d);
	}
	if(fdiff)
	vacfiledecref(fdiff);

	/*
	* Record the maximum qid so that vacs can be merged
	* without introducing overlapping qids. Older versions
	* of vac arranged that the root would have the largest
	* qid in the file system, but we can't do that anymore
	* (the root gets created first!).
	*/
	if(_vacfsnextqid(fs, &qid) >= 0)
	vacfilesetqidspace(f, 0, qid);
	vacfiledecref(f);

	/*
	* Copy fsdiff's root block score into fs's slot for that,
	* so that vacfssync will copy it into root.prev for us.
	* Just nice documentation, no effect.
	*/
	if(fsdiff)
	memmove(fs->score, fsdiff->score, VtScoreSize);
	if(vacfssync(fs) < 0)
	fprint(2, "vacfssync: %r\n");

	fprint(outfd, "vac:%V\n", fs->score);
	atexitdont(removevacfile);
	vacfsclose(fs);
	vthangup(z);

	if(printstats){
	fprint(2,
	"%d files, %d files skipped, %d directories\n"
	"%lld data bytes written, %lld data bytes skipped\n",
	stats.nfile, stats.skipfiles, stats.ndir, stats.data, stats.skipdata);
	dup(2, 1);
	packetstats();
	}
	threadexitsall(0);
	}

	VacFile*
	recentarchive(VacFs fs, char path)
	{
	VacFile fp, f;
	VacDirEnum *de;
	VacDir vd;
	char buf[10];
	int year, mmdd, nn, n, n1;
	char *p;

	fp = vacfsgetroot(fs);
	de = vdeopen(fp);
	year = 0;
	if(de){
	for(; vderead(de, &vd) > 0; vdcleanup(&vd)){
	if(strlen(vd.elem) != 4)
	continue;
	if((n = strtol(vd.elem, &p, 10)) < 1900 \|\| *p != 0)
	continue;
	if(year < n)
	year = n;
	}
	}
	vdeclose(de);
	if(year == 0){
	vacfiledecref(fp);
	return nil;
	}
	snprint(buf, sizeof buf, "%04d", year);
	if((f = vacfilewalk(fp, buf)) == nil){
	fprint(2, "warning: dirread %s but cannot walk", buf);
	vacfiledecref(fp);
	return nil;
	}
	fp = f;

	de = vdeopen(fp);
	mmdd = 0;
	nn = 0;
	if(de){
	for(; vderead(de, &vd) > 0; vdcleanup(&vd)){
	if(strlen(vd.elem) < 4)
	continue;
	if((n = strtol(vd.elem, &p, 10)) < 100 \|\| n > 1231 \|\| p != vd.elem+4)
	continue;
	if(*p == '.'){
	if(p[1] == '0' \|\| (n1 = strtol(p+1, &p, 10)) == 0 \|\| *p != 0)
	continue;
	}else{
	if(*p != 0)
	continue;
	n1 = 0;
	}
	if(n < mmdd \|\| (n == mmdd && n1 < nn))
	continue;
	mmdd = n;
	nn = n1;
	}
	}
	vdeclose(de);
	if(mmdd == 0){
	vacfiledecref(fp);
	return nil;
	}
	if(nn == 0)
	snprint(buf, sizeof buf, "%04d", mmdd);
	else
	snprint(buf, sizeof buf, "%04d.%d", mmdd, nn);
	if((f = vacfilewalk(fp, buf)) == nil){
	fprint(2, "warning: dirread %s but cannot walk", buf);
	vacfiledecref(fp);
	return nil;
	}
	vacfiledecref(fp);

	sprint(path, "%04d/%s", year, buf);
	return f;
	}

	static void
	removevacfile(void)
	{
	if(vacfile)
	remove(vacfile);
	}

	void
	plan9tovacdir(VacDir vd, Dir dir)
	{
	memset(vd, 0, sizeof *vd);

	vd->elem = dir->name;
	vd->uid = dir->uid;
	vd->gid = dir->gid;
	vd->mid = dir->muid;
	if(vd->mid == nil)
	vd->mid = "";
	vd->mtime = dir->mtime;
	vd->mcount = 0;
	vd->ctime = dir->mtime; /* ctime: not available on plan 9 */
	vd->atime = dir->atime;
	vd->size = dir->length;

	vd->mode = dir->mode & 0777;
	if(dir->mode & DMDIR)
	vd->mode \|= ModeDir;
	if(dir->mode & DMAPPEND)
	vd->mode \|= ModeAppend;
	if(dir->mode & DMEXCL)
	vd->mode \|= ModeExclusive;
	#ifdef PLAN9PORT
	if(dir->mode & DMDEVICE)
	vd->mode \|= ModeDevice;
	if(dir->mode & DMNAMEDPIPE)
	vd->mode \|= ModeNamedPipe;
	if(dir->mode & DMSYMLINK)
	vd->mode \|= ModeLink;
	#endif

	vd->plan9 = 1;
	vd->p9path = dir->qid.path;
	vd->p9version = dir->qid.vers;
	}

	#ifdef PLAN9PORT
	enum {
	Special =
	DMSOCKET \|
	DMSYMLINK \|
	DMNAMEDPIPE \|
	DMDEVICE
	};
	#endif

	/*
	* Archive the file named name, which has stat info d,
	* into the vac directory fp (p = parent).
	*
	* If we're doing a vac -d against another archive, the
	* equivalent directory to fp in that archive is diffp.
	*/
	void
	vac(VacFile fp, VacFile diffp, char name, Dir d)
	{
	char elem, s;
	static char *buf;
	int fd, i, n, bsize;
	vlong off;
	Dir *dk; // kids
	VacDir vd, vddiff;
	VacFile f, fdiff;
	VtEntry e;

	if(!includefile(name)){
	warn("excluding %s%s", name, (d->mode&DMDIR) ? "/" : "");
	return;
	}

	if(d->mode&DMDIR)
	stats.ndir++;
	else
	stats.nfile++;

	if(merge && vacmerge(fp, name) >= 0)
	return;

	if(verbose)
	fprint(2, "%s%s\n", name, (d->mode&DMDIR) ? "/" : "");

	#ifdef PLAN9PORT
	if(d->mode&Special)
	fd = -1;
	else
	#endif
	if((fd = open(name, OREAD)) < 0){
	warn("open %s: %r", name);
	return;
	}

	elem = strrchr(name, '/');
	if(elem)
	elem++;
	else
	elem = name;

	plan9tovacdir(&vd, d);
	if((f = vacfilecreate(fp, elem, vd.mode)) == nil){
	warn("vacfilecreate %s: %r", name);
	return;
	}
	if(diffp)
	fdiff = vacfilewalk(diffp, elem);
	else
	fdiff = nil;

	if(vacfilesetdir(f, &vd) < 0)
	warn("vacfilesetdir %s: %r", name);

	bsize = fs->bsize;
	if(buf == nil)
	buf = vtmallocz(bsize);

	#ifdef PLAN9PORT
	if(d->mode&(DMSOCKET\|DMNAMEDPIPE)){
	/* don't write anything */
	}
	else if(d->mode&DMSYMLINK){
	n = readlink(name, buf, sizeof buf);
	if(n > 0 && vacfilewrite(f, buf, n, 0) < 0){
	warn("venti write %s: %r", name);
	goto Out;
	}
	stats.data += n;
	}else if(d->mode&DMDEVICE){
	snprint(buf, sizeof buf, "%c %d %d",
	(char)((d->qid.path >> 16) & 0xFF),
	(int)(d->qid.path & 0xFF),
	(int)((d->qid.path >> 8) & 0xFF));
	if(vacfilewrite(f, buf, strlen(buf), 0) < 0){
	warn("venti write %s: %r", name);
	goto Out;
	}
	stats.data += strlen(buf);
	}else
	#endif
	if(d->mode&DMDIR){
	while((n = dirread(fd, &dk)) > 0){
	for(i=0; i<n; i++){
	s = vtmalloc(strlen(name)+1+strlen(dk[i].name)+1);
	strcpy(s, name);
	strcat(s, "/");
	strcat(s, dk[i].name);
	vac(f, fdiff, s, &dk[i]);
	free(s);
	}
	free(dk);
	}
	}else{
	off = 0;
	if(fdiff){
	/*
	* Copy fdiff's contents into f by moving the score.
	* We'll diff and update below.
	*/
	if(vacfilegetentries(fdiff, &e, nil) >= 0)
	if(vacfilesetentries(f, &e, nil) >= 0){
	bsize = e.dsize;

	/*
	* Or if -q is set, and the metadata looks the same,
	* don't even bother reading the file.
	*/
	if(qdiff && vacfilegetdir(fdiff, &vddiff) >= 0){
	if(vddiff.mtime == vd.mtime)
	if(vddiff.size == vd.size)
	if(!vddiff.plan9 \|\| (/* vddiff.p9path == vd.p9path && */ vddiff.p9version == vd.p9version)){
	stats.skipfiles++;
	stats.nfile--;
	vdcleanup(&vddiff);
	goto Out;
	}

	/*
	* Skip over presumably-unchanged prefix
	* of an append-only file.
	*/
	if(vd.mode&ModeAppend)
	if(vddiff.size < vd.size)
	if(vddiff.plan9 && vd.plan9)
	if(vddiff.p9path == vd.p9path){
	off = vd.size/bsize*bsize;
	if(seek(fd, off, 0) >= 0)
	stats.skipdata += off;
	else{
	seek(fd, 0, 0); // paranoia
	off = 0;
	}
	}

	vdcleanup(&vddiff);
	// XXX different verbose chatty prints for kaminsky?
	}
	}
	}
	if(qdiff && verbose)
	fprint(2, "+%s\n", name);
	while((n = readn(fd, buf, bsize)) > 0){
	if(fdiff && sha1matches(f, off/bsize, (uchar*)buf, n)){
	off += n;
	stats.skipdata += n;
	continue;
	}
	if(vacfilewrite(f, buf, n, off) < 0){
	warn("venti write %s: %r", name);
	goto Out;
	}
	stats.data += n;
	off += n;
	}
	/*
	* Since we started with fdiff's contents,
	* set the size in case fdiff was bigger.
	*/
	if(fdiff && vacfilesetsize(f, off) < 0)
	warn("vtfilesetsize %s: %r", name);
	}

	Out:
	vacfileflush(f, 1);
	vacfiledecref(f);
	if(fdiff)
	vacfiledecref(fdiff);
	close(fd);
	}

	void
	vacstdin(VacFile fp, char name)
	{
	vlong off;
	VacFile *f;
	static char buf[8192];
	int n;

	if((f = vacfilecreate(fp, name, 0666)) == nil){
	warn("vacfilecreate %s: %r", name);
	return;
	}

	off = 0;
	while((n = read(0, buf, sizeof buf)) > 0){
	if(vacfilewrite(f, buf, n, off) < 0){
	warn("venti write %s: %r", name);
	vacfiledecref(f);
	return;
	}
	off += n;
	}
	vacfileflush(f, 1);
	vacfiledecref(f);
	}

	/*
	* fp is the directory we're writing.
	* mp is the directory whose contents we're merging in.
	* d is the directory entry of the file from mp that we want to add to fp.
	* vacfile is the name of the .vac file, for error messages.
	* offset is the qid that qid==0 in mp should correspond to.
	* max is the maximum qid we expect to see (not really needed).
	*/
	int
	vacmergefile(VacFile fp, VacFile mp, VacDir d, char vacfile,
	vlong offset, vlong max)
	{
	VtEntry ed, em;
	VacFile *mf;
	VacFile *f;

	mf = vacfilewalk(mp, d->elem);
	if(mf == nil){
	warn("could not walk %s in %s", d->elem, vacfile);
	return -1;
	}
	if(vacfilegetentries(mf, &ed, &em) < 0){
	warn("could not get entries for %s in %s", d->elem, vacfile);
	vacfiledecref(mf);
	return -1;
	}

	if((f = vacfilecreate(fp, d->elem, d->mode)) == nil){
	warn("vacfilecreate %s: %r", d->elem);
	vacfiledecref(mf);
	return -1;
	}
	if(d->qidspace){
	d->qidoffset += offset;
	d->qidmax += offset;
	}else{
	d->qidspace = 1;
	d->qidoffset = offset;
	d->qidmax = max;
	}
	if(vacfilesetdir(f, d) < 0
	\|\| vacfilesetentries(f, &ed, &em) < 0
	\|\| vacfilesetqidspace(f, d->qidoffset, d->qidmax) < 0){
	warn("vacmergefile %s: %r", d->elem);
	vacfiledecref(mf);
	vacfiledecref(f);
	return -1;
	}

	vacfiledecref(mf);
	vacfiledecref(f);
	return 0;
	}

	int
	vacmerge(VacFile fp, char name)
	{
	VacFs *mfs;
	VacDir vd;
	VacDirEnum *de;
	VacFile *mp;
	uvlong maxqid, offset;

	if(strlen(name) < 4 \|\| strcmp(name+strlen(name)-4, ".vac") != 0)
	return -1;
	if((mfs = vacfsopen(z, name, VtOREAD, CacheSize)) == nil)
	return -1;
	if(verbose)
	fprint(2, "merging %s\n", name);

	mp = vacfsgetroot(mfs);
	de = vdeopen(mp);
	if(de){
	offset = 0;
	if(vacfsgetmaxqid(mfs, &maxqid) >= 0){
	_vacfsnextqid(fs, &offset);
	vacfsjumpqid(fs, maxqid+1);
	}
	while(vderead(de, &vd) > 0){
	if(vd.qid > maxqid){
	warn("vacmerge %s: maxqid=%lld but %s has %lld",
	name, maxqid, vd.elem, vd.qid);
	vacfsjumpqid(fs, vd.qid - maxqid);
	maxqid = vd.qid;
	}
	vacmergefile(fp, mp, &vd, name,
	offset, maxqid);
	vdcleanup(&vd);
	}
	vdeclose(de);
	}
	vacfiledecref(mp);
	vacfsclose(mfs);
	return 0;
	}

	#define TWID64 ((u64int)~(u64int)0)

	static u64int
	unittoull(char *s)
	{
	char *es;
	u64int n;

	if(s == nil)
	return TWID64;
	n = strtoul(s, &es, 0);
	if(es == 'k' \|\| es == 'K'){
	n *= 1024;
	es++;
	}else if(es == 'm' \|\| es == 'M'){
	n = 10241024;
	es++;
	}else if(es == 'g' \|\| es == 'G'){
	n = 10241024*1024;
	es++;
	}
	if(*es != '\0')
	return TWID64;
	return n;
	}

	static void
	warn(char *fmt, ...)
	{
	va_list arg;

	va_start(arg, fmt);
	fprint(2, "vac: ");
	vfprint(2, fmt, arg);
	fprint(2, "\n");
	va_end(arg);
	}