depend.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <auth.h>
#include <fcall.h>
#include <thread.h>
#include <bio.h>

typedef struct Args Args;

struct Args {
	int	argc;
	char	**argv;
};

typedef struct Dfile Dfile;
typedef struct Fid Fid;
typedef struct File File;
typedef struct Fs Fs;
typedef struct Request Request;
typedef struct Symbol Symbol;
typedef struct Tardir Tardir;

extern int threadrforkflag = RFNAMEG;

enum{
	Nstat = 1024,	/* plenty for this application */
	MAXSIZE = 8192+IOHDRSZ,
};

int messagesize = MAXSIZE;

void
fatal(char *fmt, ...)
{
	va_list arg;
	char buf[1024];

	write(2, "depend: ", 8);
	va_start(arg, fmt);
	vseprint(buf, buf+1024, fmt, arg);
	va_end(arg);
	write(2, buf, strlen(buf));
	write(2, "\n", 1);
	threadexitsall(fmt);
}

enum
{
	Nfidhash=	64,
	Ndfhash=	128,
};

struct Symbol
{
	Symbol	*next;		/* hash list chaining */
	char	*sym;
	int	fno;		/* file symbol is defined in */
};

/* source file */
struct File
{
	QLock;

	char	*name;
	Symbol	*ref;
	uchar	*refvec;	/* files resolving the references */
	uint	len;		/* length of file */
	uint	tarlen;		/* length of tar file */
	uint	mode;
	uint	mtime;

	int	use;
	int	fd;
};

/* .depend file */
struct Dfile
{
	Lock;
	int	use;		/* use count */
	int	old;		/* true if this is an superceded dfile */

	File	*file;		/* files */
	int	nfile;		/* number of files */
	int	flen;		/* length of file table */

	Symbol	**dhash;	/* hash table of symbols */
	int	hlen;		/* length of hash table */

	Dfile	*next;		/* hash chain */
	char	*path;		/* path name of dependency file */
	Qid	qid;		/* qid of the dependency file */
};

struct Fid
{
	Fid	*next;
	int	fid;
	int	ref;

	int	attached;
	int	open;
	Qid	qid;
	char	*path;
	Dfile	*df;
	Symbol	*dp;
	int	fd;
	Dir	*dir;
	int	ndir;
	int	dirindex;
};

struct Request
{
	Request	*next;
	Fid	*fid;
	Fcall	f;
	uchar	buf[1];
};

enum
{
	Tblocksize=	512,	/* tar block size */
	Tnamesize=	100,	/* tar name size */
};

struct Tardir
{
	char	name[Tnamesize];
	char	mode[8];
	char	uid[8];
	char	gid[8];
	char	size[12];
	char	mtime[12];
	char	chksum[8];
	char	linkflag;
	char	linkname[Tnamesize];
};

struct Fs
{
	Lock;

	int	fd;		/* to kernel mount point */
	Fid	*hash[Nfidhash];
	char	*root;
	Qid	rootqid;

};

struct Fsarg
{
	Fs	*fs;
	int	fd;
	char *root;
};


extern	void	fsrun(void*);
extern	Fid*	fsgetfid(Fs*, int);
extern	void	fsputfid(Fs*, Fid*);
extern	void	fsreply(Fs*, Request*, char*);
extern	void	fsversion(Fs*, Request*, Fid*);
extern	void	fsauth(Fs*, Request*, Fid*);
extern	void	fsflush(Fs*, Request*, Fid*);
extern	void	fsattach(Fs*, Request*, Fid*);
extern	void	fswalk(Fs*, Request*, Fid*);
extern	void	fsopen(Fs*, Request*, Fid*);
extern	void	fscreate(Fs*, Request*, Fid*);
extern	void	fsread(Fs*, Request*, Fid*);
extern	void	fswrite(Fs*, Request*, Fid*);
extern	void	fsclunk(Fs*, Request*, Fid*);
extern	void	fsremove(Fs*, Request*, Fid*);
extern	void	fsstat(Fs*, Request*, Fid*);
extern	void	fswstat(Fs*, Request*, Fid*);

void 	(*fcall[])(Fs*, Request*, Fid*) =
{
	[Tflush]	fsflush,
	[Tversion]	fsversion,
	[Tauth]	fsauth,
	[Tattach]	fsattach,
	[Twalk]		fswalk,
	[Topen]		fsopen,
	[Tcreate]	fscreate,
	[Tread]		fsread,
	[Twrite]	fswrite,
	[Tclunk]	fsclunk,
	[Tremove]	fsremove,
	[Tstat]		fsstat,
	[Twstat]	fswstat
};

char Eperm[]   = "permission denied";
char Eexist[]  = "file does not exist";
char Enotdir[] = "not a directory";
char Eisopen[] = "file already open";
char Enofid[] = "no such fid";
char mallocerr[]	= "malloc: %r";
char Etoolong[]	= "name too long";

char *dependlog = "depend";

int debug;
Dfile *dfhash[Ndfhash];		/* dependency file hash */
QLock dfhlock[Ndfhash];
QLock iolock;

Request*	allocreq(int);
Dfile*	getdf(char*);
void	releasedf(Dfile*);
Symbol*	dfsearch(Dfile*, char*);
void	dfresolve(Dfile*, int);
char*	mkpath(char*, char*);
int	mktar(Dfile*, Symbol*, uchar*, uint, int);
void	closetar(Dfile*, Symbol*);

void*
emalloc(uint n)
{
	void *p;

	p = malloc(n);
	if(p == nil)
		fatal(mallocerr);
	memset(p, 0, n);
	return p;
}

void *
erealloc(void *ReallocP, int ReallocN)
{
	if(ReallocN == 0)
		ReallocN = 1;
	if(!ReallocP)
		ReallocP = emalloc(ReallocN);
	else if(!(ReallocP = realloc(ReallocP, ReallocN)))
		fatal("unable to allocate %d bytes",ReallocN);
	return(ReallocP);
}

char*
estrdup(char *s)
{
	char *d, *d0;

	if(!s)
		return 0;
	d = d0 = emalloc(strlen(s)+1);
	while(*d++ = *s++)
		;
	return d0;
}

/*
 *  mount the user interface and start one request processor
 *  per CPU
 */
void
realmain(void *a)
{
	Fs *fs;
	int pfd[2];
	int srv;
	char service[128];
	struct Fsarg fsarg;
	Args *args;
	int argc;
	char **argv;

	args = a;
	argc = args->argc;
	argv = args->argv;

	fmtinstall('F', fcallfmt);

	ARGBEGIN{
		case 'd':
			debug++;
			break;
	}ARGEND
	if(argc != 2){
		fprint(2, "usage: %s [-d] svc-name directory\n", argv0);
		exits("usage");
	}
	snprint(service, sizeof service, "#s/%s", argv[0]);
	if(argv[1][0] != '/')
		fatal("directory must be rooted");

	if(pipe(pfd) < 0)
		fatal("opening pipe: %r");

	/* Typically mounted before /srv exists */
	srv = create(service, OWRITE, 0666);
	if(srv < 0)
		fatal("post: %r");
	fprint(srv, "%d", pfd[1]);
	close(srv);
	close(pfd[1]);

	time(nil);	/* open fd for time before losing / */
	if(bind(argv[1], "/", MREPL) == 0)
		fatal("can't bind %s to /", argv[1]);

	fs = emalloc(sizeof(Fs));
	fsarg.fs = fs;
	fsarg.fd = pfd[0];
	fsarg.root = argv[1];
	proccreate(fsrun, &fsarg, 16*1024);
	proccreate(fsrun, &fsarg, 16*1024);
	fsrun(&fsarg);
	exits(nil);
}

void
threadmain(int argc, char *argv[])
{
	static Args args;

	args.argc = argc;
	args.argv = argv;
	rfork(RFNAMEG);
	proccreate(realmain, &args, 16*1024);
}

char*
mkpath(char *dir, char *file)
{
	int len;
	char *path;

	len = strlen(dir) + 1;
	if(file != nil)
		len += strlen(file) + 1;
	path = emalloc(len);
	if(file != nil)
		sprint(path, "%s/%s", dir, file);
	else
		sprint(path, "%s", dir);
	return path;
}

void
fsrun(void *a)
{
	struct Fsarg *fsarg;
	Fs* fs;
	char *root;
	int n, t;
	Request *r;
	Fid *f;
	Dir *d;

	fsarg = a;
	fs = fsarg->fs;
	fs->fd = fsarg->fd;
	root = fsarg->root;
	d = dirstat("/");
	if(d == nil)
		fatal("root %s inaccessible: %r", root);
	fs->rootqid = d->qid;
	free(d);

	for(;;){
		r = allocreq(messagesize);
		qlock(&iolock);
		n = read9pmsg(fs->fd, r->buf, messagesize);
		qunlock(&iolock);
		if(n <= 0)
			fatal("read9pmsg error: %r");

		if(convM2S(r->buf, n, &r->f) == 0){
			fprint(2, "can't convert %ux %ux %ux\n", r->buf[0],
				r->buf[1], r->buf[2]);
			free(r);
			continue;
		}

		f = fsgetfid(fs, r->f.fid);
		r->fid = f;
		if(debug)
			fprint(2, "%F path %llux\n", &r->f, f->qid.path);

		t = r->f.type;
		r->f.type++;
		(*fcall[t])(fs, r, f);
		fsputfid(fs, f);
	}

}

/*
 *  any request that can get queued for a delayed reply
 */
Request*
allocreq(int bufsize)
{
	Request *r;

	r = emalloc(sizeof(Request)+bufsize);
	r->next = nil;
	return r;
}

Fid*
fsgetfid(Fs *fs, int fid)
{
	Fid *f, *nf;

	lock(fs);
	for(f = fs->hash[fid%Nfidhash]; f; f = f->next){
		if(f->fid == fid){
			f->ref++;
			unlock(fs);
			return f;
		}
	}

	nf = emalloc(sizeof(Fid));
	nf->next = fs->hash[fid%Nfidhash];
	fs->hash[fid%Nfidhash] = nf;
	nf->fid = fid;
	nf->ref = 1;
	nf->fd = -1;
	unlock(fs);
	return nf;
}

void
fsputfid(Fs *fs, Fid *f)
{
	Fid **l, *nf;

	lock(fs);
	if(--f->ref > 0){
		unlock(fs);
		return;
	}
	for(l = &fs->hash[f->fid%Nfidhash]; nf = *l; l = &nf->next)
		if(nf == f){
			*l = f->next;
			break;
		}
	unlock(fs);
	free(f);
}

void
fsreply(Fs *fs, Request *r, char *err)
{
	int n;
	uchar buf[MAXSIZE];

	if(err){
		r->f.type = Rerror;
		r->f.ename = err;
	}
	if(debug)
		fprint(2, "%F path %llux\n", &r->f, r->fid->qid.path);
	n = convS2M(&r->f, buf, messagesize);
	if(n == 0)
		fatal("bad convS2M");
	if(write(fs->fd, buf, n) != n)
		fatal("unmounted");
	free(r);
}

void
fsversion(Fs *fs, Request *r, Fid*)
{
	if(r->f.msize < 256){
		fsreply(fs, r, "version: bad message size");
		return;
	}
	if(messagesize > r->f.msize)
		messagesize = r->f.msize;
	r->f.msize = messagesize;
	r->f.version = "9P2000";
	fsreply(fs, r, nil);
}

void
fsauth(Fs *fs, Request *r, Fid*)
{
	fsreply(fs, r, "depend: authentication not required");
}

void
fsflush(Fs*, Request*, Fid*)
{
}

void
fsattach(Fs *fs, Request *r, Fid *f)
{
	f->qid = fs->rootqid;
	f->path = strdup("/");
	f->df = getdf(mkpath(f->path, ".depend"));

	/* hold down the fid till the clunk */
	f->attached = 1;
	lock(fs);
	f->ref++;
	unlock(fs);

	r->f.qid = f->qid;
	fsreply(fs, r, nil);
}

void
fswalk(Fs *fs, Request *r, Fid *f)
{
	Fid *nf;
	char *name, *tmp;
	int i, nqid, nwname;
	char errbuf[ERRMAX], *err;
	Qid qid[MAXWELEM];
	Dfile *lastdf;
	char *path, *npath;
	Dir *d;
	Symbol *dp;

	if(f->attached == 0){
		fsreply(fs, r, Eexist);
		return;
	}

	if(f->fd >= 0 || f->open)
		fatal("walk of an open file");

	nf = nil;
	if(r->f.newfid != r->f.fid){
		nf = fsgetfid(fs, r->f.newfid);
		nf->attached = 1;
		nf->open = f->open;
		nf->path = strdup(f->path);
		nf->qid = f->qid;
		nf->dp = f->dp;
		nf->fd = f->fd;
		nf->df = f->df;
		if(nf->df){
			lock(nf->df);
			nf->df->use++;
			unlock(nf->df);
		}
		if(r->f.nwname == 0){
			r->f.nwqid = 0;
			fsreply(fs, r, nil);
			return;
		}
		f = nf;
	}

	err = nil;
	path = strdup(f->path);
	if(path == nil)
		fatal(mallocerr);
	nqid = 0;
	nwname = r->f.nwname;
	lastdf = f->df;

	if(nwname > 0){
		for(; nqid<nwname; nqid++){
			name = r->f.wname[nqid];

			if(strcmp(name, ".") == 0){
	Noop:
				if(nqid == 0)
					qid[nqid] = f->qid;
				else
					qid[nqid] = qid[nqid-1];
				continue;
			}

			if(strcmp(name, "..") == 0){
				name = strrchr(path, '/');
				if(name){
					if(name == path)	/* at root */
						goto Noop;
					*name = '\0';
				}
				d = dirstat(path);
				if(d == nil){
					*name = '/';
					errstr(errbuf, sizeof errbuf);
					err = errbuf;
					break;
				}
	Directory:
				qid[nqid] = d->qid;
				free(d);
				releasedf(lastdf);
				lastdf = getdf(mkpath(path, ".depend"));
				continue;
			}

			npath = mkpath(path, name);
			free(path);
			path = npath;
			d = dirstat(path);

			if(d !=nil && (d->qid.type & QTDIR))
				goto Directory;
			free(d);

			qid[nqid].type = QTFILE;
			qid[nqid].path = 0;
			qid[nqid].vers = 0;

			dp = dfsearch(lastdf, name);
			if(dp == nil){
				tmp = strdup(name);
				if(tmp == nil)
					fatal("mallocerr");
				i = strlen(tmp);
				if(i > 4 && strcmp(&tmp[i-4], ".tar") == 0){
					tmp[i-4] = 0;
					dp = dfsearch(lastdf, tmp);
				}
				free(tmp);
			}

			if(dp == nil){
				err = Eexist;
				break;
			}
			qid[nqid].path = (uvlong)dp;
			qid[nqid].vers = 0;
		}
		if(nqid == 0 && err == nil)
			err = "file does not exist";
	}

	/* for error or partial success, put the cloned fid back*/
	if(nf!=nil && (err != nil || nqid < nwname)){
		releasedf(nf->df);
		nf->df = nil;
		fsputfid(fs, nf);
	}

	if(err == nil){
		/* return (possibly short) list of qids */
		for(i=0; i<nqid; i++)
			r->f.wqid[i] = qid[i];
		r->f.nwqid = nqid;

		/* for full success, advance f */
		if(nqid > 0 && nqid == nwname){
			free(f->path);
			f->path = path;
			path = nil;

			f->qid = qid[nqid-1];
			f->dp = (Symbol*)f->qid.path;

			if(f->df != lastdf){
				releasedf(f->df);
				f->df = lastdf;
				lastdf = nil;
			}

		}
	}

	releasedf(lastdf);
	free(path);

	fsreply(fs, r, err);
}

#ifdef adf
void
fsclone(Fs *fs, Request *r, Fid *f)
{
	Fid *nf;

	if(f->attached == 0){
		fsreply(fs, r, Eexist);
		return;
	}
	nf = fsgetfid(fs, r->f.newfid);

	nf->attached = 1;
	nf->open = f->open;
	nf->path = strdup(f->path);
	nf->qid = f->qid;
	nf->dp = f->dp;
	nf->fd = f->fd;
	nf->df = f->df;
	if(nf->df){
		lock(nf->df);
		nf->df->use++;
		unlock(nf->df);
	}
	fsreply(fs, r, nil);
}

void
fswalk(Fs *fs, Request *r, Fid *f)
{
	char *name;
	int i;
	Dir d;
	char errbuf[ERRLEN];
	char *path;
	Symbol *dp;

	if(f->attached == 0){
		fsreply(fs, r, Enofid);
		return;
	}

	if(f->fd >= 0 || f->open)
		fatal("walk of an open file");

	name = r->f.name;
	if(strcmp(name, ".") == 0){
		fsreply(fs, r, nil);
		return;
	}
	if(strcmp(name, "..") == 0){
		name = strrchr(f->path, '/');
		if(name){
			if(name == f->path){
				fsreply(fs, r, nil);
				return;
			}
			*name = 0;
		}
		if(dirstat(f->path, &d) < 0){
			*name = '/';
			errstr(errbuf);
			fsreply(fs, r, errbuf);
			return;
		}
		r->f.qid = f->qid = d.qid;

		releasedf(f->df);
		f->df = getdf(mkpath(f->path, ".depend"));

		fsreply(fs, r, nil);
		return;
	}

	path = mkpath(f->path, name);
	if(dirstat(path, &d) < 0 || (d.qid.path & CHDIR) == 0){
		dp = dfsearch(f->df, name);
		if(dp == nil){
			i = strlen(name);
			if(i > 4 && strcmp(&name[i-4], ".tar") == 0){
				name[i-4] = 0;
				dp = dfsearch(f->df, name);
			}
		}
		if(dp == nil){
			fsreply(fs, r, Eexist);
			free(path);
			return;
		}
		f->dp = dp;
		d.qid.path = (uint)dp;