dbz.c

早期freebsd实现

		return(-1);
	f = fopen(fn, "w");
	free((POINTER)fn);
	if (f == NULL) {
		DEBUG(("dbzfresh: unable to create/truncate .pag file\n"));
		return(-1);
	} else
		(void) fclose(f);

	/* and punt to dbminit for the hard work */
	return(dbminit(name));
}

/*
 - dbzsize - what's a good table size to hold this many entries?
 */
long
dbzsize(contents)
long contents;			/* 0 means what's the default */
{
	register long n;

	if (contents <= 0) {	/* foulup or default inquiry */
		DEBUG(("dbzsize: preposterous input (%ld)\n", contents));
		return(DEFSIZE);
	}
	n = (contents/2)*3;	/* try to keep table at most 2/3 full */
	if (!(n&01))		/* make it odd */
		n++;
	DEBUG(("dbzsize: tentative size %ld\n", n));
	while (!isprime(n))	/* and look for a prime */
		n += 2;
	DEBUG(("dbzsize: final size %ld\n", n));

	return(n);
}

/*
 - isprime - is a number prime?
 *
 * This is not a terribly efficient approach.
 */
static int			/* predicate */
isprime(x)
register long x;
{
	static int quick[] = { 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 0 };
	register int *ip;
	register long div;
	register long stop;

	/* hit the first few primes quickly to eliminate easy ones */
	/* this incidentally prevents ridiculously small tables */
	for (ip = quick; (div = *ip) != 0; ip++)
		if (x%div == 0) {
			DEBUG(("isprime: quick result on %ld\n", (long)x));
			return(0);
		}

	/* approximate square root of x */
	for (stop = x; x/stop < stop; stop >>= 1)
		continue;
	stop <<= 1;

	/* try odd numbers up to stop */
	for (div = *--ip; div < stop; div += 2)
		if (x%div == 0)
			return(0);

	return(1);
}

/*
 - dbzagain - set up a new database to be a rebuild of an old one
 */
int				/* 0 success, -1 failure */
dbzagain(name, oldname)
char *name;			/* base name; .dir and .pag must exist */
char *oldname;			/* base name; all must exist */
{
	register char *fn;
	struct dbzconfig c;
	register int i;
	register long top;
	register FILE *f;
	register int newtable;
	register of_t newsize;
	struct stat sb;
	register of_t m;

	if (pagf != NULL) {
		DEBUG(("dbzagain: database already open\n"));
		return(-1);
	}

	/* pick up the old configuration */
	fn = enstring(oldname, dir);
	if (fn == NULL)
		return(-1);
	f = fopen(fn, "r");
	free((POINTER)fn);
	if (f == NULL) {
		DEBUG(("dbzagain: cannot open old .dir file\n"));
		return(-1);
	}
	i = getconf(f, (FILE *)NULL, &c);
	(void) fclose(f);
	if (i < 0) {
		DEBUG(("dbzagain: getconf failed\n"));
		return(-1);
	}

	/* calculate tagging from old file */
	if (stat(oldname, &sb) != -1) {
		 for (m = 1, i = 0; m < sb.st_size; i++, m <<= 1)
			 continue;
		 
		 /* if we had more tags than the default, use the new data */
		 if ((c.tagmask | c.tagenb) && m > (1 << TAGSHIFT)) {
			  c.tagshift = i;
			  c.tagmask = (~(unsigned long)0) >> (i + 1);
			  c.tagenb = (c.tagmask << 1) & ~c.tagmask;
		 }
	}

	/* tinker with it */
	top = 0;
	newtable = 0;
	for (i = 0; i < NUSEDS; i++) {
		if (top < c.used[i])
			top = c.used[i];
		if (c.used[i] == 0)
			newtable = 1;	/* hasn't got full usage history yet */
	}
	if (top == 0) {
		DEBUG(("dbzagain: old table has no contents!\n"));
		newtable = 1;
	}
	for (i = NUSEDS-1; i > 0; i--)
		c.used[i] = c.used[i-1];
	c.used[0] = 0;
	newsize = dbzsize(top);
	if (!newtable || newsize > c.tsize)	/* don't shrink new table */
		c.tsize = newsize;

	/* write it out */
	fn = enstring(name, dir);
	if (fn == NULL)
		return(-1);
	f = fopen(fn, "w");
	free((POINTER)fn);
	if (f == NULL) {
		DEBUG(("dbzagain: unable to write new .dir\n"));
		return(-1);
	}
	i = putconf(f, &c);
	(void) fclose(f);
	if (i < 0) {
		DEBUG(("dbzagain: putconf failed\n"));
		return(-1);
	}

	/* create/truncate .pag */
	fn = enstring(name, pag);
	if (fn == NULL)
		return(-1);
	f = fopen(fn, "w");
	free((POINTER)fn);
	if (f == NULL) {
		DEBUG(("dbzagain: unable to create/truncate .pag file\n"));
		return(-1);
	} else
		(void) fclose(f);

	/* and let dbminit do the work */
	return(dbminit(name));
}

/*
 - dbminit - open a database, creating it (using defaults) if necessary
 *
 * We try to leave errno set plausibly, to the extent that underlying
 * functions permit this, since many people consult it if dbminit() fails.
 */
int 				/* 0 success, -1 failure */
dbminit(name)
char *name;
{
	register int i;
	register size_t s;
	register char *dirfname;
	register char *pagfname;

	if (pagf != NULL) {
		DEBUG(("dbminit: dbminit already called once\n"));
		errno = 0;
		return(-1);
	}

	/* open the .dir file */
	dirfname = enstring(name, dir);
	if (dirfname == NULL)
		return(-1);
	dirf = fopen(dirfname, "r+");
	if (dirf == NULL) {
		dirf = fopen(dirfname, "r");
		dirronly = 1;
	} else
		dirronly = 0;
	free((POINTER)dirfname);
	if (dirf == NULL) {
		DEBUG(("dbminit: can't open .dir file\n"));
		return(-1);
	}
	CloseOnExec((int)fileno(dirf), 1);

	/* open the .pag file */
	pagfname = enstring(name, pag);
	if (pagfname == NULL) {
		(void) fclose(dirf);
		return(-1);
	}
	pagf = fopen(pagfname, "r+b");
	if (pagf == NULL) {
		pagf = fopen(pagfname, "rb");
		if (pagf == NULL) {
			DEBUG(("dbminit: .pag open failed\n"));
			(void) fclose(dirf);
			free((POINTER)pagfname);
			return(-1);
		}
		pagronly = 1;
	} else if (dirronly)
		pagronly = 1;
	else
		pagronly = 0;
	if (pagf != NULL)
		CloseOnExec((int)fileno(pagf), 1);
#ifdef NOBUFFER
	/*
	 * B News does not do adequate locking on its database accesses.
	 * Why it doesn't get into trouble using dbm is a mystery.  In any
	 * case, doing unbuffered i/o does not cure the problem, but does
	 * enormously reduce its incidence.
	 */
	(void) setbuf(pagf, (char *)NULL);
#else
#ifdef _IOFBF
	(void) setvbuf(pagf, (char *)pagbuf, _IOFBF, sizeof(pagbuf));
#endif
#endif
	pagpos = -1;
	/* don't free pagfname, need it below */

	/* open the base file */
	basef = fopen(name, "r");
	if (basef == NULL) {
		DEBUG(("dbminit: basefile open failed\n"));
		basefname = enstring(name, "");
		if (basefname == NULL) {
			(void) fclose(pagf);
			(void) fclose(dirf);
			free((POINTER)pagfname);
			pagf = NULL;
			return(-1);
		}
	} else
		basefname = NULL;
	if (basef != NULL)
		CloseOnExec((int)fileno(basef), 1);
#ifdef _IOFBF
	if (basef != NULL)
		(void) setvbuf(basef, basebuf, _IOFBF, sizeof(basebuf));
#endif

	/* pick up configuration */
	if (getconf(dirf, pagf, &conf) < 0) {
		DEBUG(("dbminit: getconf failure\n"));
		(void) fclose(basef);
		(void) fclose(pagf);
		(void) fclose(dirf);
		free((POINTER)pagfname);
		pagf = NULL;
		errno = EDOM;	/* kind of a kludge, but very portable */
		return(-1);
	}
	tagbits = conf.tagmask << conf.tagshift;
	taghere = conf.tagenb << conf.tagshift;
	tagboth = tagbits | taghere;
	mybytemap(mybmap);
	bytesame = 1;
	for (i = 0; i < SOF; i++)
		if (mybmap[i] != conf.bytemap[i])
			bytesame = 0;

	/* get first table into core, if it looks desirable and feasible */
	s = (size_t)conf.tsize * SOF;
	if (incore && (of_t)(s/SOF) == conf.tsize) {
		bufpagf = fopen(pagfname, (pagronly) ? "rb" : "r+b");
		if (bufpagf != NULL) {
			corepag = getcore(bufpagf);
			CloseOnExec((int)fileno(bufpagf), 1);
		}
	} else {
		bufpagf = NULL;
		corepag = NULL;
	}
	free((POINTER)pagfname);

	/* misc. setup */
	crcinit();
	written = 0;
	prevp = FRESH;
	DEBUG(("dbminit: succeeded\n"));
	return(0);
}

/*
 - enstring - concatenate two strings into a malloced area
 */
static char *			/* NULL if malloc fails */
enstring(s1, s2)
char *s1;
char *s2;
{
	register char *p;

	p = malloc((size_t)strlen(s1) + (size_t)strlen(s2) + 1);
	if (p != NULL) {
		(void) strcpy(p, s1);
		(void) strcat(p, s2);
	} else {
		DEBUG(("enstring(%s, %s) out of memory\n", s1, s2));
	}
	return(p);
}

/*
 - dbmclose - close a database
 */
int
dbmclose()
{
	register int ret = 0;

	if (pagf == NULL) {
		DEBUG(("dbmclose: not opened!\n"));
		return(-1);
	}

	if (fclose(pagf) == EOF) {
		DEBUG(("dbmclose: fclose(pagf) failed\n"));
		ret = -1;
	}
	pagf = basef;		/* ensure valid pointer; dbzsync checks it */
	if (dbzsync() < 0)
		ret = -1;
	if (bufpagf != NULL && fclose(bufpagf) == EOF) {
		DEBUG(("dbmclose: fclose(bufpagf) failed\n"));
		ret = -1;
	}
	if (corepag != NULL)
#ifdef MMAP
		if (munmap(corepag, (int)conf.tsize * SOF) == -1) {
			DEBUG(("dbmclose: munmap failed\n"));
			ret = -1;
		}
#else
		free((POINTER)corepag);
#endif
	corepag = NULL;
	if (fclose(basef) == EOF) {
		DEBUG(("dbmclose: fclose(basef) failed\n"));
		ret = -1;
	}
	if (basefname != NULL)
		free((POINTER)basefname);
	basef = NULL;
	pagf = NULL;
	if (fclose(dirf) == EOF) {
		DEBUG(("dbmclose: fclose(dirf) failed\n"));
		ret = -1;
	}

	DEBUG(("dbmclose: %s\n", (ret == 0) ? "succeeded" : "failed"));
	return(ret);
}

/*
 - dbzsync - push all in-core data out to disk
 */
int
dbzsync()
{
	register int ret = 0;

	if (pagf == NULL) {
		DEBUG(("dbzsync: not opened!\n"));
		return(-1);
	}
	if (!written)
		return(0);

#ifndef MMAP
	if (corepag != NULL && !writethrough) {
		if (putcore(corepag, bufpagf) < 0) {
			DEBUG(("dbzsync: putcore failed\n"));
			ret = -1;
		}
	}
#endif
	if (!conf.olddbz)
		if (putconf(dirf, &conf) < 0)
			ret = -1;

	DEBUG(("dbzsync: %s\n", (ret == 0) ? "succeeded" : "failed"));
	return(ret);
}

/*
 - dbzcancel - cancel writing of in-core data
 * Mostly for use from child processes.
 * Note that we don't need to futz around with stdio buffers, because we
 * always fflush them immediately anyway and so they never have stale data.
 */
int
dbzcancel()
{
	if (pagf == NULL) {
		DEBUG(("dbzcancel: not opened!\n"));
		return(-1);
	}

	written = 0;
	return(0);
}

/*
 - dbzfetch - fetch() with case mapping built in
 */
datum
dbzfetch(key)
datum key;
{
	char buffer[DBZMAXKEY + 1];
	datum mappedkey;
	register size_t keysize;

	DEBUG(("dbzfetch: (%s)\n", key.dptr));

	/* Key is supposed to be less than DBZMAXKEY */
	keysize = key.dsize;
	if (keysize >= DBZMAXKEY) {
		keysize = DBZMAXKEY;
		DEBUG(("keysize is %d - truncated to %d\n", key.dsize, DBZMAXKEY));
	}

	mappedkey.dptr = mapcase(buffer, key.dptr, keysize);
	buffer[keysize] = '\0';	/* just a debug aid */
	mappedkey.dsize = keysize;

	return(fetch(mappedkey));
}

/*
 - fetch - get an entry from the database
 *
 * Disgusting fine point, in the name of backward compatibility:  if the
 * last character of "key" is a NUL, that character is (effectively) not
 * part of the comparison against the stored keys.
 */
datum				/* dptr NULL, dsize 0 means failure */
fetch(key)
datum key;
{
	char buffer[DBZMAXKEY + 1];
	static of_t key_ptr;		/* return value points here */
	datum output;
	register size_t keysize;
	register size_t cmplen;