ndbm.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifndef lint
static char sccsid[] = "@(#)ndbm.c	4.1     (ultrix)        7/3/90";
#endif
  
/*
 *			Copyright (c) 1985 by
 *		Digital Equipment Corporation, Maynard, MA
 *			All rights reserved.
 *								
 *	This software is furnished under a license and may be used and
 *	copied  only  in accordance with the terms of such license and
 *	with the  inclusion  of  the  above  copyright  notice.   This
 *	software  or  any  other copies thereof may not be provided or
 *	otherwise made available to any other person.  No title to and
 *	ownership of the software is hereby transferred.		
 *								
 *	This software is  derived  from  software  received  from  the
 *	University    of   California,   Berkeley,   and   from   Bell
 *	Laboratories.  Use, duplication, or disclosure is  subject  to
 *	restrictions  under  license  agreements  with  University  of
 *	California and with AT&T.					
 *								
 *	The information in this software is subject to change  without
 *	notice  and should not be construed as a commitment by Digital
 *	Equipment Corporation.					
 *								
 *	Digital assumes no responsibility for the use  or  reliability
 *	of its software on equipment which is not supplied by Digital.
*/

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <stdio.h>
#include <errno.h>
#include <ndbm.h>

#define BYTESIZ 8
#undef setbit

static  datum makdatum();
static  long hashinc();
static  long dcalchash();
extern  int errno;

DBM *
dbm_open(file, flags, mode)
	char *file;
	int flags, mode;
{
	struct stat statb;
	register DBM *db;

	if ((db = (DBM *)malloc(sizeof *db)) == 0) {
		errno = ENOMEM;
		return ((DBM *)0);
	}
	db->dbm_flags = (flags & 03) == O_RDONLY ? _DBM_RDONLY : 0;
	if ((flags & 03) == O_WRONLY)
		flags = (flags & ~03) | O_RDWR;
	strcpy(db->dbm_pagbuf, file);
	strcat(db->dbm_pagbuf, ".pag");
	db->dbm_pagf = open(db->dbm_pagbuf, flags, mode);
	if (db->dbm_pagf < 0)
		goto bad;
	strcpy(db->dbm_pagbuf, file);
	strcat(db->dbm_pagbuf, ".dir");
	db->dbm_dirf = open(db->dbm_pagbuf, flags, mode);
	if (db->dbm_dirf < 0)
		goto bad1;
	fstat(db->dbm_dirf, &statb);
	db->dbm_maxbno = statb.st_size*BYTESIZ-1;
	db->dbm_pagbno = db->dbm_dirbno = -1;
	return (db);
bad1:
	(void) close(db->dbm_pagf);
bad:
	free((char *)db);
	return ((DBM *)0);
}

void
dbm_close(db)
	DBM *db;
{

	(void) close(db->dbm_dirf);
	(void) close(db->dbm_pagf);
	free((char *)db);
}

long
dbm_forder(db, key)
	register DBM *db;
	datum key;
{
	long hash;

	hash = dcalchash(key);
	for (db->dbm_hmask=0;; db->dbm_hmask=(db->dbm_hmask<<1)+1) {
		db->dbm_blkno = hash & db->dbm_hmask;
		db->dbm_bitno = db->dbm_blkno + db->dbm_hmask;
		if (getbit(db) == 0)
			break;
	}
	return (db->dbm_blkno);
}

datum
dbm_fetch(db, key)
	register DBM *db;
	datum key;
{
	register i;
	datum item;

	if (dbm_error(db))
		goto err;
	dbm_access(db, dcalchash(key));
	if ((i = finddatum(db->dbm_pagbuf, key)) >= 0) {
		item = makdatum(db->dbm_pagbuf, i+1);
		if (item.dptr != NULL)
			return (item);
	}
err:
	item.dptr = NULL;
	item.dsize = 0;
	return (item);
}

dbm_delete(db, key)
	register DBM *db;
	datum key;
{
	register i;
	datum item;

	if (dbm_error(db))
		return (-1);
	if (dbm_rdonly(db)) {
		errno = EPERM;
		return (-1);
	}
	dbm_access(db, dcalchash(key));
	if ((i = finddatum(db->dbm_pagbuf, key)) < 0)
		return (-1);
	if (!delitem(db->dbm_pagbuf, i))
		goto err;
	db->dbm_pagbno = db->dbm_blkno;
	(void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, L_SET);
	if (write(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ) {
	err:
		db->dbm_flags |= _DBM_IOERR;
		return (-1);
	}
	return (0);
}

dbm_store(db, key, dat, replace)
	register DBM *db;
	datum key, dat;
	int replace;
{
	register i;
	datum item, item1;
	char ovfbuf[PBLKSIZ];

	if (dbm_error(db))
		return (-1);
	if (dbm_rdonly(db)) {
		errno = EPERM;
		return (-1);
	}
loop:
	dbm_access(db, dcalchash(key));
	if ((i = finddatum(db->dbm_pagbuf, key)) >= 0) {
		if (!replace)
			return (1);
		if (!delitem(db->dbm_pagbuf, i)) {
			db->dbm_flags |= _DBM_IOERR;
			return (-1);
		}
	}
	if (!additem(db->dbm_pagbuf, key, dat))
		goto split;
	db->dbm_pagbno = db->dbm_blkno;
	(void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, L_SET);
	if (write(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ) {
		db->dbm_flags |= _DBM_IOERR;
		return (-1);
	}
	return (0);

split:
	if (key.dsize+dat.dsize+3*sizeof(short) >= PBLKSIZ) {
		db->dbm_flags |= _DBM_IOERR;
		errno = ENOSPC;
		return (-1);
	}
	bzero(ovfbuf, PBLKSIZ);
	for (i=0;;) {
		item = makdatum(db->dbm_pagbuf, i);
		if (item.dptr == NULL)
			break;
		if (dcalchash(item) & (db->dbm_hmask+1)) {
			item1 = makdatum(db->dbm_pagbuf, i+1);
			if (item1.dptr == NULL) {
				fprintf(stderr, "ndbm: split not paired\n");
				db->dbm_flags |= _DBM_IOERR;
				break;
			}
			if (!additem(ovfbuf, item, item1) ||
			    !delitem(db->dbm_pagbuf, i)) {
				db->dbm_flags |= _DBM_IOERR;
				return (-1);
			}
			continue;
		}
		i += 2;
	}
	db->dbm_pagbno = db->dbm_blkno;
	(void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, L_SET);
	if (write(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ) {
		db->dbm_flags |= _DBM_IOERR;
		return (-1);
	}
	(void) lseek(db->dbm_pagf, (db->dbm_blkno+db->dbm_hmask+1)*PBLKSIZ, L_SET);
	if (write(db->dbm_pagf, ovfbuf, PBLKSIZ) != PBLKSIZ) {
		db->dbm_flags |= _DBM_IOERR;
		return (-1);
	}
	setbit(db);
	goto loop;
}

datum
dbm_firstkey(db)
	DBM *db;
{

	db->dbm_blkptr = 0L;
	db->dbm_keyptr = 0;
	return (dbm_nextkey(db));
}

datum
dbm_nextkey(db)
	register DBM *db;
{
	struct stat statb;
	datum item;

	if (dbm_error(db) || fstat(db->dbm_pagf, &statb) < 0)
		goto err;
	statb.st_size /= PBLKSIZ;
	for (;;) {
		if (db->dbm_blkptr != db->dbm_pagbno) {
			db->dbm_pagbno = db->dbm_blkptr;
			(void) lseek(db->dbm_pagf, db->dbm_blkptr*PBLKSIZ, L_SET);
			if (read(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ)
				bzero(db->dbm_pagbuf, PBLKSIZ);
#ifdef DEBUG
			else if (chkblk(db->dbm_pagbuf) < 0)
				db->dbm_flags |= _DBM_IOERR;
#endif
		}
		if (((short *)db->dbm_pagbuf)[0] != 0) {
			item = makdatum(db->dbm_pagbuf, db->dbm_keyptr);
			if (item.dptr != NULL) {
				db->dbm_keyptr += 2;
				return (item);
			}
			db->dbm_keyptr = 0;
		}
		if (++db->dbm_blkptr >= statb.st_size)
			break;
	}
err:
	item.dptr = NULL;
	item.dsize = 0;
	return (item);
}

static
dbm_access(db, hash)
	register DBM *db;
	long hash;
{

	for (db->dbm_hmask=0;; db->dbm_hmask=(db->dbm_hmask<<1)+1) {
		db->dbm_blkno = hash & db->dbm_hmask;
		db->dbm_bitno = db->dbm_blkno + db->dbm_hmask;
		if (getbit(db) == 0)
			break;
	}
	if (db->dbm_blkno != db->dbm_pagbno) {
		db->dbm_pagbno = db->dbm_blkno;
		(void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, L_SET);
		if (read(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ)
			bzero(db->dbm_pagbuf, PBLKSIZ);
#ifdef DEBUG
		else if (chkblk(db->dbm_pagbuf) < 0)
			db->dbm_flags |= _DBM_IOERR;
#endif
	}
}

static
getbit(db)
	register DBM *db;
{
	long bn;
	register b, i, n;
	

	if (db->dbm_bitno > db->dbm_maxbno)
		return (0);
	n = db->dbm_bitno % BYTESIZ;
	bn = db->dbm_bitno / BYTESIZ;
	i = bn % DBLKSIZ;
	b = bn / DBLKSIZ;
	if (b != db->dbm_dirbno) {
		db->dbm_dirbno = b;
		(void) lseek(db->dbm_dirf, (long)b*DBLKSIZ, L_SET);
		if (read(db->dbm_dirf, db->dbm_dirbuf, DBLKSIZ) != DBLKSIZ)
			bzero(db->dbm_dirbuf, DBLKSIZ);
	}
	return (db->dbm_dirbuf[i] & (1<<n));
}

static
setbit(db)
	register DBM *db;
{
	long bn;
	register i, n, b;

	if (db->dbm_bitno > db->dbm_maxbno)
		db->dbm_maxbno = db->dbm_bitno;
	n = db->dbm_bitno % BYTESIZ;
	bn = db->dbm_bitno / BYTESIZ;
	i = bn % DBLKSIZ;
	b = bn / DBLKSIZ;
	if (b != db->dbm_dirbno) {
		db->dbm_dirbno = b;
		(void) lseek(db->dbm_dirf, (long)b*DBLKSIZ, L_SET);
		if (read(db->dbm_dirf, db->dbm_dirbuf, DBLKSIZ) != DBLKSIZ)
			bzero(db->dbm_dirbuf, DBLKSIZ);
	}
	db->dbm_dirbuf[i] |= 1<<n;
	db->dbm_dirbno = b;
	(void) lseek(db->dbm_dirf, (long)b*DBLKSIZ, L_SET);
	if (write(db->dbm_dirf, db->dbm_dirbuf, DBLKSIZ) != DBLKSIZ)
		db->dbm_flags |= _DBM_IOERR;
}

static datum
makdatum(buf, n)
	char buf[PBLKSIZ];
{
	register short *sp;
	register t;
	datum item;

	sp = (short *)buf;
	if ((unsigned)n >= sp[0]) {
		item.dptr = NULL;
		item.dsize = 0;
		return (item);
	}
	t = PBLKSIZ;
	if (n > 0)
		t = sp[n];
	item.dptr = buf+sp[n+1];
	item.dsize = t - sp[n+1];
	return (item);
}

static
finddatum(buf, item)
	char buf[PBLKSIZ];
	datum item;
{
	register short *sp;
	register int i, n, j;

	sp = (short *)buf;
	n = PBLKSIZ;
	for (i=0, j=sp[0]; i<j; i+=2, n = sp[i]) {
		n -= sp[i+1];
		if (n != item.dsize)
			continue;
		if (n == 0 || bcmp(&buf[sp[i+1]], item.dptr, n) == 0)
			return (i);
	}
	return (-1);
}

static  int hitab[16]
/* ken's
{
	055,043,036,054,063,014,004,005,
	010,064,077,000,035,027,025,071,
};
*/
 = {    61, 57, 53, 49, 45, 41, 37, 33,
	29, 25, 21, 17, 13,  9,  5,  1,
};
static  long hltab[64]
 = {
	06100151277L,06106161736L,06452611562L,05001724107L,
	02614772546L,04120731531L,04665262210L,07347467531L,
	06735253126L,06042345173L,03072226605L,01464164730L,
	03247435524L,07652510057L,01546775256L,05714532133L,
	06173260402L,07517101630L,02431460343L,01743245566L,
	00261675137L,02433103631L,03421772437L,04447707466L,
	04435620103L,03757017115L,03641531772L,06767633246L,
	02673230344L,00260612216L,04133454451L,00615531516L,
	06137717526L,02574116560L,02304023373L,07061702261L,
	05153031405L,05322056705L,07401116734L,06552375715L,
	06165233473L,05311063631L,01212221723L,01052267235L,
	06000615237L,01075222665L,06330216006L,04402355630L,
	01451177262L,02000133436L,06025467062L,07121076461L,
	03123433522L,01010635225L,01716177066L,05161746527L,
	01736635071L,06243505026L,03637211610L,01756474365L,
	04723077174L,03642763134L,05750130273L,03655541561L,
};

static long
hashinc(db, hash)
	register DBM *db;
	long hash;
{
	long bit;

	hash &= db->dbm_hmask;
	bit = db->dbm_hmask+1;
	for (;;) {
		bit >>= 1;
		if (bit == 0)
			return (0L);
		if ((hash & bit) == 0)
			return (hash | bit);
		hash &= ~bit;
	}
}

static long
dcalchash(item)
	datum item;
{
	register int s, c, j;
	register char *cp;
	register long hashl;
	register int hashi;

	hashl = 0;
	hashi = 0;
	for (cp = item.dptr, s=item.dsize; --s >= 0; ) {
		c = *cp++;
		for (j=0; j<BYTESIZ; j+=4) {
			hashi += hitab[c&017];
			hashl += hltab[hashi&63];
			c >>= 4;
		}
	}
	return (hashl);
}

/*
 * Delete pairs of items (n & n+1).
 */
static
delitem(buf, n)
	char buf[PBLKSIZ];
{
	register short *sp, *sp1;
	register i1, i2;

	sp = (short *)buf;
	i2 = sp[0];
	if ((unsigned)n >= i2 || (n & 1))
		return (0);
	if (n == i2-2) {
		sp[0] -= 2;
		return (1);
	}
	i1 = PBLKSIZ;
	if (n > 0)
		i1 = sp[n];
	i1 -= sp[n+2];
	if (i1 > 0) {
		i2 = sp[i2];
		bcopy(&buf[i2], &buf[i2 + i1], sp[n+2] - i2);
	}
	sp[0] -= 2;
	for (sp1 = sp + sp[0], sp += n+1; sp <= sp1; sp++)
		sp[0] = sp[2] + i1;
	return (1);
}

/*
 * Add pairs of items (item & item1).
 */
static
additem(buf, item, item1)
	char buf[PBLKSIZ];
	datum item, item1;
{
	register short *sp;
	register i1, i2;

	sp = (short *)buf;
	i1 = PBLKSIZ;
	i2 = sp[0];
	if (i2 > 0)
		i1 = sp[i2];
	i1 -= item.dsize + item1.dsize;
	if (i1 <= (i2+3) * (int)sizeof(short))
		return (0);
	sp[0] += 2;
	sp[++i2] = i1 + item1.dsize;
	bcopy(item.dptr, &buf[i1 + item1.dsize], item.dsize);
	sp[++i2] = i1;
	bcopy(item1.dptr, &buf[i1], item1.dsize);
	return (1);
}

#ifdef DEBUG
static
chkblk(buf)
	char buf[PBLKSIZ];
{
	register short *sp;
	register t, i;

	sp = (short *)buf;
	t = PBLKSIZ;
	for (i=0; i<sp[0]; i++) {
		if (sp[i+1] > t)
			return (-1);
		t = sp[i+1];
	}
	if (t < (sp[0]+1)*sizeof(short))
		return (-1);
	return (0);
}
#endif