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/*
* sdbm - ndbm work-alike hashed database library
* based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
* author: oz@nexus.yorku.ca
* status: public domain.
*
* core routines
*/
#include "sdbm.h"
#include "sdbm_tune.h"
#include "sdbm_pair.h"
#include <sys/types.h>
#include <sys/stat.h>
#ifdef BSD42
#include <sys/file.h>
#else
#include <fcntl.h>
#include <memory.h>
#endif
#include <errno.h>
#include <string.h>
#include <unistd.h>
#ifdef __STDC__
#include <stddef.h>
#include <stdlib.h>
#endif
#ifndef NULL
#define NULL 0
#endif
/*
* forward
*/
static int getdbit (SDBM *, long);
static int setdbit (SDBM *, long);
static int getpage (SDBM *, long);
static datum getnext (SDBM *);
static int makroom (SDBM *, long, int);
/*
* useful macros
*/
#define bad(x) ((x).dptr == NULL || (x).dsize <= 0)
#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
#define ioerr(db) ((db)->flags |= SDBM_IOERR)
#define OFF_PAG(off) (long) (off) * PBLKSIZ
#define OFF_DIR(off) (long) (off) * DBLKSIZ
static long masks[] = {
000000000000, 000000000001, 000000000003, 000000000007,
000000000017, 000000000037, 000000000077, 000000000177,
000000000377, 000000000777, 000000001777, 000000003777,
000000007777, 000000017777, 000000037777, 000000077777,
000000177777, 000000377777, 000000777777, 000001777777,
000003777777, 000007777777, 000017777777, 000037777777,
000077777777, 000177777777, 000377777777, 000777777777,
001777777777, 003777777777, 007777777777, 017777777777
};
datum nullitem = {NULL, 0};
SDBM *
sdbm_open(file, flags, mode)
register char *file;
register int flags;
register int mode;
{
register SDBM *db;
register char *dirname;
register char *pagname;
register int n;
if (file == NULL || !*file)
return errno = EINVAL, (SDBM *) NULL;
/*
* need space for two seperate filenames
*/
n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;
if ((dirname = malloc((unsigned) n)) == NULL)
return errno = ENOMEM, (SDBM *) NULL;
/*
* build the file names
*/
dirname = strcat(strcpy(dirname, file), DIRFEXT);
pagname = strcpy(dirname + strlen(dirname) + 1, file);
pagname = strcat(pagname, PAGFEXT);
db = sdbm_prep(dirname, pagname, flags, mode);
free((char *) dirname);
return db;
}
SDBM *
sdbm_prep(dirname, pagname, flags, mode)
char *dirname;
char *pagname;
int flags;
int mode;
{
register SDBM *db;
struct stat dstat;
if ((db = (SDBM *) malloc(sizeof(SDBM))) == NULL)
return errno = ENOMEM, (SDBM *) NULL;
db->flags = 0;
db->hmask = 0;
db->blkptr = 0;
db->keyptr = 0;
/*
* adjust user flags so that WRONLY becomes RDWR,
* as required by this package. Also set our internal
* flag for RDONLY if needed.
*/
if (flags & O_WRONLY)
flags = (flags & ~O_WRONLY) | O_RDWR;
else if ((flags & 03) == O_RDONLY)
db->flags = SDBM_RDONLY;
/*
* open the files in sequence, and stat the dirfile.
* If we fail anywhere, undo everything, return NULL.
*/
if ((db->pagf = open(pagname, flags, mode)) > -1) {
if ((db->dirf = open(dirname, flags, mode)) > -1) {
/*
* need the dirfile size to establish max bit number.
*/
if (fstat(db->dirf, &dstat) == 0) {
/*
* zero size: either a fresh database, or one with a single,
* unsplit data page: dirpage is all zeros.
*/
db->dirbno = (!dstat.st_size) ? 0 : -1;
db->pagbno = -1;
db->maxbno = dstat.st_size * BYTESIZ;
(void) memset(db->pagbuf, 0, PBLKSIZ);
(void) memset(db->dirbuf, 0, DBLKSIZ);
/*
* success
*/
return db;
}
(void) close(db->dirf);
}
(void) close(db->pagf);
}
free((char *) db);
return (SDBM *) NULL;
}
void
sdbm_close(db)
register SDBM *db;
{
if (db == NULL)
errno = EINVAL;
else {
(void) close(db->dirf);
(void) close(db->pagf);
free((char *) db);
}
}
datum
sdbm_fetch(db, key)
register SDBM *db;
datum key;
{
if (db == NULL || bad(key))
return errno = EINVAL, nullitem;
if (getpage(db, exhash(key)))
return sdbm_getpair(db->pagbuf, key);
return ioerr(db), nullitem;
}
int
sdbm_delete(db, key)
register SDBM *db;
datum key;
{
if (db == NULL || bad(key))
return errno = EINVAL, -1;
if (sdbm_rdonly(db))
return errno = EPERM, -1;
if (getpage(db, exhash(key))) {
if (!sdbm_delpair(db->pagbuf, key))
return -1;
/*
* update the page file
*/
if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return ioerr(db), -1;
return 0;
}
return ioerr(db), -1;
}
int
sdbm_store(db, key, val, flags)
register SDBM *db;
datum key;
datum val;
int flags;
{
int need;
register long hash;
if (db == NULL || bad(key))
return errno = EINVAL, -1;
if (sdbm_rdonly(db))
return errno = EPERM, -1;
need = key.dsize + val.dsize;
/*
* is the pair too big (or too small) for this database ??
*/
if (need < 0 || need > PAIRMAX)
return errno = EINVAL, -1;
if (getpage(db, (hash = exhash(key)))) {
/*
* if we need to replace, delete the key/data pair
* first. If it is not there, ignore.
*/
if (flags == SDBM_REPLACE)
(void) sdbm_delpair(db->pagbuf, key);
#ifdef SEEDUPS
else if (sdbm_duppair(db->pagbuf, key))
return 1;
#endif
/*
* if we do not have enough room, we have to split.
*/
if (!sdbm_fitpair(db->pagbuf, need))
if (!makroom(db, hash, need))
return ioerr(db), -1;
/*
* we have enough room or split is successful. insert the key,
* and update the page file.
*/
(void) sdbm_putpair(db->pagbuf, key, val);
if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return ioerr(db), -1;
/*
* success
*/
return 0;
}
return ioerr(db), -1;
}
/*
* makroom - make room by splitting the overfull page
* this routine will attempt to make room for SPLTMAX times before
* giving up.
*/
static int
makroom(db, hash, need)
register SDBM *db;
long hash;
int need;
{
long newp;
char twin[PBLKSIZ];
char *pag = db->pagbuf;
char *new = twin;
register int smax = SPLTMAX;
do {
/*
* split the current page
*/
(void) sdbm_splpage(pag, new, db->hmask + 1);
/*
* address of the new page
*/
newp = (hash & db->hmask) | (db->hmask + 1);
/*
* write delay, read avoidence/cache shuffle:
* select the page for incoming pair: if key is to go to the new page,
* write out the previous one, and copy the new one over, thus making
* it the current page. If not, simply write the new page, and we are
* still looking at the page of interest. current page is not updated
* here, as dbm_store will do so, after it inserts the incoming pair.
*/
if (hash & (db->hmask + 1)) {
if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return 0;
db->pagbno = newp;
(void) memcpy(pag, new, PBLKSIZ);
}
else if (lseek(db->pagf, OFF_PAG(newp), SEEK_SET) < 0
|| write(db->pagf, new, PBLKSIZ) < 0)
return 0;
if (!setdbit(db, db->curbit))
return 0;
/*
* see if we have enough room now
*/
if (sdbm_fitpair(pag, need))
return 1;
/*
* try again... update curbit and hmask as getpage would have
* done. because of our update of the current page, we do not
* need to read in anything. BUT we have to write the current
* [deferred] page out, as the window of failure is too great.
*/
db->curbit = 2 * db->curbit +
((hash & (db->hmask + 1)) ? 2 : 1);
db->hmask |= db->hmask + 1;
if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return 0;
} while (--smax);
/*
* if we are here, this is real bad news. After SPLTMAX splits,
* we still cannot fit the key. say goodnight.
*/
#ifdef BADMESS
(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
#endif
return 0;
}
/*
* the following two routines will break if
* deletions aren't taken into account. (ndbm bug)
*/
datum
sdbm_firstkey(db)
register SDBM *db;
{
if (db == NULL)
return errno = EINVAL, nullitem;
/*
* start at page 0
*/
if (lseek(db->pagf, OFF_PAG(0), SEEK_SET) < 0
|| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return ioerr(db), nullitem;
db->pagbno = 0;
db->blkptr = 0;
db->keyptr = 0;
return getnext(db);
}
datum
sdbm_nextkey(db)
register SDBM *db;
{
if (db == NULL)
return errno = EINVAL, nullitem;
return getnext(db);
}
/*
* all important binary trie traversal
*/
static int
getpage(db, hash)
register SDBM *db;
register long hash;
{
register int hbit;
register long dbit;
register long pagb;
dbit = 0;
hbit = 0;
while (dbit < db->maxbno && getdbit(db, dbit))
dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);
debug(("dbit: %d...", dbit));
db->curbit = dbit;
db->hmask = masks[hbit];
pagb = hash & db->hmask;
/*
* see if the block we need is already in memory.
* note: this lookaside cache has about 10% hit rate.
*/
if (pagb != db->pagbno) {
/*
* note: here, we assume a "hole" is read as 0s.
* if not, must zero pagbuf first.
*/
if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
|| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return 0;
if (!sdbm_chkpage(db->pagbuf))
return 0;
db->pagbno = pagb;
debug(("pag read: %d\n", pagb));
}
return 1;
}
static int
getdbit(db, dbit)
register SDBM *db;
register long dbit;
{
register long c;
register long dirb;
c = dbit / BYTESIZ;
dirb = c / DBLKSIZ;
if (dirb != db->dirbno) {
if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
|| read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
return 0;
db->dirbno = dirb;
debug(("dir read: %d\n", dirb));
}
return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
}
static int
setdbit(db, dbit)
register SDBM *db;
register long dbit;
{
register long c;
register long dirb;
c = dbit / BYTESIZ;
dirb = c / DBLKSIZ;
if (dirb != db->dirbno) {
if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
|| read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
return 0;
db->dirbno = dirb;
debug(("dir read: %d\n", dirb));
}
db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
if (dbit >= db->maxbno)
db->maxbno += DBLKSIZ * BYTESIZ;
if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
|| write(db->dirf, db->dirbuf, DBLKSIZ) < 0)
return 0;
return 1;
}
/*
* getnext - get the next key in the page, and if done with
* the page, try the next page in sequence
*/
static datum
getnext(db)
register SDBM *db;
{
datum key;
for (;;) {
db->keyptr++;
key = sdbm_getnkey(db->pagbuf, db->keyptr);
if (key.dptr != NULL)
return key;
/*
* we either run out, or there is nothing on this page..
* try the next one... If we lost our position on the
* file, we will have to seek.
*/
db->keyptr = 0;
if (db->pagbno != db->blkptr++)
if (lseek(db->pagf, OFF_PAG(db->blkptr), SEEK_SET) < 0)
break;
db->pagbno = db->blkptr;
if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
break;
if (!sdbm_chkpage(db->pagbuf))
break;
}
return ioerr(db), nullitem;
}
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