493 lines
11 KiB
C
493 lines
11 KiB
C
/*
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* sdbm - ndbm work-alike hashed database library
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* based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
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* author: oz@nexus.yorku.ca
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* status: public domain.
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*
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* core routines
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*/
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#include "INTERN.h"
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#include "config.h"
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#include "sdbm.h"
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#include "tune.h"
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#include "pair.h"
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#ifdef I_FCNTL
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# include <fcntl.h>
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#endif
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#ifdef I_SYS_FILE
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# include <sys/file.h>
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#endif
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#ifdef I_STRING
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# include <string.h>
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#else
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# include <strings.h>
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#endif
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/*
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* externals
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*/
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#ifndef WIN32
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#ifndef sun
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extern int errno;
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#endif
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extern Malloc_t malloc proto((MEM_SIZE));
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extern Free_t free proto((Malloc_t));
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extern Off_t lseek(int, Off_t, int);
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#endif
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/*
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* forward
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*/
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static int getdbit proto((DBM *, long));
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static int setdbit proto((DBM *, long));
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static int getpage proto((DBM *, long));
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static datum getnext proto((DBM *));
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static int makroom proto((DBM *, long, int));
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/*
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* useful macros
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*/
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#define bad(x) ((x).dptr == NULL || (x).dsize < 0)
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#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
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#define ioerr(db) ((db)->flags |= DBM_IOERR)
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#define OFF_PAG(off) (long) (off) * PBLKSIZ
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#define OFF_DIR(off) (long) (off) * DBLKSIZ
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static long masks[] = {
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000000000000, 000000000001, 000000000003, 000000000007,
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000000000017, 000000000037, 000000000077, 000000000177,
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000000000377, 000000000777, 000000001777, 000000003777,
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000000007777, 000000017777, 000000037777, 000000077777,
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000000177777, 000000377777, 000000777777, 000001777777,
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000003777777, 000007777777, 000017777777, 000037777777,
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000077777777, 000177777777, 000377777777, 000777777777,
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001777777777, 003777777777, 007777777777, 017777777777
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};
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DBM *
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sdbm_open(register char *file, register int flags, register int mode)
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{
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register DBM *db;
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register char *dirname;
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register char *pagname;
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register int n;
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if (file == NULL || !*file)
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return errno = EINVAL, (DBM *) NULL;
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/*
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* need space for two seperate filenames
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*/
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n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;
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if ((dirname = (char *) malloc((unsigned) n)) == NULL)
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return errno = ENOMEM, (DBM *) NULL;
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/*
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* build the file names
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*/
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dirname = strcat(strcpy(dirname, file), DIRFEXT);
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pagname = strcpy(dirname + strlen(dirname) + 1, file);
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pagname = strcat(pagname, PAGFEXT);
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db = sdbm_prep(dirname, pagname, flags, mode);
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free((char *) dirname);
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return db;
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}
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DBM *
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sdbm_prep(char *dirname, char *pagname, int flags, int mode)
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{
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register DBM *db;
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struct stat dstat;
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if ((db = (DBM *) malloc(sizeof(DBM))) == NULL)
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return errno = ENOMEM, (DBM *) NULL;
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db->flags = 0;
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db->hmask = 0;
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db->blkptr = 0;
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db->keyptr = 0;
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/*
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* adjust user flags so that WRONLY becomes RDWR,
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* as required by this package. Also set our internal
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* flag for RDONLY if needed.
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*/
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if (flags & O_WRONLY)
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flags = (flags & ~O_WRONLY) | O_RDWR;
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else if ((flags & 03) == O_RDONLY)
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db->flags = DBM_RDONLY;
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/*
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* open the files in sequence, and stat the dirfile.
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* If we fail anywhere, undo everything, return NULL.
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*/
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#if defined(OS2) || defined(MSDOS) || defined(WIN32)
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flags |= O_BINARY;
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# endif
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if ((db->pagf = open(pagname, flags, mode)) > -1) {
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if ((db->dirf = open(dirname, flags, mode)) > -1) {
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/*
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* need the dirfile size to establish max bit number.
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*/
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if (fstat(db->dirf, &dstat) == 0) {
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/*
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* zero size: either a fresh database, or one with a single,
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* unsplit data page: dirpage is all zeros.
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*/
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db->dirbno = (!dstat.st_size) ? 0 : -1;
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db->pagbno = -1;
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db->maxbno = dstat.st_size * BYTESIZ;
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(void) memset(db->pagbuf, 0, PBLKSIZ);
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(void) memset(db->dirbuf, 0, DBLKSIZ);
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/*
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* success
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*/
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return db;
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}
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(void) close(db->dirf);
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}
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(void) close(db->pagf);
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}
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free((char *) db);
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return (DBM *) NULL;
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}
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void
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sdbm_close(register DBM *db)
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{
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if (db == NULL)
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errno = EINVAL;
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else {
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(void) close(db->dirf);
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(void) close(db->pagf);
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free((char *) db);
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}
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}
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datum
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sdbm_fetch(register DBM *db, datum key)
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{
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if (db == NULL || bad(key))
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return errno = EINVAL, nullitem;
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if (getpage(db, exhash(key)))
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return getpair(db->pagbuf, key);
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return ioerr(db), nullitem;
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}
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int
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sdbm_delete(register DBM *db, datum key)
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{
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if (db == NULL || bad(key))
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return errno = EINVAL, -1;
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if (sdbm_rdonly(db))
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return errno = EPERM, -1;
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if (getpage(db, exhash(key))) {
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if (!delpair(db->pagbuf, key))
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return -1;
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/*
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* update the page file
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*/
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if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
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|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
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return ioerr(db), -1;
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return 0;
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}
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return ioerr(db), -1;
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}
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int
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sdbm_store(register DBM *db, datum key, datum val, int flags)
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{
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int need;
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register long hash;
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if (db == NULL || bad(key))
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return errno = EINVAL, -1;
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if (sdbm_rdonly(db))
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return errno = EPERM, -1;
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need = key.dsize + val.dsize;
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/*
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* is the pair too big (or too small) for this database ??
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*/
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if (need < 0 || need > PAIRMAX)
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return errno = EINVAL, -1;
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if (getpage(db, (hash = exhash(key)))) {
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/*
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* if we need to replace, delete the key/data pair
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* first. If it is not there, ignore.
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*/
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if (flags == DBM_REPLACE)
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(void) delpair(db->pagbuf, key);
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#ifdef SEEDUPS
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else if (duppair(db->pagbuf, key))
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return 1;
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#endif
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/*
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* if we do not have enough room, we have to split.
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*/
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if (!fitpair(db->pagbuf, need))
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if (!makroom(db, hash, need))
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return ioerr(db), -1;
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/*
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* we have enough room or split is successful. insert the key,
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* and update the page file.
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*/
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(void) putpair(db->pagbuf, key, val);
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if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
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|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
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return ioerr(db), -1;
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/*
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* success
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*/
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return 0;
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}
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return ioerr(db), -1;
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}
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/*
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* makroom - make room by splitting the overfull page
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* this routine will attempt to make room for SPLTMAX times before
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* giving up.
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*/
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static int
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makroom(register DBM *db, long int hash, int need)
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{
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long newp;
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char twin[PBLKSIZ];
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char *pag = db->pagbuf;
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char *New = twin;
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register int smax = SPLTMAX;
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do {
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/*
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* split the current page
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*/
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(void) splpage(pag, New, db->hmask + 1);
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/*
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* address of the new page
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*/
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newp = (hash & db->hmask) | (db->hmask + 1);
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/*
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* write delay, read avoidence/cache shuffle:
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* select the page for incoming pair: if key is to go to the new page,
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* write out the previous one, and copy the new one over, thus making
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* it the current page. If not, simply write the new page, and we are
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* still looking at the page of interest. current page is not updated
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* here, as sdbm_store will do so, after it inserts the incoming pair.
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*/
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if (hash & (db->hmask + 1)) {
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if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
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|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
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return 0;
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db->pagbno = newp;
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(void) memcpy(pag, New, PBLKSIZ);
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}
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else if (lseek(db->pagf, OFF_PAG(newp), SEEK_SET) < 0
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|| write(db->pagf, New, PBLKSIZ) < 0)
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return 0;
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if (!setdbit(db, db->curbit))
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return 0;
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/*
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* see if we have enough room now
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*/
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if (fitpair(pag, need))
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return 1;
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/*
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* try again... update curbit and hmask as getpage would have
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* done. because of our update of the current page, we do not
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* need to read in anything. BUT we have to write the current
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* [deferred] page out, as the window of failure is too great.
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*/
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db->curbit = 2 * db->curbit +
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((hash & (db->hmask + 1)) ? 2 : 1);
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db->hmask |= db->hmask + 1;
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if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
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|| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
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return 0;
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} while (--smax);
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/*
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* if we are here, this is real bad news. After SPLTMAX splits,
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* we still cannot fit the key. say goodnight.
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*/
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#ifdef BADMESS
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(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
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#endif
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return 0;
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}
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/*
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* the following two routines will break if
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* deletions aren't taken into account. (ndbm bug)
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*/
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datum
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sdbm_firstkey(register DBM *db)
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{
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if (db == NULL)
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return errno = EINVAL, nullitem;
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/*
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* start at page 0
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*/
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if (lseek(db->pagf, OFF_PAG(0), SEEK_SET) < 0
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|| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
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return ioerr(db), nullitem;
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db->pagbno = 0;
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db->blkptr = 0;
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db->keyptr = 0;
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return getnext(db);
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}
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datum
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sdbm_nextkey(register DBM *db)
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{
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if (db == NULL)
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return errno = EINVAL, nullitem;
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return getnext(db);
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}
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/*
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* all important binary trie traversal
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*/
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static int
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getpage(register DBM *db, register long int hash)
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{
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register int hbit;
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register long dbit;
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register long pagb;
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dbit = 0;
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hbit = 0;
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while (dbit < db->maxbno && getdbit(db, dbit))
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dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);
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debug(("dbit: %d...", dbit));
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db->curbit = dbit;
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db->hmask = masks[hbit];
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pagb = hash & db->hmask;
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/*
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* see if the block we need is already in memory.
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* note: this lookaside cache has about 10% hit rate.
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*/
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if (pagb != db->pagbno) {
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/*
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* note: here, we assume a "hole" is read as 0s.
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* if not, must zero pagbuf first.
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*/
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if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
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|| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
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return 0;
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if (!chkpage(db->pagbuf))
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return 0;
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db->pagbno = pagb;
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debug(("pag read: %d\n", pagb));
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}
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return 1;
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}
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static int
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getdbit(register DBM *db, register long int dbit)
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{
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register long c;
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register long dirb;
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c = dbit / BYTESIZ;
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dirb = c / DBLKSIZ;
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if (dirb != db->dirbno) {
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if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
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|| read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
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return 0;
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db->dirbno = dirb;
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debug(("dir read: %d\n", dirb));
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}
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return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
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}
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static int
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setdbit(register DBM *db, register long int dbit)
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{
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register long c;
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register long dirb;
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c = dbit / BYTESIZ;
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dirb = c / DBLKSIZ;
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if (dirb != db->dirbno) {
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if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
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|| read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
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return 0;
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db->dirbno = dirb;
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debug(("dir read: %d\n", dirb));
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}
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db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
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if (dbit >= db->maxbno)
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db->maxbno += DBLKSIZ * BYTESIZ;
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if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
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|| write(db->dirf, db->dirbuf, DBLKSIZ) < 0)
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return 0;
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return 1;
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}
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/*
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* getnext - get the next key in the page, and if done with
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* the page, try the next page in sequence
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*/
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static datum
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getnext(register DBM *db)
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{
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datum key;
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for (;;) {
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db->keyptr++;
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key = getnkey(db->pagbuf, db->keyptr);
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if (key.dptr != NULL)
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return key;
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/*
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* we either run out, or there is nothing on this page..
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* try the next one... If we lost our position on the
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* file, we will have to seek.
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*/
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db->keyptr = 0;
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if (db->pagbno != db->blkptr++)
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if (lseek(db->pagf, OFF_PAG(db->blkptr), SEEK_SET) < 0)
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break;
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db->pagbno = db->blkptr;
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if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
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break;
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if (!chkpage(db->pagbuf))
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break;
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}
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return ioerr(db), nullitem;
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}
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