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DEFINITIONS
This source file includes following definitions.
- sdbm_open
- fd_set_cloexec
- sdbm_prep
- sdbm_close
- sdbm_fetch
- sdbm_delete
- sdbm_store
- makroom
- sdbm_firstkey
- sdbm_nextkey
- getpage
- getdbit
- setdbit
- getnext
- fitpair
- putpair
- getpair
- duppair
- getnkey
- delpair
- seepair
- splpage
- chkpage
- sdbm_hash
/*
* 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 "ruby/ruby.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "sdbm.h"
/*
* sdbm - ndbm work-alike hashed database library
* tuning and portability constructs [not nearly enough]
* author: oz@nexus.yorku.ca
*/
#define BYTESIZ 8
#ifdef BSD42
#define SEEK_SET L_SET
#define memset(s,c,n) bzero((s), (n)) /* only when c is zero */
#define memcpy(s1,s2,n) bcopy((s2), (s1), (n))
#define memcmp(s1,s2,n) bcmp((s1),(s2),(n))
#endif
/*
* important tuning parms (hah)
*/
#ifndef SEEDUPS
#define SEEDUPS 1 /* always detect duplicates */
#endif
#ifndef BADMESS
#define BADMESS 1 /* generate a message for worst case:
cannot make room after SPLTMAX splits */
#endif
/*
* misc
*/
#ifdef DEBUG
#define debug(x) printf x
#else
#define debug(x)
#endif
#ifdef BIG_E
#define GET_SHORT(p, i) (((unsigned)((unsigned char *)(p))[(i)*2] << 8) + (((unsigned char *)(p))[(i)*2 + 1]))
#define PUT_SHORT(p, i, s) (((unsigned char *)(p))[(i)*2] = (unsigned char)((s) >> 8), ((unsigned char *)(p))[(i)*2 + 1] = (unsigned char)(s))
#else
#define GET_SHORT(p, i) ((p)[(i)])
#define PUT_SHORT(p, i, s) ((p)[(i)] = (s))
#endif
/*#include "pair.h"*/
static int fitpair proto((char *, int));
static void putpair proto((char *, datum, datum));
static datum getpair proto((char *, datum));
static int delpair proto((char *, datum));
static int chkpage proto((char *));
static datum getnkey proto((char *, int));
static void splpage proto((char *, char *, long));
#if SEEDUPS
static int duppair proto((char *, datum));
#endif
#include <stdio.h>
#include <stdlib.h>
#ifdef DOSISH
#include <io.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#ifdef BSD42
#include <sys/file.h>
#else
#include <fcntl.h>
/*#include <memory.h>*/
#endif
#ifndef O_BINARY
#define O_BINARY 0
#endif
#include <errno.h>
#ifndef EPERM
#define EPERM EACCES
#endif
#include <string.h>
#ifdef __STDC__
#include <stddef.h>
#endif
#ifndef NULL
#define NULL 0
#endif
/*
* externals
*/
#if !defined(__sun) && !defined(_WIN32) && !defined(__CYGWIN__) && !defined(errno)
extern int errno;
#endif
/*
* forward
*/
static int getdbit proto((DBM *, long));
static int setdbit proto((DBM *, long));
static int getpage proto((DBM *, long));
static datum getnext proto((DBM *));
static int makroom proto((DBM *, 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 |= DBM_IOERR)
#define OFF_PAG(off) (long) (off) * PBLKSIZ
#define OFF_DIR(off) (long) (off) * DBLKSIZ
static long masks[] = {
000000000000L, 000000000001L, 000000000003L,
000000000007L, 000000000017L, 000000000037L,
000000000077L, 000000000177L, 000000000377L,
000000000777L, 000000001777L, 000000003777L,
000000007777L, 000000017777L, 000000037777L,
000000077777L, 000000177777L, 000000377777L,
000000777777L, 000001777777L, 000003777777L,
000007777777L, 000017777777L, 000037777777L,
000077777777L, 000177777777L, 000377777777L,
000777777777L, 001777777777L, 003777777777L,
007777777777L, 017777777777L
};
datum nullitem = {NULL, 0};
DBM *
sdbm_open(register char *file, register int flags, register int mode)
{
register DBM *db;
register char *dirname;
register char *pagname;
register size_t n;
if (file == NULL || !*file)
return errno = EINVAL, (DBM *) NULL;
/*
* need space for two separate filenames
*/
n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;
if ((dirname = malloc(n)) == NULL)
return errno = ENOMEM, (DBM *) 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;
}
static int
fd_set_cloexec(int fd)
{
/* MinGW don't have F_GETFD and FD_CLOEXEC. [ruby-core:40281] */
#ifdef F_GETFD
int flags, ret;
flags = fcntl(fd, F_GETFD); /* should not fail except EBADF. */
if (flags == -1) {
return -1;
}
if (2 < fd) {
if (!(flags & FD_CLOEXEC)) {
flags |= FD_CLOEXEC;
ret = fcntl(fd, F_SETFD, flags);
if (ret == -1) {
return -1;
}
}
}
#endif
return 0;
}
DBM *
sdbm_prep(char *dirname, char *pagname, int flags, int mode)
{
register DBM *db;
struct stat dstat;
if ((db = (DBM *) malloc(sizeof(DBM))) == NULL)
return errno = ENOMEM, (DBM *) NULL;
db->pagf = -1;
db->dirf = -1;
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 (flags & O_WRONLY)
flags = (flags & ~O_WRONLY) | O_RDWR;
if (flags & O_RDONLY)
db->flags = DBM_RDONLY;
/*
* open the files in sequence, and stat the dirfile.
* If we fail anywhere, undo everything, return NULL.
*/
flags |= O_BINARY;
#ifdef O_CLOEXEC
flags |= O_CLOEXEC;
#endif
if ((db->pagf = open(pagname, flags, mode)) == -1) goto err;
if (fd_set_cloexec(db->pagf) == -1) goto err;
if ((db->dirf = open(dirname, flags, mode)) == -1) goto err;
if (fd_set_cloexec(db->dirf) == -1) goto err;
/*
* need the dirfile size to establish max bit number.
*/
if (fstat(db->dirf, &dstat) == -1) goto err;
/*
* 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 * (long) BYTESIZ;
(void) memset(db->pagbuf, 0, PBLKSIZ);
(void) memset(db->dirbuf, 0, DBLKSIZ);
/*
* success
*/
return db;
err:
if (db->pagf != -1)
(void) close(db->pagf);
if (db->dirf != -1)
(void) close(db->dirf);
free((char *) db);
return (DBM *) NULL;
}
void
sdbm_close(register DBM *db)
{
if (db == NULL)
errno = EINVAL;
else {
(void) close(db->dirf);
(void) close(db->pagf);
free((char *) db);
}
}
datum
sdbm_fetch(register DBM *db, datum key)
{
if (db == NULL || bad(key))
return errno = EINVAL, nullitem;
if (getpage(db, exhash(key)))
return getpair(db->pagbuf, key);
return ioerr(db), nullitem;
}
int
sdbm_delete(register DBM *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 (!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(register DBM *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 == DBM_REPLACE)
(void) delpair(db->pagbuf, key);
#if SEEDUPS
else if (duppair(db->pagbuf, key))
return 1;
#endif
/*
* if we do not have enough room, we have to split.
*/
if (!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) 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(register DBM *db, long int hash, int need)
{
long newp;
char twin[PBLKSIZ];
#if defined _WIN32
char zer[PBLKSIZ];
long oldtail;
#endif
char *pag = db->pagbuf;
char *new = twin;
register int smax = SPLTMAX;
do {
/*
* split the current page
*/
(void) splpage(pag, new, db->hmask + 1);
/*
* address of the new page
*/
newp = (hash & db->hmask) | (db->hmask + 1);
debug(("newp: %ld\n", newp));
/*
* write delay, read avoidance/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 sdbm_store will do so, after it inserts the incoming pair.
*/
#if defined _WIN32
/*
* Fill hole with 0 if made it.
* (hole is NOT read as 0)
*/
oldtail = lseek(db->pagf, 0L, SEEK_END);
memset(zer, 0, PBLKSIZ);
while (OFF_PAG(newp) > oldtail) {
if (lseek(db->pagf, 0L, SEEK_END) < 0 ||
write(db->pagf, zer, PBLKSIZ) < 0) {
return 0;
}
oldtail += PBLKSIZ;
}
#endif
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 (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.
*/
#if BADMESS
(void) (write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44) < 0);
#endif
return 0;
}
/*
* the following two routines will break if
* deletions aren't taken into account. (ndbm bug)
*/
datum
sdbm_firstkey(register DBM *db)
{
if (db == NULL)
return errno = EINVAL, nullitem;
/*
* start at page 0
*/
(void) memset(db->pagbuf, 0, PBLKSIZ);
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(register DBM *db)
{
if (db == NULL)
return errno = EINVAL, nullitem;
return getnext(db);
}
/*
* all important binary trie traversal
*/
static int
getpage(register DBM *db, register long int 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 & ((long) 1 << hbit++)) ? 2 : 1);
debug(("dbit: %ld...", 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.
*/
(void) memset(db->pagbuf, 0, PBLKSIZ);
if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
|| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
return 0;
if (!chkpage(db->pagbuf)) {
return 0;
}
db->pagbno = pagb;
debug(("pag read: %ld\n", pagb));
}
return 1;
}
static int
getdbit(register DBM *db, register long int 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: %ld\n", dirb));
}
return db->dirbuf[c % DBLKSIZ] & (1 << (dbit % BYTESIZ));
}
static int
setdbit(register DBM *db, register long int 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: %ld\n", dirb));
}
db->dirbuf[c % DBLKSIZ] |= (1 << (dbit % BYTESIZ));
if (dbit >= db->maxbno)
db->maxbno += (long) 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(register DBM *db)
{
datum key;
for (;;) {
db->keyptr++;
key = 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 (!chkpage(db->pagbuf)) {
break;
}
}
return ioerr(db), nullitem;
}
/* pair.c */
/*
* 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.
*
* page-level routines
*/
#ifndef BSD42
/*#include <memory.h>*/
#endif
#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
/*
* forward
*/
static int seepair proto((char *, int, char *, int));
/*
* page format:
* +------------------------------+
* ino | n | keyoff | datoff | keyoff |
* +------------+--------+--------+
* | datoff | - - - ----> |
* +--------+---------------------+
* | F R E E A R E A |
* +--------------+---------------+
* | <---- - - - | data |
* +--------+-----+----+----------+
* | key | data | key |
* +--------+----------+----------+
*
* calculating the offsets for free area: if the number
* of entries (ino[0]) is zero, the offset to the END of
* the free area is the block size. Otherwise, it is the
* nth (ino[ino[0]]) entry's offset.
*/
static int
fitpair(char *pag, int need)
{
register int n;
register int off;
register int free;
register short *ino = (short *) pag;
off = ((n = GET_SHORT(ino,0)) > 0) ? GET_SHORT(ino,n) : PBLKSIZ;
free = off - (n + 1) * (int)sizeof(short);
need += 2 * (int)sizeof(short);
debug(("free %d need %d\n", free, need));
return need <= free;
}
static void
putpair(char *pag, datum key, datum val)
{
register int n;
register int off;
register short *ino = (short *) pag;
off = ((n = GET_SHORT(ino,0)) > 0) ? GET_SHORT(ino,n) : PBLKSIZ;
/*
* enter the key first
*/
off -= key.dsize;
if (key.dsize)
(void) memcpy(pag + off, key.dptr, key.dsize);
PUT_SHORT(ino,n + 1,off);
/*
* now the data
*/
off -= val.dsize;
if (val.dsize)
(void) memcpy(pag + off, val.dptr, val.dsize);
PUT_SHORT(ino,n + 2,off);
/*
* adjust item count
*/
PUT_SHORT(ino,0,GET_SHORT(ino,0) + 2);
}
static datum
getpair(char *pag, datum key)
{
register int i;
register int n;
datum val;
register short *ino = (short *) pag;
if ((n = GET_SHORT(ino,0)) == 0)
return nullitem;
if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0)
return nullitem;
val.dptr = pag + GET_SHORT(ino,i + 1);
val.dsize = GET_SHORT(ino,i) - GET_SHORT(ino,i + 1);
return val;
}
#if SEEDUPS
static int
duppair(char *pag, datum key)
{
register short *ino = (short *) pag;
return GET_SHORT(ino,0) > 0 &&
seepair(pag, GET_SHORT(ino,0), key.dptr, key.dsize) > 0;
}
#endif
static datum
getnkey(char *pag, int num)
{
datum key;
register int off;
register short *ino = (short *) pag;
num = num * 2 - 1;
if (GET_SHORT(ino,0) == 0 || num > GET_SHORT(ino,0))
return nullitem;
off = (num > 1) ? GET_SHORT(ino,num - 1) : PBLKSIZ;
key.dptr = pag + GET_SHORT(ino,num);
key.dsize = off - GET_SHORT(ino,num);
return key;
}
static int
delpair(char *pag, datum key)
{
register int n;
register int i;
register short *ino = (short *) pag;
if ((n = GET_SHORT(ino,0)) == 0)
return 0;
if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0)
return 0;
/*
* found the key. if it is the last entry
* [i.e. i == n - 1] we just adjust the entry count.
* hard case: move all data down onto the deleted pair,
* shift offsets onto deleted offsets, and adjust them.
* [note: 0 < i < n]
*/
if (i < n - 1) {
register int m;
register char *dst = pag + (i == 1 ? PBLKSIZ : GET_SHORT(ino,i - 1));
register char *src = pag + GET_SHORT(ino,i + 1);
register ptrdiff_t zoo = dst - src;
debug(("free-up %"PRIdPTRDIFF" ", zoo));
/*
* shift data/keys down
*/
m = GET_SHORT(ino,i + 1) - GET_SHORT(ino,n);
#ifdef DUFF
#define MOVB *--dst = *--src
if (m > 0) {
register int loop = (m + 8 - 1) >> 3;
switch (m & (8 - 1)) {
case 0: do {
MOVB; case 7: MOVB;
case 6: MOVB; case 5: MOVB;
case 4: MOVB; case 3: MOVB;
case 2: MOVB; case 1: MOVB;
} while (--loop);
}
}
#else
#ifdef MEMMOVE
memmove(dst-m, src-m, m);
#else
while (m--)
*--dst = *--src;
#endif
#endif
/*
* adjust offset index up
*/
while (i < n - 1) {
PUT_SHORT(ino,i, GET_SHORT(ino,i + 2) + zoo);
i++;
}
}
PUT_SHORT(ino, 0, GET_SHORT(ino, 0) - 2);
return 1;
}
/*
* search for the key in the page.
* return offset index in the range 0 < i < n.
* return 0 if not found.
*/
static int
seepair(char *pag, register int n, register char *key, register int siz)
{
register int i;
register int off = PBLKSIZ;
register short *ino = (short *) pag;
for (i = 1; i < n; i += 2) {
if (siz == off - GET_SHORT(ino,i) &&
memcmp(key, pag + GET_SHORT(ino,i), siz) == 0)
return i;
off = GET_SHORT(ino,i + 1);
}
return 0;
}
static void
splpage(char *pag, char *new, long int sbit)
{
datum key;
datum val;
register int n;
register int off = PBLKSIZ;
char cur[PBLKSIZ];
register short *ino = (short *) cur;
(void) memcpy(cur, pag, PBLKSIZ);
(void) memset(pag, 0, PBLKSIZ);
(void) memset(new, 0, PBLKSIZ);
n = GET_SHORT(ino,0);
for (ino++; n > 0; ino += 2) {
key.dptr = cur + GET_SHORT(ino,0);
key.dsize = off - GET_SHORT(ino,0);
val.dptr = cur + GET_SHORT(ino,1);
val.dsize = GET_SHORT(ino,0) - GET_SHORT(ino,1);
/*
* select the page pointer (by looking at sbit) and insert
*/
(void) putpair((exhash(key) & sbit) ? new : pag, key, val);
off = GET_SHORT(ino,1);
n -= 2;
}
debug(("%d split %d/%d\n", ((short *) cur)[0] / 2,
((short *) new)[0] / 2,
((short *) pag)[0] / 2));
}
/*
* check page sanity:
* number of entries should be something
* reasonable, and all offsets in the index should be in order.
* this could be made more rigorous.
*/
static int
chkpage(char *pag)
{
register int n;
register int off;
register short *ino = (short *) pag;
if ((n = GET_SHORT(ino,0)) < 0 || n > PBLKSIZ / (int)sizeof(short))
return 0;
if (n > 0) {
off = PBLKSIZ;
for (ino++; n > 0; ino += 2) {
if (GET_SHORT(ino,0) > off || GET_SHORT(ino,1) > off ||
GET_SHORT(ino,1) > GET_SHORT(ino,0))
return 0;
off = GET_SHORT(ino,1);
n -= 2;
}
}
return 1;
}
/* hash.c */
/*
* 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. keep it that way.
*
* hashing routine
*/
/*
* polynomial conversion ignoring overflows
* [this seems to work remarkably well, in fact better
* then the ndbm hash function. Replace at your own risk]
* use: 65599 nice.
* 65587 even better.
*/
long
sdbm_hash(register char *str, register int len)
{
register unsigned long n = 0;
#ifdef DUFF
#define HASHC n = *str++ + 65599 * n
if (len > 0) {
register int loop = (len + 8 - 1) >> 3;
switch(len & (8 - 1)) {
case 0: do {
HASHC; case 7: HASHC;
case 6: HASHC; case 5: HASHC;
case 4: HASHC; case 3: HASHC;
case 2: HASHC; case 1: HASHC;
} while (--loop);
}
}
#else
while (len--)
n = ((*str++) & 255) + 65587L * n;
#endif
return n;
}
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