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DEFINITIONS
This source file includes following definitions.
- database_cleanup
- prep
- APU_DECLARE
- APU_DECLARE
- APU_DECLARE
- write_page
- APU_DECLARE
- APU_DECLARE
- makroom
- read_from
- APU_DECLARE
- APU_DECLARE
- getpage
- getdbit
- setdbit
- getnext
- APU_DECLARE
/* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* sdbm - ndbm work-alike hashed database library
* based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
* author: oz@nexus.yorku.ca
* ex-public domain, ported to APR for Apache 2
* core routines
*/
#include "apr.h"
#include "apr_file_io.h"
#include "apr_strings.h"
#include "apr_errno.h"
#include "apr_sdbm.h"
#include "sdbm_tune.h"
#include "sdbm_pair.h"
#include "sdbm_private.h"
#include <string.h> /* for memset() */
#include <stdlib.h> /* for malloc() and free() */
/*
* forward
*/
static int getdbit (apr_sdbm_t *, long);
static apr_status_t setdbit(apr_sdbm_t *, long);
static apr_status_t getpage(apr_sdbm_t *db, long);
static apr_status_t getnext(apr_sdbm_datum_t *key, apr_sdbm_t *db);
static apr_status_t makroom(apr_sdbm_t *, long, int);
/*
* useful macros
*/
#define bad(x) ((x).dptr == NULL || (x).dsize <= 0)
#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
#define OFF_PAG(off) (apr_off_t) (off) * PBLKSIZ
#define OFF_DIR(off) (apr_off_t) (off) * DBLKSIZ
static const 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
};
const apr_sdbm_datum_t sdbm_nullitem = { NULL, 0 };
static apr_status_t database_cleanup(void *data)
{
apr_sdbm_t *db = data;
/*
* Can't rely on apr_sdbm_unlock, since it will merely
* decrement the refcnt if several locks are held.
*/
if (db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK))
(void) apr_file_unlock(db->dirf);
(void) apr_file_close(db->dirf);
(void) apr_file_close(db->pagf);
free(db);
return APR_SUCCESS;
}
static apr_status_t prep(apr_sdbm_t **pdb, const char *dirname, const char *pagname,
apr_int32_t flags, apr_fileperms_t perms, apr_pool_t *p)
{
apr_sdbm_t *db;
apr_status_t status;
*pdb = NULL;
db = malloc(sizeof(*db));
memset(db, 0, sizeof(*db));
db->pool = p;
/*
* adjust user flags so that WRONLY becomes RDWR,
* as required by this package. Also set our internal
* flag for RDONLY if needed.
*/
if (!(flags & APR_WRITE)) {
db->flags |= SDBM_RDONLY;
}
/*
* adjust the file open flags so that we handle locking
* on our own (don't rely on any locking behavior within
* an apr_file_t, in case it's ever introduced, and set
* our own flag.
*/
if (flags & APR_SHARELOCK) {
db->flags |= SDBM_SHARED;
flags &= ~APR_SHARELOCK;
}
flags |= APR_BINARY | APR_READ;
/*
* open the files in sequence, and stat the dirfile.
* If we fail anywhere, undo everything, return NULL.
*/
if ((status = apr_file_open(&db->dirf, dirname, flags, perms, p))
!= APR_SUCCESS)
goto error;
if ((status = apr_file_open(&db->pagf, pagname, flags, perms, p))
!= APR_SUCCESS)
goto error;
if ((status = apr_sdbm_lock(db, (db->flags & SDBM_RDONLY)
? APR_FLOCK_SHARED
: APR_FLOCK_EXCLUSIVE))
!= APR_SUCCESS)
goto error;
/* apr_pcalloc zeroed the buffers
* apr_sdbm_lock stated the dirf->size and invalidated the cache
*/
/*
* if we are opened in SHARED mode, unlock ourself
*/
if (db->flags & SDBM_SHARED)
if ((status = apr_sdbm_unlock(db)) != APR_SUCCESS)
goto error;
/* make sure that we close the database at some point */
apr_pool_cleanup_register(p, db, database_cleanup, apr_pool_cleanup_null);
/* Done! */
*pdb = db;
return APR_SUCCESS;
error:
if (db->dirf && db->pagf)
(void) apr_sdbm_unlock(db);
if (db->dirf != NULL)
(void) apr_file_close(db->dirf);
if (db->pagf != NULL) {
(void) apr_file_close(db->pagf);
}
free(db);
return status;
}
APU_DECLARE(apr_status_t) apr_sdbm_open(apr_sdbm_t **db, const char *file,
apr_int32_t flags,
apr_fileperms_t perms, apr_pool_t *p)
{
char *dirname = apr_pstrcat(p, file, APR_SDBM_DIRFEXT, NULL);
char *pagname = apr_pstrcat(p, file, APR_SDBM_PAGFEXT, NULL);
return prep(db, dirname, pagname, flags, perms, p);
}
APU_DECLARE(apr_status_t) apr_sdbm_close(apr_sdbm_t *db)
{
return apr_pool_cleanup_run(db->pool, db, database_cleanup);
}
APU_DECLARE(apr_status_t) apr_sdbm_fetch(apr_sdbm_t *db, apr_sdbm_datum_t *val,
apr_sdbm_datum_t key)
{
apr_status_t status;
if (db == NULL || bad(key))
return APR_EINVAL;
if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
return status;
if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
*val = getpair(db->pagbuf, key);
/* ### do we want a not-found result? */
}
(void) apr_sdbm_unlock(db);
return status;
}
static apr_status_t write_page(apr_sdbm_t *db, const char *buf, long pagno)
{
apr_status_t status;
apr_off_t off = OFF_PAG(pagno);
if ((status = apr_file_seek(db->pagf, APR_SET, &off)) == APR_SUCCESS)
status = apr_file_write_full(db->pagf, buf, PBLKSIZ, NULL);
return status;
}
APU_DECLARE(apr_status_t) apr_sdbm_delete(apr_sdbm_t *db,
const apr_sdbm_datum_t key)
{
apr_status_t status;
if (db == NULL || bad(key))
return APR_EINVAL;
if (apr_sdbm_rdonly(db))
return APR_EINVAL;
if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
return status;
if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
if (!delpair(db->pagbuf, key))
/* ### should we define some APRUTIL codes? */
status = APR_EGENERAL;
else
status = write_page(db, db->pagbuf, db->pagbno);
}
(void) apr_sdbm_unlock(db);
return status;
}
APU_DECLARE(apr_status_t) apr_sdbm_store(apr_sdbm_t *db, apr_sdbm_datum_t key,
apr_sdbm_datum_t val, int flags)
{
int need;
register long hash;
apr_status_t status;
if (db == NULL || bad(key))
return APR_EINVAL;
if (apr_sdbm_rdonly(db))
return APR_EINVAL;
need = key.dsize + val.dsize;
/*
* is the pair too big (or too small) for this database ??
*/
if (need < 0 || need > PAIRMAX)
return APR_EINVAL;
if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
return status;
if ((status = getpage(db, (hash = exhash(key)))) == APR_SUCCESS) {
/*
* if we need to replace, delete the key/data pair
* first. If it is not there, ignore.
*/
if (flags == APR_SDBM_REPLACE)
(void) delpair(db->pagbuf, key);
else if (!(flags & APR_SDBM_INSERTDUP) && duppair(db->pagbuf, key)) {
status = APR_EEXIST;
goto error;
}
/*
* if we do not have enough room, we have to split.
*/
if (!fitpair(db->pagbuf, need))
if ((status = makroom(db, hash, need)) != APR_SUCCESS)
goto error;
/*
* we have enough room or split is successful. insert the key,
* and update the page file.
*/
(void) putpair(db->pagbuf, key, val);
status = write_page(db, db->pagbuf, db->pagbno);
}
error:
(void) apr_sdbm_unlock(db);
return status;
}
/*
* makroom - make room by splitting the overfull page
* this routine will attempt to make room for SPLTMAX times before
* giving up.
*/
static apr_status_t makroom(apr_sdbm_t *db, long hash, int need)
{
long newp;
char twin[PBLKSIZ];
char *pag = db->pagbuf;
char *new = twin;
register int smax = SPLTMAX;
apr_status_t status;
do {
/*
* split the current page
*/
(void) 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 sdbm_store will do so, after it inserts the incoming pair.
*/
if (hash & (db->hmask + 1)) {
if ((status = write_page(db, db->pagbuf, db->pagbno))
!= APR_SUCCESS)
return status;
db->pagbno = newp;
(void) memcpy(pag, new, PBLKSIZ);
}
else {
if ((status = write_page(db, new, newp)) != APR_SUCCESS)
return status;
}
if ((status = setdbit(db, db->curbit)) != APR_SUCCESS)
return status;
/*
* see if we have enough room now
*/
if (fitpair(pag, need))
return APR_SUCCESS;
/*
* 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 ((status = write_page(db, db->pagbuf, db->pagbno))
!= APR_SUCCESS)
return status;
} while (--smax);
/*
* if we are here, this is real bad news. After SPLTMAX splits,
* we still cannot fit the key. say goodnight.
*/
#if 0
(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
#endif
/* ### ENOSPC not really appropriate but better than nothing */
return APR_ENOSPC;
}
/* Reads 'len' bytes from file 'f' at offset 'off' into buf.
* 'off' is given relative to the start of the file.
* If EOF is returned while reading, this is taken as success.
*/
static apr_status_t read_from(apr_file_t *f, void *buf,
apr_off_t off, apr_size_t len)
{
apr_status_t status;
if ((status = apr_file_seek(f, APR_SET, &off)) != APR_SUCCESS ||
((status = apr_file_read_full(f, buf, len, NULL)) != APR_SUCCESS)) {
/* if EOF is reached, pretend we read all zero's */
if (status == APR_EOF) {
memset(buf, 0, len);
status = APR_SUCCESS;
}
}
return status;
}
/*
* the following two routines will break if
* deletions aren't taken into account. (ndbm bug)
*/
APU_DECLARE(apr_status_t) apr_sdbm_firstkey(apr_sdbm_t *db,
apr_sdbm_datum_t *key)
{
apr_status_t status;
if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
return status;
/*
* start at page 0
*/
if ((status = read_from(db->pagf, db->pagbuf, OFF_PAG(0), PBLKSIZ))
== APR_SUCCESS) {
db->pagbno = 0;
db->blkptr = 0;
db->keyptr = 0;
status = getnext(key, db);
}
(void) apr_sdbm_unlock(db);
return status;
}
APU_DECLARE(apr_status_t) apr_sdbm_nextkey(apr_sdbm_t *db,
apr_sdbm_datum_t *key)
{
apr_status_t status;
if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
return status;
status = getnext(key, db);
(void) apr_sdbm_unlock(db);
return status;
}
/*
* all important binary tree traversal
*/
static apr_status_t getpage(apr_sdbm_t *db, long hash)
{
register int hbit;
register long dbit;
register long pagb;
apr_status_t status;
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.
* ### joe: this assumption was surely never correct? but
* ### we make it so in read_from anyway.
*/
if ((status = read_from(db->pagf, db->pagbuf, OFF_PAG(pagb), PBLKSIZ))
!= APR_SUCCESS)
return status;
if (!chkpage(db->pagbuf))
return APR_ENOSPC; /* ### better error? */
db->pagbno = pagb;
debug(("pag read: %d\n", pagb));
}
return APR_SUCCESS;
}
static int getdbit(apr_sdbm_t *db, long dbit)
{
register long c;
register long dirb;
c = dbit / BYTESIZ;
dirb = c / DBLKSIZ;
if (dirb != db->dirbno) {
if (read_from(db->dirf, db->dirbuf, OFF_DIR(dirb), DBLKSIZ)
!= APR_SUCCESS)
return 0;
db->dirbno = dirb;
debug(("dir read: %d\n", dirb));
}
return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
}
static apr_status_t setdbit(apr_sdbm_t *db, long dbit)
{
register long c;
register long dirb;
apr_status_t status;
apr_off_t off;
c = dbit / BYTESIZ;
dirb = c / DBLKSIZ;
if (dirb != db->dirbno) {
if ((status = read_from(db->dirf, db->dirbuf, OFF_DIR(dirb), DBLKSIZ))
!= APR_SUCCESS)
return status;
db->dirbno = dirb;
debug(("dir read: %d\n", dirb));
}
db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
if (dbit >= db->maxbno)
db->maxbno += DBLKSIZ * BYTESIZ;
off = OFF_DIR(dirb);
if ((status = apr_file_seek(db->dirf, APR_SET, &off)) == APR_SUCCESS)
status = apr_file_write_full(db->dirf, db->dirbuf, DBLKSIZ, NULL);
return status;
}
/*
* getnext - get the next key in the page, and if done with
* the page, try the next page in sequence
*/
static apr_status_t getnext(apr_sdbm_datum_t *key, apr_sdbm_t *db)
{
apr_status_t status;
for (;;) {
db->keyptr++;
*key = getnkey(db->pagbuf, db->keyptr);
if (key->dptr != NULL)
return APR_SUCCESS;
/*
* 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++) {
apr_off_t off = OFF_PAG(db->blkptr);
if ((status = apr_file_seek(db->pagf, APR_SET, &off))
!= APR_SUCCESS)
return status;
}
db->pagbno = db->blkptr;
/* ### EOF acceptable here too? */
if ((status = apr_file_read_full(db->pagf, db->pagbuf, PBLKSIZ, NULL))
!= APR_SUCCESS)
return status;
if (!chkpage(db->pagbuf))
return APR_EGENERAL; /* ### need better error */
}
/* NOTREACHED */
}
APU_DECLARE(int) apr_sdbm_rdonly(apr_sdbm_t *db)
{
/* ### Should we return true if the first lock is a share lock,
* to reflect that apr_sdbm_store and apr_sdbm_delete will fail?
*/
return (db->flags & SDBM_RDONLY) != 0;
}