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/*
* This file is part of the sn package.
* Distribution of sn is covered by the GNU GPL. See file COPYING.
* Copyright 1998-2000 Harold Tay.
* Copyright 2000- Patrik Rdman.
*/
/*
* Disk based persistent hash table, like gdbm.
*
* This is specifically for the news system. The keys are message
* ids, the values are {newsgroup, serial number} tuples.
*
* The table is static in size. There a 3 files: ".table" is the hash
* table proper. It contains an array of chain "pointers". The
* other 2 files are handled by allo_*(). ".chain" is an arena of
* chain structures; ".newsgroup" contains all newsgroups.
*
* Supported opertions are insert, delete, and search.
*
* Requires allocate.c to allocate space on a disk file (".chain")
* for data.
*/
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/types.h>
#include <sys/time.h>
#include "config.h"
#include "allocate.h" /* Save ids and chains */
#include "dhash.h"
#include "newsgroup.h" /* Save newsgroup names */
#include <out.h>
#include <nap.h>
static const char ver_ctrl_id[] = "$Id: dhash.c 56 2004-07-27 16:54:48Z patrik $";
extern char dh_tablefile[];
extern char dh_chainfile[];
extern char dh_groupfile[];
extern struct table *dh_table;
extern unsigned dhhash (char *);
extern struct chain *dhlocatechain (char *);
extern bool dh_isreadonly;
extern int dhlock(void);
extern int dhunlock(void);
static char *inttochar2 (int integer)
{
static unsigned char buf[2];
buf[0] = (integer & 0xffff) >> 8;
buf[1] = integer & 0xff;
return ((char *) buf);
}
static char *inttochar3 (unsigned integer)
{
static unsigned char buf[3];
integer >>= 2; /* last 2 bits will be 0 */
buf[0] = (integer & 0xffffff) >> 16;
buf[1] = (integer & 0xffff) >> 8;
buf[2] = integer & 0xff;
return ((char *) buf);
}
int dh_insert (struct data *dp)
{
struct chain *chp;
unsigned h;
int off;
int len;
if (dh_isreadonly)
{
errno = EPERM;
return -1;
}
/* Search first; if found, cannot insert. */
if (dhlock() == -1)
return -1;
chp = dhlocatechain(dp->messageid);
while (chp != NULL)
{
unsigned index;
if (strcmp(dp->messageid, chp->messageid) == 0)
{
dhunlock();
errno = EEXIST;
return -1;
}
index = (unsigned) chp->next;
if (index == 0)
break;
chp = allo_deref(index);
if (chp == NULL)
{
LOG("dh_insert:bad deref in chain for \"<%s>\" during search", dp->messageid);
break;
}
}
len = sizeof (struct chain) + strlen(dp->messageid) + 1 - sizeof (chp->messageid);
off = allo_make(len);
chp = allo_deref(off);
if (chp == NULL)
{
LOG("dh_insert:allo_make gave bad allo_deref");
dhunlock();
return -1;
}
chp->serial = dp->serial;
strcpy(chp->messageid, dp->messageid);
{
int ident;
ident = ng_ident(dp->newsgroup);
if (-1 == ident)
if (-1 == (ident = ng_addgroup(dp->newsgroup)))
return -1;
memcpy(chp->newsgroup, inttochar2(ident), 2);
}
/*
* If someone searches before
* dh_table->next[h] is updated, they just will miss the new one.
* Readers don't need to lock, not even LOCK_SH. The worst that
* can come of this is, someone else has just inserted the same
* object, and we have two of them instead of one.
*/
h = dhhash(dp->messageid);
{
unsigned char *x = dh_table->next + h * 3;
chp->next = char3toint(x);
memcpy(x, inttochar3(off), 3);
}
dhunlock();
return 0;
}
int dh_delete (struct data *dp)
{
struct chain *oldchp = NULL;
struct chain *chp;
if (dh_isreadonly)
{
errno = EPERM;
return -1;
}
if (dhlock() == -1)
return -1;
chp = dhlocatechain(dp->messageid);
if (chp == NULL)
goto fail;
while (strcmp(chp->messageid, dp->messageid) != 0)
{
unsigned index = chp->next;
if (index == 0)
goto fail;
oldchp = chp;
chp = allo_deref(index);
if (chp == NULL)
{
LOG2("dh_delete:dereferencing bad offset");
goto fail;
}
}
*chp->messageid = '\0';
if (oldchp != NULL)
oldchp->next = chp->next;
else
{
unsigned i = chp->next;
unsigned h = dhhash(dp->messageid);
memcpy(dh_table->next + h * 3, inttochar3(i), 3);
}
allo_free(allo_ref(chp), sizeof (struct chain) + strlen(dp->messageid) + 1 - sizeof (chp->messageid));
dhunlock();
return 0;
fail:
dhunlock();
return -1; /* Not found */
}
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