lib/gencache.c

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/* 
   Unix SMB/CIFS implementation.

   Generic, persistent and shared between processes cache mechanism for use
   by various parts of the Samba code

   Copyright (C) Rafal Szczesniak    2002
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

#undef  DBGC_CLASS
#define DBGC_CLASS DBGC_TDB

#define TIMEOUT_LEN 12
#define CACHE_DATA_FMT  "%12u/%s"
#define READ_CACHE_DATA_FMT_TEMPLATE "%%12u/%%%us"

static TDB_CONTEXT *cache;
static BOOL cache_readonly;

/**
 * @file gencache.c
 * @brief Generic, persistent and shared between processes cache mechanism
 *        for use by various parts of the Samba code
 *
 **/


/**
 * Cache initialisation function. Opens cache tdb file or creates
 * it if does not exist.
 *
 * @return true on successful initialisation of the cache or
 *         false on failure
 **/

BOOL gencache_init(void)
{
        char* cache_fname = NULL;
        
        /* skip file open if it's already opened */
        if (cache) return True;

        cache_fname = lock_path("gencache.tdb");

        DEBUG(5, ("Opening cache file at %s\n", cache_fname));

        cache = tdb_open_log(cache_fname, 0, TDB_DEFAULT,
                             O_RDWR|O_CREAT, 0644);

        if (!cache && (errno == EACCES)) {
                cache = tdb_open_log(cache_fname, 0, TDB_DEFAULT, O_RDONLY, 0644);
                if (cache) {
                        cache_readonly = True;
                        DEBUG(5, ("gencache_init: Opening cache file %s read-only.\n", cache_fname));
                }
        }

        if (!cache) {
                DEBUG(5, ("Attempt to open gencache.tdb has failed.\n"));
                return False;
        }
        return True;
}


/**
 * Cache shutdown function. Closes opened cache tdb file.
 *
 * @return true on successful closing the cache or
 *         false on failure during cache shutdown
 **/
 
BOOL gencache_shutdown(void)
{
        int ret;
        /* tdb_close routine returns -1 on error */
        if (!cache) return False;
        DEBUG(5, ("Closing cache file\n"));
        ret = tdb_close(cache);
        cache = NULL;
        cache_readonly = False;
        return ret != -1;
}


/**
 * Set an entry in the cache file. If there's no such
 * one, then add it.
 *
 * @param keystr string that represents a key of this entry
 * @param value text representation value being cached
 * @param timeout time when the value is expired
 *
 * @retval true when entry is successfuly stored
 * @retval false on failure
 **/
 
BOOL gencache_set(const char *keystr, const char *value, time_t timeout)
{
        int ret;
        TDB_DATA keybuf, databuf;
        char* valstr = NULL;
        
        /* fail completely if get null pointers passed */
        SMB_ASSERT(keystr && value);

        if (!gencache_init()) return False;
        
        if (cache_readonly) {
                return False;
        }

        asprintf(&valstr, CACHE_DATA_FMT, (int)timeout, value);
        if (!valstr)
                return False;

        keybuf.dptr = CONST_DISCARD(char *, keystr);
        keybuf.dsize = strlen(keystr)+1;
        databuf.dptr = valstr;
        databuf.dsize = strlen(valstr)+1;
        DEBUG(10, ("Adding cache entry with key = %s; value = %s and timeout ="
                   " %s (%d seconds %s)\n", keybuf.dptr, value,ctime(&timeout),
                   (int)(timeout - time(NULL)), 
                   timeout > time(NULL) ? "ahead" : "in the past"));

        ret = tdb_store(cache, keybuf, databuf, 0);
        SAFE_FREE(valstr);
        
        return ret == 0;
}

/**
 * Delete one entry from the cache file.
 *
 * @param keystr string that represents a key of this entry
 *
 * @retval true upon successful deletion
 * @retval false in case of failure
 **/

BOOL gencache_del(const char *keystr)
{
        int ret;
        TDB_DATA keybuf;
        
        /* fail completely if get null pointers passed */
        SMB_ASSERT(keystr);

        if (!gencache_init()) return False;     
        
        if (cache_readonly) {
                return False;
        }

        keybuf.dptr = CONST_DISCARD(char *, keystr);
        keybuf.dsize = strlen(keystr)+1;
        DEBUG(10, ("Deleting cache entry (key = %s)\n", keystr));
        ret = tdb_delete(cache, keybuf);
        
        return ret == 0;
}


/**
 * Get existing entry from the cache file.
 *
 * @param keystr string that represents a key of this entry
 * @param valstr buffer that is allocated and filled with the entry value
 *        buffer's disposing must be done outside
 * @param timeout pointer to a time_t that is filled with entry's
 *        timeout
 *
 * @retval true when entry is successfuly fetched
 * @retval False for failure
 **/

BOOL gencache_get(const char *keystr, char **valstr, time_t *timeout)
{
        TDB_DATA keybuf, databuf;
        time_t t;
        char *endptr;

        /* fail completely if get null pointers passed */
        SMB_ASSERT(keystr);

        if (!gencache_init()) {
                return False;
        }
        
        keybuf.dptr = CONST_DISCARD(char *, keystr);
        keybuf.dsize = strlen(keystr)+1;
        databuf = tdb_fetch(cache, keybuf);

        if (databuf.dptr == NULL) {
                DEBUG(10, ("Cache entry with key = %s couldn't be found\n",
                           keystr));
                return False;
        }

        t = strtol(databuf.dptr, &endptr, 10);

        if ((endptr == NULL) || (*endptr != '/')) {
                DEBUG(2, ("Invalid gencache data format: %s\n", databuf.dptr));
                SAFE_FREE(databuf.dptr);
                return False;
        }

        DEBUG(10, ("Returning %s cache entry: key = %s, value = %s, "
                   "timeout = %s", t > time(NULL) ? "valid" :
                   "expired", keystr, endptr+1, ctime(&t)));

        if (t <= time(NULL)) {

                /* We're expired, delete the entry */
                tdb_delete(cache, keybuf);

                SAFE_FREE(databuf.dptr);
                return False;
        }

        if (valstr) {
                *valstr = SMB_STRDUP(endptr+1);
                if (*valstr == NULL) {
                        SAFE_FREE(databuf.dptr);
                        DEBUG(0, ("strdup failed\n"));
                        return False;
                }
        }
        
        SAFE_FREE(databuf.dptr);

        if (timeout) {
                *timeout = t;
        }

        return True;
} 


/**
 * Iterate through all entries which key matches to specified pattern
 *
 * @param fn pointer to the function that will be supplied with each single
 *        matching cache entry (key, value and timeout) as an arguments
 * @param data void pointer to an arbitrary data that is passed directly to the fn
 *        function on each call
 * @param keystr_pattern pattern the existing entries' keys are matched to
 *
 **/

void gencache_iterate(void (*fn)(const char* key, const char *value, time_t timeout, void* dptr),
                      void* data, const char* keystr_pattern)
{
        TDB_LIST_NODE *node, *first_node;
        TDB_DATA databuf;
        char *keystr = NULL, *valstr = NULL, *entry = NULL;
        time_t timeout = 0;
        int status;
        unsigned u;

        /* fail completely if get null pointers passed */
        SMB_ASSERT(fn && keystr_pattern);

        if (!gencache_init()) return;

        DEBUG(5, ("Searching cache keys with pattern %s\n", keystr_pattern));
        node = tdb_search_keys(cache, keystr_pattern);
        first_node = node;
        
        while (node) {
                char *fmt;

                /* ensure null termination of the key string */
                keystr = SMB_STRNDUP(node->node_key.dptr, node->node_key.dsize);
                if (!keystr) {
                        break;
                }
                
                /* 
                 * We don't use gencache_get function, because we need to iterate through
                 * all of the entries. Validity verification is up to fn routine.
                 */
                databuf = tdb_fetch(cache, node->node_key);
                if (!databuf.dptr || databuf.dsize <= TIMEOUT_LEN) {
                        SAFE_FREE(databuf.dptr);
                        SAFE_FREE(keystr);
                        node = node->next;
                        continue;
                }
                entry = SMB_STRNDUP(databuf.dptr, databuf.dsize);
                if (!entry) {
                        SAFE_FREE(databuf.dptr);
                        SAFE_FREE(keystr);
                        break;
                }

                SAFE_FREE(databuf.dptr);

                valstr = (char *)SMB_MALLOC(databuf.dsize + 1 - TIMEOUT_LEN);
                if (!valstr) {
                        SAFE_FREE(entry);
                        SAFE_FREE(keystr);
                        break;
                }

                asprintf(&fmt, READ_CACHE_DATA_FMT_TEMPLATE, (unsigned int)databuf.dsize - TIMEOUT_LEN);
                if (!fmt) {
                        SAFE_FREE(valstr);
                        SAFE_FREE(entry);
                        SAFE_FREE(keystr);
                        break;
                }
                status = sscanf(entry, fmt, &u, valstr);
                SAFE_FREE(fmt);

                if ( status != 2 ) {
                        DEBUG(0,("gencache_iterate: invalid return from sscanf %d\n",status));
                }
                timeout = u;
                
                DEBUG(10, ("Calling function with arguments (key = %s, value = %s, timeout = %s)\n",
                           keystr, valstr, ctime(&timeout)));
                fn(keystr, valstr, timeout, data);
                
                SAFE_FREE(valstr);
                SAFE_FREE(entry);
                SAFE_FREE(keystr);
                node = node->next;
        }
        
        tdb_search_list_free(first_node);
}

/********************************************************************
 lock a key
********************************************************************/

int gencache_lock_entry( const char *key )
{
        if (!gencache_init())
                return -1;
        
        return tdb_lock_bystring(cache, key);
}

/********************************************************************
 unlock a key
********************************************************************/

void gencache_unlock_entry( const char *key )
{
        if (!gencache_init())
                return;
        
        tdb_unlock_bystring(cache, key);
        return;
}

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