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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "system/time.h"
#include "system/filesys.h"
#include "tdb_wrap.h"
#include "lib/gencache/gencache.h"

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

static struct tdb_wrap *cache;

/**
 * @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(struct loadparm_context *lp_ctx)
{
	char* cache_fname = NULL;
	TALLOC_CTX *mem_ctx = talloc_autofree_context();
	
	/* skip file open if it's already opened */
	if (cache) return true;

	cache_fname = lock_path(mem_ctx, lp_ctx, "gencache.tdb");
	if (cache_fname != NULL) {
		DEBUG(5, ("Opening cache file at %s\n", cache_fname));
	} else {
		DEBUG(0, ("Filename allocation failed.\n"));
		return false;
	}

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

	talloc_free(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)
{
	if (!cache) return false;
	DEBUG(5, ("Closing cache file\n"));
	talloc_free(cache);
	return true;
}


/**
 * 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;
	
	asprintf(&valstr, CACHE_DATA_FMT, (int)timeout, value);
	if (!valstr)
		return false;

	keybuf.dptr = (uint8_t *)strdup(keystr);
	keybuf.dsize = strlen(keystr)+1;
	databuf.dptr = (uint8_t *)strdup(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->tdb, keybuf, databuf, 0);
	SAFE_FREE(valstr);
	SAFE_FREE(keybuf.dptr);
	SAFE_FREE(databuf.dptr);
	
	return ret == 0;
}


/**
 * Set existing entry to the cache file.
 *
 * @param keystr string that represents a key of this entry
 * @param valstr text representation value being cached
 * @param timeout time when the value is expired
 *
 * @retval true when entry is successfuly set
 * @retval false on failure
 **/

bool gencache_set_only(const char *keystr, const char *valstr, time_t timeout)
{
	int ret = -1;
	TDB_DATA keybuf, databuf;
	char *old_valstr, *datastr;
	time_t old_timeout;
	
	/* fail completely if get null pointers passed */
	SMB_ASSERT(keystr && valstr);

	if (!gencache_init()) return false;
			
	/* 
	 * Check whether entry exists in the cache
	 * Don't verify gencache_get exit code, since the entry may be expired
	 */	
	gencache_get(keystr, &old_valstr, &old_timeout);
	
	if (!(old_valstr && old_timeout)) return false;
		
	DEBUG(10, ("Setting cache entry with key = %s; old value = %s and old timeout \
	           = %s\n", keystr, old_valstr, ctime(&old_timeout)));

	asprintf(&datastr, CACHE_DATA_FMT, (int)timeout, valstr);
	keybuf.dptr = (uint8_t *)strdup(keystr);
	keybuf.dsize = strlen(keystr)+1;
	databuf.dptr = (uint8_t *)strdup(datastr);
	databuf.dsize = strlen(datastr)+1;
	DEBUGADD(10, ("New value = %s, new timeout = %s (%d seconds %s)", valstr,
	              ctime(&timeout), (int)(timeout - time(NULL)),
	              timeout > time(NULL) ? "ahead" : "in the past"));

		
	ret = tdb_store(cache->tdb, keybuf, databuf, TDB_REPLACE);

	SAFE_FREE(datastr);
	SAFE_FREE(old_valstr);
	SAFE_FREE(keybuf.dptr);
	SAFE_FREE(databuf.dptr);
	
	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;	
	
	keybuf.dptr = (uint8_t *)strdup(keystr);
	keybuf.dsize = strlen(keystr)+1;
	DEBUG(10, ("Deleting cache entry (key = %s)\n", keystr));
	ret = tdb_delete(cache->tdb, keybuf);
	
	SAFE_FREE(keybuf.dptr);
	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;

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

	if (!gencache_init())
		return false;
	
	keybuf.dptr = (uint8_t *)strdup(keystr);
	keybuf.dsize = strlen(keystr)+1;
	databuf = tdb_fetch(cache->tdb, keybuf);
	SAFE_FREE(keybuf.dptr);
	
	if (databuf.dptr && databuf.dsize > TIMEOUT_LEN) {
		char* entry_buf = strndup((char *)databuf.dptr, databuf.dsize);
		char *v;
		time_t t;
		unsigned i;

		v = malloc_array_p(char, databuf.dsize - TIMEOUT_LEN);
				
		SAFE_FREE(databuf.dptr);
		sscanf(entry_buf, CACHE_DATA_FMT, (int*)&i, v);
		SAFE_FREE(entry_buf);
		t = i;

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

		if (valstr)
			*valstr = v;
		else
			SAFE_FREE(v);

		if (timeout)
			*timeout = t;

		return t > time(NULL);

	} else {
		SAFE_FREE(databuf.dptr);

		if (valstr)
			*valstr = NULL;

		if (timeout)
			timeout = NULL;

		DEBUG(10, ("Cache entry with key = %s couldn't be found\n", 
			   keystr));

		return false;
	}
}


/**
 * 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;
	unsigned i;

	/* 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->tdb, keystr_pattern);
	first_node = node;
	
	while (node) {
		/* ensure null termination of the key string */
		keystr = strndup((char *)node->node_key.dptr, node->node_key.dsize);
		
		/* 
		 * 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->tdb, node->node_key);
		if (!databuf.dptr || databuf.dsize <= TIMEOUT_LEN) {
			SAFE_FREE(databuf.dptr);
			SAFE_FREE(keystr);
			node = node->next;
			continue;
		}
		entry = strndup((char *)databuf.dptr, databuf.dsize);
		SAFE_FREE(databuf.dptr);
		valstr = malloc_array_p(char, databuf.dsize - TIMEOUT_LEN);
		sscanf(entry, CACHE_DATA_FMT, (int*)(&i), valstr);
		timeout = i;
		
		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 )
{
	return tdb_lock_bystring(cache->tdb, key);
}

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

void gencache_unlock_entry( const char *key )
{
	tdb_unlock_bystring(cache->tdb, key);
}