db->pkgcache_loaded and db->grpcache_loaded

Clearly the old code was more elegant (NULL cache indicated "not loaded"),
but it had some drawbacks, so from now on we indicate the state of caches
explicitly.

Old drawbacks:
When we had an empty database (unstable), libalpm called db_populate after
every pkgcache access, because NULL pkgcache indicated "not loaded" state.
This is not a common case, but the same situation can happen with grpcache,
which is more problematic: If the user had a custom repo with no groups,
grpcache was always NULL. (grpcache is also loaded per database.) Thus
every get_grpcache call induced a load_grpcache operation, so the benefits
of grpcache was completely lost.

Signed-off-by: Nagy Gabor <ngaba@bibl.u-szeged.hu>
Signed-off-by: Dan McGee <dan@archlinux.org>

lib/libalpm/cache.c

@@ -54,6 +54,7 @@ int _alpm_db_load_pkgcache(pmdb_t *db)
 		return(-1);
 	}
 
+	db->pkgcache_loaded = 1;
 	return(0);
 }
 
@@ -61,7 +62,7 @@ void _alpm_db_free_pkgcache(pmdb_t *db)
 {
 	ALPM_LOG_FUNC;
 
-	if(db == NULL || db->pkgcache == NULL) {
+	if(db == NULL || !db->pkgcache_loaded) {
 		return;
 	}
 
@@ -71,10 +72,9 @@ void _alpm_db_free_pkgcache(pmdb_t *db)
 	alpm_list_free_inner(db->pkgcache, (alpm_list_fn_free)_alpm_pkg_free);
 	alpm_list_free(db->pkgcache);
 	db->pkgcache = NULL;
+	db->pkgcache_loaded = 0;
 
-	if(db->grpcache) {
 	_alpm_db_free_grpcache(db);
-	}
 }
 
 alpm_list_t *_alpm_db_get_pkgcache(pmdb_t *db)
@@ -85,13 +85,13 @@ alpm_list_t *_alpm_db_get_pkgcache(pmdb_t *db)
 		return(NULL);
 	}
 
-	if(!db->pkgcache) {
+	if(!db->pkgcache_loaded) {
 		_alpm_db_load_pkgcache(db);
 	}
 
 	/* hmmm, still NULL ?*/
 	if(!db->pkgcache) {
-		_alpm_log(PM_LOG_DEBUG, "error: pkgcache is NULL for db '%s'\n", db->treename);
+		_alpm_log(PM_LOG_DEBUG, "warning: pkgcache is NULL for db '%s'\n", db->treename);
 	}
 
 	return(db->pkgcache);
@@ -104,7 +104,7 @@ int _alpm_db_add_pkgincache(pmdb_t *db, pmpkg_t *pkg)
 
 	ALPM_LOG_FUNC;
 
-	if(db == NULL || pkg == NULL) {
+	if(db == NULL || !db->pkgcache_loaded || pkg == NULL) {
 		return(-1);
 	}
 
@@ -139,7 +139,7 @@ int _alpm_db_remove_pkgfromcache(pmdb_t *db, pmpkg_t *pkg)
 
 	ALPM_LOG_FUNC;
 
-	if(db == NULL || pkg == NULL) {
+	if(db == NULL || !db->pkgcache_loaded || pkg == NULL) {
 		return(-1);
 	}
 
@@ -172,7 +172,7 @@ pmpkg_t *_alpm_db_get_pkgfromcache(pmdb_t *db, const char *target)
 
 	alpm_list_t *pkgcache = _alpm_db_get_pkgcache(db);
 	if(!pkgcache) {
-		_alpm_log(PM_LOG_DEBUG, "error: failed to get '%s' from NULL pkgcache\n",
+		_alpm_log(PM_LOG_DEBUG, "warning: failed to get '%s' from NULL pkgcache\n",
 				target);
 		return(NULL);
 	}
@@ -192,10 +192,6 @@ int _alpm_db_load_grpcache(pmdb_t *db)
 		return(-1);
 	}
 
-	if(db->pkgcache == NULL) {
-		_alpm_db_load_pkgcache(db);
-	}
-
 	_alpm_log(PM_LOG_DEBUG, "loading group cache for repository '%s'\n",
 			db->treename);
 
@@ -230,6 +226,7 @@ int _alpm_db_load_grpcache(pmdb_t *db)
 		}
 	}
 
+	db->grpcache_loaded = 1;
 	return(0);
 }
 
@@ -239,15 +236,19 @@ void _alpm_db_free_grpcache(pmdb_t *db)
 
 	ALPM_LOG_FUNC;
 
-	if(db == NULL || db->grpcache == NULL) {
+	if(db == NULL || !db->grpcache_loaded) {
 		return;
 	}
 
+	_alpm_log(PM_LOG_DEBUG, "freeing group cache for repository '%s'\n",
+	                        db->treename);
+
 	for(lg = db->grpcache; lg; lg = lg->next) {
 		_alpm_grp_free(lg->data);
 		lg->data = NULL;
 	}
 	FREELIST(db->grpcache);
+	db->grpcache_loaded = 0;
 }
 
 alpm_list_t *_alpm_db_get_grpcache(pmdb_t *db)
@@ -258,7 +259,7 @@ alpm_list_t *_alpm_db_get_grpcache(pmdb_t *db)
 		return(NULL);
 	}
 
-	if(db->grpcache == NULL) {
+	if(!db->grpcache_loaded) {
 		_alpm_db_load_grpcache(db);
 	}
 

lib/libalpm/db.h

@@ -42,7 +42,9 @@ struct __pmdb_t {
 	char *path;
 	char *treename;
 	void *handle;
+	unsigned short pkgcache_loaded;
 	alpm_list_t *pkgcache;
+	unsigned short grpcache_loaded;
 	alpm_list_t *grpcache;
 	alpm_list_t *servers;
 };