settings: zms: load only subtree in the argument

If the subtree argument is not NULL in the settings_load function, load
only the setting entry that corresponds to that subtree.
If the subtree argument is NULL or it is not found in the storage, load
all the existing entries in the storage.

Signed-off-by: Riadh Ghaddab <[email protected]>

Author: rghaddab

subsys/settings/include/settings/settings_zms.h

@@ -71,7 +71,8 @@ extern "C" {
 #define ZMS_NAME_ID_FROM_LL_NODE(x) (x & ~BIT(0))
 #define ZMS_UPDATE_COLLISION_NUM(x, y)                                                             \
 	((x & ~ZMS_COLLISIONS_MASK) | ((y << 1) & ZMS_COLLISIONS_MASK))
-#define ZMS_COLLISION_NUM(x) ((x & ZMS_COLLISIONS_MASK) >> 1)
+#define ZMS_COLLISION_NUM(x)     ((x & ZMS_COLLISIONS_MASK) >> 1)
+#define ZMS_NAME_ID_FROM_HASH(x) ((x & ZMS_HASH_TOTAL_MASK) | BIT(31))
 
 struct settings_zms {
 	struct settings_store cf_store;

subsys/settings/src/settings_zms.c

@@ -207,7 +207,41 @@ static int settings_zms_load(struct settings_store *cs, const struct settings_lo
 	ssize_t rc1;
 	ssize_t rc2;
 	uint32_t ll_hash_id;
+	uint32_t name_hash;
+
+	/* If arg->subtree is not null we must load settings in that subtree */
+	if (arg->subtree != NULL) {
+		name_hash = sys_hash32(arg->subtree, strlen(arg->subtree)) & ZMS_HASH_MASK;
+		for (int i = 0; i <= cf->hash_collision_num; i++) {
+			name_hash = ZMS_UPDATE_COLLISION_NUM(name_hash, i);
+			/* Get the name entry from ZMS */
+			rc1 = zms_read(&cf->cf_zms, ZMS_NAME_ID_FROM_HASH(name_hash), &name,
+				       sizeof(name) - 1);
+			/* get the length of data and verify that it exists */
+			rc2 = zms_get_data_length(&cf->cf_zms, ZMS_NAME_ID_FROM_HASH(name_hash) +
+								       ZMS_DATA_ID_OFFSET);
+			if ((rc1 <= 0) || (rc2 <= 0)) {
+				/* Name or data doesn't exist */
+				continue;
+			}
+			/* Found a name, this might not include a trailing \0 */
+			name[rc1] = '\0';
+			if (strcmp(arg->subtree, name)) {
+				/* Names are not equal let's continue to the next collision hash
+				 * if it exists.
+				 */
+				continue;
+			}
+			/* At this steps the names are equal, let's set the handler */
+			read_fn_arg.fs = &cf->cf_zms;
+			read_fn_arg.id = ZMS_NAME_ID_FROM_HASH(name_hash) + ZMS_DATA_ID_OFFSET;
 
+			ret = settings_call_set_handler(arg->subtree, rc2, settings_zms_read_fn,
+							&read_fn_arg, (void *)arg);
+			return ret;
+		}
+	}
+	/* If subtree is NULL then we must load all found Settings */
 	ret = zms_read(&cf->cf_zms, ZMS_LL_HEAD_HASH_ID, &settings_element,
 		       sizeof(struct settings_hash_linked_list));
 	if (ret < 0) {