datastore: Add key to datastoreusage command

{Key} is the entry point from which we begin to traverse the
datastore.

Signed-off-by: Peter Neuroth <[email protected]>

lightningd/datastore.c

@@ -298,34 +298,40 @@ static struct command_result *json_datastoreusage(struct command *cmd,
 	const char **k, **key = NULL;
 	struct db_stmt *stmt;
 	const u8 *data;
-	u64 gen;
-	u64 total = 0;
+	u64 gen, total_bytes = 0;
 
-	if (!param(cmd, buffer, params, NULL))
+	if (!param(cmd, buffer, params,
+		   p_opt("key", param_list_or_string, &key),
+		   NULL))
 		return command_param_failed();
 
+	// We ignore an empty key string or key array.
+	if (key && *key[0] == '\0')
+		key = NULL;
+
 	response = json_stream_success(cmd);
-	json_array_start(response, "usage");
-
-	for (stmt = wallet_datastore_first(cmd, cmd->ld->wallet, key, 
+	json_object_start(response, "datastoreusage");
+	json_add_string(response, "key", datastore_key_fmt(tmpctx, key));
+
+	for (stmt = wallet_datastore_first(cmd, cmd->ld->wallet, key,
 					   &k, &data, &gen);
 	     stmt;
-	     stmt = wallet_datastore_next(cmd, cmd->ld->wallet, stmt, 
+	     stmt = wallet_datastore_next(cmd, key, stmt,
 	     				  &k, &data, &gen)) {
-
-		json_object_start(response, NULL);
-		json_array_start(response, "key");
-		for (size_t i = 0; i < tal_count(k); i++)
-			json_add_string(response, NULL, k[i]);
-		json_array_end(response);
-		json_add_u64(response, "size", tal_bytelen(data));
-		json_object_end(response);
-		total = tal_bytelen(data) + total;
+
+		u64 self_bytes = tal_bytelen(data);
+
+		// We use the formatted datastore key to calculate the size of
+		// the key to account for the delimiter byte in the database.
+		self_bytes += strlen(datastore_key_fmt(tmpctx, k)) - 2;
+
+		total_bytes += self_bytes;
 	};
 	tal_free(stmt);
 
-	json_array_end(response);
-	json_add_u64(response, "total", total);
+	json_add_u64(response, "total_bytes", total_bytes);
+	json_object_end(response);
+
 	return command_success(cmd, response);
 }
 
@@ -357,6 +363,6 @@ static const struct json_command datastoreusage_command = {
 	"datastoreusage",
 	"utility",
 	json_datastoreusage,
-	"List the datastore usage, similar to unix du",
+	"List the datastore usage, starting from an optional {key}",
 };
 AUTODATA(json_command, &datastoreusage_command);