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Diffstat (limited to 'common/once.js')
-rw-r--r-- | common/once.js | 74 |
1 files changed, 0 insertions, 74 deletions
diff --git a/common/once.js b/common/once.js deleted file mode 100644 index 01216bd..0000000 --- a/common/once.js +++ /dev/null @@ -1,74 +0,0 @@ -/** - * This file is part of Haketilo. - * - * Function: Wrap APIs that depend on some asynchronous initialization into - * promises. - * - * Copyright (C) 2021 Wojtek Kosior - * - * 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. - * - * As additional permission under GNU GPL version 3 section 7, you - * may distribute forms of that code without the copy of the GNU - * GPL normally required by section 4, provided you include this - * license notice and, in case of non-source distribution, a URL - * through which recipients can access the Corresponding Source. - * If you modify file(s) with this exception, you may extend this - * exception to your version of the file(s), but you are not - * obligated to do so. If you do not wish to do so, delete this - * exception statement from your version. - * - * As a special exception to the GPL, any HTML file which merely - * makes function calls to this code, and for that purpose - * includes it by reference shall be deemed a separate work for - * copyright law purposes. If you modify this code, you may extend - * this exception to your version of the code, but you are not - * obligated to do so. If you do not wish to do so, delete this - * exception statement from your version. - * - * You should have received a copy of the GNU General Public License - * along with this program. If not, see <https://www.gnu.org/licenses/>. - * - * I, Wojtek Kosior, thereby promise not to sue for violation of this file's - * license. Although I request that you do not make use of this code in a - * proprietary program, I am not going to enforce this in court. - */ - -/* - * This module provides an easy way to wrap an async function into a promise - * so that it only gets executed once. - */ - -async function assign_result(state, result_producer) -{ - state.result = await result_producer(); - state.ready = true; - for (let cb of state.waiting) - setTimeout(cb, 0, state.result); - state.waiting = undefined; -} - -async function get_result(state) -{ - if (state.ready) - return state.result; - - return new Promise((resolve, reject) => state.waiting.push(resolve)); -} - -function make_once(result_producer) -{ - let state = {waiting : [], ready : false, result : undefined}; - assign_result(state, result_producer); - return () => get_result(state); -} - -#EXPORT make_once |