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101 lines
3.6 KiB
EmacsLisp
101 lines
3.6 KiB
EmacsLisp
;;; url-future.el --- general futures facility for url.el -*- lexical-binding: t -*-
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;; Copyright (C) 2011-2020 Free Software Foundation, Inc.
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;; Author: Teodor Zlatanov <tzz@lifelogs.com>
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;; Keywords: data
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;; This file is part of GNU Emacs.
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;;
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; Make a url-future (basically a defstruct):
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;; (make-url-future :value (lambda () (calculation goes here))
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;; :callback (lambda (future) (use future on success))
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;; :errorback (lambda (future &rest error) (error handler)))
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;; Then either call it with `url-future-call' or cancel it with
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;; `url-future-cancel'. Generally the functions will return the
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;; future itself, not the value it holds. Also the functions will
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;; throw a url-future-already-done error if you try to call or cancel
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;; a future more than once.
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;; So, to get the value:
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;; (when (url-future-completed-p future) (url-future-value future))
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;; See `url-future-tests' and the code below for further details.
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;;; Code:
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(eval-when-compile (require 'cl-lib))
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(cl-defstruct url-future callback errorback status value)
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(define-inline url-future-done-p (url-future)
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(inline-quote (url-future-status ,url-future)))
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(define-inline url-future-completed-p (url-future)
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(inline-quote (eq (url-future-status ,url-future) t)))
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(define-inline url-future-errored-p (url-future)
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(inline-quote (eq (url-future-status ,url-future) 'error)))
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(define-inline url-future-cancelled-p (url-future)
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(inline-quote (eq (url-future-status ,url-future) 'cancel)))
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(defun url-future-finish (url-future &optional status)
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(if (url-future-done-p url-future)
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(signal 'error 'url-future-already-done)
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(setf (url-future-status url-future) (or status t))
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;; the status must be such that the future was completed
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;; to run the callback
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(when (url-future-completed-p url-future)
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(funcall (or (url-future-callback url-future) 'ignore)
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url-future))
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url-future))
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(defun url-future-errored (url-future errorcons)
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(if (url-future-done-p url-future)
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(signal 'error 'url-future-already-done)
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(setf (url-future-status url-future) 'error)
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(setf (url-future-value url-future) errorcons)
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(funcall (or (url-future-errorback url-future) 'ignore)
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url-future errorcons)))
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(defun url-future-call (url-future)
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(if (url-future-done-p url-future)
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(signal 'error 'url-future-already-done)
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(let ((ff (url-future-value url-future)))
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(when (functionp ff)
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(condition-case catcher
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(setf (url-future-value url-future)
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(funcall ff))
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(error (url-future-errored url-future catcher)))
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;; Unused return value.
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;;; (url-future-value url-future)
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))
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(if (url-future-errored-p url-future)
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url-future
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(url-future-finish url-future))))
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(defun url-future-cancel (url-future)
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(if (url-future-done-p url-future)
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(signal 'error 'url-future-already-done)
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(url-future-finish url-future 'cancel)))
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(provide 'url-future)
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;;; url-future.el ends here
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