lib/filestorage/file_progress.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * Simple interface for receiving progress during long-running file
  19  * operations.
  20  *
  21  * In some cases progress can be reported precisely. In other cases,
  22  * progress is indeterminate which means that the progress function is called
  23  * periodically but without information on completion.
  24  *
  25  * @package core_files
  26  * @copyright 2013 The Open University
  27  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  28  */
  29 interface file_progress {
  30     /**
  31      * @var int Constant used for indeterminate progress.
  32      */
  33     const INDETERMINATE = -1;
  34
  35     /**
  36      * Called during a file processing operation that reports progress.
  37      *
  38      * This function will be called periodically during the operation, assuming
  39      * it is successful.
  40      *
  41      * The $max value will be the same for each call to progress() within an
  42      * operation.
  43      *
  44      * If numbers (rather than INDETERMINATE) are provided, then:
  45      * - The $progress value will either be the same as last call, or increased
  46      *   by some value (not necessarily 1)
  47      * - The $progress value will be less than or equal to the $max value.
  48      *
  49      * There is no guarantee that this function will be called for every value
  50      * in the range, or that it will be called with $progress == $max.
  51      *
  52      * The function may be called very frequently (e.g. after each file) or
  53      * quite rarely (e.g. after each large file).
  54      *
  55      * When creating an implementation of this function, you probably want to
  56      * do the following:
  57      *
  58      * 1. Check the current time and do not do anything if it's less than a
  59      *    second since the last time you reported something.
  60      * 2. Update the PHP timeout (i.e. set it back to 2 minutes or whatever)
  61      *    so that the system will not time out.
  62      * 3. If the progress is unchanged since last second, still display some
  63      *    output to the user. (Setting PHP timeout is not sufficient; some
  64      *    front-end servers require that data is output to the browser every
  65      *    minute or so, or they will time out on their own.)
  66      *
  67      * @param int $progress Current progress, or INDETERMINATE if unknown
  68      * @param int $max Max progress, or INDETERMINATE if unknown
  69      */
  70     public function progress($progress = self::INDETERMINATE, $max = self::INDETERMINATE);
  71 }