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   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  }