includes/ScopedPHPTimeout.php

   1 <?php
   2 /**
   3  * Expansion of the PHP execution time limit feature for a function call.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * Class to expand PHP execution time for a function call.
  25  * On construction, set_time_limit() is called and set to $seconds.
  26  * When the object goes out of scope, the timer is restarted, with
  27  * the original time limit minus the time the object existed.
  28  */
  29 class ScopedPHPTimeout {
  30         protected $startTime; // float; seconds
  31         protected $oldTimeout; // integer; seconds
  32
  33         protected static $stackDepth = 0; // integer
  34         protected static $totalCalls = 0; // integer
  35         protected static $totalElapsed = 0; // float; seconds
  36
  37         /* Prevent callers in infinite loops from running forever */
  38         const MAX_TOTAL_CALLS = 1000000;
  39         const MAX_TOTAL_TIME = 300; // seconds
  40
  41         /**
  42          * @param $seconds integer
  43          */
  44         public function __construct( $seconds ) {
  45                 if ( ini_get( 'max_execution_time' ) > 0 ) { // CLI uses 0
  46                         if ( self::$totalCalls >= self::MAX_TOTAL_CALLS ) {
  47                                 trigger_error( "Maximum invocations of " . __CLASS__ . " exceeded." );
  48                         } elseif ( self::$totalElapsed >= self::MAX_TOTAL_TIME ) {
  49                                 trigger_error( "Time limit within invocations of " . __CLASS__ . " exceeded." );
  50                         } elseif ( self::$stackDepth > 0 ) { // recursion guard
  51                                 trigger_error( "Resursive invocation of " . __CLASS__ . " attempted." );
  52                         } else {
  53                                 $this->oldTimeout = ini_set( 'max_execution_time', $seconds );
  54                                 $this->startTime = microtime( true );
  55                                 ++self::$stackDepth;
  56                                 ++self::$totalCalls; // proof against < 1us scopes
  57                         }
  58                 }
  59         }
  60
  61         /**
  62          * Restore the original timeout.
  63          * This does not account for the timer value on __construct().
  64          */
  65         public function __destruct() {
  66                 if ( $this->oldTimeout ) {
  67                         $elapsed = microtime( true ) - $this->startTime;
  68                         // Note: a limit of 0 is treated as "forever"
  69                         set_time_limit( max( 1, $this->oldTimeout - (int)$elapsed ) );
  70                         // If each scoped timeout is for less than one second, we end up
  71                         // restoring the original timeout without any decrease in value.
  72                         // Thus web scripts in an infinite loop can run forever unless we
  73                         // take some measures to prevent this. Track total time and calls.
  74                         self::$totalElapsed += $elapsed;
  75                         --self::$stackDepth;
  76                 }
  77         }
  78 }