includes/utils/MappedIterator.php

   1 <?php
   2 /**
   3  * Convenience class for generating iterators from iterators.
   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  * @author Aaron Schulz
  22  */
  23
  24 /**
  25  * Convenience class for generating iterators from iterators.
  26  *
  27  * @since 1.21
  28  */
  29 class MappedIterator extends FilterIterator {
  30         /** @var callable */
  31         protected $vCallback;
  32         /** @var callable */
  33         protected $aCallback;
  34         /** @var array */
  35         protected $cache = array();
  36
  37         protected $rewound = false; // boolean; whether rewind() has been called
  38
  39         /**
  40          * Build an new iterator from a base iterator by having the former wrap the
  41          * later, returning the result of "value" callback for each current() invocation.
  42          * The callback takes the result of current() on the base iterator as an argument.
  43          * The keys of the base iterator are reused verbatim.
  44          *
  45          * An "accept" callback can also be provided which will be called for each value in
  46          * the base iterator (post-callback) and will return true if that value should be
  47          * included in iteration of the MappedIterator (otherwise it will be filtered out).
  48          *
  49          * @param Iterator|Array $iter
  50          * @param callable $vCallback Value transformation callback
  51          * @param array $options Options map (includes "accept") (since 1.22)
  52          * @throws MWException
  53          */
  54         public function __construct( $iter, $vCallback, array $options = array() ) {
  55                 if ( is_array( $iter ) ) {
  56                         $baseIterator = new ArrayIterator( $iter );
  57                 } elseif ( $iter instanceof Iterator ) {
  58                         $baseIterator = $iter;
  59                 } else {
  60                         throw new MWException( "Invalid base iterator provided." );
  61                 }
  62                 parent::__construct( $baseIterator );
  63                 $this->vCallback = $vCallback;
  64                 $this->aCallback = isset( $options['accept'] ) ? $options['accept'] : null;
  65         }
  66
  67         public function next() {
  68                 $this->cache = array();
  69                 parent::next();
  70         }
  71
  72         public function rewind() {
  73                 $this->rewound = true;
  74                 $this->cache = array();
  75                 parent::rewind();
  76         }
  77
  78         public function accept() {
  79                 $value = call_user_func( $this->vCallback, $this->getInnerIterator()->current() );
  80                 $ok = ( $this->aCallback ) ? call_user_func( $this->aCallback, $value ) : true;
  81                 if ( $ok ) {
  82                         $this->cache['current'] = $value;
  83                 }
  84
  85                 return $ok;
  86         }
  87
  88         public function key() {
  89                 $this->init();
  90
  91                 return parent::key();
  92         }
  93
  94         public function valid() {
  95                 $this->init();
  96
  97                 return parent::valid();
  98         }
  99
 100         public function current() {
 101                 $this->init();
 102                 if ( parent::valid() ) {
 103                         return $this->cache['current'];
 104                 } else {
 105                         return null; // out of range
 106                 }
 107         }
 108
 109         /**
 110          * Obviate the usual need for rewind() before using a FilterIterator in a manual loop
 111          */
 112         protected function init() {
 113                 if ( !$this->rewound ) {
 114                         $this->rewind();
 115                 }
 116         }
 117 }