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