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|null */
  32         protected $aCallback;
  33         /** @var array */
  34         protected $cache = [];
  35
  36         /** @var bool whether rewind() has been called */
  37         protected $rewound = false;
  38
  39         /**
  40          * Build a 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          * @phan-param array{accept?:callable} $options
  53          * @throws UnexpectedValueException
  54          */
  55         public function __construct( $iter, $vCallback, array $options = [] ) {
  56                 if ( is_array( $iter ) ) {
  57                         $baseIterator = new ArrayIterator( $iter );
  58                 } elseif ( $iter instanceof Iterator ) {
  59                         $baseIterator = $iter;
  60                 } else {
  61                         throw new UnexpectedValueException( "Invalid base iterator provided." );
  62                 }
  63                 parent::__construct( $baseIterator );
  64                 $this->vCallback = $vCallback;
  65                 $this->aCallback = $options['accept'] ?? null;
  66         }
  67
  68         public function next(): void {
  69                 $this->cache = [];
  70                 parent::next();
  71         }
  72
  73         public function rewind(): void {
  74                 $this->rewound = true;
  75                 $this->cache = [];
  76                 parent::rewind();
  77         }
  78
  79         public function accept(): bool {
  80                 $inner = $this->getInnerIterator();
  81                 '@phan-var Iterator $inner';
  82                 $value = call_user_func( $this->vCallback, $inner->current() );
  83                 $ok = ( $this->aCallback ) ? call_user_func( $this->aCallback, $value ) : true;
  84                 if ( $ok ) {
  85                         $this->cache['current'] = $value;
  86                 }
  87
  88                 return $ok;
  89         }
  90
  91         #[\ReturnTypeWillChange]
  92         public function key() {
  93                 $this->init();
  94
  95                 return parent::key();
  96         }
  97
  98         public function valid(): bool {
  99                 $this->init();
 100
 101                 return parent::valid();
 102         }
 103
 104         #[\ReturnTypeWillChange]
 105         public function current() {
 106                 $this->init();
 107                 if ( parent::valid() ) {
 108                         return $this->cache['current'];
 109                 } else {
 110                         return null; // out of range
 111                 }
 112         }
 113
 114         /**
 115          * Obviate the usual need for rewind() before using a FilterIterator in a manual loop
 116          */
 117         protected function init() {
 118                 if ( !$this->rewound ) {
 119                         $this->rewind();
 120                 }
 121         }
 122 }