includes/libs/rdbms/database/resultwrapper/ResultWrapper.php

   1 <?php
   2
   3 use Wikimedia\Rdbms\IResultWrapper;
   4
   5 /**
   6  * Result wrapper for grabbing data queried from an IDatabase object
   7  *
   8  * Note that using the Iterator methods in combination with the non-Iterator
   9  * DB result iteration functions may cause rows to be skipped or repeated.
  10  *
  11  * By default, this will use the iteration methods of the IDatabase handle if provided.
  12  * Subclasses can override methods to make it solely work on the result resource instead.
  13  * If no database is provided, and the subclass does not override the DB iteration methods,
  14  * then a RuntimeException will be thrown when iteration is attempted.
  15  *
  16  * The result resource field should not be accessed from non-Database related classes.
  17  * It is database class specific and is stored here to associate iterators with queries.
  18  *
  19  * @ingroup Database
  20  */
  21 class ResultWrapper implements IResultWrapper {
  22         /** @var resource|array|null Optional underlying result handle for subclass usage */
  23         public $result;
  24
  25         /** @var IDatabase|null */
  26         protected $db;
  27
  28         /** @var int */
  29         protected $pos = 0;
  30         /** @var stdClass|null */
  31         protected $currentRow = null;
  32
  33         /**
  34          * Create a row iterator from a result resource and an optional Database object
  35          *
  36          * Only Database-related classes should construct ResultWrapper. Other code may
  37          * use the FakeResultWrapper subclass for convenience or compatibility shims, however.
  38          *
  39          * @param IDatabase|null $db Optional database handle
  40          * @param ResultWrapper|array|resource $result Optional underlying result handle
  41          */
  42         public function __construct( IDatabase $db = null, $result ) {
  43                 $this->db = $db;
  44                 if ( $result instanceof ResultWrapper ) {
  45                         $this->result = $result->result;
  46                 } else {
  47                         $this->result = $result;
  48                 }
  49         }
  50
  51         public function numRows() {
  52                 return $this->getDB()->numRows( $this );
  53         }
  54
  55         public function fetchObject() {
  56                 return $this->getDB()->fetchObject( $this );
  57         }
  58
  59         public function fetchRow() {
  60                 return $this->getDB()->fetchRow( $this );
  61         }
  62
  63         public function seek( $row ) {
  64                 $this->getDB()->dataSeek( $this, $row );
  65         }
  66
  67         public function free() {
  68                 if ( $this->db ) {
  69                         $this->db->freeResult( $this );
  70                         $this->db = null;
  71                 }
  72                 $this->result = null;
  73         }
  74
  75         /**
  76          * @return IDatabase
  77          * @throws RuntimeException
  78          */
  79         private function getDB() {
  80                 if ( !$this->db ) {
  81                         throw new RuntimeException( get_class( $this ) . ' needs a DB handle for iteration.' );
  82                 }
  83
  84                 return $this->db;
  85         }
  86
  87         function rewind() {
  88                 if ( $this->numRows() ) {
  89                         $this->getDB()->dataSeek( $this, 0 );
  90                 }
  91                 $this->pos = 0;
  92                 $this->currentRow = null;
  93         }
  94
  95         function current() {
  96                 if ( is_null( $this->currentRow ) ) {
  97                         $this->next();
  98                 }
  99
 100                 return $this->currentRow;
 101         }
 102
 103         function key() {
 104                 return $this->pos;
 105         }
 106
 107         function next() {
 108                 $this->pos++;
 109                 $this->currentRow = $this->fetchObject();
 110
 111                 return $this->currentRow;
 112         }
 113
 114         function valid() {
 115                 return $this->current() !== false;
 116         }
 117 }