X-Git-Url: http://git.polytechnique.org/?a=blobdiff_plain;f=classes%2Fpliteratorutils.php;h=dfa8a36fabd91b016a67f27d0afd2cc1935e82be;hb=5d0c351e87013f73d7176d55814dc650f91a2939;hp=0d67ac5b03ce4b6da7c8cb273e4a707125405e87;hpb=e8ddc3f28701273de2b5c0f822146ab2a39dea91;p=platal.git

diff --git a/classes/pliteratorutils.php b/classes/pliteratorutils.php
index 0d67ac5..dfa8a36 100644
--- a/classes/pliteratorutils.php
+++ b/classes/pliteratorutils.php
@@ -1,6 +1,6 @@
 <?php
 /***************************************************************************
- *  Copyright (C) 2003-2009 Polytechnique.org                              *
+ *  Copyright (C) 2003-2010 Polytechnique.org                              *
  *  http://opensource.polytechnique.org/                                   *
  *                                                                         *
  *  This program is free software; you can redistribute it and/or modify   *
@@ -59,9 +59,64 @@ class PlIteratorUtils
     {
         return new PlMergeIterator($iterators, $callback, $sorted);
     }
-}
 
 
+    /** Build an iterator that contains only the elements of the given iterator that
+     * match the given condition. The condition should be a callback that takes an element
+     * and returns a boolean.
+     * @param iterator The source iterator
+     * @param callback The condition
+     * @return an iterator
+     */
+    public static function filter(PlIterator $iterator, $callback)
+    {
+        return new PlFilterIterator($iterator, $callback);
+    }
+
+
+    /** Build an iterator that transforms the element of another iterator. The callback
+     * takes an element and transform it into another one. Be careful: if the result
+     * of the callback is null, the iteration ends.
+     * @param iterator The source iterator
+     * @param callback The transformer.
+     */
+    public static function map(PlIterator $iterator, $callback)
+    {
+        return new PlMapIterator($iterator, $callback);
+    }
+
+    /** Build an iterator whose values are iterators too; such a 'subIterator' will end
+     * when the value of $callback changes
+     * @param iterator The source iterator
+     * @param callback The callback for detecting changes.
+     * @return an iterator
+     */
+    public static function subIterator(PlIterator $iterator, $callback)
+    {
+        return new SubIterator($iterator, $callback);
+    }
+
+    /** Returns the callback for '$x -> $x[$key]';
+     * @param $key the index to retrieve in arrays
+     * @return a callback
+     */
+    public static function arrayValueCallback($key)
+    {
+        $callback = new _GetArrayValueCallback($key);
+        return array($callback, 'get');
+    }
+
+    /** Returns the callback for '$x -> $x->prop';
+     * @param $property The property to retrieve
+     * @return a callback
+     */
+    public static function objectPropertyCallback($property)
+    {
+        $callback = new _GetObjectPropertyCallback($property);
+        return array($callback, 'get');
+    }
+}
+
 /** Iterates over an array.
  */
 class PlArrayIterator implements PlIterator
@@ -259,5 +314,268 @@ class PlMergeIterator implements PlIterator
     }
 }
 
+
+class PlFilterIterator implements PlIterator {
+    private $source;
+    private $callback;
+    private $element;
+    private $start;
+
+    public function __construct(PlIterator $source, $callback)
+    {
+        $this->source = $source;
+        $this->callback = $callback;
+        $this->start = true;
+        $this->element = null;
+    }
+
+    private function fetchNext()
+    {
+        do {
+            $current = $this->source->next();
+            if (!$current) {
+                $this->element = null;
+                $this->start   = false;
+                return;
+            }
+            $res = call_user_func($this->callback, $current);
+            if ($res) {
+                $this->element = $current;
+                return;
+            }
+        } while (true);
+    }
+
+    public function next()
+    {
+        if ($this->element && $this->start) {
+            $this->start = false;
+        }
+        $elt = $this->element;
+        if ($elt) {
+            $this->fetchNext();
+        }
+        return $elt;
+    }
+
+    public function total()
+    {
+        /* This is an approximation since the correct total
+         * cannot be computed without fetching all the elements
+         */
+        return $this->source->total();
+    }
+
+    public function first()
+    {
+        return $this->start;
+    }
+
+    public function last()
+    {
+        return !$this->start && !$this->element;
+    }
+}
+
+
+class PlMapIterator implements PlIterator
+{
+    private $source;
+    private $callback;
+
+    public function __construct(PlIterator $source, $callback)
+    {
+        $this->source = $source;
+        $this->callback = $callback;
+    }
+
+    public function next()
+    {
+        $elt = $this->source->next();
+        if ($elt) {
+            return call_user_func($this->callback, $elt);
+        } else {
+            return null;
+        }
+    }
+
+    public function total()
+    {
+        return $this->source->total();
+    }
+
+    public function first()
+    {
+        return $this->source->first();
+    }
+
+    public function last()
+    {
+        return $this->source->last();
+    }
+}
+
+class PlSubIterator implements PlIterator
+{
+    private $source;
+    private $callback;
+    private $next = null; // The next item, if it has been fetched too early by a subiterator
+
+    public function __construct(PlIterator $source, $callback)
+    {
+        $this->source = $source;
+        $this->callback = $callback;
+    }
+
+    public function next()
+    {
+        if ($this->last()) {
+            return null;
+        } else {
+            return new PlInnerSubIterator($this->source, $this->callback, $this, $this->next);
+        }
+    }
+
+    /** This will always be a too big number, but the actual result can't be easily computed
+     */
+    public function total()
+    {
+        return $this->source->total();
+    }
+
+    public function last()
+    {
+        return ($this->source->last() && $this->next == null);
+    }
+
+    public function first()
+    {
+        return $this->source->first();
+    }
+
+    // Called by a subiterator to "rewind" the core iterator
+    public function setNext($item)
+    {
+        $this->next = $item;
+    }
+}
+
+class PlInnerSubIterator implements PlIterator
+{
+    private $source;
+    private $callback;
+    private $parent;
+
+    private $next; // Not null if the source has to be "rewinded"
+
+    private $curval = null;
+    private $curelt = null;
+    private $stepped = false;
+    private $over = false;
+
+    public function __construct(PlIterator $source, $callback, PlSubIterator $parent, $next = null)
+    {
+        $this->source = $source;
+        $this->callback = $callback;
+        $this->parent = $parent;
+        $this->next = $next;
+    }
+
+    public function value()
+    {
+        $this->_step();
+        return $this->curval;
+    }
+
+    // Move one step, if the current element has been used
+    private function _step()
+    {
+        if ($this->stepped) {
+            return;
+        }
+
+        if ($this->next != null) {
+            $this->curelt = $this->next;
+            $this->next = null;
+        } else {
+            $elt = $this->source->next();
+        }
+        $this->stepped = true;
+    }
+
+    public function next()
+    {
+        $this->_step();
+        $this->stepped = false;
+
+        if ($this->elt) {
+            $val = call_user_func($this->callback, $this->elt);
+            if ($val == $this->curval) {
+                $this->curval = $val;
+                return $this->elt;
+            } else {
+                $this->parent->setNext($this->elt);
+            }
+        }
+        $this->over = true;
+        return null;
+    }
+
+    /** This will always be a too big number, but the actual result can't be easily computed
+     */
+    public function total()
+    {
+        return $this->source->total();
+    }
+
+    public function last()
+    {
+        return $this->over;
+    }
+
+    public function first()
+    {
+        return false;
+    }
+
+}
+
+// Wrapper class for 'arrayValueCallback' (get field $key of the given array)
+class _GetArrayValueCallback
+{
+    private $key;
+
+    public function __construct($key)
+    {
+        $this->key = $key;
+    }
+
+    public function get(array $arr)
+    {
+        if (array_key_exists($this->key, $arr)) {
+            return $arr[$this->key];
+        } else {
+            return null;
+        }
+    }
+}
+
+// Wrapper class for 'objectPropertyCallback' (get property ->$blah of the given object)
+class _GetObjectPropertyCallback
+{
+    private $property;
+
+    public function __construct($property)
+    {
+        $this->property = $property;
+    }
+
+    public function get($obj)
+    {
+        $p = $this->property;
+        return @$obj->$p;
+    }
+}
+
 // vim:set et sw=4 sts=4 sws=4 foldmethod=marker enc=utf-8:
 ?>