potfur · January 22, 2014 10:32 · Jan 22, 2014
diff --git a/gistfile1.php b/gistfile1.php
@@ -0,0 +1,74 @@
+<?php
+error_reporting(-1);
+
+// reader
+// reads n per call starting from last position til EOF
+$offset = 0;
+$reader = function ($n = 100) use (&$offset) {
+    $limit = $offset + $n;
+    $ln = 0;
+    $content = array();
+
+    $fp = fopen(__DIR__ . '/txt/data.txt', 'r');
+    while (($line = fgets($fp)) && $ln < $limit) {
+        $ln++;
+
+        if($ln < $offset) {
+            continue;
+        }
+
+        $content[$ln] = (int) trim($line);
+    }
+    fclose($fp);
+
+    $offset+=$n;
+    return $content;
+};
+
+// transformer
+// calculates mediane from set block
+$median = function ($block) {
+    sort($block);
+    $m = (int) floor(count($block) / 2);
+   return $m % 2 ? $block[$m] : ($block[$m] + $block[$m-1]) / 2;
+};
+
+// transformer
+// calculates average value from set block
+$average = function($block) {
+    return array_sum($block) / count($block);
+};
+
+// combiner
+// adds transformer result to array
+$combiner = function(array $data, $block) {
+    $data[] = $block;
+    return $data;
+};
+
+// reductor
+// uses reader, transformer and combiner to reduce input data
+function reductor($reader, $transformer, $combiner) {
+    if (!is_callable($reader)) {
+        throw new \InvalidArgumentException('Reader must be callable');
+    }
+
+    if (!is_callable($transformer)) {
+        throw new \InvalidArgumentException('Transformer must be callable');
+    }
+
+    if (!is_callable($combiner)) {
+        throw new \InvalidArgumentException('Combiner must be callable');
+    }
+
+    $data = array();
+
+    while ($block = $reader()) {
+        $block = $transformer($block);
+        $data = $combiner($data, $block);
+    }
+
+    return $data;
+}
+
+var_dump(reductor($reader, $median, $combiner));