Convert escapers to singletons (#239)

src/Spout/Common/Escaper/ODS.php

@@ -2,6 +2,8 @@
 
 namespace Box\Spout\Common\Escaper;
 
+use Box\Spout\Common\Singleton;
+
 /**
  * Class ODS
  * Provides functions to escape and unescape data for ODS files
@@ -10,6 +12,8 @@ namespace Box\Spout\Common\Escaper;
  */
 class ODS implements EscaperInterface
 {
+    use Singleton;
+
     /**
      * Escapes the given string to make it compatible with XLSX
      *

src/Spout/Common/Escaper/XLSX.php

@@ -2,6 +2,8 @@
 
 namespace Box\Spout\Common\Escaper;
 
+use Box\Spout\Common\Singleton;
+
 /**
  * Class XLSX
  * Provides functions to escape and unescape data for XLSX files
@@ -10,13 +12,15 @@ namespace Box\Spout\Common\Escaper;
  */
 class XLSX implements EscaperInterface
 {
+    use Singleton;
+
     /** @var string[] Control characters to be escaped */
     protected $controlCharactersEscapingMap;
 
     /**
-     *
+     * Initializes the singleton instance
      */
-    public function __construct()
+    protected function init()
     {
         $this->controlCharactersEscapingMap = $this->getControlCharactersEscapingMap();
     }

src/Spout/Common/Helper/EncodingHelper.php

@@ -59,7 +59,7 @@ class EncodingHelper
     {
         $byteOffsetToSkipBom = 0;
 
-        if ($this->hasBom($filePointer, $encoding)) {
+        if ($this->hasBOM($filePointer, $encoding)) {
             $bomUsed = $this->supportedEncodingsWithBom[$encoding];
 
             // we skip the N first bytes

src/Spout/Common/Singleton.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Box\Spout\Common;
+
+/**
+ * Class Singleton
+ * Defines a class as a singleton.
+ *
+ * @package Box\Spout\Common
+ */
+trait Singleton
+{
+    protected static $instance;
+
+    /**
+     * @return static
+     */
+    final public static function getInstance()
+    {
+        return isset(static::$instance)
+            ? static::$instance
+            : static::$instance = new static;
+    }
+
+    /**
+     * Singleton constructor.
+     */
+    final private function __construct()
+    {
+        $this->init();
+    }
+
+    /**
+     * Initializes the singleton
+     * @return void
+     */
+    protected function init() {}
+
+    final private function __wakeup() {}
+    final private function __clone() {}
+}