add lazy-loading to Jig

When working with Jig/Mapper and processing a lot of records, this lazy-mode boosts the performance. A load & save of 5000 records took me about 3min to complete. With lazy-mode it's only 4sec. But notice that lazy-mode could easier produce race-conditions or data loss on higher frequent applications. Perhaps a mutex lock can help here later.

db/jig.php

@@ -41,7 +41,9 @@ class Jig {
 		//! Jig log
 		$log,
 		//! Memory-held data
-		$data;
+		$data,
+		//! lazy load/save files
+		$lazy;
 
 	/**
 	*	Read data from memory/file
@@ -54,6 +56,8 @@ function &read($file) {
 				$this->data[$file]=[];
 			return $this->data[$file];
 		}
+		if ($this->lazy && isset($this->data[$file]))
+			return $this->data[$file];
 		$fw=\Base::instance();
 		$raw=$fw->read($dst);
 		switch ($this->format) {
@@ -75,7 +79,7 @@ function &read($file) {
 	*	@param $data array
 	**/
 	function write($file,array $data=NULL) {
-		if (!$this->dir)
+		if (!$this->dir || $this->lazy)
 			return count($this->data[$file]=$data);
 		$fw=\Base::instance();
 		switch ($this->format) {
@@ -131,6 +135,8 @@ function jot($frame) {
 	*	@return NULL
 	**/
 	function drop() {
+		if ($this->lazy) // intentional
+			$this->data=[];
 		if (!$this->dir)
 			$this->data=[];
 		elseif ($glob=@glob($this->dir.'/*',GLOB_NOSORT))
@@ -147,11 +153,23 @@ private function __clone() {
 	*	@param $dir string
 	*	@param $format int
 	**/
-	function __construct($dir=NULL,$format=self::FORMAT_JSON) {
+	function __construct($dir=NULL,$format=self::FORMAT_JSON,$lazy=FALSE) {
 		if ($dir && !is_dir($dir))
 			mkdir($dir,\Base::MODE,TRUE);
 		$this->uuid=\Base::instance()->hash($this->dir=$dir);
 		$this->format=$format;
+		$this->lazy=$lazy;
+	}
+
+	/**
+	*	save file on destruction
+	**/
+	function __destruct() {
+		if ($this->lazy) {
+			$this->lazy = FALSE;
+			foreach ($this->data as $file => $data)
+				$this->write($file,$data);
+		}
 	}
 
 }