Add function to check if object with given identifier exists

src/SeriousJSON/JsonDatabase.php

@@ -88,6 +88,32 @@ class JsonDatabase implements IJsonUnflattener
         return $retPath;
     }
 
+    public function exists(string $class, string $name, ?int $timestamp = null): bool
+    {
+        if ($class == null || empty(trim($name)))
+            return false;
+        
+        if ($name != null && !empty(trim(strval($name))))
+            $name = JSONDatabase::SanitizeIdentifier($name);
+        else
+            return false;
+        
+        $class = trim($class);
+        
+        if (!$this->audit && $timestamp != null)
+            return false;
+        
+        $objPath = $this->getObjectPath($class, $name, ($timestamp != null));
+
+        if (strlen($objPath) > PHP_MAXPATHLEN)
+            return false;
+
+        if (!is_file($objPath))
+            return false;
+        
+        return true;
+    }
+
     public function load(string $class, string $name, ?int $timestamp = null): JsonSerializable|null
     {
         if ($class == null || empty(trim($name)))

src/SeriousJSON/JsonHistoryItem.php

@@ -1,7 +0,0 @@
-<?php
-
-namespace SeriousJSON;
-
-class JsonHistoryItem extends \SeriousJSON\JsonSerializable implements \SeriousJSON\IJsonIdentifiable {
-
-}