add filesystem fopen

src/Storm/FileSystem/Abstract.php

@@ -55,4 +55,7 @@ abstract class Storm_FileSystem_Abstract {
   abstract public function readfile(string $path);
 
   abstract public function mkdir($path);
+
+  abstract public function fopen(string $filename, string $mode, bool $use_include_path=false, $context=null);
+
 }

src/Storm/FileSystem/Disk.php

@@ -92,6 +92,14 @@ class Storm_FileSystem_Disk extends Storm_FileSystem_Abstract {
   }
 
 
+  public function fopen(string $filename,
+                        string $mode,
+                        bool $use_include_path=false,
+                        $context=null) {
+    return fopen($filename, $mode, $use_include_path, $context);
+  }
+
+
   public function directoryNamesAt($path) {
     if (!file_exists($path) || !is_readable($path) )
       return [];

src/Storm/FileSystem/Volatile.php

@@ -147,6 +147,20 @@ class Storm_FileSystem_Volatile extends Storm_FileSystem_Abstract {
   }
 
 
+  public function fopen(string $filename,
+                        string $mode,
+                        bool $use_include_path=false,
+                        $context=null) {
+    if (null === ($file_content = $this->fileGetContents($filename)))
+      return false;
+
+    $content = fopen('php://memory', 'r+');
+    fwrite($content, $file_content);
+    rewind($content);
+    return $content;
+  }
+
+
   public function asPath($path) {
     return (new Storm_FileSystem_Volatile_Path($path, $this->_current_directory));
   }