Added locally_change_current_dir

dlib/misc_api.h

@@ -14,5 +14,7 @@
 #include "misc_api/posix.h"
 #endif
 
+#include "misc_api/misc_api_shared.h"
+
 #endif // DLIB_MISC_APi_
 

dlib/misc_api/misc_api_kernel_abstract.h

@@ -59,6 +59,41 @@ namespace dlib
               to change the current working directory.
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    class locally_change_current_dir : noncopyable
+    {
+        /*!
+            WHAT THIS OBJECT REPRESENTS
+                This object is a RAII tool for safely switching the current directory
+                to a new directory and then automatically switching back to the original
+                directory upon this object's destruction.
+        !*/
+    public:
+        explicit locally_change_current_dir (
+            const std::string& new_dir
+        );
+        /*!
+            ensures
+                - calls set_current_dir(new_dir)
+                - #old_dir() == The value of get_current_dir() prior to switching to new_dir.
+        !*/
+
+        const std::string& old_dir (
+        ) const;
+        /*!
+            ensures
+                - returns the directory we switch back to once this object is destructed.
+        !*/
+
+        ~locally_change_current_dir(
+        );
+        /*!
+            ensures
+                - calls set_current_dir(old_dir())
+        !*/
+    };
+
 // ----------------------------------------------------------------------------------------
 
     class dir_create_error : public error { 

dlib/misc_api/misc_api_shared.h

@@ -0,0 +1,45 @@
+// Copyright (C) 2014  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_MISC_API_ShARED_H__
+#define DLIB_MISC_API_ShARED_H__
+
+#include <string>
+#include "../noncopyable.h"
+
+namespace dlib
+{
+
+// ----------------------------------------------------------------------------------------
+
+    class locally_change_current_dir : noncopyable
+    {
+    public:
+        explicit locally_change_current_dir (
+            const std::string& new_dir
+        )
+        {
+            _old_dir = get_current_dir();
+            set_current_dir(new_dir);
+        }
+
+        ~locally_change_current_dir()
+        {
+            set_current_dir(_old_dir);
+        }
+
+        const std::string& old_dir (
+        ) const 
+        {
+            return _old_dir;
+        }
+
+    private:
+        std::string _old_dir;
+    };
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_MISC_API_ShARED_H__
+