From 672b4b27d81ad4de17385fde67b3fb3ccd694a2e Mon Sep 17 00:00:00 2001
From: Davis King <davis@dlib.net>
Date: Sat, 26 Apr 2014 15:35:45 -0400
Subject: [PATCH] Added locally_change_current_dir

---
 dlib/misc_api.h                          |  2 ++
 dlib/misc_api/misc_api_kernel_abstract.h | 35 ++++++++++++++++++
 dlib/misc_api/misc_api_shared.h          | 45 ++++++++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 dlib/misc_api/misc_api_shared.h

diff --git a/dlib/misc_api.h b/dlib/misc_api.h
index df4f73011..acf87be7c 100644
--- a/dlib/misc_api.h
+++ b/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_
 
diff --git a/dlib/misc_api/misc_api_kernel_abstract.h b/dlib/misc_api/misc_api_kernel_abstract.h
index 1e2ff1d47..103aa6612 100644
--- a/dlib/misc_api/misc_api_kernel_abstract.h
+++ b/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 { 
diff --git a/dlib/misc_api/misc_api_shared.h b/dlib/misc_api/misc_api_shared.h
new file mode 100644
index 000000000..8826c2d0f
--- /dev/null
+++ b/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__
+