From 70a16c7d47a687b8bf31b0b710af4f7aca30f4c2 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 12 Apr 2019 16:40:17 +1000
Subject: [PATCH] scoped: add optional reset modifier

---
 CMakeLists.txt  |  1 +
 scoped.hpp      |  7 ++++++-
 test/scoped.cpp | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 test/scoped.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 01b354ee..3aa150c6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -625,6 +625,7 @@ if (TESTS)
         rational
         region
         roots/bisection
+        scoped
         signal
         singleton
         stream
diff --git a/scoped.hpp b/scoped.hpp
index 9481b840..45731b24 100644
--- a/scoped.hpp
+++ b/scoped.hpp
@@ -25,10 +25,15 @@ namespace cruft::scoped {
 
         ~restore ()
         {
-            m_target = m_value;
+            if (m_restore)
+                m_target = m_value;
         }
 
+        /// Disable restoration of the value.
+        void reset (void) { m_restore = false; }
+
     private:
+        bool m_restore = true;
         ValueT &m_target;
         ValueT const m_value;
     };
diff --git a/test/scoped.cpp b/test/scoped.cpp
new file mode 100644
index 00000000..b041e4d0
--- /dev/null
+++ b/test/scoped.cpp
@@ -0,0 +1,35 @@
+#include "scoped.hpp"
+#include "tap.hpp"
+
+
+///////////////////////////////////////////////////////////////////////////////
+void test_restore (cruft::TAP::logger &tap)
+{
+    int value = 42;
+
+    {
+        cruft::scoped::restore raii (value);
+        tap.expect_eq (value, 42, "restorer constructor doesn't modifier value");
+        value = 7;
+    }
+
+    tap.expect_eq (value, 42, "restorer restores value at destruction");
+
+
+    {
+        cruft::scoped::restore raii (value);
+        value = 7;
+        raii.reset ();
+    }
+
+    tap.expect_eq (value, 7, "restorer reset doesn't modify value at destruction");
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+int main ()
+{
+    cruft::TAP::logger tap;
+    test_restore (tap);
+    return tap.status ();
+}
\ No newline at end of file