about summary refs log tree commit diff
path: root/src/libutil/ref.hh
diff options
context:
space:
mode:
authorEelco Dolstra <eelco.dolstra@logicblox.com>2016-02-23T12·53+0100
committerEelco Dolstra <eelco.dolstra@logicblox.com>2016-02-23T12·53+0100
commitc0b7a8a0b576d5fcbcb25c412836dc885b7eb0fe (patch)
treeb4c5e73f52bd27576eba404f2e473db0e54a451e /src/libutil/ref.hh
parent8f71bc33d5af7bc6d4728e5e36e89bcad27d2096 (diff)
Move ref<t> into a separate header
Diffstat (limited to 'src/libutil/ref.hh')
-rw-r--r--src/libutil/ref.hh67
1 files changed, 67 insertions, 0 deletions
diff --git a/src/libutil/ref.hh b/src/libutil/ref.hh
new file mode 100644
index 000000000000..a6d338d79622
--- /dev/null
+++ b/src/libutil/ref.hh
@@ -0,0 +1,67 @@
+#pragma once
+
+#include <memory>
+#include <exception>
+
+namespace nix {
+
+/* A simple non-nullable reference-counted pointer. Actually a wrapper
+   around std::shared_ptr that prevents non-null constructions. */
+template<typename T>
+class ref
+{
+private:
+
+    std::shared_ptr<T> p;
+
+public:
+
+    ref<T>(const ref<T> & r)
+        : p(r.p)
+    { }
+
+    explicit ref<T>(const std::shared_ptr<T> & p)
+        : p(p)
+    {
+        if (!p)
+            throw std::invalid_argument("null pointer cast to ref");
+    }
+
+    T* operator ->() const
+    {
+        return &*p;
+    }
+
+    T& operator *() const
+    {
+        return *p;
+    }
+
+    operator std::shared_ptr<T> ()
+    {
+        return p;
+    }
+
+    template<typename T2>
+    operator ref<T2> ()
+    {
+        return ref<T2>((std::shared_ptr<T2>) p);
+    }
+
+private:
+
+    template<typename T2, typename... Args>
+    friend ref<T2>
+    make_ref(Args&&... args);
+
+};
+
+template<typename T, typename... Args>
+inline ref<T>
+make_ref(Args&&... args)
+{
+    auto p = std::make_shared<T>(std::forward<Args>(args)...);
+    return ref<T>(p);
+}
+
+}