From cff59487ae60fe5c8e509a4ee0fc373ba18604a8 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@bnl.gov>
Date: Tue, 9 Jul 2013 18:21:13 -0400
Subject: [PATCH] shared_vector freeze and thaw

---
 pvDataApp/misc/sharedVector.h    | 36 ++++++++++++++++++++++++++++++++
 testApp/pv/testPVScalarArray.cpp |  4 +---
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/pvDataApp/misc/sharedVector.h b/pvDataApp/misc/sharedVector.h
index d932b19..bc90ae8 100644
--- a/pvDataApp/misc/sharedVector.h
+++ b/pvDataApp/misc/sharedVector.h
@@ -670,6 +670,42 @@ const_shared_vector_cast(const shared_vector<const TYPE>& src)
             src.dataCount());
 }
 
+/** @brief transform a shared_vector<T> to shared_vector<const T>
+ *
+ * Transform a reference to mutable data into a reference to read-only data.
+ * Throws an exception unless the reference to mutable data is unique.
+ * On success the reference to mutable data is cleared.
+ */
+template<typename SRC>
+static FORCE_INLINE
+shared_vector<typename meta::decorate_const<typename SRC::value_type>::type>
+freeze(SRC& src)
+{
+    if(!src.unique())
+        throw std::runtime_error("Can't freeze non-unique vector");
+    typedef typename meta::decorate_const<typename SRC::value_type>::type const_value;
+    shared_vector<const_value> ret(src);
+    src.clear();
+    return ret;
+}
+
+/** @brief transform a shared_vector<const T> to shared_vector<T>
+ *
+ * Transform a reference to read-only data into a unique reference to mutable data.
+ *
+ * The reference to read-only data is cleared.
+ */
+template<typename SRC>
+static FORCE_INLINE
+shared_vector<typename meta::strip_const<typename SRC::value_type>::type>
+thaw(SRC& src)
+{
+    typedef typename meta::strip_const<typename SRC::value_type>::type value;
+    shared_vector<value> ret(const_shared_vector_cast<value>(src));
+    src.clear();
+    ret.make_unique();
+    return ret;
+}
 
 
 namespace ScalarTypeFunc {
diff --git a/testApp/pv/testPVScalarArray.cpp b/testApp/pv/testPVScalarArray.cpp
index 54f3fb8..e5de290 100644
--- a/testApp/pv/testPVScalarArray.cpp
+++ b/testApp/pv/testPVScalarArray.cpp
@@ -133,9 +133,7 @@ static void testBasic()
 
     testOk1(idata.at(1)==10);
 
-    PVIntArray::svector wdata(const_shared_vector_cast<int32>(idata));
-    idata.clear();
-    wdata.make_unique();
+    PVIntArray::svector wdata(thaw(idata));
 
     wdata.at(1) = 42;