IVGCVSW-4483 Introduce polymorphic_downcast implementation

Change-Id: I958dd719162337eb5c7e71f4ac49dd5784564b1a
Signed-off-by: Derek Lamberti <derek.lamberti@arm.com>

2 files changed, 60 insertions, 0 deletions

diff --git a/include/armnn/Exceptions.hpp b/include/armnn/Exceptions.hpp
index cb62079b76..05b740614d 100644
--- a/include/armnn/Exceptions.hpp
+++ b/include/armnn/Exceptions.hpp
@@ -143,6 +143,13 @@ public:
     using Exception::Exception;
 };
 
+class PolymorphicDowncastException : public Exception
+{
+public:
+    using Exception::Exception;
+};
+
+
 template <typename ExceptionType>
 void ConditionalThrow(bool condition, const std::string& message)
 {
@@ -152,6 +159,16 @@ void ConditionalThrow(bool condition, const std::string& message)
     }
 }
 
+template <typename ExceptionType>
+void ConditionalThrow(bool condition)
+{
+    if (!condition)
+    {
+        throw ExceptionType();
+    }
+}
+
+
 ///
 /// ComparedType must support:
 ///   operator==(const ComparedType&)
diff --git a/include/armnn/utility/PolymorphicDowncast.hpp b/include/armnn/utility/PolymorphicDowncast.hpp
new file mode 100644
index 0000000000..d529867474
--- /dev/null
+++ b/include/armnn/utility/PolymorphicDowncast.hpp
@@ -0,0 +1,43 @@
+//
+// Copyright © 2020 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#pragma once
+
+#include "Assert.hpp"
+
+#include <armnn/Exceptions.hpp>
+
+#include <type_traits>
+
+namespace armnn
+{
+
+// If we are testing then throw an exception, otherwise regular assert
+#if defined(ARMNN_POLYMORPHIC_CAST_TESTABLE)
+#   define ARMNN_POLYMORPHIC_CAST_CHECK_METHOD(cond) ConditionalThrow<std::bad_cast>(cond)
+#else
+#   define ARMNN_POLYMORPHIC_CAST_CHECK_METHOD(cond) ARMNN_ASSERT(cond)
+#endif
+
+//Only check the condition if debug build or during testing
+#if !defined(NDEBUG) || defined(ARMNN_POLYMORPHIC_CAST_TESTABLE)
+#   define ARMNN_POLYMORPHIC_CAST_CHECK(cond)  ARMNN_POLYMORPHIC_CAST_CHECK_METHOD(cond)
+#else
+#   define ARMNN_POLYMORPHIC_CAST_CHECK(cond) // release builds dont check the cast
+#endif
+
+
+template<typename DestType, typename SourceType>
+DestType polymorphic_downcast(SourceType value)
+{
+    static_assert(std::is_pointer<SourceType>::value &&
+                  std::is_pointer<DestType>::value,
+                  "polymorphic_downcast only works with pointer types.");
+
+    ARMNN_POLYMORPHIC_CAST_CHECK(dynamic_cast<DestType>(value) == static_cast<DestType>(value));
+    return static_cast<DestType>(value);
+}
+
+} //namespace armnn
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