From 4d4e0e2530629ae9ecfcb379bf0f27c6b18b6891 Mon Sep 17 00:00:00 2001
From: Derek Lamberti <derek.lamberti@arm.com>
Date: Wed, 19 Feb 2020 13:30:47 +0000
Subject: IVGCVSW-4483 Introduce polymorphic_downcast implementation

Change-Id: I958dd719162337eb5c7e71f4ac49dd5784564b1a
Signed-off-by: Derek Lamberti <derek.lamberti@arm.com>
---
 CMakeLists.txt                                |  2 +
 include/armnn/Exceptions.hpp                  | 17 ++++++++
 include/armnn/utility/PolymorphicDowncast.hpp | 43 ++++++++++++++++++++
 src/armnn/test/UtilityTests.cpp               | 56 +++++++++++++++++++++++++++
 4 files changed, 118 insertions(+)
 create mode 100644 include/armnn/utility/PolymorphicDowncast.hpp
 create mode 100644 src/armnn/test/UtilityTests.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2f8761aa94..046ef834ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -249,6 +249,7 @@ list(APPEND armnn_sources
     include/armnn/profiling/ISendTimelinePacket.hpp
     include/armnn/utility/Assert.hpp
     include/armnn/utility/IgnoreUnused.hpp
+    include/armnn/utility/PolymorphicDowncast.hpp
     profiling/common/include/SocketConnectionException.hpp
     src/armnn/layers/LayerCloneBase.hpp
     src/armnn/layers/LayerWithParameters.hpp
@@ -648,6 +649,7 @@ if(BUILD_UNIT_TESTS)
         src/armnn/test/TestNameAndDescriptorLayerVisitor.cpp
         src/armnn/test/TestUtils.cpp
         src/armnn/test/TestUtils.hpp
+        src/armnn/test/UtilityTests.cpp
         src/armnn/test/UnitTests.cpp
         src/armnn/test/UnitTests.hpp
         src/armnn/test/UtilsTests.cpp
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
\ No newline at end of file
diff --git a/src/armnn/test/UtilityTests.cpp b/src/armnn/test/UtilityTests.cpp
new file mode 100644
index 0000000000..5309d82ce4
--- /dev/null
+++ b/src/armnn/test/UtilityTests.cpp
@@ -0,0 +1,56 @@
+//
+// Copyright © 2020 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#include <boost/test/unit_test.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/polymorphic_cast.hpp>
+
+#define ARMNN_POLYMORPHIC_CAST_TESTABLE
+
+#include <armnn/utility/IgnoreUnused.hpp>
+#include <armnn/utility/PolymorphicDowncast.hpp>
+
+#include <armnn/Exceptions.hpp>
+
+// Tests of include/Utility files
+BOOST_AUTO_TEST_SUITE(UtilityTests)
+
+BOOST_AUTO_TEST_CASE(PolymorphicDowncast)
+{
+    using namespace armnn;
+    class Base
+    {
+    public:
+        virtual ~Base(){}
+        float v;
+    };
+
+    class Child1 : public Base
+    {
+    public:
+        int j;
+    };
+
+    class Child2 : public Base
+    {
+    public:
+        char b;
+    };
+
+    Child1 child1;
+    Base* base1 = &child1;
+    auto ptr1 = dynamic_cast<Child1*>(base1);
+    BOOST_CHECK(ptr1 != nullptr);
+    BOOST_CHECK_NO_THROW(polymorphic_downcast<Child1*>(base1));
+    BOOST_CHECK(polymorphic_downcast<Child1*>(base1) == ptr1);
+
+    auto ptr2 = dynamic_cast<Child2*>(base1);
+    BOOST_CHECK(ptr2 == nullptr);
+    BOOST_CHECK_THROW(polymorphic_downcast<Child2*>(base1), std::bad_cast);
+
+    armnn::IgnoreUnused(ptr1, ptr2);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
-- 
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