From 636e1990c72b89210fad1c323819799702d5a6f9 Mon Sep 17 00:00:00 2001
From: Jeff Ithier <jeff@ithier.dev>
Date: Thu, 7 Nov 2024 12:33:31 +0100
Subject: [PATCH] [#490] Make const MutableSlice also prevent mutation of
 elements

---
 iceoryx2-ffi/cxx/include/iox/slice.hpp     | 20 ++++++++++----------
 iceoryx2-ffi/cxx/tests/src/slice_tests.cpp |  9 +++++----
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/iceoryx2-ffi/cxx/include/iox/slice.hpp b/iceoryx2-ffi/cxx/include/iox/slice.hpp
index 217d29dda..7edd953fe 100644
--- a/iceoryx2-ffi/cxx/include/iox/slice.hpp
+++ b/iceoryx2-ffi/cxx/include/iox/slice.hpp
@@ -29,7 +29,8 @@ namespace iox {
 template <typename T>
 class Slice {
   public:
-    using Iterator = std::conditional_t<std::is_const_v<T>, const T*, T*>;
+    using Iterator = T*;
+    using ConstIterator = const T*;
     using ValueType = std::remove_const_t<T>;
 
     /// @brief Constructs a Slice object.
@@ -49,7 +50,7 @@ class Slice {
     /// @param[in] n The index of the element to access.
     /// @return A const reference to the element at the specified index.
     /// @pre The index must be less than the number of elements in the slice.
-    auto operator[](uint64_t n) const -> std::conditional_t<std::is_const_v<T>, const ValueType&, ValueType&>;
+    auto operator[](uint64_t n) const -> const ValueType&;
 
     /// @brief Accesses the element at the specified index (non-const version).
     /// @param[in] n The index of the element to access.
@@ -59,7 +60,7 @@ class Slice {
 
     /// @brief Returns an iterator to the beginning of the slice (const version).
     /// @return An iterator pointing to the first element of the slice.
-    auto begin() const -> Iterator;
+    auto begin() const -> ConstIterator;
 
     /// @brief Returns an iterator to the beginning of the slice (non-const version).
     /// @return An iterator pointing to the first element of the slice.
@@ -67,7 +68,7 @@ class Slice {
 
     /// @brief Returns an iterator to the end of the slice (const version).
     /// @return An iterator pointing one past the last element of the slice.
-    auto end() const -> Iterator;
+    auto end() const -> ConstIterator;
 
     /// @brief Returns an iterator to the end of the slice (non-const version).
     /// @return An iterator pointing one past the last element of the slice.
@@ -75,7 +76,7 @@ class Slice {
 
     /// @brief Returns a pointer to the underlying data of the slice (const version).
     /// @return A pointer to the first element of the slice.
-    auto data() const -> Iterator;
+    auto data() const -> ConstIterator;
 
     /// @brief Returns a pointer to the underlying data of the slice (non-const version).
     /// @return A pointer to the first element of the slice.
@@ -110,8 +111,7 @@ auto Slice<T>::number_of_elements() const -> uint64_t {
 }
 
 template <typename T>
-auto Slice<T>::operator[](const uint64_t n) const
-    -> std::conditional_t<std::is_const_v<T>, const ValueType&, ValueType&> {
+auto Slice<T>::operator[](const uint64_t n) const -> const ValueType& {
     IOX_ASSERT(n < m_number_of_elements, "Index out of bounds");
     return *(m_data + n);
 }
@@ -128,7 +128,7 @@ auto Slice<T>::begin() -> Iterator {
 }
 
 template <typename T>
-auto Slice<T>::begin() const -> Iterator {
+auto Slice<T>::begin() const -> ConstIterator {
     return m_data;
 }
 
@@ -138,7 +138,7 @@ auto Slice<T>::end() -> Iterator {
 }
 
 template <typename T>
-auto Slice<T>::end() const -> Iterator {
+auto Slice<T>::end() const -> ConstIterator {
     return m_data + m_number_of_elements;
 }
 
@@ -148,7 +148,7 @@ auto Slice<T>::data() -> Iterator {
 }
 
 template <typename T>
-auto Slice<T>::data() const -> Iterator {
+auto Slice<T>::data() const -> ConstIterator {
     return m_data;
 }
 
diff --git a/iceoryx2-ffi/cxx/tests/src/slice_tests.cpp b/iceoryx2-ffi/cxx/tests/src/slice_tests.cpp
index 9c0cbf95d..d9ff1aeb2 100644
--- a/iceoryx2-ffi/cxx/tests/src/slice_tests.cpp
+++ b/iceoryx2-ffi/cxx/tests/src/slice_tests.cpp
@@ -35,11 +35,12 @@ TEST(SliceTest, const_correctness_is_maintained) {
     ASSERT_FALSE(std::is_const_v<std::remove_pointer_t<decltype(mutable_slice.data())>>);
     ASSERT_FALSE(std::is_const_v<std::remove_reference_t<decltype(mutable_slice[0])>>);
 
+    // const instances of MutableSlice are also not mutable
     const auto const_mutable_slice = iox::MutableSlice<DummyData>(elements.data(), SLICE_MAX_LENGTH);
-    ASSERT_FALSE(std::is_const_v<std::remove_pointer_t<decltype(const_mutable_slice.begin())>>);
-    ASSERT_FALSE(std::is_const_v<std::remove_pointer_t<decltype(const_mutable_slice.end())>>);
-    ASSERT_FALSE(std::is_const_v<std::remove_pointer_t<decltype(const_mutable_slice.data())>>);
-    ASSERT_FALSE(std::is_const_v<std::remove_reference_t<decltype(const_mutable_slice[0])>>);
+    ASSERT_TRUE(std::is_const_v<std::remove_pointer_t<decltype(const_mutable_slice.begin())>>);
+    ASSERT_TRUE(std::is_const_v<std::remove_pointer_t<decltype(const_mutable_slice.end())>>);
+    ASSERT_TRUE(std::is_const_v<std::remove_pointer_t<decltype(const_mutable_slice.data())>>);
+    ASSERT_TRUE(std::is_const_v<std::remove_reference_t<decltype(const_mutable_slice[0])>>);
 
     auto immutable_slice = iox::ImmutableSlice<DummyData>(elements.data(), SLICE_MAX_LENGTH);
     ASSERT_TRUE(std::is_const_v<std::remove_pointer_t<decltype(immutable_slice.begin())>>);