kstd/vector: allow self-referential pushes

Previously, calling `v.push_back(v.front())` might have resulted in
undefined behavior if reallocation needed to occur. This patch provides
for this and allows self-referential pushes.

1 files changed, 45 insertions, 15 deletions

diff --git a/libs/kstd/include/kstd/vector b/libs/kstd/include/kstd/vector
index 7042ff1..a49572b 100644
--- a/libs/kstd/include/kstd/vector
+++ b/libs/kstd/include/kstd/vector
@@ -590,16 +590,42 @@ namespace kstd
     //! Append a given element to this vector via copy construction.
     constexpr auto push_back(value_type const & value) -> void
     {
-      increase_capacity_if_full();
-      std::allocator_traits<allocator_type>::construct(m_allocator, data() + size(), value);
+      if (m_capacity == m_size)
+      {
+        auto new_capacity = m_capacity == 0 ? 1 : m_capacity * 2;
+        auto new_data = allocate_n(new_capacity);
+        std::allocator_traits<allocator_type>::construct(m_allocator, new_data + m_size, value);
+        uninitialized_move_with_allocator(begin(), new_data, size());
+        destroy_n(begin(), size());
+        deallocate();
+        m_data = new_data;
+        m_capacity = new_capacity;
+      }
+      else
+      {
+        std::allocator_traits<allocator_type>::construct(m_allocator, data() + size(), value);
+      }
       ++m_size;
     }
 
     //! Append a given element to this vector via move construction.
     constexpr auto push_back(value_type && value) -> void
     {
-      increase_capacity_if_full();
-      std::allocator_traits<allocator_type>::construct(m_allocator, data() + size(), std::move(value));
+      if (m_capacity == m_size)
+      {
+        auto new_capacity = m_capacity == 0 ? 1 : m_capacity * 2;
+        auto new_data = allocate_n(new_capacity);
+        std::allocator_traits<allocator_type>::construct(m_allocator, new_data + m_size, std::move(value));
+        uninitialized_move_with_allocator(begin(), new_data, size());
+        destroy_n(begin(), size());
+        deallocate();
+        m_data = new_data;
+        m_capacity = new_capacity;
+      }
+      else
+      {
+        std::allocator_traits<allocator_type>::construct(m_allocator, data() + size(), std::move(value));
+      }
       ++m_size;
     }
 
@@ -607,8 +633,21 @@ namespace kstd
     template<class... Args>
     constexpr auto emplace_back(Args &&... args) -> reference
     {
-      increase_capacity_if_full();
-      std::allocator_traits<allocator_type>::construct(m_allocator, data() + size(), std::forward<Args>(args)...);
+      if (m_capacity == m_size)
+      {
+        auto new_capacity = m_capacity == 0 ? 1 : m_capacity * 2;
+        auto new_data = allocate_n(new_capacity);
+        std::allocator_traits<allocator_type>::construct(m_allocator, new_data + m_size, std::forward<Args>(args)...);
+        uninitialized_move_with_allocator(begin(), new_data, size());
+        destroy_n(begin(), size());
+        deallocate();
+        m_data = new_data;
+        m_capacity = new_capacity;
+      }
+      else
+      {
+        std::allocator_traits<allocator_type>::construct(m_allocator, data() + size(), std::forward<Args>(args)...);
+      }
       ++m_size;
       return this->back();
     }
@@ -675,15 +714,6 @@ namespace kstd
       });
     }
 
-    //! Check if there is still room in this vector, and if not allocate more space.
-    constexpr auto increase_capacity_if_full() -> void
-    {
-      if (m_size == m_capacity)
-      {
-        reserve(m_capacity == 0U ? 1U : m_capacity * 2U);
-      }
-    }
-
     //! Move a number of elements from one storage location to another.
     //!
     //! @param from The start of the source range.