Create tiny frame allocator which holds only 3 frames

2 files changed, 49 insertions, 3 deletions

diff --git a/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp b/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp
index 599723f..6135184 100644
--- a/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp
+++ b/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp
@@ -27,7 +27,7 @@ namespace teachos::arch::memory::allocator
     area_frame_allocator(multiboot::memory_information mem_info);
 
     /**
-     * @brief Allocate memory by finding and returning a free physical_frame.
+     * @brief Allocate memory by finding and returning a free physical frame.
      *
      * @note The physical_frame allocation executes multiple checks before returning
      * the physical_frame that is available to allocate. It must at least
@@ -35,17 +35,19 @@ namespace teachos::arch::memory::allocator
      * - check if the next_free_frame is within the current_area
      * - check if the next_free_frame is actually free
      * - update the next_free_frame after finding a free physical_frame
+     *
+     * @return next free physical frame or nullopt if none was found.
      */
     auto allocate_frame() -> std::optional<physical_frame>;
 
     /**
-     * @brief Deallocates a previously allocated physical_frame.
+     * @brief Deallocates a previously allocated physical frame.
      *
      * @note Simply does nothing, because the simply area frame
      * allocator implementation does not keep track of free or used frames and can therefore not deallocate, because it
      * does not know which frames have ben alocated in the first place.
      *
-     * @param physical_frame Previously allocated physical_frame that should be allocated.
+     * @param physical_frame Previously allocated physical_frame that should be deallocated.
      */
     auto deallocate_frame(physical_frame physical_frame) -> void;
 
diff --git a/arch/x86_64/include/arch/memory/allocator/tiny_frame_allocator.hpp b/arch/x86_64/include/arch/memory/allocator/tiny_frame_allocator.hpp
new file mode 100644
index 0000000..70c7de6
--- /dev/null
+++ b/arch/x86_64/include/arch/memory/allocator/tiny_frame_allocator.hpp
@@ -0,0 +1,44 @@
+#ifndef TEACHOS_ARCH_X86_64_MEMORY_ALLOCATOR_TINY_FRAME_ALLOCATOR_HPP
+#define TEACHOS_ARCH_X86_64_MEMORY_ALLOCATOR_TINY_FRAME_ALLOCATOR_HPP
+
+#include "arch/memory/allocator/physical_frame.hpp"
+
+#include <array>
+#include <optional>
+
+namespace teachos::arch::memory::allocator
+{
+  /**
+   * @brief Allocates memory using memory areas read from the multiboot2 information pointer.
+   */
+  struct tiny_frame_allocator
+  {
+    /**
+     * @brief Defaulted constructor.
+     */
+    tiny_frame_allocator() = default;
+
+    /**
+     * @brief Allocate memory by finding and returning one of the three free physical frames.
+     *
+     * @return First free physical frames of the three frames held by this allocator or nullopt if we used up all three
+     * frames already.
+     */
+    auto allocate_frame() -> std::optional<physical_frame>;
+
+    /**
+     * @brief Deallocates one of the three previously allocated physical frames.
+     *
+     * @note If more than the three frames are deallocated the method will halt execution, because it can only hold 3
+     * frames.
+     *
+     * @param physical_frame Previously allocated physical_frame that should be deallocated.
+     */
+    auto deallocate_frame(physical_frame physical_frame) -> void;
+
+  private:
+    std::array<std::optional<physical_frame>, 3U> frames = {};
+  };
+}  // namespace teachos::arch::memory::allocator
+
+#endif  // TEACHOS_ARCH_X86_64_MEMORY_ALLOCATOR_TINY_FRAME_ALLOCATOR_HPP