Add aligned stack class.

This will be used for storing thread tasks aligned in continous memory, allowing different theads to work on the data without interfearing.

lib/pls/CMakeLists.txt

@@ -7,7 +7,10 @@ add_library(pls STATIC
             src/internal/scheduling/abstract_task.cpp include/pls/internal/scheduling/abstract_task.h
             src/internal/scheduling/scheduler.cpp include/pls/internal/scheduling/scheduler.h
             src/internal/scheduling/thread_state.cpp  include/pls/internal/scheduling/thread_state.h
-            src/internal/base/barrier.cpp include/pls/internal/base/barrier.h include/pls/internal/scheduling/root_master_task.h src/internal/scheduling/root_master_task.cpp)
+            src/internal/base/barrier.cpp include/pls/internal/base/barrier.h
+            src/internal/scheduling/root_master_task.cpp include/pls/internal/scheduling/root_master_task.h
+            src/internal/base/aligned_stack.cpp include/pls/internal/base/aligned_stack.h
+            include/pls/internal/base/system_details.h)
 
 # Add everything in `./include` to be in the include path of this project
 target_include_directories(pls

lib/pls/include/pls/internal/base/aligned_stack.h

+
+#ifndef PLS_ALIGNED_STACK_H
+#define PLS_ALIGNED_STACK_H
+
+#include <cstdint>
+#include <cstdlib>
+
+namespace pls {
+    namespace internal {
+        namespace base {
+            class aligned_stack {
+                // Keep bounds of our memory block
+                char* memory_start_;
+                char* memory_end_;
+
+                // Current head will always be aligned to cache lines
+                char* head_;
+
+                static std::uintptr_t next_alignment(std::uintptr_t size);
+                static char* next_alignment(char* pointer);
+            public:
+                explicit aligned_stack(char* memory_region, const std::size_t size):
+                    memory_start_{memory_region},
+                    memory_end_{memory_region + size},
+                    head_{next_alignment(memory_start_)} {}
+
+                template<typename T>
+                T* push(T object) {
+                    T* result = reinterpret_cast<T*>(head_);
+
+                    // Move head to next aligned position after new object
+                    head_ = next_alignment(head_ + sizeof(T));
+                    if (head_ >= memory_end_) {
+                        exit(1); // TODO: Exception Handling
+                    }
+
+                    *result = object;
+                    return result;
+                }
+
+                template<typename T>
+                T pop() {
+                    head_ = head_ - next_alignment(sizeof(T));
+
+                    return *reinterpret_cast<T*>(head_);
+                }
+            };
+        }
+    }
+}
+
+#endif //PLS_ALIGNED_STACK_H

lib/pls/include/pls/internal/base/system_details.h

+
+#ifndef PLS_SYSTEM_DETAILS_H
+#define PLS_SYSTEM_DETAILS_H
+
+#include <cstdint>
+
+namespace pls {
+    namespace internal {
+        namespace base {
+            constexpr std::uintptr_t CACHE_LINE_SIZE = 64;
+        }
+    }
+}
+
+#endif //PLS_SYSTEM_DETAILS_H

lib/pls/src/internal/base/aligned_stack.cpp

+#include "pls/internal/base/aligned_stack.h"
+#include "pls/internal/base/system_details.h"
+
+namespace pls {
+    namespace internal {
+        namespace base {
+            std::uintptr_t aligned_stack::next_alignment(std::uintptr_t size) {
+                std::uintptr_t miss_alignment = size % CACHE_LINE_SIZE;
+                if (miss_alignment == 0) {
+                    return size;
+                } else {
+                    return size + (CACHE_LINE_SIZE - miss_alignment);
+                }
+            }
+
+            char* aligned_stack::next_alignment(char* pointer) {
+                return reinterpret_cast<char*>(next_alignment(reinterpret_cast<std::uintptr_t >(pointer)));
+            }
+        }
+    }
+}

test/base_tests.cpp

 #include <catch.hpp>
 #include <pls/internal/base/thread.h>
 #include <pls/internal/base/spin_lock.h>
+#include <pls/internal/base/aligned_stack.h>
+#include <pls/internal/base/system_details.h>
 
 #include <vector>
 #include <mutex>
@@ -82,3 +84,66 @@ TEST_CASE( "spinlock protects concurrent counter", "[internal/base/spinlock.h]")
         REQUIRE(base_tests_shared_counter == 0);
     }
 }
+
+TEST_CASE( "aligned stack stores objects correctly", "[internal/base/aligned_stack.h]") {
+    constexpr long data_size = 1024;
+    char data[data_size];
+    aligned_stack stack{data, data_size};
+
+    SECTION( "stack correctly pushes sub linesize objects" ) {
+        std::array<char, 5> small_data_one{'a', 'b', 'c', 'd', 'e'};
+        std::array<char, 64> small_data_two{};
+        std::array<char, 1> small_data_three{'A'};
+
+        auto pointer_one = stack.push(small_data_one);
+        auto pointer_two = stack.push(small_data_two);
+        auto pointer_three = stack.push(small_data_three);
+
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_one) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_two) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_three) % CACHE_LINE_SIZE == 0);
+    }
+
+    SECTION( "stack correctly pushes above linesize objects" ) {
+        std::array<char, 5> small_data_one{'a', 'b', 'c', 'd', 'e'};
+        std::array<char, CACHE_LINE_SIZE + 10> big_data_one{};
+
+        auto big_pointer_one = stack.push(big_data_one);
+        auto small_pointer_one = stack.push(small_data_one);
+
+        REQUIRE(reinterpret_cast<std::uintptr_t>(big_pointer_one) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(small_pointer_one) % CACHE_LINE_SIZE == 0);
+    }
+
+    SECTION( "stack correctly stores and retrieves objects" ) {
+        std::array<char, 5> data_one{'a', 'b', 'c', 'd', 'e'};
+
+        stack.push(data_one);
+        auto retrieved_data = stack.pop<std::array<char, 5>>();
+
+        REQUIRE(retrieved_data == std::array<char, 5>{'a', 'b', 'c', 'd', 'e'});
+    }
+
+    SECTION( "stack can push and pop multiple times with correct alignment" ) {
+        std::array<char, 5> small_data_one{'a', 'b', 'c', 'd', 'e'};
+        std::array<char, 64> small_data_two{};
+        std::array<char, 1> small_data_three{'A'};
+
+        auto pointer_one = stack.push(small_data_one);
+        auto pointer_two = stack.push(small_data_two);
+        auto pointer_three = stack.push(small_data_three);
+        stack.pop<typeof(small_data_three)>();
+        stack.pop<typeof(small_data_two)>();
+        auto pointer_four = stack.push(small_data_two);
+        auto pointer_five = stack.push(small_data_three);
+
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_one) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_two) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_three) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_four) % CACHE_LINE_SIZE == 0);
+        REQUIRE(reinterpret_cast<std::uintptr_t>(pointer_five) % CACHE_LINE_SIZE == 0);
+
+        REQUIRE(pointer_four == pointer_two);
+        REQUIRE(pointer_five == pointer_three);
+    }
+}