From 17d41a408dd7ae4604c030080beb3384d9a1184a Mon Sep 17 00:00:00 2001
From: Victor Olin <victor.vieweg@icloud.com>
Date: Thu, 9 Feb 2023 13:18:58 +0100
Subject: [PATCH] Started with a rough structure

---
 src/GC/allocator.cpp         |  0
 src/GC/include/allocator.hpp | 27 ++++++++++++++++
 src/GC/include/heap.hpp      | 62 ++++++++++++++++++++++++++++++++++++
 src/GC/include/heap_obj.hpp  | 16 ++++++++++
 src/GC/todo.md               | 34 ++++++++++++++++++++
 src/MarkSweep.cpp            | 25 ++++++++-------
 6 files changed, 153 insertions(+), 11 deletions(-)
 create mode 100644 src/GC/allocator.cpp
 create mode 100644 src/GC/include/allocator.hpp
 create mode 100644 src/GC/include/heap.hpp
 create mode 100644 src/GC/include/heap_obj.hpp
 create mode 100644 src/GC/todo.md

diff --git a/src/GC/allocator.cpp b/src/GC/allocator.cpp
new file mode 100644
index 0000000..e69de29
diff --git a/src/GC/include/allocator.hpp b/src/GC/include/allocator.hpp
new file mode 100644
index 0000000..bd30e17
--- /dev/null
+++ b/src/GC/include/allocator.hpp
@@ -0,0 +1,27 @@
+#pragma once
+
+#include <assert.h>
+#include <memory>
+#include <stdlib.h>
+
+namespace GC {
+
+class Allocator {
+public:
+    Allocator(size_t size) {
+        alloc_size = size;
+    }
+
+    size_t getSize() {
+        return alloc_size;
+    }
+
+    void *alloc();
+
+private:
+    size_t alloc_size;
+
+
+};
+
+}
\ No newline at end of file
diff --git a/src/GC/include/heap.hpp b/src/GC/include/heap.hpp
new file mode 100644
index 0000000..a8a1304
--- /dev/null
+++ b/src/GC/include/heap.hpp
@@ -0,0 +1,62 @@
+#pragma once
+
+#include <assert.h>
+#include <iostream>
+#include <setjmp.h>
+#include <stdlib.h>
+#include <vector>
+
+#include "allocator.hpp"
+
+#define HEAP_SIZE   65536
+
+namespace GC {
+
+class Heap {
+public:
+
+    static Heap &the() {
+        if (s_instance)
+            return *s_instance;
+        s_instance = new Heap();
+        return *s_instance;
+    }
+
+    ~Heap() {
+
+    }
+
+    size_t getHeapSize() {
+        return heap_size;
+    }
+
+    Allocator *getAllocator(size_t size) {
+        for (auto *alloc : h_allocs) {
+            if (alloc->getSize() >= size)
+                return alloc;
+        }
+        std::cout << "Object too big" << std::endl;
+        assert(false);
+    }
+
+    void collect();
+
+private:
+    inline static Heap *s_instance = nullptr;
+
+    Heap() {
+        h_allocs.push_back(new Allocator(16));
+        h_allocs.push_back(new Allocator(32));
+        h_allocs.push_back(new Allocator(64));
+        h_allocs.push_back(new Allocator(128));
+        h_allocs.push_back(new Allocator(256));
+        h_allocs.push_back(new Allocator(512));
+        h_allocs.push_back(new Allocator(1024));
+    }
+
+    char _heap[HEAP_SIZE] = {0};
+    size_t heap_size = 0;
+    std::vector<Allocator *> h_allocs;
+};
+
+}
\ No newline at end of file
diff --git a/src/GC/include/heap_obj.hpp b/src/GC/include/heap_obj.hpp
new file mode 100644
index 0000000..21490ae
--- /dev/null
+++ b/src/GC/include/heap_obj.hpp
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <cstdlib>
+
+class HeapObj {
+public:
+    HeapObj(size_t size_) {
+        size = size_;
+    }
+
+    ~HeapObj() { }
+
+private:
+    size_t size { 0 };
+    bool marked { false };
+};
\ No newline at end of file
diff --git a/src/GC/todo.md b/src/GC/todo.md
new file mode 100644
index 0000000..436ae30
--- /dev/null
+++ b/src/GC/todo.md
@@ -0,0 +1,34 @@
+# Garbage collection
+
+## Algorithm
+
+Potential algorithms:
+- mark & sweep
+    - easy to implement
+    - slow
+- mark & compact
+    - no memory fragmentation
+    - slow
+- stop-copy algorithms (?)
+    - no memory fragmentation
+    - slow
+    - maybe good for FP langs?
+
+## Type hierarchy
+
+- Heap class
+    - Holds all memory
+        - Resizeable array?
+    - Singleton instance
+
+- Allocator class
+    - Allocates chunks of memory
+    - keeps track of chunks that are available and their sizes
+    - Several instances of allocator class with different sizes?
+
+- HeapObj class
+    - parent of all heap objects
+    - contains metadata
+        - size
+        - location
+        - marked bit
\ No newline at end of file
diff --git a/src/MarkSweep.cpp b/src/MarkSweep.cpp
index 706f24f..ab219d2 100644
--- a/src/MarkSweep.cpp
+++ b/src/MarkSweep.cpp
@@ -15,8 +15,11 @@ struct ObjectHeader {
 struct Object : ObjectHeader {
     char name; // should be something like id, but for testing sake its char
     Object* child;
-    //Object(char name) {}
-    //Object(char name, Object* child) {}
+    // Object(char name_) {}
+    Object(char name_, Object* child_) {
+        name = name_;
+        child = child_;
+    }
 };
 
 // Representing the heap as a simple struct for now
@@ -57,15 +60,15 @@ class MarkSweep {
 };
 
 int main() {
-    Object* b = new Object();
-    b->name = 'B';
-    b->child = nullptr;
-    Object* c = new Object();
-    c->name = 'C';
-    c->child = b; // c -> d
-    Object* d = new Object();
-    d->name = 'D';
-    d->child = nullptr;
+    Object* b = new Object('B', nullptr);
+    // b->name = 'B';
+    // b->child = nullptr;
+    Object* c = new Object('C', b);
+    // c->name = 'C';
+    // c->child = b; // c -> d
+    Object* d = new Object('D', nullptr);
+    // d->name = 'D';
+    // d->child = nullptr;
 
     //Heap* heap = new Heap{*c, *b, *d};
     vector<Object*> worklist = {c, b, d};