From 87b1a0d4a833dd0b2164481be45f7d1c59375040 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Fri, 15 Oct 2021 17:58:05 +0200
Subject: Add boilerplate for GC allocator

---
 src/bootstrap/gc.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 src/bootstrap/gc.c

(limited to 'src/bootstrap/gc.c')

diff --git a/src/bootstrap/gc.c b/src/bootstrap/gc.c
new file mode 100644
index 0000000..fff4201
--- /dev/null
+++ b/src/bootstrap/gc.c
@@ -0,0 +1,48 @@
+typedef struct GC {
+    Object *obj_list;
+    // Free list keeps track of the offset numbers from the obj_list
+    size_t *free_list;
+    size_t obj_size;
+    size_t obj_cap;
+    size_t fl_pos;
+    size_t available_slots;
+} GC;
+
+// FIXME: small value for testing purposes
+#define GC_INITIAL_HEAP 100000
+
+static GC gc;
+
+void
+init_gc(void) {
+    gc = (GC){
+        .obj_cap = GC_INITIAL_HEAP,
+        .available_slots = GC_INITIAL_HEAP,
+    };
+    gc.free_list = malloc(GC_INITIAL_HEAP * sizeof(size_t *));
+    gc.obj_list = malloc(GC_INITIAL_HEAP * sizeof(Object *));
+
+    // The free list stores the offset from the initial position for all
+    // available slots.
+    for (size_t i = 0; i < gc.obj_cap; i++) {
+        gc.free_list[i] = i;
+    }
+}
+
+Object *
+alloc_object(ObjectType type) {
+    if (gc.available_slots == 0) {
+        // TODO: trigger garbage collection.
+        if (gc.available_slots == 0) {
+            // TODO: grow heap tables.
+            // NOTE: When growing the tables, we might lose the pointer
+            // references! Should we work with offsets all the way?  That is for
+            // cdr and car? Should we have a utility function?
+        }
+    }
+    size_t slot = gc.free_list[gc.fl_pos++];
+    gc.available_slots--;
+    Object *obj = gc.obj_list + slot;
+    obj->type = type;
+    return obj;
+}
-- 
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