Merge branch 'tree_alloc' of gitea:cameron/cs241-project into tree_alloc

tree_alloc.c

@@ -209,11 +209,54 @@ void insert_left(TreeAlloc** root_ptr, TreeAlloc* to_insert, TreeAlloc* before)
 	repair_tree_after_insert(to_insert);
 }
 
-void *unalloc(Arena *arena, void *addr) {
+void unalloc(Arena *arena, void *addr) {
   if (arena->root_treealloc == NULL) {
     arena->error("attempt to unallocate when there are no allocations!");
+    return;
   }
+  // Find the node this address belongs to
   TreeAlloc *node = search_by_address(arena->root_treealloc, addr);
+  if (node == NULL) {
+    arena->error("attempt to free memory outside any allocations!");
+    return;
+  }
+  // Handle the watermark allocator in this region
+  if (node->type == RT_WATERMARK) {
+    // TODO: handle watermark deallocation
+    return;
+  }
+  // Get rid of it
+  remove_node(&arena->root_treealloc, node);
+  // If there's free space on either side of it, merge it with the free space into a bigger chunk of
+  // free space.
+  uintptr_t size = node->size;
+  FreeSpace *start = (FreeSpace*) node;
+  if (node->before != NULL && node->before->type == RT_FREESPACE) {
+    start = (FreeSpace*) node->before;
+    size += node->before->size;
+    remove_node((TreeAlloc**) &arena->root_freespace, node->before);
+  }
+  if (node->after != NULL && node->after->type == RT_FREESPACE) {
+    size += node->after->size;
+    remove_node((TreeAlloc**) &arena->root_freespace, node->after);
+  }
+  start->type = RT_FREESPACE;
+  start->size = size;
+  // And finally, insert the resulting free space.
+  if (arena->root_freespace == NULL) {
+    insert_singleton((TreeAlloc**) &arena->root_freespace, (TreeAlloc*) start);
+  } else {
+    TreeAlloc *insert_point = search_by_size((TreeAlloc*) arena->root_freespace, 0, 1, size);
+    if (insert_point == NULL) {
+      TreeAlloc *head = (TreeAlloc*) arena->root_freespace;
+      while (head->right != NULL) {
+        head = head->right;
+      }
+      insert_right((TreeAlloc**) &arena->root_freespace, (TreeAlloc*) start, head);
+    } else {
+      insert_left((TreeAlloc**) &arena->root_freespace, (TreeAlloc*) start, insert_point);
+    }
+  }
   // TODO
 }