From b6cf1d104da53ec9c30dc45c35d9de48812f0afc Mon Sep 17 00:00:00 2001
From: Xander Swan <email>
Date: Wed, 3 Dec 2025 09:52:13 -0500
Subject: Initial commit

---
 src/entity_list.odin | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 src/entity_list.odin

(limited to 'src/entity_list.odin')

diff --git a/src/entity_list.odin b/src/entity_list.odin
new file mode 100644
index 0000000..4890d2c
--- /dev/null
+++ b/src/entity_list.odin
@@ -0,0 +1,81 @@
+package demonchime
+
+// import "core:math"
+
+Entity_Handle :: struct {
+  idx: u32,
+  uses: u32,
+}
+
+Entity_List :: struct($T: typeid) {
+  items: [dynamic]T,
+  holes: [dynamic]Entity_Handle,
+}
+
+delete_entity_list :: proc(list: Entity_List($T)) {
+  delete(list.items)
+  delete(list.holes)
+}
+
+make_entity :: proc(list: ^Entity_List($T), ent: T) -> (Entity_Handle, ^T) {
+  handle: Entity_Handle
+
+  if len(list.holes) > 0 {
+    handle = pop(&list.holes)
+    handle.uses += 1
+  } else {
+    // because index 0 in a handle is considered a null handle
+    resize(&list.items, math.max(2, len(list.items) + 1))
+    handle.idx = u32(len(list.items) - 1)
+    handle.uses = 1
+  }
+
+  list.items[handle.idx] = ent
+  list.items[handle.idx].handle = handle
+  return handle, &list.items[handle.idx]
+}
+
+delete_entity :: proc(list: ^Entity_List($T), handle: Entity_Handle) {
+  if handle.idx <= 0 || int(handle.idx) >= len(list.items) {
+    return
+  }
+  if list.items[handle.idx].handle != handle {
+    return
+  }
+
+  append(&list.holes, handle)
+  list.items[handle.idx] = {}
+}
+
+get_entity :: proc(list: Entity_List($T), h: Entity_Handle) -> ^T {
+  if h.idx < 1 || h.idx >= len(list.items) || list.items[h.idx].handle == h {
+    return nil
+  }
+  return &list.items[h.idx]
+}
+
+active_entity_count :: proc(list: Entity_List($T)) -> int {
+  // - 1 because there's an empty slot at the beginning
+  return len(list.items) - len(list.holes) - 1
+}
+
+Entity_List_Iter :: struct($T: typeid) {
+  list: Entity_List(T),
+  idx: int,
+}
+
+iter_entity_list :: proc(list: Entity_List($T)) -> Entity_List_Iter(T) {
+  return Entity_List_Iter(T) { list = list }
+}
+
+entity_list_iter :: proc(it: ^Entity_List_Iter($T)) -> (^T, bool) {
+  for it.idx < len(it.list.items) {
+    if it.list.items[it.idx].handle.idx > 0 {
+      entity := &it.list.items[it.idx]
+      it.idx += 1
+      return entity, true
+    }
+    it.idx += 1
+  }
+  return nil, false
+}
-- 
cgit v1.3-2-g0d8e