From daf0bc236df25c0e9f44bc3e30839c16cda3f638 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Mon, 11 Nov 2024 00:11:22 +0100
Subject: refactor(ecs): use same ID for entities & components

---
 ecs/src/uid.rs | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 ecs/src/uid.rs

(limited to 'ecs/src/uid.rs')

diff --git a/ecs/src/uid.rs b/ecs/src/uid.rs
new file mode 100644
index 0000000..56d84f9
--- /dev/null
+++ b/ecs/src/uid.rs
@@ -0,0 +1,42 @@
+use std::mem::transmute;
+use std::sync::atomic::{AtomicU32, Ordering};
+
+static NEXT: AtomicU32 = AtomicU32::new(1);
+
+// Bit 0 and 1 for the kind
+const KIND_BITS: u64 = 0x03;
+
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[repr(u8)]
+pub enum Kind
+{
+    Entity = 2,
+    Component = 1,
+}
+
+/// Unique entity/component ID.
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Uid
+{
+    inner: u64,
+}
+
+impl Uid
+{
+    /// Returns a new unique entity/component ID.
+    pub fn new_unique(kind: Kind) -> Self
+    {
+        let id_part = NEXT.fetch_add(1, Ordering::Relaxed);
+
+        Self {
+            inner: ((id_part as u64) << 32) | kind as u64,
+        }
+    }
+
+    pub fn kind(&self) -> Kind
+    {
+        // SAFETY: The kind bits cannot be invalid since they are set using the Kind enum
+        // in the new_unique function
+        unsafe { transmute((self.inner & KIND_BITS) as u8) }
+    }
+}
-- 
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