in midst of refactor

orchid-host/src/expr.rs

@@ -0,0 +1,41 @@
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, RwLock};
+
+use hashbrown::HashMap;
+use orchid_api::expr::ExprTicket;
+
+use crate::host::AtomHand;
+use lazy_static::lazy_static;
+
+#[derive(Clone, Debug)]
+pub struct RtExpr {
+  is_canonical: Arc<AtomicBool>,
+  data: Arc<()>,
+}
+impl RtExpr {
+  pub fn as_atom(&self) -> Option<AtomHand> { todo!() }
+  pub fn strong_count(&self) -> usize { todo!() }
+  pub fn id(&self) -> u64 { self.data.as_ref() as *const () as usize as u64 }
+  pub fn canonicalize(&self) -> ExprTicket {
+    if !self.is_canonical.swap(true, Ordering::Relaxed) {
+      KNOWN_EXPRS.write().unwrap().entry(self.id()).or_insert_with(|| self.clone());
+    }
+    self.id()
+  }
+  pub fn resolve(tk: ExprTicket) -> Option<Self> { KNOWN_EXPRS.read().unwrap().get(&tk).cloned() }
+}
+impl Drop for RtExpr {
+  fn drop(&mut self) {
+    // If the only two references left are this and known, remove from known
+    if Arc::strong_count(&self.data) == 2 && self.is_canonical.load(Ordering::Relaxed) {
+      // if known is poisoned, a leak is preferable to a panicking destructor
+      if let Ok(mut w) = KNOWN_EXPRS.write() {
+        w.remove(&self.id());
+      }
+    }
+  }
+}
+
+lazy_static!{
+  static ref KNOWN_EXPRS: RwLock<HashMap<ExprTicket, RtExpr>> = RwLock::default();
+}