From 5f52b590ccffe0849524d5f1f69afc1df39403f5 Mon Sep 17 00:00:00 2001
From: Joakim Soderlund <joakim.soderlund@gmail.com>
Date: Fri, 22 May 2020 23:52:09 +0200
Subject: [PATCH] Add interner for static reference sharing

---
 src/archive/interner.rs | 35 +++++++++++++++++++++++++++++++++++
 src/archive/mod.rs      |  1 +
 2 files changed, 36 insertions(+)
 create mode 100644 src/archive/interner.rs

diff --git a/src/archive/interner.rs b/src/archive/interner.rs
new file mode 100644
index 0000000..42020bc
--- /dev/null
+++ b/src/archive/interner.rs
@@ -0,0 +1,35 @@
+//! Interner module.
+
+use std::collections::HashSet;
+use std::sync::RwLock;
+
+pub struct Interner<T: 'static>(RwLock<HashSet<&'static T>>);
+
+impl<T> Interner<T>
+where
+    T: Eq + std::hash::Hash,
+{
+    pub fn new() -> Self {
+        Self(RwLock::new(HashSet::new()))
+    }
+
+    fn get(&self, value: &T) -> Option<&'static T> {
+        let store = self.0.read().unwrap();
+
+        store.get(value).map(|value| *value)
+    }
+
+    fn set(&self, value: T) -> &'static T {
+        let boxed: Box<T> = Box::new(value);
+        let leaked: &'static T = Box::leak(boxed);
+        let mut store = self.0.write().unwrap();
+
+        store.insert(leaked);
+
+        leaked
+    }
+
+    pub fn intern(&self, value: T) -> &'static T {
+        self.get(&value).unwrap_or_else(|| self.set(value))
+    }
+}
diff --git a/src/archive/mod.rs b/src/archive/mod.rs
index 1216681..0882039 100644
--- a/src/archive/mod.rs
+++ b/src/archive/mod.rs
@@ -1,6 +1,7 @@
 //! Archive module.
 
 mod fetcher;
+mod interner;
 mod parser;
 mod story;