added test/example data structure SingletonStore

this probably won"t ever be useful but w/e

Fortune for transfer's current commit: Small curse − 小凶

src/main.rs

@@ -20,6 +20,7 @@ use color_eyre::{
 use futures::Future;
 
 mod sock;
+mod store;
 mod config;
 
 fn setup() -> eyre::Result<()>

src/store.rs

@@ -0,0 +1,58 @@
+//! Arbitrary object store
+use std::any::{
+    TypeId,
+    Any,
+};
+use std::collections::HashMap;
+
+/// Arbitrarily typed singleton store.
+///
+/// Stores one object per type.
+#[derive(Debug)]
+pub struct SingletonStore
+{
+    objects: HashMap<TypeId, Box<dyn Any + 'static>>,
+}
+
+#[inline] fn unbox_to<T: Any>(b: Box<dyn Any + 'static>) -> Option<T>
+{
+    b.downcast().map(|ok| *ok).ok()
+}
+
+impl SingletonStore
+{
+    pub fn has<T: Any>(&self) -> bool
+    {
+	self.objects.contains_key(&TypeId::of::<T>())
+    }
+    
+    pub fn remove<T: Any>(&mut self) -> Option<T>
+    {
+	self.objects.remove(&TypeId::of::<T>())
+	    .and_then(|x| x.downcast().ok())
+	    .map(|x| *x)
+    }
+    pub fn insert<T: Any>(&mut self, value: T) -> Option<T>
+    {
+	self.objects.insert(TypeId::of::<T>(), Box::new(value))
+	    .and_then(unbox_to)
+    }
+
+    pub fn get_mut<T: Any>(&mut self) -> Option<&mut T>
+    {
+	self.objects.get_mut(&TypeId::of::<T>())
+	    .and_then(|x| x.downcast_mut())
+    }
+    pub fn get<T: Any>(&self) -> Option<&T>
+    {
+	self.objects.get(&TypeId::of::<T>())
+	    .and_then(|x| x.downcast_ref())
+    }
+
+    pub fn new() -> Self
+    {
+	Self {
+	    objects: HashMap::new(),
+	}
+    }
+}