1 files changed, 273 insertions, 0 deletions
diff --git a/src/bootstrap/cache.rs b/src/bootstrap/cache.rs
new file mode 100644
index 000000000..be5c9bb07
--- /dev/null
+++ b/src/bootstrap/cache.rs
@@ -0,0 +1,273 @@
+use std::any::{Any, TypeId};
+use std::borrow::Borrow;
+use std::cell::RefCell;
+use std::cmp::{Ord, Ordering, PartialOrd};
+use std::collections::HashMap;
+use std::convert::AsRef;
+use std::fmt;
+use std::hash::{Hash, Hasher};
+use std::marker::PhantomData;
+use std::mem;
+use std::ops::Deref;
+use std::path::PathBuf;
+use std::sync::Mutex;
+
+// FIXME: replace with std::lazy after it gets stabilized and reaches beta
+use once_cell::sync::Lazy;
+
+use crate::builder::Step;
+
+pub struct Interned<T>(usize, PhantomData<*const T>);
+
+impl<T: Internable + Default> Default for Interned<T> {
+    fn default() -> Self {
+        T::default().intern()
+    }
+}
+
+impl<T> Copy for Interned<T> {}
+impl<T> Clone for Interned<T> {
+    fn clone(&self) -> Interned<T> {
+        *self
+    }
+}
+
+impl<T> PartialEq for Interned<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+impl<T> Eq for Interned<T> {}
+
+impl PartialEq<str> for Interned<String> {
+    fn eq(&self, other: &str) -> bool {
+        *self == other
+    }
+}
+impl<'a> PartialEq<&'a str> for Interned<String> {
+    fn eq(&self, other: &&str) -> bool {
+        **self == **other
+    }
+}
+impl<'a, T> PartialEq<&'a Interned<T>> for Interned<T> {
+    fn eq(&self, other: &&Self) -> bool {
+        self.0 == other.0
+    }
+}
+impl<'a, T> PartialEq<Interned<T>> for &'a Interned<T> {
+    fn eq(&self, other: &Interned<T>) -> bool {
+        self.0 == other.0
+    }
+}
+
+unsafe impl<T> Send for Interned<T> {}
+unsafe impl<T> Sync for Interned<T> {}
+
+impl fmt::Display for Interned<String> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s: &str = &*self;
+        f.write_str(s)
+    }
+}
+
+impl<T, U: ?Sized + fmt::Debug> fmt::Debug for Interned<T>
+where
+    Self: Deref<Target = U>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s: &U = &*self;
+        f.write_fmt(format_args!("{:?}", s))
+    }
+}
+
+impl<T: Internable + Hash> Hash for Interned<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        let l = T::intern_cache().lock().unwrap();
+        l.get(*self).hash(state)
+    }
+}
+
+impl<T: Internable + Deref> Deref for Interned<T> {
+    type Target = T::Target;
+    fn deref(&self) -> &'static Self::Target {
+        let l = T::intern_cache().lock().unwrap();
+        unsafe { mem::transmute::<&Self::Target, &'static Self::Target>(l.get(*self)) }
+    }
+}
+
+impl<T: Internable + AsRef<U>, U: ?Sized> AsRef<U> for Interned<T> {
+    fn as_ref(&self) -> &'static U {
+        let l = T::intern_cache().lock().unwrap();
+        unsafe { mem::transmute::<&U, &'static U>(l.get(*self).as_ref()) }
+    }
+}
+
+impl<T: Internable + PartialOrd> PartialOrd for Interned<T> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        let l = T::intern_cache().lock().unwrap();
+        l.get(*self).partial_cmp(l.get(*other))
+    }
+}
+
+impl<T: Internable + Ord> Ord for Interned<T> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        let l = T::intern_cache().lock().unwrap();
+        l.get(*self).cmp(l.get(*other))
+    }
+}
+
+struct TyIntern<T: Clone + Eq> {
+    items: Vec<T>,
+    set: HashMap<T, Interned<T>>,
+}
+
+impl<T: Hash + Clone + Eq> Default for TyIntern<T> {
+    fn default() -> Self {
+        TyIntern { items: Vec::new(), set: Default::default() }
+    }
+}
+
+impl<T: Hash + Clone + Eq> TyIntern<T> {
+    fn intern_borrow<B>(&mut self, item: &B) -> Interned<T>
+    where
+        B: Eq + Hash + ToOwned<Owned = T> + ?Sized,
+        T: Borrow<B>,
+    {
+        if let Some(i) = self.set.get(&item) {
+            return *i;
+        }
+        let item = item.to_owned();
+        let interned = Interned(self.items.len(), PhantomData::<*const T>);
+        self.set.insert(item.clone(), interned);
+        self.items.push(item);
+        interned
+    }
+
+    fn intern(&mut self, item: T) -> Interned<T> {
+        if let Some(i) = self.set.get(&item) {
+            return *i;
+        }
+        let interned = Interned(self.items.len(), PhantomData::<*const T>);
+        self.set.insert(item.clone(), interned);
+        self.items.push(item);
+        interned
+    }
+
+    fn get(&self, i: Interned<T>) -> &T {
+        &self.items[i.0]
+    }
+}
+
+#[derive(Default)]
+pub struct Interner {
+    strs: Mutex<TyIntern<String>>,
+    paths: Mutex<TyIntern<PathBuf>>,
+    lists: Mutex<TyIntern<Vec<String>>>,
+}
+
+trait Internable: Clone + Eq + Hash + 'static {
+    fn intern_cache() -> &'static Mutex<TyIntern<Self>>;
+
+    fn intern(self) -> Interned<Self> {
+        Self::intern_cache().lock().unwrap().intern(self)
+    }
+}
+
+impl Internable for String {
+    fn intern_cache() -> &'static Mutex<TyIntern<Self>> {
+        &INTERNER.strs
+    }
+}
+
+impl Internable for PathBuf {
+    fn intern_cache() -> &'static Mutex<TyIntern<Self>> {
+        &INTERNER.paths
+    }
+}
+
+impl Internable for Vec<String> {
+    fn intern_cache() -> &'static Mutex<TyIntern<Self>> {
+        &INTERNER.lists
+    }
+}
+
+impl Interner {
+    pub fn intern_str(&self, s: &str) -> Interned<String> {
+        self.strs.lock().unwrap().intern_borrow(s)
+    }
+    pub fn intern_string(&self, s: String) -> Interned<String> {
+        self.strs.lock().unwrap().intern(s)
+    }
+
+    pub fn intern_path(&self, s: PathBuf) -> Interned<PathBuf> {
+        self.paths.lock().unwrap().intern(s)
+    }
+
+    pub fn intern_list(&self, v: Vec<String>) -> Interned<Vec<String>> {
+        self.lists.lock().unwrap().intern(v)
+    }
+}
+
+pub static INTERNER: Lazy<Interner> = Lazy::new(Interner::default);
+
+/// This is essentially a `HashMap` which allows storing any type in its input and
+/// any type in its output. It is a write-once cache; values are never evicted,
+/// which means that references to the value can safely be returned from the
+/// `get()` method.
+#[derive(Debug)]
+pub struct Cache(
+    RefCell<
+        HashMap<
+            TypeId,
+            Box<dyn Any>, // actually a HashMap<Step, Interned<Step::Output>>
+        >,
+    >,
+);
+
+impl Cache {
+    pub fn new() -> Cache {
+        Cache(RefCell::new(HashMap::new()))
+    }
+
+    pub fn put<S: Step>(&self, step: S, value: S::Output) {
+        let mut cache = self.0.borrow_mut();
+        let type_id = TypeId::of::<S>();
+        let stepcache = cache
+            .entry(type_id)
+            .or_insert_with(|| Box::new(HashMap::<S, S::Output>::new()))
+            .downcast_mut::<HashMap<S, S::Output>>()
+            .expect("invalid type mapped");
+        assert!(!stepcache.contains_key(&step), "processing {:?} a second time", step);
+        stepcache.insert(step, value);
+    }
+
+    pub fn get<S: Step>(&self, step: &S) -> Option<S::Output> {
+        let mut cache = self.0.borrow_mut();
+        let type_id = TypeId::of::<S>();
+        let stepcache = cache
+            .entry(type_id)
+            .or_insert_with(|| Box::new(HashMap::<S, S::Output>::new()))
+            .downcast_mut::<HashMap<S, S::Output>>()
+            .expect("invalid type mapped");
+        stepcache.get(step).cloned()
+    }
+}
+
+#[cfg(test)]
+impl Cache {
+    pub fn all<S: Ord + Clone + Step>(&mut self) -> Vec<(S, S::Output)> {
+        let cache = self.0.get_mut();
+        let type_id = TypeId::of::<S>();
+        let mut v = cache
+            .remove(&type_id)
+            .map(|b| b.downcast::<HashMap<S, S::Output>>().expect("correct type"))
+            .map(|m| m.into_iter().collect::<Vec<_>>())
+            .unwrap_or_default();
+        v.sort_by_key(|(s, _)| s.clone());
+        v
+    }
+
+    pub fn contains<S: Step>(&self) -> bool {
+        self.0.borrow().contains_key(&TypeId::of::<S>())
+    }
+}