Remove use of 'unsafe' in 'Fairings'.

core/lib/src/fairing/fairings.rs

@@ -1,13 +1,16 @@
 use {Rocket, Request, Response, Data};
 use fairing::{Fairing, Kind};
 
+use yansi::Paint;
+
 #[derive(Default)]
 pub struct Fairings {
     all_fairings: Vec<Box<Fairing>>,
     attach_failures: Vec<&'static str>,
-    launch: Vec<&'static Fairing>,
-    request: Vec<&'static Fairing>,
-    response: Vec<&'static Fairing>,
+    // The vectors below hold indices into `all_fairings`.
+    launch: Vec<usize>,
+    request: Vec<usize>,
+    response: Vec<usize>,
 }
 
 impl Fairings {
@@ -30,32 +33,14 @@ impl Fairings {
     }
 
     fn add(&mut self, fairing: Box<Fairing>) {
-        // The `Fairings` structure separates `all_fairings` into kind groups so
-        // we don't have to search through all fairings and do a comparison at
-        // runtime. We need references since a single structure can be multiple
-        // kinds. The lifetime of that reference is really the lifetime of the
-        // `Box` for referred fairing, but that lifetime is dynamic; there's no
-        // way to express it. So we cheat and say that the lifetime is
-        // `'static` and cast it here. For this to be safe, the following must
-        // be preserved:
-        //
-        //  1) The references can never be exposed with a `'static` lifetime.
-        //  2) The `Box<Fairing>` must live for the lifetime of the reference.
-        //
-        // We maintain these invariants by not exposing the references and never
-        // deallocating `Box<Fairing>` structures. As such, the references will
-        // always be valid. Note: `ptr` doesn't point into the `Vec`, so
-        // reallocations there are irrelevant. Instead, it points into the heap.
-        //
-        // Also, we don't save attach fairings since we don't need them anymore.
         let kind = fairing.info().kind;
         if !kind.is_exactly(Kind::Attach) {
-            let ptr: &'static Fairing = unsafe { ::std::mem::transmute(&*fairing) };
-
+            let index = self.all_fairings.len();
             self.all_fairings.push(fairing);
-            if kind.is(Kind::Launch) { self.launch.push(ptr); }
-            if kind.is(Kind::Request) { self.request.push(ptr); }
-            if kind.is(Kind::Response) { self.response.push(ptr); }
+
+            if kind.is(Kind::Launch) { self.launch.push(index); }
+            if kind.is(Kind::Request) { self.request.push(index); }
+            if kind.is(Kind::Response) { self.response.push(index); }
         }
     }
 
@@ -67,22 +52,22 @@ impl Fairings {
 
     #[inline(always)]
     pub fn handle_launch(&self, rocket: &Rocket) {
-        for fairing in &self.launch {
-            fairing.on_launch(rocket);
+        for &i in &self.launch {
+            self.all_fairings[i].on_launch(rocket);
         }
     }
 
     #[inline(always)]
     pub fn handle_request(&self, req: &mut Request, data: &Data) {
-        for fairing in &self.request {
-            fairing.on_request(req, data);
+        for &i in &self.request {
+            self.all_fairings[i].on_request(req, data);
         }
     }
 
     #[inline(always)]
     pub fn handle_response(&self, request: &Request, response: &mut Response) {
-        for fairing in &self.response {
-            fairing.on_response(request, response);
+        for &i in &self.response {
+            self.all_fairings[i].on_response(request, response);
         }
     }
 
@@ -94,14 +79,11 @@ impl Fairings {
         }
     }
 
-    pub fn pretty_print_counts(&self) {
-        use yansi::Paint;
-
-        fn info_if_nonempty(kind: &str, fairings: &[&Fairing]) {
+    fn info_for(&self, kind: &str, fairings: &[usize]) {
         if !fairings.is_empty() {
             let num = fairings.len();
-                let names = fairings.iter()
-                    .map(|f| f.info().name)
+            let names = fairings.iter().cloned()
+                .map(|i| self.all_fairings[i].info().name)
                 .collect::<Vec<_>>()
                 .join(", ");
 
@@ -109,11 +91,12 @@ impl Fairings {
         }
     }
 
+    pub fn pretty_print_counts(&self) {
         if !self.all_fairings.is_empty() {
             info!("{}{}:", Paint::masked("📡  "), Paint::purple("Fairings"));
-            info_if_nonempty("launch", &self.launch);
-            info_if_nonempty("request", &self.request);
-            info_if_nonempty("response", &self.response);
+            self.info_for("launch", &self.launch);
+            self.info_for("request", &self.request);
+            self.info_for("response", &self.response);
         }
     }
 }