Replace ReseedWithDefault with ReseedWithNew

Author: pitdicker

src/lib.rs

@@ -276,6 +276,7 @@ use prng::Isaac64Rng as IsaacWordRng;
 
 use distributions::{Range, IndependentSample};
 use distributions::range::SampleRange;
+use reseeding::{ReseedingRng, ReseedWithNew};
 
 // public modules
 pub mod distributions;
@@ -933,58 +934,39 @@ pub fn weak_rng() -> XorShiftRng {
     XorShiftRng::new().unwrap()
 }
 
-/// Controls how the thread-local RNG is reseeded.
-#[cfg(feature="std")]
-#[derive(Debug)]
-struct ThreadRngReseeder;
-
-#[cfg(feature="std")]
-impl reseeding::Reseeder<StdRng> for ThreadRngReseeder {
-    fn reseed(&mut self, rng: &mut StdRng) {
-        match StdRng::new() {
-            Ok(r) => *rng = r,
-            Err(e) => panic!("No entropy available: {}", e),
-        }
-    }
-}
-#[cfg(feature="std")]
-const THREAD_RNG_RESEED_THRESHOLD: u64 = 32_768;
-#[cfg(feature="std")]
-type ThreadRngInner = reseeding::ReseedingRng<StdRng, ThreadRngReseeder>;
 
 /// The thread-local RNG.
 #[cfg(feature="std")]
 #[derive(Clone, Debug)]
 pub struct ThreadRng {
-    rng: Rc<RefCell<ThreadRngInner>>,
+    rng: Rc<RefCell<ReseedingRng<StdRng, ReseedWithNew>>>,
 }
 
-/// Retrieve the lazily-initialized thread-local random number
-/// generator, seeded by the system. Intended to be used in method
-/// chaining style, e.g. `thread_rng().gen::<i32>()`.
-///
-/// After generating a certain amount of randomness, the RNG will reseed itself
-/// from the operating system or, if the operating system RNG returns an error,
-/// a seed based on the current system time.
-///
-/// The internal RNG used is platform and architecture dependent, even
-/// if the operating system random number generator is rigged to give
-/// the same sequence always. If absolute consistency is required,
-/// explicitly select an RNG, e.g. `IsaacRng` or `Isaac64Rng`.
 #[cfg(feature="std")]
-pub fn thread_rng() -> ThreadRng {
-    // used to make space in TLS for a random number generator
-    thread_local!(static THREAD_RNG_KEY: Rc<RefCell<ThreadRngInner>> = {
+thread_local!(
+    static THREAD_RNG_KEY: Rc<RefCell<ReseedingRng<StdRng, ReseedWithNew>>> = {
+        const THREAD_RNG_RESEED_THRESHOLD: u64 = 32_768;
         let r = match StdRng::new() {
             Ok(r) => r,
-            Err(e) => panic!("No entropy available: {}", e),
+            Err(e) => panic!("could not initialize thread_rng: {:?}", e)
         };
-        let rng = reseeding::ReseedingRng::new(r,
-                                               THREAD_RNG_RESEED_THRESHOLD,
-                                               ThreadRngReseeder);
+        let rng = ReseedingRng::new(r,
+                                    THREAD_RNG_RESEED_THRESHOLD,
+                                    ReseedWithNew);
         Rc::new(RefCell::new(rng))
-    });
+    }
+);
 
+/// Retrieve the lazily-initialized thread-local random number
+/// generator, seeded by the system. Intended to be used in method
+/// chaining style, e.g. `thread_rng().gen::<i32>()`.
+///
+/// The internal RNG used is the one defined by `StdRng`. After generating 32KiB
+/// of random bytes, the RNG will reseed itself from the operating system or, if
+/// the operating system RNG returns an error, the `JitterRng` entropy
+/// collector.
+#[cfg(feature="std")]
+pub fn thread_rng() -> ThreadRng {
     ThreadRng { rng: THREAD_RNG_KEY.with(|t| t.clone()) }
 }
 

src/reseeding.rs

@@ -11,9 +11,9 @@
 //! A wrapper around another RNG that reseeds it after it
 //! generates a certain number of random bytes.
 
-use core::default::Default;
-
 use {Rng, Error};
+#[cfg(feature="std")]
+use NewSeeded;
 
 /// A wrapper around any RNG which reseeds the underlying RNG after it
 /// has generated a certain number of random bytes.
@@ -47,7 +47,7 @@ impl<R: Rng, Rsdr: Reseeder<R>> ReseedingRng<R, Rsdr> {
     /// generated exceed the threshold.
     pub fn reseed_if_necessary(&mut self) {
         if self.bytes_generated >= self.generation_threshold {
-            self.reseeder.reseed(&mut self.rng);
+            self.reseeder.reseed(&mut self.rng).unwrap();
             self.bytes_generated = 0;
         }
     }
@@ -85,30 +85,31 @@ impl<R: Rng, Rsdr: Reseeder<R>> Rng for ReseedingRng<R, Rsdr> {
 /// Note that implementations should support `Clone` only if reseeding is
 /// deterministic (no external entropy source). This is so that a `ReseedingRng`
 /// only supports `Clone` if fully deterministic.
-pub trait Reseeder<R> {
+pub trait Reseeder<R: ?Sized> {
     /// Reseed the given RNG.
-    fn reseed(&mut self, rng: &mut R);
+    ///
+    /// On error, this should just forward the source error; errors are handled
+    /// by the caller.
+    fn reseed(&mut self, rng: &mut R) -> Result<(), Error>;
 }
 
-/// Reseed an RNG using a `Default` instance. This reseeds by
-/// replacing the RNG with the result of a `Default::default` call.
-#[derive(Clone, Copy, Debug)]
-pub struct ReseedWithDefault;
+/// Reseed an RNG using `NewSeeded` to replace the current instance.
+#[cfg(feature="std")]
+#[derive(Debug)]
+pub struct ReseedWithNew;
 
-impl<R: Rng + Default> Reseeder<R> for ReseedWithDefault {
-    fn reseed(&mut self, rng: &mut R) {
-        *rng = Default::default();
+#[cfg(feature="std")]
+impl<R: Rng + NewSeeded> Reseeder<R> for ReseedWithNew {
+    fn reseed(&mut self, rng: &mut R) -> Result<(), Error> {
+        R::new().map(|result| *rng = result)
     }
 }
-impl Default for ReseedWithDefault {
-    fn default() -> ReseedWithDefault { ReseedWithDefault }
-}
 
 #[cfg(test)]
 mod test {
     use {impls, le};
     use core::default::Default;
-    use super::{ReseedingRng, ReseedWithDefault};
+    use super::{ReseedingRng, ReseedWithNew};
     use {SeedableRng, Rng};
 
     struct Counter {
@@ -142,11 +143,10 @@ mod test {
             Counter { i: seed_u32[0] }
         }
     }
-    type MyRng = ReseedingRng<Counter, ReseedWithDefault>;
 
     #[test]
     fn test_reseeding() {
-        let mut rs = ReseedingRng::new(Counter {i:0}, 400, ReseedWithDefault);
+        let mut rs = ReseedingRng::new(Counter {i:0}, 400, ReseedWithNew);
 
         let mut i = 0;
         for _ in 0..1000 {