1 files changed, 81 insertions, 0 deletions
diff --git a/rand/src/rngs/std.rs b/rand/src/rngs/std.rs
new file mode 100644
index 0000000..ce1658b
--- /dev/null
+++ b/rand/src/rngs/std.rs
@@ -0,0 +1,81 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The standard RNG
+
+use {RngCore, CryptoRng, Error, SeedableRng};
+use rand_hc::Hc128Rng;
+
+/// The standard RNG. The PRNG algorithm in `StdRng` is chosen to be efficient
+/// on the current platform, to be statistically strong and unpredictable
+/// (meaning a cryptographically secure PRNG).
+///
+/// The current algorithm used on all platforms is [HC-128].
+///
+/// Reproducibility of output from this generator is however not required, thus
+/// future library versions may use a different internal generator with
+/// different output. Further, this generator may not be portable and can
+/// produce different output depending on the architecture. If you require
+/// reproducible output, use a named RNG, for example [`ChaChaRng`].
+///
+/// [HC-128]: ../../rand_hc/struct.Hc128Rng.html
+/// [`ChaChaRng`]: ../../rand_chacha/struct.ChaChaRng.html
+#[derive(Clone, Debug)]
+pub struct StdRng(Hc128Rng);
+
+impl RngCore for StdRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for StdRng {
+    type Seed = <Hc128Rng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        StdRng(Hc128Rng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        Hc128Rng::from_rng(rng).map(StdRng)
+    }
+}
+
+impl CryptoRng for StdRng {}
+
+
+#[cfg(test)]
+mod test {
+    use {RngCore, SeedableRng};
+    use rngs::StdRng;
+
+    #[test]
+    fn test_stdrng_construction() {
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng1 = StdRng::from_seed(seed);
+        assert_eq!(rng1.next_u64(), 15759097995037006553);
+
+        let mut rng2 = StdRng::from_rng(rng1).unwrap();
+        assert_eq!(rng2.next_u64(), 6766915756997287454);
+    }
+}