1 files changed, 98 insertions, 0 deletions
diff --git a/third_party/rust/rand/src/rngs/std.rs b/third_party/rust/rand/src/rngs/std.rs
new file mode 100644
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+++ b/third_party/rust/rand/src/rngs/std.rs
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+// 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 crate::{CryptoRng, Error, RngCore, SeedableRng};
+
+pub(crate) use rand_chacha::ChaCha12Core as Core;
+
+use rand_chacha::ChaCha12Rng as Rng;
+
+/// 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 is the ChaCha block cipher with 12 rounds. Please
+/// see this relevant [rand issue] for the discussion. This may change as new 
+/// evidence of cipher security and performance becomes available.
+///
+/// The algorithm is deterministic but should not be considered reproducible
+/// due to dependence on configuration and possible replacement in future
+/// library versions. For a secure reproducible generator, we recommend use of
+/// the [rand_chacha] crate directly.
+///
+/// [rand_chacha]: https://crates.io/crates/rand_chacha
+/// [rand issue]: https://github.com/rust-random/rand/issues/932
+#[cfg_attr(doc_cfg, doc(cfg(feature = "std_rng")))]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StdRng(Rng);
+
+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()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for StdRng {
+    type Seed = <Rng as SeedableRng>::Seed;
+
+    #[inline(always)]
+    fn from_seed(seed: Self::Seed) -> Self {
+        StdRng(Rng::from_seed(seed))
+    }
+
+    #[inline(always)]
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        Rng::from_rng(rng).map(StdRng)
+    }
+}
+
+impl CryptoRng for StdRng {}
+
+
+#[cfg(test)]
+mod test {
+    use crate::rngs::StdRng;
+    use crate::{RngCore, SeedableRng};
+
+    #[test]
+    fn test_stdrng_construction() {
+        // Test value-stability of StdRng. This is expected to break any time
+        // the algorithm is changed.
+        #[rustfmt::skip]
+        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 target = [10719222850664546238, 14064965282130556830];
+
+        let mut rng0 = StdRng::from_seed(seed);
+        let x0 = rng0.next_u64();
+
+        let mut rng1 = StdRng::from_rng(rng0).unwrap();
+        let x1 = rng1.next_u64();
+
+        assert_eq!([x0, x1], target);
+    }
+}