Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 124 insertions, 0 deletions

diff --git a/third_party/rust/rand/src/rngs/thread.rs b/third_party/rust/rand/src/rngs/thread.rs
new file mode 100644
index 0000000000..2006f4176f
--- /dev/null
+++ b/third_party/rust/rand/src/rngs/thread.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.
+
+//! Thread-local random number generator
+
+use std::cell::UnsafeCell;
+use std::ptr::NonNull;
+
+use crate::{RngCore, CryptoRng, SeedableRng, Error};
+use crate::rngs::adapter::ReseedingRng;
+use crate::rngs::OsRng;
+use super::std::Core;
+
+// Rationale for using `UnsafeCell` in `ThreadRng`:
+//
+// Previously we used a `RefCell`, with an overhead of ~15%. There will only
+// ever be one mutable reference to the interior of the `UnsafeCell`, because
+// we only have such a reference inside `next_u32`, `next_u64`, etc. Within a
+// single thread (which is the definition of `ThreadRng`), there will only ever
+// be one of these methods active at a time.
+//
+// A possible scenario where there could be multiple mutable references is if
+// `ThreadRng` is used inside `next_u32` and co. But the implementation is
+// completely under our control. We just have to ensure none of them use
+// `ThreadRng` internally, which is nonsensical anyway. We should also never run
+// `ThreadRng` in destructors of its implementation, which is also nonsensical.
+
+
+// Number of generated bytes after which to reseed `ThreadRng`.
+// According to benchmarks, reseeding has a noticable impact with thresholds
+// of 32 kB and less. We choose 64 kB to avoid significant overhead.
+const THREAD_RNG_RESEED_THRESHOLD: u64 = 1024 * 64;
+
+/// The type returned by [`thread_rng`], essentially just a reference to the
+/// PRNG in thread-local memory.
+///
+/// `ThreadRng` uses the same PRNG as [`StdRng`] for security and performance.
+/// As hinted by the name, the generator is thread-local. `ThreadRng` is a
+/// handle to this generator and thus supports `Copy`, but not `Send` or `Sync`.
+///
+/// Unlike `StdRng`, `ThreadRng` uses the  [`ReseedingRng`] wrapper to reseed
+/// the PRNG from fresh entropy every 64 kiB of random data.
+/// [`OsRng`] is used to provide seed data.
+///
+/// Note that the reseeding is done as an extra precaution against side-channel
+/// attacks and mis-use (e.g. if somehow weak entropy were supplied initially).
+/// The PRNG algorithms used are assumed to be secure.
+///
+/// [`ReseedingRng`]: crate::rngs::adapter::ReseedingRng
+/// [`StdRng`]: crate::rngs::StdRng
+#[derive(Copy, Clone, Debug)]
+pub struct ThreadRng {
+    // inner raw pointer implies type is neither Send nor Sync
+    rng: NonNull<ReseedingRng<Core, OsRng>>,
+}
+
+thread_local!(
+    static THREAD_RNG_KEY: UnsafeCell<ReseedingRng<Core, OsRng>> = {
+        let r = Core::from_rng(OsRng).unwrap_or_else(|err|
+                panic!("could not initialize thread_rng: {}", err));
+        let rng = ReseedingRng::new(r,
+                                    THREAD_RNG_RESEED_THRESHOLD,
+                                    OsRng);
+        UnsafeCell::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>()`, or cached locally, e.g.
+/// `let mut rng = thread_rng();`.  Invoked by the `Default` trait, making
+/// `ThreadRng::default()` equivalent.
+///
+/// For more information see [`ThreadRng`].
+pub fn thread_rng() -> ThreadRng {
+    let raw = THREAD_RNG_KEY.with(|t| t.get());
+    let nn = NonNull::new(raw).unwrap();
+    ThreadRng { rng: nn }
+}
+
+impl Default for ThreadRng {
+    fn default() -> ThreadRng {
+        crate::prelude::thread_rng()
+    }
+}
+
+impl RngCore for ThreadRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        unsafe { self.rng.as_mut().next_u32() }
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        unsafe { self.rng.as_mut().next_u64() }
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        unsafe { self.rng.as_mut().fill_bytes(dest) }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        unsafe { self.rng.as_mut().try_fill_bytes(dest) }
+    }
+}
+
+impl CryptoRng for ThreadRng {}
+
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_thread_rng() {
+        use crate::Rng;
+        let mut r = crate::thread_rng();
+        r.gen::<i32>();
+        assert_eq!(r.gen_range(0, 1), 0);
+    }
+}