Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

5 files changed, 1320 insertions, 0 deletions

diff --git a/vendor/rand_core/src/block.rs b/vendor/rand_core/src/block.rs
new file mode 100644
index 0000000..7d91263
--- /dev/null
+++ b/vendor/rand_core/src/block.rs
@@ -0,0 +1,433 @@
+// 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 `BlockRngCore` trait and implementation helpers
+//!
+//! The [`BlockRngCore`] trait exists to assist in the implementation of RNGs
+//! which generate a block of data in a cache instead of returning generated
+//! values directly.
+//!
+//! Usage of this trait is optional, but provides two advantages:
+//! implementations only need to concern themselves with generation of the
+//! block, not the various [`RngCore`] methods (especially [`fill_bytes`], where
+//! the optimal implementations are not trivial), and this allows
+//! `ReseedingRng` (see [`rand`](https://docs.rs/rand) crate) perform periodic
+//! reseeding with very low overhead.
+//!
+//! # Example
+//!
+//! ```norun
+//! use rand_core::block::{BlockRngCore, BlockRng};
+//!
+//! struct MyRngCore;
+//!
+//! impl BlockRngCore for MyRngCore {
+//!     type Results = [u32; 16];
+//!
+//!     fn generate(&mut self, results: &mut Self::Results) {
+//!         unimplemented!()
+//!     }
+//! }
+//!
+//! impl SeedableRng for MyRngCore {
+//!     type Seed = unimplemented!();
+//!     fn from_seed(seed: Self::Seed) -> Self {
+//!         unimplemented!()
+//!     }
+//! }
+//!
+//! // optionally, also implement CryptoRng for MyRngCore
+//!
+//! // Final RNG.
+//! type MyRng = BlockRng<u32, MyRngCore>;
+//! ```
+//!
+//! [`BlockRngCore`]: crate::block::BlockRngCore
+//! [`fill_bytes`]: RngCore::fill_bytes
+
+use core::convert::AsRef;
+use core::{fmt, ptr};
+use {RngCore, CryptoRng, SeedableRng, Error};
+use impls::{fill_via_u32_chunks, fill_via_u64_chunks};
+
+/// A trait for RNGs which do not generate random numbers individually, but in
+/// blocks (typically `[u32; N]`). This technique is commonly used by
+/// cryptographic RNGs to improve performance.
+///
+/// See the [module][crate::block] documentation for details.
+pub trait BlockRngCore {
+    /// Results element type, e.g. `u32`.
+    type Item;
+
+    /// Results type. This is the 'block' an RNG implementing `BlockRngCore`
+    /// generates, which will usually be an array like `[u32; 16]`.
+    type Results: AsRef<[Self::Item]> + AsMut<[Self::Item]> + Default;
+
+    /// Generate a new block of results.
+    fn generate(&mut self, results: &mut Self::Results);
+}
+
+
+/// A wrapper type implementing [`RngCore`] for some type implementing
+/// [`BlockRngCore`] with `u32` array buffer; i.e. this can be used to implement
+/// a full RNG from just a `generate` function.
+///
+/// The `core` field may be accessed directly but the results buffer may not.
+/// PRNG implementations can simply use a type alias
+/// (`pub type MyRng = BlockRng<MyRngCore>;`) but might prefer to use a
+/// wrapper type (`pub struct MyRng(BlockRng<MyRngCore>);`); the latter must
+/// re-implement `RngCore` but hides the implementation details and allows
+/// extra functionality to be defined on the RNG
+/// (e.g. `impl MyRng { fn set_stream(...){...} }`).
+///
+/// `BlockRng` has heavily optimized implementations of the [`RngCore`] methods
+/// reading values from the results buffer, as well as
+/// calling [`BlockRngCore::generate`] directly on the output array when
+/// [`fill_bytes`] / [`try_fill_bytes`] is called on a large array. These methods
+/// also handle the bookkeeping of when to generate a new batch of values.
+///
+/// No whole generated `u32` values are thown away and all values are consumed
+/// in-order. [`next_u32`] simply takes the next available `u32` value.
+/// [`next_u64`] is implemented by combining two `u32` values, least
+/// significant first. [`fill_bytes`] and [`try_fill_bytes`] consume a whole
+/// number of `u32` values, converting each `u32` to a byte slice in
+/// little-endian order. If the requested byte length is not a multiple of 4,
+/// some bytes will be discarded.
+///
+/// See also [`BlockRng64`] which uses `u64` array buffers. Currently there is
+/// no direct support for other buffer types.
+///
+/// For easy initialization `BlockRng` also implements [`SeedableRng`].
+///
+/// [`next_u32`]: RngCore::next_u32
+/// [`next_u64`]: RngCore::next_u64
+/// [`fill_bytes`]: RngCore::fill_bytes
+/// [`try_fill_bytes`]: RngCore::try_fill_bytes
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct BlockRng<R: BlockRngCore + ?Sized> {
+    results: R::Results,
+    index: usize,
+    /// The *core* part of the RNG, implementing the `generate` function.
+    pub core: R,
+}
+
+// Custom Debug implementation that does not expose the contents of `results`.
+impl<R: BlockRngCore + fmt::Debug> fmt::Debug for BlockRng<R> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("BlockRng")
+           .field("core", &self.core)
+           .field("result_len", &self.results.as_ref().len())
+           .field("index", &self.index)
+           .finish()
+    }
+}
+
+impl<R: BlockRngCore> BlockRng<R> {
+    /// Create a new `BlockRng` from an existing RNG implementing
+    /// `BlockRngCore`. Results will be generated on first use.
+    #[inline]
+    pub fn new(core: R) -> BlockRng<R>{
+        let results_empty = R::Results::default();
+        BlockRng {
+            core,
+            index: results_empty.as_ref().len(),
+            results: results_empty,
+        }
+    }
+
+    /// Get the index into the result buffer.
+    ///
+    /// If this is equal to or larger than the size of the result buffer then
+    /// the buffer is "empty" and `generate()` must be called to produce new
+    /// results.
+    #[inline(always)]
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// Reset the number of available results.
+    /// This will force a new set of results to be generated on next use.
+    #[inline]
+    pub fn reset(&mut self) {
+        self.index = self.results.as_ref().len();
+    }
+
+    /// Generate a new set of results immediately, setting the index to the
+    /// given value.
+    #[inline]
+    pub fn generate_and_set(&mut self, index: usize) {
+        assert!(index < self.results.as_ref().len());
+        self.core.generate(&mut self.results);
+        self.index = index;
+    }
+}
+
+impl<R: BlockRngCore<Item=u32>> RngCore for BlockRng<R>
+where <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
+{
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        if self.index >= self.results.as_ref().len() {
+            self.generate_and_set(0);
+        }
+
+        let value = self.results.as_ref()[self.index];
+        self.index += 1;
+        value
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        let read_u64 = |results: &[u32], index| {
+            if cfg!(any(target_endian = "little")) {
+                // requires little-endian CPU
+                let ptr: *const u64 = results[index..index+2].as_ptr() as *const u64;
+                unsafe { ptr::read_unaligned(ptr) }
+            } else {
+                let x = u64::from(results[index]);
+                let y = u64::from(results[index + 1]);
+                (y << 32) | x
+            }
+        };
+
+        let len = self.results.as_ref().len();
+
+        let index = self.index;
+        if index < len-1 {
+            self.index += 2;
+            // Read an u64 from the current index
+            read_u64(self.results.as_ref(), index)
+        } else if index >= len {
+            self.generate_and_set(2);
+            read_u64(self.results.as_ref(), 0)
+        } else {
+            let x = u64::from(self.results.as_ref()[len-1]);
+            self.generate_and_set(1);
+            let y = u64::from(self.results.as_ref()[0]);
+            (y << 32) | x
+        }
+    }
+
+    #[inline]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let mut read_len = 0;
+        while read_len < dest.len() {
+            if self.index >= self.results.as_ref().len() {
+                self.generate_and_set(0);
+            }
+            let (consumed_u32, filled_u8) =
+                fill_via_u32_chunks(&self.results.as_ref()[self.index..],
+                                    &mut dest[read_len..]);
+
+            self.index += consumed_u32;
+            read_len += filled_u8;
+        }
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
+
+impl<R: BlockRngCore + SeedableRng> SeedableRng for BlockRng<R> {
+    type Seed = R::Seed;
+
+    #[inline(always)]
+    fn from_seed(seed: Self::Seed) -> Self {
+        Self::new(R::from_seed(seed))
+    }
+
+    #[inline(always)]
+    fn seed_from_u64(seed: u64) -> Self {
+        Self::new(R::seed_from_u64(seed))
+    }
+
+    #[inline(always)]
+    fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> {
+        Ok(Self::new(R::from_rng(rng)?))
+    }
+}
+
+
+
+/// A wrapper type implementing [`RngCore`] for some type implementing
+/// [`BlockRngCore`] with `u64` array buffer; i.e. this can be used to implement
+/// a full RNG from just a `generate` function.
+///
+/// This is similar to [`BlockRng`], but specialized for algorithms that operate
+/// on `u64` values.
+///
+/// No whole generated `u64` values are thrown away and all values are consumed
+/// in-order. [`next_u64`] simply takes the next available `u64` value.
+/// [`next_u32`] is however a bit special: half of a `u64` is consumed, leaving
+/// the other half in the buffer. If the next function called is [`next_u32`]
+/// then the other half is then consumed, however both [`next_u64`] and
+/// [`fill_bytes`] discard the rest of any half-consumed `u64`s when called.
+///
+/// [`fill_bytes`] and [`try_fill_bytes`] consume a whole number of `u64`
+/// values. If the requested length is not a multiple of 8, some bytes will be
+/// discarded.
+///
+/// [`next_u32`]: RngCore::next_u32
+/// [`next_u64`]: RngCore::next_u64
+/// [`fill_bytes`]: RngCore::fill_bytes
+/// [`try_fill_bytes`]: RngCore::try_fill_bytes
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct BlockRng64<R: BlockRngCore + ?Sized> {
+    results: R::Results,
+    index: usize,
+    half_used: bool, // true if only half of the previous result is used
+    /// The *core* part of the RNG, implementing the `generate` function.
+    pub core: R,
+}
+
+// Custom Debug implementation that does not expose the contents of `results`.
+impl<R: BlockRngCore + fmt::Debug> fmt::Debug for BlockRng64<R> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("BlockRng64")
+           .field("core", &self.core)
+           .field("result_len", &self.results.as_ref().len())
+           .field("index", &self.index)
+           .field("half_used", &self.half_used)
+           .finish()
+    }
+}
+
+impl<R: BlockRngCore> BlockRng64<R> {
+    /// Create a new `BlockRng` from an existing RNG implementing
+    /// `BlockRngCore`. Results will be generated on first use.
+    #[inline]
+    pub fn new(core: R) -> BlockRng64<R>{
+        let results_empty = R::Results::default();
+        BlockRng64 {
+            core,
+            index: results_empty.as_ref().len(),
+            half_used: false,
+            results: results_empty,
+        }
+    }
+
+    /// Get the index into the result buffer.
+    ///
+    /// If this is equal to or larger than the size of the result buffer then
+    /// the buffer is "empty" and `generate()` must be called to produce new
+    /// results.
+    #[inline(always)]
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// Reset the number of available results.
+    /// This will force a new set of results to be generated on next use.
+    #[inline]
+    pub fn reset(&mut self) {
+        self.index = self.results.as_ref().len();
+        self.half_used = false;
+    }
+
+    /// Generate a new set of results immediately, setting the index to the
+    /// given value.
+    #[inline]
+    pub fn generate_and_set(&mut self, index: usize) {
+        assert!(index < self.results.as_ref().len());
+        self.core.generate(&mut self.results);
+        self.index = index;
+        self.half_used = false;
+    }
+}
+
+impl<R: BlockRngCore<Item=u64>> RngCore for BlockRng64<R>
+where <R as BlockRngCore>::Results: AsRef<[u64]> + AsMut<[u64]>
+{
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        let mut index = self.index * 2 - self.half_used as usize;
+        if index >= self.results.as_ref().len() * 2 {
+            self.core.generate(&mut self.results);
+            self.index = 0;
+            // `self.half_used` is by definition `false`
+            self.half_used = false;
+            index = 0;
+        }
+
+        self.half_used = !self.half_used;
+        self.index += self.half_used as usize;
+
+        // Index as if this is a u32 slice.
+        unsafe {
+            let results =
+                &*(self.results.as_ref() as *const [u64] as *const [u32]);
+            if cfg!(target_endian = "little") {
+                *results.get_unchecked(index)
+            } else {
+                *results.get_unchecked(index ^ 1)
+            }
+        }
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        if self.index >= self.results.as_ref().len() {
+            self.core.generate(&mut self.results);
+            self.index = 0;
+        }
+
+        let value = self.results.as_ref()[self.index];
+        self.index += 1;
+        self.half_used = false;
+        value
+    }
+
+    #[inline]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let mut read_len = 0;
+        self.half_used = false;
+        while read_len < dest.len() {
+            if self.index as usize >= self.results.as_ref().len() {
+                self.core.generate(&mut self.results);
+                self.index = 0;
+            }
+
+            let (consumed_u64, filled_u8) =
+                fill_via_u64_chunks(&self.results.as_ref()[self.index as usize..],
+                                    &mut dest[read_len..]);
+
+            self.index += consumed_u64;
+            read_len += filled_u8;
+        }
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
+
+impl<R: BlockRngCore + SeedableRng> SeedableRng for BlockRng64<R> {
+    type Seed = R::Seed;
+
+    #[inline(always)]
+    fn from_seed(seed: Self::Seed) -> Self {
+        Self::new(R::from_seed(seed))
+    }
+
+    #[inline(always)]
+    fn seed_from_u64(seed: u64) -> Self {
+        Self::new(R::seed_from_u64(seed))
+    }
+
+    #[inline(always)]
+    fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> {
+        Ok(Self::new(R::from_rng(rng)?))
+    }
+}
+
+impl<R: BlockRngCore + CryptoRng> CryptoRng for BlockRng<R> {}
diff --git a/vendor/rand_core/src/error.rs b/vendor/rand_core/src/error.rs
new file mode 100644
index 0000000..5a8459e
--- /dev/null
+++ b/vendor/rand_core/src/error.rs
@@ -0,0 +1,177 @@
+// 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.
+
+//! Error types
+
+use core::fmt;
+
+#[cfg(feature="std")]
+use std::error::Error as stdError;
+#[cfg(feature="std")]
+use std::io;
+
+/// Error kind which can be matched over.
+#[derive(PartialEq, Eq, Debug, Copy, Clone)]
+pub enum ErrorKind {
+    /// Feature is not available; not recoverable.
+    /// 
+    /// This is the most permanent failure type and implies the error cannot be
+    /// resolved simply by retrying (e.g. the feature may not exist in this
+    /// build of the application or on the current platform).
+    Unavailable,
+    /// General failure; there may be a chance of recovery on retry.
+    /// 
+    /// This is the catch-all kind for errors from known and unknown sources
+    /// which do not have a more specific kind / handling method.
+    /// 
+    /// It is suggested to retry a couple of times or retry later when
+    /// handling; some error sources may be able to resolve themselves,
+    /// although this is not likely.
+    Unexpected,
+    /// A transient failure which likely can be resolved or worked around.
+    /// 
+    /// This error kind exists for a few specific cases where it is known that
+    /// the error likely can be resolved internally, but is reported anyway.
+    Transient,
+    /// Not ready yet: recommended to try again a little later.
+    /// 
+    /// This error kind implies the generator needs more time or needs some
+    /// other part of the application to do something else first before it is
+    /// ready for use; for example this may be used by external generators
+    /// which require time for initialization.
+    NotReady,
+    #[doc(hidden)]
+    __Nonexhaustive,
+}
+
+impl ErrorKind {
+    /// True if this kind of error may resolve itself on retry.
+    /// 
+    /// See also `should_wait()`.
+    pub fn should_retry(self) -> bool {
+        self != ErrorKind::Unavailable
+    }
+    
+    /// True if we should retry but wait before retrying
+    /// 
+    /// This implies `should_retry()` is true.
+    pub fn should_wait(self) -> bool {
+        self == ErrorKind::NotReady
+    }
+    
+    /// A description of this error kind
+    pub fn description(self) -> &'static str {
+        match self {
+            ErrorKind::Unavailable => "permanently unavailable",
+            ErrorKind::Unexpected => "unexpected failure",
+            ErrorKind::Transient => "transient failure",
+            ErrorKind::NotReady => "not ready yet",
+            ErrorKind::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
+
+
+/// Error type of random number generators
+/// 
+/// This is a relatively simple error type, designed for compatibility with and
+/// without the Rust `std` library. It embeds a "kind" code, a message (static
+/// string only), and an optional chained cause (`std` only). The `kind` and
+/// `msg` fields can be accessed directly; cause can be accessed via
+/// `std::error::Error::cause` or `Error::take_cause`. Construction can only be
+/// done via `Error::new` or `Error::with_cause`.
+#[derive(Debug)]
+pub struct Error {
+    /// The error kind
+    pub kind: ErrorKind,
+    /// The error message
+    pub msg: &'static str,
+    #[cfg(feature="std")]
+    cause: Option<Box<stdError + Send + Sync>>,
+}
+
+impl Error {
+    /// Create a new instance, with specified kind and a message.
+    pub fn new(kind: ErrorKind, msg: &'static str) -> Self {
+        #[cfg(feature="std")] {
+            Error { kind, msg, cause: None }
+        }
+        #[cfg(not(feature="std"))] {
+            Error { kind, msg }
+        }
+    }
+    
+    /// Create a new instance, with specified kind, message, and a
+    /// chained cause.
+    /// 
+    /// Note: `stdError` is an alias for `std::error::Error`.
+    /// 
+    /// If not targetting `std` (i.e. `no_std`), this function is replaced by
+    /// another with the same prototype, except that there are no bounds on the
+    /// type `E` (because both `Box` and `stdError` are unavailable), and the
+    /// `cause` is ignored.
+    #[cfg(feature="std")]
+    pub fn with_cause<E>(kind: ErrorKind, msg: &'static str, cause: E) -> Self
+        where E: Into<Box<stdError + Send + Sync>>
+    {
+        Error { kind, msg, cause: Some(cause.into()) }
+    }
+    
+    /// Create a new instance, with specified kind, message, and a
+    /// chained cause.
+    /// 
+    /// In `no_std` mode the *cause* is ignored.
+    #[cfg(not(feature="std"))]
+    pub fn with_cause<E>(kind: ErrorKind, msg: &'static str, _cause: E) -> Self {
+        Error { kind, msg }
+    }
+    
+    /// Take the cause, if any. This allows the embedded cause to be extracted.
+    /// This uses `Option::take`, leaving `self` with no cause.
+    #[cfg(feature="std")]
+    pub fn take_cause(&mut self) -> Option<Box<stdError + Send + Sync>> {
+        self.cause.take()
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        #[cfg(feature="std")] {
+            if let Some(ref cause) = self.cause {
+                return write!(f, "{} ({}); cause: {}",
+                        self.msg, self.kind.description(), cause);
+            }
+        }
+        write!(f, "{} ({})", self.msg, self.kind.description())
+    }
+}
+
+#[cfg(feature="std")]
+impl stdError for Error {
+    fn description(&self) -> &str {
+        self.msg
+    }
+
+    fn cause(&self) -> Option<&stdError> {
+        self.cause.as_ref().map(|e| e.as_ref() as &stdError)
+    }
+}
+
+#[cfg(feature="std")]
+impl From<Error> for io::Error {
+    fn from(error: Error) -> Self {
+        use std::io::ErrorKind::*;
+        match error.kind {
+            ErrorKind::Unavailable => io::Error::new(NotFound, error),
+            ErrorKind::Unexpected |
+            ErrorKind::Transient => io::Error::new(Other, error),
+            ErrorKind::NotReady => io::Error::new(WouldBlock, error),
+            ErrorKind::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
diff --git a/vendor/rand_core/src/impls.rs b/vendor/rand_core/src/impls.rs
new file mode 100644
index 0000000..57bdd07
--- /dev/null
+++ b/vendor/rand_core/src/impls.rs
@@ -0,0 +1,165 @@
+// 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.
+
+//! Helper functions for implementing `RngCore` functions.
+//!
+//! For cross-platform reproducibility, these functions all use Little Endian:
+//! least-significant part first. For example, `next_u64_via_u32` takes `u32`
+//! values `x, y`, then outputs `(y << 32) | x`. To implement `next_u32`
+//! from `next_u64` in little-endian order, one should use `next_u64() as u32`.
+//!
+//! Byte-swapping (like the std `to_le` functions) is only needed to convert
+//! to/from byte sequences, and since its purpose is reproducibility,
+//! non-reproducible sources (e.g. `OsRng`) need not bother with it.
+
+use core::intrinsics::transmute;
+use core::ptr::copy_nonoverlapping;
+use core::slice;
+use core::cmp::min;
+use core::mem::size_of;
+use RngCore;
+
+
+/// Implement `next_u64` via `next_u32`, little-endian order.
+pub fn next_u64_via_u32<R: RngCore + ?Sized>(rng: &mut R) -> u64 {
+    // Use LE; we explicitly generate one value before the next.
+    let x = u64::from(rng.next_u32());
+    let y = u64::from(rng.next_u32());
+    (y << 32) | x
+}
+
+/// Implement `fill_bytes` via `next_u64` and `next_u32`, little-endian order.
+///
+/// The fastest way to fill a slice is usually to work as long as possible with
+/// integers. That is why this method mostly uses `next_u64`, and only when
+/// there are 4 or less bytes remaining at the end of the slice it uses
+/// `next_u32` once.
+pub fn fill_bytes_via_next<R: RngCore + ?Sized>(rng: &mut R, dest: &mut [u8]) {
+    let mut left = dest;
+    while left.len() >= 8 {
+        let (l, r) = {left}.split_at_mut(8);
+        left = r;
+        let chunk: [u8; 8] = unsafe {
+            transmute(rng.next_u64().to_le())
+        };
+        l.copy_from_slice(&chunk);
+    }
+    let n = left.len();
+    if n > 4 {
+        let chunk: [u8; 8] = unsafe {
+            transmute(rng.next_u64().to_le())
+        };
+        left.copy_from_slice(&chunk[..n]);
+    } else if n > 0 {
+        let chunk: [u8; 4] = unsafe {
+            transmute(rng.next_u32().to_le())
+        };
+        left.copy_from_slice(&chunk[..n]);
+    }
+}
+
+macro_rules! impl_uint_from_fill {
+    ($rng:expr, $ty:ty, $N:expr) => ({
+        debug_assert!($N == size_of::<$ty>());
+
+        let mut int: $ty = 0;
+        unsafe {
+            let ptr = &mut int as *mut $ty as *mut u8;
+            let slice = slice::from_raw_parts_mut(ptr, $N);
+            $rng.fill_bytes(slice);
+        }
+        int
+    });
+}
+
+macro_rules! fill_via_chunks {
+    ($src:expr, $dst:expr, $ty:ty, $size:expr) => ({
+        let chunk_size_u8 = min($src.len() * $size, $dst.len());
+        let chunk_size = (chunk_size_u8 + $size - 1) / $size;
+        if cfg!(target_endian="little") {
+            unsafe {
+                copy_nonoverlapping(
+                    $src.as_ptr() as *const u8,
+                    $dst.as_mut_ptr(),
+                    chunk_size_u8);
+            }
+        } else {
+            for (&n, chunk) in $src.iter().zip($dst.chunks_mut($size)) {
+                let tmp = n.to_le();
+                let src_ptr = &tmp as *const $ty as *const u8;
+                unsafe {
+                    copy_nonoverlapping(src_ptr,
+                                        chunk.as_mut_ptr(),
+                                        chunk.len());
+                }
+            }
+        }
+
+        (chunk_size, chunk_size_u8)
+    });
+}
+
+/// Implement `fill_bytes` by reading chunks from the output buffer of a block
+/// based RNG.
+///
+/// The return values are `(consumed_u32, filled_u8)`.
+///
+/// `filled_u8` is the number of filled bytes in `dest`, which may be less than
+/// the length of `dest`.
+/// `consumed_u32` is the number of words consumed from `src`, which is the same
+/// as `filled_u8 / 4` rounded up.
+///
+/// # Example
+/// (from `IsaacRng`)
+///
+/// ```ignore
+/// fn fill_bytes(&mut self, dest: &mut [u8]) {
+///     let mut read_len = 0;
+///     while read_len < dest.len() {
+///         if self.index >= self.rsl.len() {
+///             self.isaac();
+///         }
+///
+///         let (consumed_u32, filled_u8) =
+///             impls::fill_via_u32_chunks(&mut self.rsl[self.index..],
+///                                        &mut dest[read_len..]);
+///
+///         self.index += consumed_u32;
+///         read_len += filled_u8;
+///     }
+/// }
+/// ```
+pub fn fill_via_u32_chunks(src: &[u32], dest: &mut [u8]) -> (usize, usize) {
+    fill_via_chunks!(src, dest, u32, 4)
+}
+
+/// Implement `fill_bytes` by reading chunks from the output buffer of a block
+/// based RNG.
+///
+/// The return values are `(consumed_u64, filled_u8)`.
+/// `filled_u8` is the number of filled bytes in `dest`, which may be less than
+/// the length of `dest`.
+/// `consumed_u64` is the number of words consumed from `src`, which is the same
+/// as `filled_u8 / 8` rounded up.
+///
+/// See `fill_via_u32_chunks` for an example.
+pub fn fill_via_u64_chunks(src: &[u64], dest: &mut [u8]) -> (usize, usize) {
+    fill_via_chunks!(src, dest, u64, 8)
+}
+
+/// Implement `next_u32` via `fill_bytes`, little-endian order.
+pub fn next_u32_via_fill<R: RngCore + ?Sized>(rng: &mut R) -> u32 {
+    impl_uint_from_fill!(rng, u32, 4)
+}
+
+/// Implement `next_u64` via `fill_bytes`, little-endian order.
+pub fn next_u64_via_fill<R: RngCore + ?Sized>(rng: &mut R) -> u64 {
+    impl_uint_from_fill!(rng, u64, 8)
+}
+
+// TODO: implement tests for the above
diff --git a/vendor/rand_core/src/le.rs b/vendor/rand_core/src/le.rs
new file mode 100644
index 0000000..266651f
--- /dev/null
+++ b/vendor/rand_core/src/le.rs
@@ -0,0 +1,68 @@
+// 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.
+
+//! Little-Endian utilities
+//! 
+//! Little-Endian order has been chosen for internal usage; this makes some
+//! useful functions available.
+
+use core::ptr;
+
+macro_rules! read_slice {
+    ($src:expr, $dst:expr, $size:expr, $which:ident) => {{
+        assert_eq!($src.len(), $size * $dst.len());
+
+        unsafe {
+            ptr::copy_nonoverlapping(
+                $src.as_ptr(),
+                $dst.as_mut_ptr() as *mut u8,
+                $src.len());
+        }
+        for v in $dst.iter_mut() {
+            *v = v.$which();
+        }
+    }};
+}
+
+/// Reads unsigned 32 bit integers from `src` into `dst`.
+/// Borrowed from the `byteorder` crate.
+#[inline]
+pub fn read_u32_into(src: &[u8], dst: &mut [u32]) {
+    read_slice!(src, dst, 4, to_le);
+}
+
+/// Reads unsigned 64 bit integers from `src` into `dst`.
+/// Borrowed from the `byteorder` crate.
+#[inline]
+pub fn read_u64_into(src: &[u8], dst: &mut [u64]) {
+    read_slice!(src, dst, 8, to_le);
+}
+
+#[test]
+fn test_read() {
+    let bytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    
+    let mut buf = [0u32; 4];
+    read_u32_into(&bytes, &mut buf);
+    assert_eq!(buf[0], 0x04030201);
+    assert_eq!(buf[3], 0x100F0E0D);
+    
+    let mut buf = [0u32; 3];
+    read_u32_into(&bytes[1..13], &mut buf);  // unaligned
+    assert_eq!(buf[0], 0x05040302);
+    assert_eq!(buf[2], 0x0D0C0B0A);
+    
+    let mut buf = [0u64; 2];
+    read_u64_into(&bytes, &mut buf);
+    assert_eq!(buf[0], 0x0807060504030201);
+    assert_eq!(buf[1], 0x100F0E0D0C0B0A09);
+    
+    let mut buf = [0u64; 1];
+    read_u64_into(&bytes[7..15], &mut buf); // unaligned
+    assert_eq!(buf[0], 0x0F0E0D0C0B0A0908);
+}
diff --git a/vendor/rand_core/src/lib.rs b/vendor/rand_core/src/lib.rs
new file mode 100644
index 0000000..28e7ac1
--- /dev/null
+++ b/vendor/rand_core/src/lib.rs
@@ -0,0 +1,477 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2017-2018 The Rust Project Developers.
+//
+// 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.
+
+//! Random number generation traits
+//!
+//! This crate is mainly of interest to crates publishing implementations of
+//! [`RngCore`]. Other users are encouraged to use the [`rand`] crate instead
+//! which re-exports the main traits and error types.
+//!
+//! [`RngCore`] is the core trait implemented by algorithmic pseudo-random number
+//! generators and external random-number sources.
+//!
+//! [`SeedableRng`] is an extension trait for construction from fixed seeds and
+//! other random number generators.
+//!
+//! [`Error`] is provided for error-handling. It is safe to use in `no_std`
+//! environments.
+//!
+//! The [`impls`] and [`le`] sub-modules include a few small functions to assist
+//! implementation of [`RngCore`].
+//!
+//! [`rand`]: https://docs.rs/rand
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+#![doc(test(attr(allow(unused_variables), deny(warnings))))]
+
+#![cfg_attr(not(feature="std"), no_std)]
+#![cfg_attr(all(feature="alloc", not(feature="std")), feature(alloc))]
+
+#[cfg(feature="std")] extern crate core;
+#[cfg(all(feature = "alloc", not(feature="std")))] extern crate alloc;
+#[cfg(feature="serde1")] extern crate serde;
+#[cfg(feature="serde1")] #[macro_use] extern crate serde_derive;
+
+
+use core::default::Default;
+use core::convert::AsMut;
+use core::ptr::copy_nonoverlapping;
+
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::boxed::Box;
+
+pub use error::{ErrorKind, Error};
+
+
+mod error;
+pub mod block;
+pub mod impls;
+pub mod le;
+
+
+/// The core of a random number generator.
+///
+/// This trait encapsulates the low-level functionality common to all
+/// generators, and is the "back end", to be implemented by generators.
+/// End users should normally use the `Rng` trait from the [`rand`] crate,
+/// which is automatically implemented for every type implementing `RngCore`.
+///
+/// Three different methods for generating random data are provided since the
+/// optimal implementation of each is dependent on the type of generator. There
+/// is no required relationship between the output of each; e.g. many
+/// implementations of [`fill_bytes`] consume a whole number of `u32` or `u64`
+/// values and drop any remaining unused bytes.
+///
+/// The [`try_fill_bytes`] method is a variant of [`fill_bytes`] allowing error
+/// handling; it is not deemed sufficiently useful to add equivalents for
+/// [`next_u32`] or [`next_u64`] since the latter methods are almost always used
+/// with algorithmic generators (PRNGs), which are normally infallible.
+///
+/// Algorithmic generators implementing [`SeedableRng`] should normally have
+/// *portable, reproducible* output, i.e. fix Endianness when converting values
+/// to avoid platform differences, and avoid making any changes which affect
+/// output (except by communicating that the release has breaking changes).
+///
+/// Typically implementators will implement only one of the methods available
+/// in this trait directly, then use the helper functions from the
+/// [`impls`] module to implement the other methods.
+///
+/// It is recommended that implementations also implement:
+///
+/// - `Debug` with a custom implementation which *does not* print any internal
+///   state (at least, [`CryptoRng`]s should not risk leaking state through
+///   `Debug`).
+/// - `Serialize` and `Deserialize` (from Serde), preferably making Serde
+///   support optional at the crate level in PRNG libs.
+/// - `Clone`, if possible.
+/// - *never* implement `Copy` (accidental copies may cause repeated values).
+/// - *do not* implement `Default` for pseudorandom generators, but instead
+///   implement [`SeedableRng`], to guide users towards proper seeding.
+///   External / hardware RNGs can choose to implement `Default`.
+/// - `Eq` and `PartialEq` could be implemented, but are probably not useful.
+///
+/// # Example
+///
+/// A simple example, obviously not generating very *random* output:
+///
+/// ```
+/// #![allow(dead_code)]
+/// use rand_core::{RngCore, Error, impls};
+///
+/// struct CountingRng(u64);
+///
+/// impl RngCore for CountingRng {
+///     fn next_u32(&mut self) -> u32 {
+///         self.next_u64() as u32
+///     }
+///
+///     fn next_u64(&mut self) -> u64 {
+///         self.0 += 1;
+///         self.0
+///     }
+///
+///     fn fill_bytes(&mut self, dest: &mut [u8]) {
+///         impls::fill_bytes_via_next(self, dest)
+///     }
+///
+///     fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+///         Ok(self.fill_bytes(dest))
+///     }
+/// }
+/// ```
+///
+/// [`rand`]: https://docs.rs/rand
+/// [`try_fill_bytes`]: RngCore::try_fill_bytes
+/// [`fill_bytes`]: RngCore::fill_bytes
+/// [`next_u32`]: RngCore::next_u32
+/// [`next_u64`]: RngCore::next_u64
+pub trait RngCore {
+    /// Return the next random `u32`.
+    ///
+    /// RNGs must implement at least one method from this trait directly. In
+    /// the case this method is not implemented directly, it can be implemented
+    /// using `self.next_u64() as u32` or via
+    /// [`fill_bytes`](impls::next_u32_via_fill).
+    fn next_u32(&mut self) -> u32;
+
+    /// Return the next random `u64`.
+    ///
+    /// RNGs must implement at least one method from this trait directly. In
+    /// the case this method is not implemented directly, it can be implemented
+    /// via [`next_u32`](impls::next_u64_via_u32) or via
+    /// [`fill_bytes`](impls::next_u64_via_fill).
+    fn next_u64(&mut self) -> u64;
+
+    /// Fill `dest` with random data.
+    ///
+    /// RNGs must implement at least one method from this trait directly. In
+    /// the case this method is not implemented directly, it can be implemented
+    /// via [`next_u*`](impls::fill_bytes_via_next) or
+    /// via [`try_fill_bytes`](RngCore::try_fill_bytes); if this generator can
+    /// fail the implementation must choose how best to handle errors here
+    /// (e.g. panic with a descriptive message or log a warning and retry a few
+    /// times).
+    ///
+    /// This method should guarantee that `dest` is entirely filled
+    /// with new data, and may panic if this is impossible
+    /// (e.g. reading past the end of a file that is being used as the
+    /// source of randomness).
+    fn fill_bytes(&mut self, dest: &mut [u8]);
+
+    /// Fill `dest` entirely with random data.
+    ///
+    /// This is the only method which allows an RNG to report errors while
+    /// generating random data thus making this the primary method implemented
+    /// by external (true) RNGs (e.g. `OsRng`) which can fail. It may be used
+    /// directly to generate keys and to seed (infallible) PRNGs.
+    ///
+    /// Other than error handling, this method is identical to [`fill_bytes`];
+    /// thus this may be implemented using `Ok(self.fill_bytes(dest))` or
+    /// `fill_bytes` may be implemented with
+    /// `self.try_fill_bytes(dest).unwrap()` or more specific error handling.
+    ///
+    /// [`fill_bytes`]: RngCore::fill_bytes
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>;
+}
+
+/// A marker trait used to indicate that an [`RngCore`] or [`BlockRngCore`]
+/// implementation is supposed to be cryptographically secure.
+///
+/// *Cryptographically secure generators*, also known as *CSPRNGs*, should
+/// satisfy an additional properties over other generators: given the first
+/// *k* bits of an algorithm's output
+/// sequence, it should not be possible using polynomial-time algorithms to
+/// predict the next bit with probability significantly greater than 50%.
+///
+/// Some generators may satisfy an additional property, however this is not
+/// required by this trait: if the CSPRNG's state is revealed, it should not be
+/// computationally-feasible to reconstruct output prior to this. Some other
+/// generators allow backwards-computation and are consided *reversible*.
+///
+/// Note that this trait is provided for guidance only and cannot guarantee
+/// suitability for cryptographic applications. In general it should only be
+/// implemented for well-reviewed code implementing well-regarded algorithms.
+///
+/// Note also that use of a `CryptoRng` does not protect against other
+/// weaknesses such as seeding from a weak entropy source or leaking state.
+///
+/// [`BlockRngCore`]: block::BlockRngCore
+pub trait CryptoRng {}
+
+/// A random number generator that can be explicitly seeded.
+///
+/// This trait encapsulates the low-level functionality common to all
+/// pseudo-random number generators (PRNGs, or algorithmic generators).
+///
+/// The `FromEntropy` trait from the [`rand`] crate is automatically
+/// implemented for every type implementing `SeedableRng`, providing
+/// a convenient `from_entropy()` constructor.
+///
+/// [`rand`]: https://docs.rs/rand
+pub trait SeedableRng: Sized {
+    /// Seed type, which is restricted to types mutably-dereferencable as `u8`
+    /// arrays (we recommend `[u8; N]` for some `N`).
+    ///
+    /// It is recommended to seed PRNGs with a seed of at least circa 100 bits,
+    /// which means an array of `[u8; 12]` or greater to avoid picking RNGs with
+    /// partially overlapping periods.
+    ///
+    /// For cryptographic RNG's a seed of 256 bits is recommended, `[u8; 32]`.
+    ///
+    ///
+    /// # Implementing `SeedableRng` for RNGs with large seeds
+    ///
+    /// Note that the required traits `core::default::Default` and
+    /// `core::convert::AsMut<u8>` are not implemented for large arrays
+    /// `[u8; N]` with `N` > 32. To be able to implement the traits required by
+    /// `SeedableRng` for RNGs with such large seeds, the newtype pattern can be
+    /// used:
+    ///
+    /// ```
+    /// use rand_core::SeedableRng;
+    ///
+    /// const N: usize = 64;
+    /// pub struct MyRngSeed(pub [u8; N]);
+    /// pub struct MyRng(MyRngSeed);
+    ///
+    /// impl Default for MyRngSeed {
+    ///     fn default() -> MyRngSeed {
+    ///         MyRngSeed([0; N])
+    ///     }
+    /// }
+    ///
+    /// impl AsMut<[u8]> for MyRngSeed {
+    ///     fn as_mut(&mut self) -> &mut [u8] {
+    ///         &mut self.0
+    ///     }
+    /// }
+    ///
+    /// impl SeedableRng for MyRng {
+    ///     type Seed = MyRngSeed;
+    ///
+    ///     fn from_seed(seed: MyRngSeed) -> MyRng {
+    ///         MyRng(seed)
+    ///     }
+    /// }
+    /// ```
+    type Seed: Sized + Default + AsMut<[u8]>;
+
+    /// Create a new PRNG using the given seed.
+    ///
+    /// PRNG implementations are allowed to assume that bits in the seed are
+    /// well distributed. That means usually that the number of one and zero
+    /// bits are about equal, and values like 0, 1 and (size - 1) are unlikely.
+    ///
+    /// PRNG implementations are recommended to be reproducible. A PRNG seeded
+    /// using this function with a fixed seed should produce the same sequence
+    /// of output in the future and on different architectures (with for example
+    /// different endianness).
+    ///
+    /// It is however not required that this function yield the same state as a
+    /// reference implementation of the PRNG given equivalent seed; if necessary
+    /// another constructor replicating behaviour from a reference
+    /// implementation can be added.
+    ///
+    /// PRNG implementations should make sure `from_seed` never panics. In the
+    /// case that some special values (like an all zero seed) are not viable
+    /// seeds it is preferable to map these to alternative constant value(s),
+    /// for example `0xBAD5EEDu32` or `0x0DDB1A5E5BAD5EEDu64` ("odd biases? bad
+    /// seed"). This is assuming only a small number of values must be rejected.
+    fn from_seed(seed: Self::Seed) -> Self;
+
+    /// Create a new PRNG using a `u64` seed.
+    ///
+    /// This is a convenience-wrapper around `from_seed` to allow construction
+    /// of any `SeedableRng` from a simple `u64` value. It is designed such that
+    /// low Hamming Weight numbers like 0 and 1 can be used and should still
+    /// result in good, independent seeds to the PRNG which is returned.
+    ///
+    /// This **is not suitable for cryptography**, as should be clear given that
+    /// the input size is only 64 bits.
+    ///
+    /// Implementations for PRNGs *may* provide their own implementations of
+    /// this function, but the default implementation should be good enough for
+    /// all purposes. *Changing* the implementation of this function should be
+    /// considered a value-breaking change.
+    fn seed_from_u64(mut state: u64) -> Self {
+        // We use PCG32 to generate a u32 sequence, and copy to the seed
+        const MUL: u64 = 6364136223846793005;
+        const INC: u64 = 11634580027462260723;
+
+        let mut seed = Self::Seed::default();
+        for chunk in seed.as_mut().chunks_mut(4) {
+            // We advance the state first (to get away from the input value,
+            // in case it has low Hamming Weight).
+            state = state.wrapping_mul(MUL).wrapping_add(INC);
+
+            // Use PCG output function with to_le to generate x:
+            let xorshifted = (((state >> 18) ^ state) >> 27) as u32;
+            let rot = (state >> 59) as u32;
+            let x = xorshifted.rotate_right(rot).to_le();
+
+            unsafe {
+                let p = &x as *const u32 as *const u8;
+                copy_nonoverlapping(p, chunk.as_mut_ptr(), chunk.len());
+            }
+        }
+
+        Self::from_seed(seed)
+    }
+
+    /// Create a new PRNG seeded from another `Rng`.
+    ///
+    /// This is the recommended way to initialize PRNGs with fresh entropy. The
+    /// `FromEntropy` trait from the [`rand`] crate provides a convenient
+    /// `from_entropy` method based on `from_rng`.
+    ///
+    /// Usage of this method is not recommended when reproducibility is required
+    /// since implementing PRNGs are not required to fix Endianness and are
+    /// allowed to modify implementations in new releases.
+    ///
+    /// It is important to use a good source of randomness to initialize the
+    /// PRNG. Cryptographic PRNG may be rendered insecure when seeded from a
+    /// non-cryptographic PRNG or with insufficient entropy.
+    /// Many non-cryptographic PRNGs will show statistical bias in their first
+    /// results if their seed numbers are small or if there is a simple pattern
+    /// between them.
+    ///
+    /// Prefer to seed from a strong external entropy source like `OsRng` from
+    /// the [`rand_os`] crate or from a cryptographic PRNG; if creating a new
+    /// generator for cryptographic uses you *must* seed from a strong source.
+    ///
+    /// Seeding a small PRNG from another small PRNG is possible, but
+    /// something to be careful with. An extreme example of how this can go
+    /// wrong is seeding an Xorshift RNG from another Xorshift RNG, which
+    /// will effectively clone the generator. In general seeding from a
+    /// generator which is hard to predict is probably okay.
+    ///
+    /// PRNG implementations are allowed to assume that a good RNG is provided
+    /// for seeding, and that it is cryptographically secure when appropriate.
+    ///
+    /// [`rand`]: https://docs.rs/rand
+    /// [`rand_os`]: https://docs.rs/rand_os
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, Error> {
+        let mut seed = Self::Seed::default();
+        rng.try_fill_bytes(seed.as_mut())?;
+        Ok(Self::from_seed(seed))
+    }
+}
+
+// Implement `RngCore` for references to an `RngCore`.
+// Force inlining all functions, so that it is up to the `RngCore`
+// implementation and the optimizer to decide on inlining.
+impl<'a, R: RngCore + ?Sized> RngCore for &'a mut R {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        (**self).next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        (**self).next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        (**self).fill_bytes(dest)
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        (**self).try_fill_bytes(dest)
+    }
+}
+
+// Implement `RngCore` for boxed references to an `RngCore`.
+// Force inlining all functions, so that it is up to the `RngCore`
+// implementation and the optimizer to decide on inlining.
+#[cfg(feature="alloc")]
+impl<R: RngCore + ?Sized> RngCore for Box<R> {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        (**self).next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        (**self).next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        (**self).fill_bytes(dest)
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        (**self).try_fill_bytes(dest)
+    }
+}
+
+#[cfg(feature="std")]
+impl std::io::Read for RngCore {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, std::io::Error> {
+        self.try_fill_bytes(buf)?;
+        Ok(buf.len())
+    }
+}
+
+// Implement `CryptoRng` for references to an `CryptoRng`.
+impl<'a, R: CryptoRng + ?Sized> CryptoRng for &'a mut R {}
+
+// Implement `CryptoRng` for boxed references to an `CryptoRng`.
+#[cfg(feature="alloc")]
+impl<R: CryptoRng + ?Sized> CryptoRng for Box<R> {}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_seed_from_u64() {
+        struct SeedableNum(u64);
+        impl SeedableRng for SeedableNum {
+            type Seed = [u8; 8];
+            fn from_seed(seed: Self::Seed) -> Self {
+                let mut x = [0u64; 1];
+                le::read_u64_into(&seed, &mut x);
+                SeedableNum(x[0])
+            }
+        }
+
+        const N: usize = 8;
+        const SEEDS: [u64; N] = [0u64, 1, 2, 3, 4, 8, 16, -1i64 as u64];
+        let mut results = [0u64; N];
+        for (i, seed) in SEEDS.iter().enumerate() {
+            let SeedableNum(x) = SeedableNum::seed_from_u64(*seed);
+            results[i] = x;
+        }
+
+        for (i1, r1) in results.iter().enumerate() {
+            let weight = r1.count_ones();
+            // This is the binomial distribution B(64, 0.5), so chance of
+            // weight < 20 is binocdf(19, 64, 0.5) = 7.8e-4, and same for
+            // weight > 44.
+            assert!(weight >= 20 && weight <= 44);
+
+            for (i2, r2) in results.iter().enumerate() {
+                if i1 == i2 { continue; }
+                let diff_weight = (r1 ^ r2).count_ones();
+                assert!(diff_weight >= 20);
+            }
+        }
+
+        // value-breakage test:
+        assert_eq!(results[0], 5029875928683246316);
+    }
+}