Import rand_chacha-0.2.2

Change-Id: Ib26dd3e44313754c040f56665de1760fd2390ec1
diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
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index 0000000..0739f24
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+  "git": {
+    "sha1": "e2112c4404c61d3850c0e91f48114db5daf06569"
+  }
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- /dev/null
+++ b/CHANGELOG.md
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+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.2.2] - 2020-03-09
+- Integrate `c2-chacha`, reducing dependency count (#931)
+- Add CryptoRng to ChaChaXCore (#944)
+
+## [0.2.1] - 2019-07-22
+- Force enable the `simd` feature of `c2-chacha` (#845)
+
+## [0.2.0] - 2019-06-06
+- Rewrite based on the much faster `c2-chacha` crate (#789)
+
+## [0.1.1] - 2019-01-04
+- Disable `i128` and `u128` if the `target_os` is `emscripten` (#671: work-around Emscripten limitation)
+- Update readme and doc links
+
+## [0.1.0] - 2018-10-17
+- Pulled out of the Rand crate
diff --git a/COPYRIGHT b/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..dea94e9
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,42 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+edition = "2018"
+name = "rand_chacha"
+version = "0.2.2"
+authors = ["The Rand Project Developers", "The Rust Project Developers", "The CryptoCorrosion Contributors"]
+description = "ChaCha random number generator\n"
+homepage = "https://crates.io/crates/rand_chacha"
+documentation = "https://rust-random.github.io/rand/rand_chacha/"
+readme = "README.md"
+keywords = ["random", "rng", "chacha"]
+categories = ["algorithms", "no-std"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-random/rand"
+[dependencies.ppv-lite86]
+version = "0.2.6"
+features = ["simd"]
+default-features = false
+
+[dependencies.rand_core]
+version = "0.5"
+
+[features]
+default = ["std", "simd"]
+simd = []
+std = ["ppv-lite86/std"]
+[badges.appveyor]
+repository = "rust-random/rand"
+
+[badges.travis-ci]
+repository = "rust-random/rand"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
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--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,28 @@
+[package]
+name = "rand_chacha"
+version = "0.2.2"
+authors = ["The Rand Project Developers", "The Rust Project Developers", "The CryptoCorrosion Contributors"]
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_chacha/"
+homepage = "https://crates.io/crates/rand_chacha"
+description = """
+ChaCha random number generator
+"""
+keywords = ["random", "rng", "chacha"]
+categories = ["algorithms", "no-std"]
+edition = "2018"
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[dependencies]
+rand_core = { path = "../rand_core", version = "0.5" }
+ppv-lite86 = { version = "0.2.6", default-features = false, features = ["simd"] }
+
+[features]
+default = ["std", "simd"]
+std = ["ppv-lite86/std"]
+simd = [] # deprecated
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..d93b5ba
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright 2018 Developers of the Rand project
+Copyright (c) 2014 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
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+The above copyright notice and this permission notice
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+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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diff --git a/README.md b/README.md
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index 0000000..69a0ce7
--- /dev/null
+++ b/README.md
@@ -0,0 +1,49 @@
+# rand_chacha
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_chacha.svg)](https://crates.io/crates/rand_chacha)
+[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_chacha)
+[![API](https://docs.rs/rand_chacha/badge.svg)](https://docs.rs/rand_chacha)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.32+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+A cryptographically secure random number generator that uses the ChaCha
+algorithm.
+
+ChaCha is a stream cipher designed by Daniel J. Bernstein[^1], that we use
+as an RNG. It is an improved variant of the Salsa20 cipher family, which was
+selected as one of the "stream ciphers suitable for widespread adoption" by
+eSTREAM[^2].
+
+The RNGs provided by this crate are implemented via the fast stream ciphers of
+the [`c2-chacha`](https://crates.io/crates/c2-chacha) crate.
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_chacha)
+-   [API documentation (docs.rs)](https://docs.rs/rand_chacha)
+-   [Changelog](https://github.com/rust-random/rand/blob/master/rand_chacha/CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+[^1]: D. J. Bernstein, [*ChaCha, a variant of Salsa20*](
+      https://cr.yp.to/chacha.html)
+
+[^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
+      http://www.ecrypt.eu.org/stream/)
+
+
+## Crate Features
+
+`rand_chacha` is `no_std` compatible when disabling default features; the `std`
+feature can be explicitly required to re-enable `std` support. Using `std`
+allows detection of CPU features and thus better optimisation.
+
+
+# License
+
+`rand_chacha` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/src/chacha.rs b/src/chacha.rs
new file mode 100644
index 0000000..cf68c52
--- /dev/null
+++ b/src/chacha.rs
@@ -0,0 +1,459 @@
+// 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 ChaCha random number generator.
+
+#[cfg(not(feature = "std"))] use core;
+#[cfg(feature = "std")] use std as core;
+
+use self::core::fmt;
+use crate::guts::ChaCha;
+use rand_core::block::{BlockRng, BlockRngCore};
+use rand_core::{CryptoRng, Error, RngCore, SeedableRng};
+
+const STREAM_PARAM_NONCE: u32 = 1;
+const STREAM_PARAM_BLOCK: u32 = 0;
+
+pub struct Array64<T>([T; 64]);
+impl<T> Default for Array64<T>
+where T: Default
+{
+    #[rustfmt::skip]
+    fn default() -> Self {
+        Self([
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+            T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(), T::default(),
+        ])
+    }
+}
+impl<T> AsRef<[T]> for Array64<T> {
+    fn as_ref(&self) -> &[T] {
+        &self.0
+    }
+}
+impl<T> AsMut<[T]> for Array64<T> {
+    fn as_mut(&mut self) -> &mut [T] {
+        &mut self.0
+    }
+}
+impl<T> Clone for Array64<T>
+where T: Copy + Default
+{
+    fn clone(&self) -> Self {
+        let mut new = Self::default();
+        new.0.copy_from_slice(&self.0);
+        new
+    }
+}
+impl<T> fmt::Debug for Array64<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Array64 {{}}")
+    }
+}
+
+macro_rules! chacha_impl {
+    ($ChaChaXCore:ident, $ChaChaXRng:ident, $rounds:expr, $doc:expr) => {
+        #[doc=$doc]
+        #[derive(Clone)]
+        pub struct $ChaChaXCore {
+            state: ChaCha,
+        }
+
+        // Custom Debug implementation that does not expose the internal state
+        impl fmt::Debug for $ChaChaXCore {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                write!(f, "ChaChaXCore {{}}")
+            }
+        }
+
+        impl BlockRngCore for $ChaChaXCore {
+            type Item = u32;
+            type Results = Array64<u32>;
+            #[inline]
+            fn generate(&mut self, r: &mut Self::Results) {
+                // Fill slice of words by writing to equivalent slice of bytes, then fixing endianness.
+                self.state.refill4($rounds, unsafe {
+                    &mut *(&mut *r as *mut Array64<u32> as *mut [u8; 256])
+                });
+                for x in r.as_mut() {
+                    *x = x.to_le();
+                }
+            }
+        }
+
+        impl SeedableRng for $ChaChaXCore {
+            type Seed = [u8; 32];
+            #[inline]
+            fn from_seed(seed: Self::Seed) -> Self {
+                $ChaChaXCore { state: ChaCha::new(&seed, &[0u8; 8]) }
+            }
+        }
+
+        impl CryptoRng for $ChaChaXCore {}
+
+        /// A cryptographically secure random number generator that uses the ChaCha algorithm.
+        ///
+        /// ChaCha is a stream cipher designed by Daniel J. Bernstein[^1], that we use as an RNG. It is
+        /// an improved variant of the Salsa20 cipher family, which was selected as one of the "stream
+        /// ciphers suitable for widespread adoption" by eSTREAM[^2].
+        ///
+        /// ChaCha uses add-rotate-xor (ARX) operations as its basis. These are safe against timing
+        /// attacks, although that is mostly a concern for ciphers and not for RNGs. We provide a SIMD
+        /// implementation to support high throughput on a variety of common hardware platforms.
+        ///
+        /// With the ChaCha algorithm it is possible to choose the number of rounds the core algorithm
+        /// should run. The number of rounds is a tradeoff between performance and security, where 8
+        /// rounds is the minimum potentially secure configuration, and 20 rounds is widely used as a
+        /// conservative choice.
+        ///
+        /// We use a 64-bit counter and 64-bit stream identifier as in Bernstein's implementation[^1]
+        /// except that we use a stream identifier in place of a nonce. A 64-bit counter over 64-byte
+        /// (16 word) blocks allows 1 ZiB of output before cycling, and the stream identifier allows
+        /// 2<sup>64</sup> unique streams of output per seed. Both counter and stream are initialized
+        /// to zero but may be set via the `set_word_pos` and `set_stream` methods.
+        ///
+        /// The word layout is:
+        ///
+        /// ```text
+        /// constant  constant  constant  constant
+        /// seed      seed      seed      seed
+        /// seed      seed      seed      seed
+        /// counter   counter   stream_id stream_id
+        /// ```
+        ///
+        /// This implementation uses an output buffer of sixteen `u32` words, and uses
+        /// [`BlockRng`] to implement the [`RngCore`] methods.
+        ///
+        /// [^1]: D. J. Bernstein, [*ChaCha, a variant of Salsa20*](
+        ///       https://cr.yp.to/chacha.html)
+        ///
+        /// [^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
+        ///       http://www.ecrypt.eu.org/stream/)
+        #[derive(Clone, Debug)]
+        pub struct $ChaChaXRng {
+            rng: BlockRng<$ChaChaXCore>,
+        }
+
+        impl SeedableRng for $ChaChaXRng {
+            type Seed = [u8; 32];
+            #[inline]
+            fn from_seed(seed: Self::Seed) -> Self {
+                let core = $ChaChaXCore::from_seed(seed);
+                Self {
+                    rng: BlockRng::new(core),
+                }
+            }
+        }
+
+        impl RngCore for $ChaChaXRng {
+            #[inline]
+            fn next_u32(&mut self) -> u32 {
+                self.rng.next_u32()
+            }
+            #[inline]
+            fn next_u64(&mut self) -> u64 {
+                self.rng.next_u64()
+            }
+            #[inline]
+            fn fill_bytes(&mut self, bytes: &mut [u8]) {
+                self.rng.fill_bytes(bytes)
+            }
+            #[inline]
+            fn try_fill_bytes(&mut self, bytes: &mut [u8]) -> Result<(), Error> {
+                self.rng.try_fill_bytes(bytes)
+            }
+        }
+
+        impl $ChaChaXRng {
+            // The buffer is a 4-block window, i.e. it is always at a block-aligned position in the
+            // stream but if the stream has been seeked it may not be self-aligned.
+
+            /// Get the offset from the start of the stream, in 32-bit words.
+            ///
+            /// Since the generated blocks are 16 words (2<sup>4</sup>) long and the
+            /// counter is 64-bits, the offset is a 68-bit number. Sub-word offsets are
+            /// not supported, hence the result can simply be multiplied by 4 to get a
+            /// byte-offset.
+            #[inline]
+            pub fn get_word_pos(&self) -> u128 {
+                let mut block = u128::from(self.rng.core.state.get_stream_param(STREAM_PARAM_BLOCK));
+                // counter is incremented *after* filling buffer
+                block -= 4;
+                (block << 4) + self.rng.index() as u128
+            }
+
+            /// Set the offset from the start of the stream, in 32-bit words.
+            ///
+            /// As with `get_word_pos`, we use a 68-bit number. Since the generator
+            /// simply cycles at the end of its period (1 ZiB), we ignore the upper
+            /// 60 bits.
+            #[inline]
+            pub fn set_word_pos(&mut self, word_offset: u128) {
+                let block = (word_offset >> 4) as u64;
+                self.rng
+                    .core
+                    .state
+                    .set_stream_param(STREAM_PARAM_BLOCK, block);
+                self.rng.generate_and_set((word_offset & 15) as usize);
+            }
+
+            /// Set the stream number.
+            ///
+            /// This is initialized to zero; 2<sup>64</sup> unique streams of output
+            /// are available per seed/key.
+            ///
+            /// Note that in order to reproduce ChaCha output with a specific 64-bit
+            /// nonce, one can convert that nonce to a `u64` in little-endian fashion
+            /// and pass to this function. In theory a 96-bit nonce can be used by
+            /// passing the last 64-bits to this function and using the first 32-bits as
+            /// the most significant half of the 64-bit counter (which may be set
+            /// indirectly via `set_word_pos`), but this is not directly supported.
+            #[inline]
+            pub fn set_stream(&mut self, stream: u64) {
+                self.rng
+                    .core
+                    .state
+                    .set_stream_param(STREAM_PARAM_NONCE, stream);
+                if self.rng.index() != 64 {
+                    let wp = self.get_word_pos();
+                    self.set_word_pos(wp);
+                }
+            }
+        }
+
+        impl CryptoRng for $ChaChaXRng {}
+
+        impl From<$ChaChaXCore> for $ChaChaXRng {
+            fn from(core: $ChaChaXCore) -> Self {
+                $ChaChaXRng {
+                    rng: BlockRng::new(core),
+                }
+            }
+        }
+    }
+}
+
+chacha_impl!(ChaCha20Core, ChaCha20Rng, 10, "ChaCha with 20 rounds");
+chacha_impl!(ChaCha12Core, ChaCha12Rng, 6, "ChaCha with 12 rounds");
+chacha_impl!(ChaCha8Core, ChaCha8Rng, 4, "ChaCha with 8 rounds");
+
+#[cfg(test)]
+mod test {
+    use rand_core::{RngCore, SeedableRng};
+
+    type ChaChaRng = super::ChaCha20Rng;
+
+    #[test]
+    fn test_chacha_construction() {
+        let seed = [
+            0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0,
+            0, 0, 0,
+        ];
+        let mut rng1 = ChaChaRng::from_seed(seed);
+        assert_eq!(rng1.next_u32(), 137206642);
+
+        let mut rng2 = ChaChaRng::from_rng(rng1).unwrap();
+        assert_eq!(rng2.next_u32(), 1325750369);
+    }
+
+    #[test]
+    fn test_chacha_true_values_a() {
+        // Test vectors 1 and 2 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        let seed = [0u8; 32];
+        let mut rng = ChaChaRng::from_seed(seed);
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() {
+            *i = rng.next_u32();
+        }
+        let expected = [
+            0xade0b876, 0x903df1a0, 0xe56a5d40, 0x28bd8653, 0xb819d2bd, 0x1aed8da0, 0xccef36a8,
+            0xc70d778b, 0x7c5941da, 0x8d485751, 0x3fe02477, 0x374ad8b8, 0xf4b8436a, 0x1ca11815,
+            0x69b687c3, 0x8665eeb2,
+        ];
+        assert_eq!(results, expected);
+
+        for i in results.iter_mut() {
+            *i = rng.next_u32();
+        }
+        let expected = [
+            0xbee7079f, 0x7a385155, 0x7c97ba98, 0x0d082d73, 0xa0290fcb, 0x6965e348, 0x3e53c612,
+            0xed7aee32, 0x7621b729, 0x434ee69c, 0xb03371d5, 0xd539d874, 0x281fed31, 0x45fb0a51,
+            0x1f0ae1ac, 0x6f4d794b,
+        ];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_true_values_b() {
+        // Test vector 3 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        let seed = [
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 1,
+        ];
+        let mut rng = ChaChaRng::from_seed(seed);
+
+        // Skip block 0
+        for _ in 0..16 {
+            rng.next_u32();
+        }
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() {
+            *i = rng.next_u32();
+        }
+        let expected = [
+            0x2452eb3a, 0x9249f8ec, 0x8d829d9b, 0xddd4ceb1, 0xe8252083, 0x60818b01, 0xf38422b8,
+            0x5aaa49c9, 0xbb00ca8e, 0xda3ba7b4, 0xc4b592d1, 0xfdf2732f, 0x4436274e, 0x2561b3c8,
+            0xebdd4aa6, 0xa0136c00,
+        ];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_true_values_c() {
+        // Test vector 4 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        let seed = [
+            0, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0,
+        ];
+        let expected = [
+            0xfb4dd572, 0x4bc42ef1, 0xdf922636, 0x327f1394, 0xa78dea8f, 0x5e269039, 0xa1bebbc1,
+            0xcaf09aae, 0xa25ab213, 0x48a6b46c, 0x1b9d9bcb, 0x092c5be6, 0x546ca624, 0x1bec45d5,
+            0x87f47473, 0x96f0992e,
+        ];
+        let expected_end = 3 * 16;
+        let mut results = [0u32; 16];
+
+        // Test block 2 by skipping block 0 and 1
+        let mut rng1 = ChaChaRng::from_seed(seed);
+        for _ in 0..32 {
+            rng1.next_u32();
+        }
+        for i in results.iter_mut() {
+            *i = rng1.next_u32();
+        }
+        assert_eq!(results, expected);
+        assert_eq!(rng1.get_word_pos(), expected_end);
+
+        // Test block 2 by using `set_word_pos`
+        let mut rng2 = ChaChaRng::from_seed(seed);
+        rng2.set_word_pos(2 * 16);
+        for i in results.iter_mut() {
+            *i = rng2.next_u32();
+        }
+        assert_eq!(results, expected);
+        assert_eq!(rng2.get_word_pos(), expected_end);
+
+        // Test skipping behaviour with other types
+        let mut buf = [0u8; 32];
+        rng2.fill_bytes(&mut buf[..]);
+        assert_eq!(rng2.get_word_pos(), expected_end + 8);
+        rng2.fill_bytes(&mut buf[0..25]);
+        assert_eq!(rng2.get_word_pos(), expected_end + 15);
+        rng2.next_u64();
+        assert_eq!(rng2.get_word_pos(), expected_end + 17);
+        rng2.next_u32();
+        rng2.next_u64();
+        assert_eq!(rng2.get_word_pos(), expected_end + 20);
+        rng2.fill_bytes(&mut buf[0..1]);
+        assert_eq!(rng2.get_word_pos(), expected_end + 21);
+    }
+
+    #[test]
+    fn test_chacha_multiple_blocks() {
+        let seed = [
+            0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0, 5, 0, 0, 0, 6, 0, 0, 0, 7,
+            0, 0, 0,
+        ];
+        let mut rng = ChaChaRng::from_seed(seed);
+
+        // Store the 17*i-th 32-bit word,
+        // i.e., the i-th word of the i-th 16-word block
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() {
+            *i = rng.next_u32();
+            for _ in 0..16 {
+                rng.next_u32();
+            }
+        }
+        let expected = [
+            0xf225c81a, 0x6ab1be57, 0x04d42951, 0x70858036, 0x49884684, 0x64efec72, 0x4be2d186,
+            0x3615b384, 0x11cfa18e, 0xd3c50049, 0x75c775f6, 0x434c6530, 0x2c5bad8f, 0x898881dc,
+            0x5f1c86d9, 0xc1f8e7f4,
+        ];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_true_bytes() {
+        let seed = [0u8; 32];
+        let mut rng = ChaChaRng::from_seed(seed);
+        let mut results = [0u8; 32];
+        rng.fill_bytes(&mut results);
+        let expected = [
+            118, 184, 224, 173, 160, 241, 61, 144, 64, 93, 106, 229, 83, 134, 189, 40, 189, 210,
+            25, 184, 160, 141, 237, 26, 168, 54, 239, 204, 139, 119, 13, 199,
+        ];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_nonce() {
+        // Test vector 5 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        // Although we do not support setting a nonce, we try it here anyway so
+        // we can use this test vector.
+        let seed = [0u8; 32];
+        let mut rng = ChaChaRng::from_seed(seed);
+        // 96-bit nonce in LE order is: 0,0,0,0, 0,0,0,0, 0,0,0,2
+        rng.set_stream(2u64 << (24 + 32));
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() {
+            *i = rng.next_u32();
+        }
+        let expected = [
+            0x374dc6c2, 0x3736d58c, 0xb904e24a, 0xcd3f93ef, 0x88228b1a, 0x96a4dfb3, 0x5b76ab72,
+            0xc727ee54, 0x0e0e978a, 0xf3145c95, 0x1b748ea8, 0xf786c297, 0x99c28f5f, 0x628314e8,
+            0x398a19fa, 0x6ded1b53,
+        ];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_clone_streams() {
+        let seed = [
+            0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0, 5, 0, 0, 0, 6, 0, 0, 0, 7,
+            0, 0, 0,
+        ];
+        let mut rng = ChaChaRng::from_seed(seed);
+        let mut clone = rng.clone();
+        for _ in 0..16 {
+            assert_eq!(rng.next_u64(), clone.next_u64());
+        }
+
+        rng.set_stream(51);
+        for _ in 0..7 {
+            assert!(rng.next_u32() != clone.next_u32());
+        }
+        clone.set_stream(51); // switch part way through block
+        for _ in 7..16 {
+            assert_eq!(rng.next_u32(), clone.next_u32());
+        }
+    }
+}
diff --git a/src/guts.rs b/src/guts.rs
new file mode 100644
index 0000000..7561c1b
--- /dev/null
+++ b/src/guts.rs
@@ -0,0 +1,243 @@
+// Copyright 2019 The CryptoCorrosion Contributors
+// Copyright 2020 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 ChaCha random number generator.
+
+use ppv_lite86::{dispatch, dispatch_light128};
+
+pub use ppv_lite86::Machine;
+use ppv_lite86::{vec128_storage, ArithOps, BitOps32, LaneWords4, MultiLane, StoreBytes, Vec4};
+
+pub(crate) const BLOCK: usize = 64;
+pub(crate) const BLOCK64: u64 = BLOCK as u64;
+const LOG2_BUFBLOCKS: u64 = 2;
+const BUFBLOCKS: u64 = 1 << LOG2_BUFBLOCKS;
+pub(crate) const BUFSZ64: u64 = BLOCK64 * BUFBLOCKS;
+pub(crate) const BUFSZ: usize = BUFSZ64 as usize;
+
+#[derive(Clone)]
+pub struct ChaCha {
+    pub(crate) b: vec128_storage,
+    pub(crate) c: vec128_storage,
+    pub(crate) d: vec128_storage,
+}
+
+#[derive(Clone)]
+pub struct State<V> {
+    pub(crate) a: V,
+    pub(crate) b: V,
+    pub(crate) c: V,
+    pub(crate) d: V,
+}
+
+#[inline(always)]
+pub(crate) fn round<V: ArithOps + BitOps32>(mut x: State<V>) -> State<V> {
+    x.a += x.b;
+    x.d = (x.d ^ x.a).rotate_each_word_right16();
+    x.c += x.d;
+    x.b = (x.b ^ x.c).rotate_each_word_right20();
+    x.a += x.b;
+    x.d = (x.d ^ x.a).rotate_each_word_right24();
+    x.c += x.d;
+    x.b = (x.b ^ x.c).rotate_each_word_right25();
+    x
+}
+
+#[inline(always)]
+pub(crate) fn diagonalize<V: LaneWords4>(mut x: State<V>) -> State<V> {
+    x.b = x.b.shuffle_lane_words3012();
+    x.c = x.c.shuffle_lane_words2301();
+    x.d = x.d.shuffle_lane_words1230();
+    x
+}
+#[inline(always)]
+pub(crate) fn undiagonalize<V: LaneWords4>(mut x: State<V>) -> State<V> {
+    x.b = x.b.shuffle_lane_words1230();
+    x.c = x.c.shuffle_lane_words2301();
+    x.d = x.d.shuffle_lane_words3012();
+    x
+}
+
+impl ChaCha {
+    #[inline(always)]
+    pub fn new(key: &[u8; 32], nonce: &[u8]) -> Self {
+        init_chacha(key, nonce)
+    }
+
+    #[inline(always)]
+    fn pos64<M: Machine>(&self, m: M) -> u64 {
+        let d: M::u32x4 = m.unpack(self.d);
+        ((d.extract(1) as u64) << 32) | d.extract(0) as u64
+    }
+
+    /// Produce 4 blocks of output, advancing the state
+    #[inline(always)]
+    pub fn refill4(&mut self, drounds: u32, out: &mut [u8; BUFSZ]) {
+        refill_wide(self, drounds, out)
+    }
+
+    #[inline(always)]
+    pub fn set_stream_param(&mut self, param: u32, value: u64) {
+        set_stream_param(self, param, value)
+    }
+
+    #[inline(always)]
+    pub fn get_stream_param(&self, param: u32) -> u64 {
+        get_stream_param(self, param)
+    }
+}
+
+#[inline(always)]
+fn refill_wide_impl<Mach: Machine>(
+    m: Mach, state: &mut ChaCha, drounds: u32, out: &mut [u8; BUFSZ],
+) {
+    let k = m.vec([0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574]);
+    let mut pos = state.pos64(m);
+    let d0: Mach::u32x4 = m.unpack(state.d);
+    pos += 1;
+    let d1 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+    pos += 1;
+    let d2 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+    pos += 1;
+    let d3 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+
+    let b = m.unpack(state.b);
+    let c = m.unpack(state.c);
+    let mut x = State {
+        a: Mach::u32x4x4::from_lanes([k, k, k, k]),
+        b: Mach::u32x4x4::from_lanes([b, b, b, b]),
+        c: Mach::u32x4x4::from_lanes([c, c, c, c]),
+        d: m.unpack(Mach::u32x4x4::from_lanes([d0, d1, d2, d3]).into()),
+    };
+    for _ in 0..drounds {
+        x = round(x);
+        x = undiagonalize(round(diagonalize(x)));
+    }
+    let mut pos = state.pos64(m);
+    let d0: Mach::u32x4 = m.unpack(state.d);
+    pos += 1;
+    let d1 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+    pos += 1;
+    let d2 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+    pos += 1;
+    let d3 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+    pos += 1;
+    let d4 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
+
+    let (a, b, c, d) = (
+        x.a.to_lanes(),
+        x.b.to_lanes(),
+        x.c.to_lanes(),
+        x.d.to_lanes(),
+    );
+    let sb = m.unpack(state.b);
+    let sc = m.unpack(state.c);
+    let sd = [m.unpack(state.d), d1, d2, d3];
+    state.d = d4.into();
+    let mut words = out.chunks_exact_mut(16);
+    for ((((&a, &b), &c), &d), &sd) in a.iter().zip(&b).zip(&c).zip(&d).zip(&sd) {
+        (a + k).write_le(words.next().unwrap());
+        (b + sb).write_le(words.next().unwrap());
+        (c + sc).write_le(words.next().unwrap());
+        (d + sd).write_le(words.next().unwrap());
+    }
+}
+
+dispatch!(m, Mach, {
+    fn refill_wide(state: &mut ChaCha, drounds: u32, out: &mut [u8; BUFSZ]) {
+        refill_wide_impl(m, state, drounds, out);
+    }
+});
+
+// Single-block, rounds-only; shared by try_apply_keystream for tails shorter than BUFSZ
+// and XChaCha's setup step.
+dispatch!(m, Mach, {
+    fn refill_narrow_rounds(state: &mut ChaCha, drounds: u32) -> State<vec128_storage> {
+        let k: Mach::u32x4 = m.vec([0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574]);
+        let mut x = State {
+            a: k,
+            b: m.unpack(state.b),
+            c: m.unpack(state.c),
+            d: m.unpack(state.d),
+        };
+        for _ in 0..drounds {
+            x = round(x);
+            x = undiagonalize(round(diagonalize(x)));
+        }
+        State {
+            a: x.a.into(),
+            b: x.b.into(),
+            c: x.c.into(),
+            d: x.d.into(),
+        }
+    }
+});
+
+dispatch_light128!(m, Mach, {
+    fn set_stream_param(state: &mut ChaCha, param: u32, value: u64) {
+        let d: Mach::u32x4 = m.unpack(state.d);
+        state.d = d
+            .insert((value >> 32) as u32, (param << 1) | 1)
+            .insert(value as u32, param << 1)
+            .into();
+    }
+});
+
+dispatch_light128!(m, Mach, {
+    fn get_stream_param(state: &ChaCha, param: u32) -> u64 {
+        let d: Mach::u32x4 = m.unpack(state.d);
+        ((d.extract((param << 1) | 1) as u64) << 32) | d.extract(param << 1) as u64
+    }
+});
+
+fn read_u32le(xs: &[u8]) -> u32 {
+    assert_eq!(xs.len(), 4);
+    u32::from(xs[0]) | (u32::from(xs[1]) << 8) | (u32::from(xs[2]) << 16) | (u32::from(xs[3]) << 24)
+}
+
+dispatch_light128!(m, Mach, {
+    fn init_chacha(key: &[u8; 32], nonce: &[u8]) -> ChaCha {
+        let ctr_nonce = [
+            0,
+            if nonce.len() == 12 {
+                read_u32le(&nonce[0..4])
+            } else {
+                0
+            },
+            read_u32le(&nonce[nonce.len() - 8..nonce.len() - 4]),
+            read_u32le(&nonce[nonce.len() - 4..]),
+        ];
+        let key0: Mach::u32x4 = m.read_le(&key[..16]);
+        let key1: Mach::u32x4 = m.read_le(&key[16..]);
+        ChaCha {
+            b: key0.into(),
+            c: key1.into(),
+            d: ctr_nonce.into(),
+        }
+    }
+});
+
+dispatch_light128!(m, Mach, {
+    fn init_chacha_x(key: &[u8; 32], nonce: &[u8; 24], rounds: u32) -> ChaCha {
+        let key0: Mach::u32x4 = m.read_le(&key[..16]);
+        let key1: Mach::u32x4 = m.read_le(&key[16..]);
+        let nonce0: Mach::u32x4 = m.read_le(&nonce[..16]);
+        let mut state = ChaCha {
+            b: key0.into(),
+            c: key1.into(),
+            d: nonce0.into(),
+        };
+        let x = refill_narrow_rounds(&mut state, rounds);
+        let ctr_nonce1 = [0, 0, read_u32le(&nonce[16..20]), read_u32le(&nonce[20..24])];
+        state.b = x.a;
+        state.c = x.d;
+        state.d = ctr_nonce1.into();
+        state
+    }
+});
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..24125b4
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,33 @@
+// 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 ChaCha random number generator.
+
+#![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)]
+
+pub use rand_core;
+
+mod chacha;
+mod guts;
+
+pub use crate::chacha::{
+    ChaCha12Core, ChaCha12Rng, ChaCha20Core, ChaCha20Rng, ChaCha8Core, ChaCha8Rng,
+};
+
+/// ChaCha with 20 rounds
+pub type ChaChaRng = ChaCha20Rng;
+/// ChaCha with 20 rounds, low-level interface
+pub type ChaChaCore = ChaCha20Core;