Snap for 6686656 from 229d13742c7bdbaf4a83b1618524b3e52dd7bc48 to sdk-release
Change-Id: I31cf7f29fa34f418b6ef632688968f69d017756f
diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..ecc9adc
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+ "git": {
+ "sha1": "d877ed528248b52d947e0484364a4e1ae59ca502"
+ }
+}
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..e78ff16
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,22 @@
+// This file is generated by cargo2android.py --device --run --features=std --dependencies.
+
+rust_library {
+ name: "librand_core",
+ host_supported: true,
+ crate_name: "rand_core",
+ srcs: ["src/lib.rs"],
+ edition: "2018",
+ features: [
+ "alloc",
+ "getrandom",
+ "std",
+ ],
+ rustlibs: [
+ "libgetrandom",
+ ],
+}
+
+// dependent_library ["feature_list"]
+// cfg-if-0.1.10
+// getrandom-0.1.14 "std"
+// libc-0.2.72
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..dfdd692
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,58 @@
+# 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).
+
+## [0.5.1] - 2019-08-28
+- `OsRng` added to `rand_core` (#863)
+- `Error::INTERNAL_START` and `Error::CUSTOM_START` constants (#864)
+- `Error::raw_os_error` method (#864)
+- `Debug` and `Display` formatting for `getrandom` error codes without `std` (#864)
+### Changed
+- `alloc` feature in `no_std` is available since Rust 1.36 (#856)
+- Added `#[inline]` to `Error` conversion methods (#864)
+
+## [0.5.0] - 2019-06-06
+### Changed
+- Enable testing with Miri and fix incorrect pointer usages (#779, #780, #781, #783, #784)
+- Rewrite `Error` type and adjust API (#800)
+- Adjust usage of `#[inline]` for `BlockRng` and `BlockRng64`
+
+## [0.4.0] - 2019-01-24
+### Changed
+- Disable the `std` feature by default (#702)
+
+## [0.3.0] - 2018-09-24
+### Added
+- Add `SeedableRng::seed_from_u64` for convenient seeding. (#537)
+
+## [0.2.1] - 2018-06-08
+### Added
+- References to a `CryptoRng` now also implement `CryptoRng`. (#470)
+
+## [0.2.0] - 2018-05-21
+### Changed
+- Enable the `std` feature by default. (#409)
+- Remove `BlockRng{64}::inner` and `BlockRng::inner_mut`; instead making `core` public
+- Change `BlockRngCore::Results` bound to also require `AsMut<[Self::Item]>`. (#419)
+### Added
+- Add `BlockRng{64}::index` and `BlockRng{64}::generate_and_set`. (#374, #419)
+- Implement `std::io::Read` for RngCore. (#434)
+
+## [0.1.0] - 2018-04-17
+(Split out of the Rand crate, changes here are relative to rand 0.4.2.)
+### Added
+- `RngCore` and `SeedableRng` are now part of `rand_core`. (#288)
+- Add modules to help implementing RNGs `impl` and `le`. (#209, #228)
+- Add `Error` and `ErrorKind`. (#225)
+- Add `CryptoRng` marker trait. (#273)
+- Add `BlockRngCore` trait. (#281)
+- Add `BlockRng` and `BlockRng64` wrappers to help implementations. (#281, #325)
+- Add `RngCore::try_fill_bytes`. (#225)
+### Changed
+- Revise the `SeedableRng` trait. (#233)
+- Remove default implementations for `RngCore::next_u64` and `RngCore::fill_bytes`. (#288)
+
+## [0.0.1] - 2017-09-14 (yanked)
+Experimental version as part of the rand crate refactor.
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..572276e
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,43 @@
+# 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_core"
+version = "0.5.1"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
+description = "Core random number generator traits and tools for implementation.\n"
+homepage = "https://crates.io/crates/rand_core"
+documentation = "https://rust-random.github.io/rand/rand_core/"
+readme = "README.md"
+keywords = ["random", "rng"]
+categories = ["algorithms", "no-std"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-random/rand"
+[dependencies.getrandom]
+version = "0.1"
+optional = true
+
+[dependencies.serde]
+version = "1"
+features = ["derive"]
+optional = true
+
+[features]
+alloc = []
+serde1 = ["serde"]
+std = ["alloc", "getrandom", "getrandom/std"]
+[badges.appveyor]
+repository = "rust-random/rand"
+
+[badges.travis-ci]
+repository = "rust-random/rand"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..e52af5f
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,28 @@
+[package]
+name = "rand_core"
+version = "0.5.1"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_core/"
+homepage = "https://crates.io/crates/rand_core"
+description = """
+Core random number generator traits and tools for implementation.
+"""
+keywords = ["random", "rng"]
+categories = ["algorithms", "no-std"]
+edition = "2018"
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[features]
+std = ["alloc", "getrandom", "getrandom/std"] # use std library; should be default but for above bug
+alloc = [] # enables Vec and Box support without std
+serde1 = ["serde"] # enables serde for BlockRng wrapper
+
+[dependencies]
+serde = { version = "1", features = ["derive"], optional = true }
+getrandom = { version = "0.1", optional = true }
diff --git a/LICENSE b/LICENSE
new file mode 120000
index 0000000..6b579aa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+LICENSE-APACHE
\ No newline at end of file
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+ Apache License
+ Version 2.0, January 2004
+ https://www.apache.org/licenses/
+
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+
+1. Definitions.
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+ any Contribution intentionally submitted for inclusion in the Work
+ by You to the Licensor shall be under the terms and conditions of
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+ Notwithstanding the above, nothing herein shall supersede or modify
+ the terms of any separate license agreement you may have executed
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+6. Trademarks. This License does not grant permission to use the trade
+ names, trademarks, service marks, or product names of the Licensor,
+ except as required for reasonable and customary use in describing the
+ origin of the Work and reproducing the content of the NOTICE file.
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+8. Limitation of Liability. In no event and under no legal theory,
+ whether in tort (including negligence), contract, or otherwise,
+ unless required by applicable law (such as deliberate and grossly
+ negligent acts) or agreed to in writing, shall any Contributor be
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+ of your accepting any such warranty or additional liability.
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+
+Unless required by applicable law or agreed to in writing, software
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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
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..8f7c83f
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,17 @@
+name: "rand_core"
+description:
+ "Core random number generator traits and tools for implementation."
+
+third_party {
+ url {
+ type: HOMEPAGE
+ value: "https://crates.io/crates/rand_core"
+ }
+ url {
+ type: GIT
+ value: "https://github.com/rust-random/rand"
+ }
+ version: "0.5.1"
+ last_upgrade_date { year: 2020 month: 6 day: 18 }
+ license_type: NOTICE
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..467e66f
--- /dev/null
+++ b/README.md
@@ -0,0 +1,82 @@
+# rand_core
+
+[](https://travis-ci.org/rust-random/rand)
+[](https://ci.appveyor.com/project/rust-random/rand)
+[](https://crates.io/crates/rand_core)
+[](https://rust-random.github.io/book/)
+[](https://rust-random.github.io/rand/rand_core)
+[](https://docs.rs/rand_core)
+[](https://github.com/rust-random/rand#rust-version-requirements)
+
+Core traits and error types of the [rand] library, plus tools for implementing
+RNGs.
+
+This crate is intended for use when implementing the core trait, `RngCore`; it
+defines the core traits to be implemented as well as several small functions to
+aid in their implementation and types required for error handling.
+
+The main [rand] crate re-exports most items defined in this crate, along with
+tools to convert the integer samples generated by `RngCore` to many different
+applications (including sampling from restricted ranges, conversion to floating
+point, list permutations and secure initialisation of RNGs). Most users should
+prefer to use the main [rand] crate.
+
+Links:
+
+- [API documentation (master)](https://rust-random.github.io/rand/rand_core)
+- [API documentation (docs.rs)](https://docs.rs/rand_core)
+- [Changelog](https://github.com/rust-random/rand/blob/master/rand_core/CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+
+
+## Functionality
+
+The `rand_core` crate provides:
+
+- base random number generator traits
+- error-reporting types
+- functionality to aid implementation of RNGs
+
+The traits and error types are also available via `rand`.
+
+## Versions
+
+The current version is:
+```
+rand_core = "0.5.0"
+```
+
+Rand libs have inter-dependencies and make use of the
+[semver trick](https://github.com/dtolnay/semver-trick/) in order to make traits
+compatible across crate versions. (This is especially important for `RngCore`
+and `SeedableRng`.) A few crate releases are thus compatibility shims,
+depending on the *next* lib version (e.g. `rand_core` versions `0.2.2` and
+`0.3.1`). This means, for example, that `rand_core_0_4_0::SeedableRng` and
+`rand_core_0_3_0::SeedableRng` are distinct, incompatible traits, which can
+cause build errors. Usually, running `cargo update` is enough to fix any issues.
+
+## Crate Features
+
+`rand_core` supports `no_std` and `alloc`-only configurations, as well as full
+`std` functionality. The differences between `no_std` and full `std` are small,
+comprising `RngCore` support for `Box<R>` types where `R: RngCore`,
+`std::io::Read` support for types supporting `RngCore`, and
+extensions to the `Error` type's functionality.
+
+The `std` feature is *not enabled by default*. This is primarily to avoid build
+problems where one crate implicitly requires `rand_core` with `std` support and
+another crate requires `rand` *without* `std` support. However, the `rand` crate
+continues to enable `std` support by default, both for itself and `rand_core`.
+
+The `serde1` feature can be used to derive `Serialize` and `Deserialize` for RNG
+implementations that use the `BlockRng` or `BlockRng64` wrappers.
+
+
+# License
+
+`rand_core` 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/block.rs b/src/block.rs
new file mode 100644
index 0000000..0ab7458
--- /dev/null
+++ b/src/block.rs
@@ -0,0 +1,437 @@
+// 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};
+#[cfg(feature="serde1")] use serde::{Serialize, Deserialize};
+use crate::{RngCore, CryptoRng, SeedableRng, Error};
+use crate::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
+ #[allow(clippy::cast_ptr_alignment)] // false positive
+ let ptr: *const u64 = results[index..=index+1].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> {
+ self.fill_bytes(dest);
+ Ok(())
+ }
+}
+
+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> {
+ self.fill_bytes(dest);
+ Ok(())
+ }
+}
+
+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/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..30b095c
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,190 @@
+// 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;
+use core::num::NonZeroU32;
+
+
+/// Error type of random number generators
+///
+/// In order to be compatible with `std` and `no_std`, this type has two
+/// possible implementations: with `std` a boxed `Error` trait object is stored,
+/// while with `no_std` we merely store an error code.
+pub struct Error {
+ #[cfg(feature="std")]
+ inner: Box<dyn std::error::Error + Send + Sync + 'static>,
+ #[cfg(not(feature="std"))]
+ code: NonZeroU32,
+}
+
+impl Error {
+ /// Construct from any type supporting `std::error::Error`
+ ///
+ /// Available only when configured with `std`.
+ ///
+ /// See also `From<NonZeroU32>`, which is available with and without `std`.
+ #[cfg(feature="std")]
+ #[inline]
+ pub fn new<E>(err: E) -> Self
+ where E: Into<Box<dyn std::error::Error + Send + Sync + 'static>>
+ {
+ Error { inner: err.into() }
+ }
+
+ /// Reference the inner error (`std` only)
+ ///
+ /// When configured with `std`, this is a trivial operation and never
+ /// panics. Without `std`, this method is simply unavailable.
+ #[cfg(feature="std")]
+ #[inline]
+ pub fn inner(&self) -> &(dyn std::error::Error + Send + Sync + 'static) {
+ &*self.inner
+ }
+
+ /// Unwrap the inner error (`std` only)
+ ///
+ /// When configured with `std`, this is a trivial operation and never
+ /// panics. Without `std`, this method is simply unavailable.
+ #[cfg(feature="std")]
+ #[inline]
+ pub fn take_inner(self) -> Box<dyn std::error::Error + Send + Sync + 'static> {
+ self.inner
+ }
+
+ /// Codes below this point represent OS Errors (i.e. positive i32 values).
+ /// Codes at or above this point, but below [`Error::CUSTOM_START`] are
+ /// reserved for use by the `rand` and `getrandom` crates.
+ pub const INTERNAL_START: u32 = 1 << 31;
+
+ /// Codes at or above this point can be used by users to define their own
+ /// custom errors.
+ pub const CUSTOM_START: u32 = (1 << 31) + (1 << 30);
+
+ /// Extract the raw OS error code (if this error came from the OS)
+ ///
+ /// This method is identical to `std::io::Error::raw_os_error()`, except
+ /// that it works in `no_std` contexts. If this method returns `None`, the
+ /// error value can still be formatted via the `Diplay` implementation.
+ #[inline]
+ pub fn raw_os_error(&self) -> Option<i32> {
+ #[cfg(feature="std")] {
+ if let Some(e) = self.inner.downcast_ref::<std::io::Error>() {
+ return e.raw_os_error();
+ }
+ }
+ match self.code() {
+ Some(code) if u32::from(code) < Self::INTERNAL_START =>
+ Some(u32::from(code) as i32),
+ _ => None,
+ }
+ }
+
+ /// Retrieve the error code, if any.
+ ///
+ /// If this `Error` was constructed via `From<NonZeroU32>`, then this method
+ /// will return this `NonZeroU32` code (for `no_std` this is always the
+ /// case). Otherwise, this method will return `None`.
+ #[inline]
+ pub fn code(&self) -> Option<NonZeroU32> {
+ #[cfg(feature="std")] {
+ self.inner.downcast_ref::<ErrorCode>().map(|c| c.0)
+ }
+ #[cfg(not(feature="std"))] {
+ Some(self.code)
+ }
+ }
+}
+
+impl fmt::Debug for Error {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ #[cfg(feature="std")] {
+ write!(f, "Error {{ inner: {:?} }}", self.inner)
+ }
+ #[cfg(all(feature="getrandom", not(feature="std")))] {
+ getrandom::Error::from(self.code).fmt(f)
+ }
+ #[cfg(not(feature="getrandom"))] {
+ write!(f, "Error {{ code: {} }}", self.code)
+ }
+ }
+}
+
+impl fmt::Display for Error {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ #[cfg(feature="std")] {
+ write!(f, "{}", self.inner)
+ }
+ #[cfg(all(feature="getrandom", not(feature="std")))] {
+ getrandom::Error::from(self.code).fmt(f)
+ }
+ #[cfg(not(feature="getrandom"))] {
+ write!(f, "error code {}", self.code)
+ }
+ }
+}
+
+impl From<NonZeroU32> for Error {
+ #[inline]
+ fn from(code: NonZeroU32) -> Self {
+ #[cfg(feature="std")] {
+ Error { inner: Box::new(ErrorCode(code)) }
+ }
+ #[cfg(not(feature="std"))] {
+ Error { code }
+ }
+ }
+}
+
+#[cfg(feature="getrandom")]
+impl From<getrandom::Error> for Error {
+ #[inline]
+ fn from(error: getrandom::Error) -> Self {
+ #[cfg(feature="std")] {
+ Error { inner: Box::new(error) }
+ }
+ #[cfg(not(feature="std"))] {
+ Error { code: error.code() }
+ }
+ }
+}
+
+#[cfg(feature="std")]
+impl std::error::Error for Error {
+ #[inline]
+ fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+ self.inner.source()
+ }
+}
+
+#[cfg(feature="std")]
+impl From<Error> for std::io::Error {
+ #[inline]
+ fn from(error: Error) -> Self {
+ if let Some(code) = error.raw_os_error() {
+ std::io::Error::from_raw_os_error(code)
+ } else {
+ std::io::Error::new(std::io::ErrorKind::Other, error)
+ }
+ }
+}
+
+#[cfg(feature="std")]
+#[derive(Debug, Copy, Clone)]
+struct ErrorCode(NonZeroU32);
+
+#[cfg(feature="std")]
+impl fmt::Display for ErrorCode {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "error code {}", self.0)
+ }
+}
+
+#[cfg(feature="std")]
+impl std::error::Error for ErrorCode {}
diff --git a/src/impls.rs b/src/impls.rs
new file mode 100644
index 0000000..dee4ed1
--- /dev/null
+++ b/src/impls.rs
@@ -0,0 +1,158 @@
+// 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::ptr::copy_nonoverlapping;
+use core::slice;
+use core::cmp::min;
+use core::mem::size_of;
+use crate::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] = rng.next_u64().to_le_bytes();
+ l.copy_from_slice(&chunk);
+ }
+ let n = left.len();
+ if n > 4 {
+ let chunk: [u8; 8] = rng.next_u64().to_le_bytes();
+ left.copy_from_slice(&chunk[..n]);
+ } else if n > 0 {
+ let chunk: [u8; 4] = rng.next_u32().to_le_bytes();
+ 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/src/le.rs b/src/le.rs
new file mode 100644
index 0000000..266651f
--- /dev/null
+++ b/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/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..d8e0189
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,492 @@
+// 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))))]
+
+#![allow(clippy::unreadable_literal)]
+
+#![cfg_attr(not(feature="std"), no_std)]
+
+
+use core::default::Default;
+use core::convert::AsMut;
+use core::ptr::copy_nonoverlapping;
+
+#[cfg(all(feature="alloc", not(feature="std")))] extern crate alloc;
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::boxed::Box;
+
+pub use error::Error;
+#[cfg(feature="getrandom")] pub use os::OsRng;
+
+
+mod error;
+pub mod block;
+pub mod impls;
+pub mod le;
+#[cfg(feature="getrandom")] mod os;
+
+
+/// 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).
+///
+/// [`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 roughly equal, and values like 0, 1 and (size - 1) are unlikely.
+ /// Note that many non-cryptographic PRNGs will show poor quality output
+ /// if this is not adhered to. If you wish to seed from simple numbers, use
+ /// `seed_from_u64` instead.
+ ///
+ /// All PRNG implementations should be reproducible unless otherwise noted:
+ /// given a fixed `seed`, the same sequence of output should be produced
+ /// on all runs, library versions and architectures (e.g. check endianness).
+ /// Any "value-breaking" changes to the generator should require bumping at
+ /// least the minor version and documentation of the change.
+ ///
+ /// It is 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 may be useful when needing to rapidly seed many PRNGs from a master
+ /// PRNG, and to allow forking of PRNGs. It may be considered deterministic.
+ ///
+ /// The master PRNG should be at least as high quality as the child PRNGs.
+ /// When seeding non-cryptographic child PRNGs, we recommend using a
+ /// different algorithm for the master PRNG (ideally a CSPRNG) to avoid
+ /// correlations between the child PRNGs. If this is not possible (e.g.
+ /// forking using small non-crypto PRNGs) ensure that your PRNG has a good
+ /// mixing function on the output or consider use of a hash function with
+ /// `from_seed`.
+ ///
+ /// Note that seeding `XorShiftRng` from another `XorShiftRng` provides an
+ /// extreme example of what can go wrong: the new PRNG will be a clone
+ /// of the parent.
+ ///
+ /// PRNG implementations are allowed to assume that a good RNG is provided
+ /// for seeding, and that it is cryptographically secure when appropriate.
+ /// As of `rand` 0.7 / `rand_core` 0.5, implementations overriding this
+ /// method should ensure the implementation satisfies reproducibility
+ /// (in prior versions this was not required).
+ ///
+ /// [`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))
+ }
+
+ /// Creates a new instance of the RNG seeded via [`getrandom`].
+ ///
+ /// This method is the recommended way to construct non-deterministic PRNGs
+ /// since it is convenient and secure.
+ ///
+ /// In case the overhead of using [`getrandom`] to seed *many* PRNGs is an
+ /// issue, one may prefer to seed from a local PRNG, e.g.
+ /// `from_rng(thread_rng()).unwrap()`.
+ ///
+ /// # Panics
+ ///
+ /// If [`getrandom`] is unable to provide secure entropy this method will panic.
+ ///
+ /// [`getrandom`]: https://docs.rs/getrandom
+ #[cfg(feature="getrandom")]
+ fn from_entropy() -> Self {
+ let mut seed = Self::Seed::default();
+ if let Err(err) = getrandom::getrandom(seed.as_mut()) {
+ panic!("from_entropy failed: {}", err);
+ }
+ 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 dyn 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);
+ }
+}
diff --git a/src/os.rs b/src/os.rs
new file mode 100644
index 0000000..fc23a57
--- /dev/null
+++ b/src/os.rs
@@ -0,0 +1,85 @@
+// Copyright 2019 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.
+
+//! Interface to the random number generator of the operating system.
+// Note: keep this code in sync with the rand_os crate!
+
+use getrandom::getrandom;
+use crate::{CryptoRng, RngCore, Error, impls};
+
+/// A random number generator that retrieves randomness from from the
+/// operating system.
+///
+/// This is a zero-sized struct. It can be freely constructed with `OsRng`.
+///
+/// The implementation is provided by the [getrandom] crate. Refer to
+/// [getrandom] documentation for details.
+///
+/// This struct is only available when specifying the crate feature `getrandom`
+/// or `std`. When using the `rand` lib, it is also available as `rand::rngs::OsRng`.
+///
+/// # Blocking and error handling
+///
+/// It is possible that when used during early boot the first call to `OsRng`
+/// will block until the system's RNG is initialised. It is also possible
+/// (though highly unlikely) for `OsRng` to fail on some platforms, most
+/// likely due to system mis-configuration.
+///
+/// After the first successful call, it is highly unlikely that failures or
+/// significant delays will occur (although performance should be expected to
+/// be much slower than a user-space PRNG).
+///
+/// # Usage example
+/// ```
+/// use rand_core::{RngCore, OsRng};
+///
+/// let mut key = [0u8; 16];
+/// OsRng.fill_bytes(&mut key);
+/// let random_u64 = OsRng.next_u64();
+/// ```
+///
+/// [getrandom]: https://crates.io/crates/getrandom
+#[derive(Clone, Copy, Debug, Default)]
+pub struct OsRng;
+
+impl CryptoRng for OsRng {}
+
+impl RngCore for OsRng {
+ fn next_u32(&mut self) -> u32 {
+ impls::next_u32_via_fill(self)
+ }
+
+ fn next_u64(&mut self) -> u64 {
+ impls::next_u64_via_fill(self)
+ }
+
+ fn fill_bytes(&mut self, dest: &mut [u8]) {
+ if let Err(e) = self.try_fill_bytes(dest) {
+ panic!("Error: {}", e);
+ }
+ }
+
+ fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+ getrandom(dest)?;
+ Ok(())
+ }
+}
+
+#[test]
+fn test_os_rng() {
+ let x = OsRng.next_u64();
+ let y = OsRng.next_u64();
+ assert!(x != 0);
+ assert!(x != y);
+}
+
+#[test]
+fn test_construction() {
+ let mut rng = OsRng::default();
+ assert!(rng.next_u64() != 0);
+}
