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Diffstat (limited to 'rand/rand_core/src/block.rs')
| -rw-r--r-- | rand/rand_core/src/block.rs | 437 |
1 files changed, 0 insertions, 437 deletions
diff --git a/rand/rand_core/src/block.rs b/rand/rand_core/src/block.rs deleted file mode 100644 index 0ab7458..0000000 --- a/rand/rand_core/src/block.rs +++ /dev/null @@ -1,437 +0,0 @@ -// 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> {} |