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Simplify trait BlockRngCore and rename to Generator #26

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Merged
dhardy merged 9 commits into from
Dec 5, 2025
Merged

Simplify trait BlockRngCore and rename to Generator #26

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01d4237
Simplify trait BlockRngCore: remove assoc. type Item
dhardy Nov 17, 2025
e34c1f3
Allow *any* unused code in doc tests
dhardy Nov 17, 2025
977f74e
Rename BlockRngCore -> Generator
dhardy Nov 17, 2025
ed22701
Rename Generator::Results -> Output
dhardy Nov 30, 2025
5f59956
Rename R -> G: Generator
dhardy Nov 30, 2025
84c23d8
BlockRng: remove bound on <G as Generator>::Output in Debug impl
dhardy Nov 30, 2025
fdf3885
Remove unnecessary calls to as_ref / as_mut
dhardy Dec 1, 2025
49ff793
Replace usages of results.len() with N
dhardy Dec 1, 2025
3777037
Update CHANGELOG
dhardy Dec 1, 2025
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Rename Generator::Results -> Output
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@dhardy
dhardy committed Nov 30, 2025
commit ed22701baec3044ae31ef5b55420ab0e4a760fb7
57 changes: 30 additions & 27 deletions src/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,9 +20,9 @@
//! struct MyRngCore;
//!
//! impl Generator for MyRngCore {
//! type Results = [u32; 16];
//! type Output = [u32; 16];
//!
//! fn generate(&mut self, results: &mut Self::Results) {
//! fn generate(&mut self, output: &mut Self::Output) {
//! unimplemented!()
//! }
//! }
Expand Down Expand Up @@ -50,12 +50,15 @@ use core::fmt;

/// A random (block) generator
pub trait Generator {
/// Results type. This is the 'block' an RNG implementing `BlockRngCore`
/// generates, which will usually be an array like `[u32; 16]`.
type Results;
/// The output type.
///
/// For use with [`rand_core::block`](crate::block) code this must be `[u32; _]` or `[u64; _]`.
type Output;

/// Generate a new block of results.
fn generate(&mut self, results: &mut Self::Results);
/// Generate a new block of `output`.
///
/// This must fill `output` with random data.
fn generate(&mut self, output: &mut Self::Output);
}

/// A cryptographically secure generator
Expand Down Expand Up @@ -105,14 +108,14 @@ pub trait CryptoGenerator: Generator {}
/// [`fill_bytes`]: RngCore::fill_bytes
#[derive(Clone)]
pub struct BlockRng<R: Generator> {
results: R::Results,
results: R::Output,
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<const N: usize, R: Generator<Results = [u32; N]> + fmt::Debug> fmt::Debug for BlockRng<R> {
impl<const N: usize, R: Generator<Output = [u32; N]> + fmt::Debug> fmt::Debug for BlockRng<R> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("BlockRng")
.field("core", &self.core)
Expand All @@ -122,7 +125,7 @@ impl<const N: usize, R: Generator<Results = [u32; N]> + fmt::Debug> fmt::Debug f
}
}

impl<const N: usize, R: Generator<Results = [u32; N]>> BlockRng<R> {
impl<const N: usize, R: Generator<Output = [u32; N]>> BlockRng<R> {
/// Create a new `BlockRng` from an existing RNG implementing
/// `Generator`. Results will be generated on first use.
#[inline]
Expand Down Expand Up @@ -161,7 +164,7 @@ impl<const N: usize, R: Generator<Results = [u32; N]>> BlockRng<R> {
}
}

impl<const N: usize, R: Generator<Results = [u32; N]>> RngCore for BlockRng<R> {
impl<const N: usize, R: Generator<Output = [u32; N]>> RngCore for BlockRng<R> {
#[inline]
fn next_u32(&mut self) -> u32 {
if self.index >= self.results.as_ref().len() {
Expand Down Expand Up @@ -214,7 +217,7 @@ impl<const N: usize, R: Generator<Results = [u32; N]>> RngCore for BlockRng<R> {
}
}

impl<const N: usize, R: Generator<Results = [u32; N]> + SeedableRng> SeedableRng for BlockRng<R> {
impl<const N: usize, R: Generator<Output = [u32; N]> + SeedableRng> SeedableRng for BlockRng<R> {
type Seed = R::Seed;

#[inline(always)]
Expand All @@ -238,7 +241,7 @@ impl<const N: usize, R: Generator<Results = [u32; N]> + SeedableRng> SeedableRng
}
}

impl<const N: usize, R: CryptoGenerator<Results = [u32; N]>> CryptoRng for BlockRng<R> {}
impl<const N: usize, R: CryptoGenerator<Output = [u32; N]>> CryptoRng for BlockRng<R> {}

/// A wrapper type implementing [`RngCore`] for some type implementing
/// [`Generator`] with `u64` array buffer; i.e. this can be used to implement
Expand All @@ -262,15 +265,15 @@ impl<const N: usize, R: CryptoGenerator<Results = [u32; N]>> CryptoRng for Block
/// [`fill_bytes`]: RngCore::fill_bytes
#[derive(Clone)]
pub struct BlockRng64<R: Generator + ?Sized> {
results: R::Results,
results: R::Output,
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<const N: usize, R: Generator<Results = [u64; N]> + fmt::Debug> fmt::Debug for BlockRng64<R> {
impl<const N: usize, R: Generator<Output = [u64; N]> + fmt::Debug> fmt::Debug for BlockRng64<R> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("BlockRng64")
.field("core", &self.core)
Expand All @@ -281,7 +284,7 @@ impl<const N: usize, R: Generator<Results = [u64; N]> + fmt::Debug> fmt::Debug f
}
}

impl<const N: usize, R: Generator<Results = [u64; N]>> BlockRng64<R> {
impl<const N: usize, R: Generator<Output = [u64; N]>> BlockRng64<R> {
/// Create a new `BlockRng` from an existing RNG implementing
/// `Generator`. Results will be generated on first use.
#[inline]
Expand Down Expand Up @@ -324,7 +327,7 @@ impl<const N: usize, R: Generator<Results = [u64; N]>> BlockRng64<R> {
}
}

impl<const N: usize, R: Generator<Results = [u64; N]>> RngCore for BlockRng64<R> {
impl<const N: usize, R: Generator<Output = [u64; N]>> RngCore for BlockRng64<R> {
#[inline]
fn next_u32(&mut self) -> u32 {
let mut index = self.index - self.half_used as usize;
Expand Down Expand Up @@ -376,7 +379,7 @@ impl<const N: usize, R: Generator<Results = [u64; N]>> RngCore for BlockRng64<R>
}
}

impl<const N: usize, R: Generator<Results = [u64; N]> + SeedableRng> SeedableRng for BlockRng64<R> {
impl<const N: usize, R: Generator<Output = [u64; N]> + SeedableRng> SeedableRng for BlockRng64<R> {
type Seed = R::Seed;

#[inline(always)]
Expand All @@ -400,7 +403,7 @@ impl<const N: usize, R: Generator<Results = [u64; N]> + SeedableRng> SeedableRng
}
}

impl<const N: usize, R: CryptoGenerator<Results = [u64; N]>> CryptoRng for BlockRng64<R> {}
impl<const N: usize, R: CryptoGenerator<Output = [u64; N]>> CryptoRng for BlockRng64<R> {}

#[cfg(test)]
mod test {
Expand All @@ -413,11 +416,11 @@ mod test {
}

impl Generator for DummyRng {
type Results = [u32; 16];
type Output = [u32; 16];

fn generate(&mut self, results: &mut Self::Results) {
for r in results {
*r = self.counter;
fn generate(&mut self, output: &mut Self::Output) {
for item in output {
*item = self.counter;
self.counter = self.counter.wrapping_add(3511615421);
}
}
Expand Down Expand Up @@ -463,11 +466,11 @@ mod test {
}

impl Generator for DummyRng64 {
type Results = [u64; 8];
type Output = [u64; 8];

fn generate(&mut self, results: &mut Self::Results) {
for r in results {
*r = self.counter;
fn generate(&mut self, output: &mut Self::Output) {
for item in output {
*item = self.counter;
self.counter = self.counter.wrapping_add(2781463553396133981);
}
}
Expand Down