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// Copyright (c) Facebook, Inc. and its affiliates.
//
// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.
//! This crates contains functions for generating random values.
//!
//! These functions are intended to be used in tests, benchmarks, and examples. When compiled to
//! WebAssembly target, all of the functions are omitted.
pub use internal::*;
#[cfg(not(target_family = "wasm"))]
mod internal {
use core::{convert::TryInto, fmt::Debug};
use rand::prelude::*;
use utils::Randomizable;
// RANDOM VALUE GENERATION
// ============================================================================================
/// Returns a single random value of the specified type.
///
/// # Panics
/// Panics if:
/// * A valid value requires over 32 bytes.
/// * A valid value could not be generated after 1000 tries.
pub fn rand_value<R: Randomizable>() -> R {
for _ in 0..1000 {
let bytes = rand::thread_rng().gen::<[u8; 32]>();
if let Some(value) = R::from_random_bytes(&bytes[..R::VALUE_SIZE]) {
return value;
}
}
panic!("failed generate a random field element");
}
/// Returns a vector of random value of the specified type and the specified length.
///
/// # Panics
/// Panics if:
/// * A valid value requires at over 32 bytes.
/// * A valid value could not be generated after 1000 tries.
pub fn rand_vector<R: Randomizable>(n: usize) -> Vec<R> {
let mut result = Vec::with_capacity(n);
let seed = rand::thread_rng().gen::<[u8; 32]>();
let mut g = StdRng::from_seed(seed);
for _ in 0..1000 * n {
let bytes = g.gen::<[u8; 32]>();
if let Some(element) = R::from_random_bytes(&bytes[..R::VALUE_SIZE]) {
result.push(element);
if result.len() == n {
return result;
}
}
}
panic!("failed to generate enough random field elements");
}
/// Returns an array of random value of the specified type and the specified length.
///
/// # Panics
/// Panics if:
/// * A valid value requires at over 32 bytes.
/// * A valid value could not be generated after 1000 tries.
pub fn rand_array<R: Randomizable + Debug, const N: usize>() -> [R; N] {
let elements = rand_vector(N);
elements
.try_into()
.expect("failed to convert vector to array")
}
/// Returns a vector of value of the specified type and the specified length generated
/// pseudo-randomly from the specified `seed`.
///
/// # Panics
/// Panics if:
/// * A valid value requires at over 32 bytes.
/// * A valid value could not be generated after 1000 tries.
pub fn prng_vector<R: Randomizable>(seed: [u8; 32], n: usize) -> Vec<R> {
let mut result = Vec::with_capacity(n);
let mut g = StdRng::from_seed(seed);
for _ in 0..1000 * n {
let bytes = g.gen::<[u8; 32]>();
if let Some(element) = R::from_random_bytes(&bytes[..R::VALUE_SIZE]) {
result.push(element);
if result.len() == n {
return result;
}
}
}
panic!("failed to generate enough random field elements");
}
/// Returns an array of value of the specified type and the specified length generated
/// pseudo-randomly from the specified `seed`.
///
/// # Panics
/// Panics if:
/// * A valid value requires at over 32 bytes.
/// * A valid value could not be generated after 1000 tries.
pub fn prng_array<R: Randomizable + Debug, const N: usize>(seed: [u8; 32]) -> [R; N] {
let elements = prng_vector(seed, N);
elements
.try_into()
.expect("failed to convert vector to array")
}
// SHUFFLING
// ============================================================================================
/// Randomly shuffles slice elements.
pub fn shuffle<T>(values: &mut [T]) {
values.shuffle(&mut thread_rng());
}
}
#[cfg(target_family = "wasm")]
mod internal {}
// TESTS
// ================================================================================================
#[cfg(test)]
mod tests {
use super::{rand_array, rand_value};
#[test]
fn rand_primitives() {
let a = rand_value::<u16>();
let b = rand_value::<u16>();
assert_ne!(a, b);
let a = rand_value::<u32>();
let b = rand_value::<u32>();
assert_ne!(a, b);
let a = rand_value::<u64>();
let b = rand_value::<u64>();
assert_ne!(a, b);
let a = rand_value::<u128>();
let b = rand_value::<u128>();
assert_ne!(a, b);
}
#[test]
fn rand_byte_array() {
let a = rand_array::<u8, 30>();
let b = rand_array::<u8, 30>();
assert_ne!(a, b);
let a = rand_array::<u8, 32>();
let b = rand_array::<u8, 32>();
assert_ne!(a, b);
let a = rand_array::<u8, 34>();
let b = rand_array::<u8, 34>();
assert_ne!(a, b);
}
}