reallyme-crypto-csprng 0.3.3

Cryptographically secure random byte generation for ReallyMe Crypto.
Documentation 
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// SPDX-FileCopyrightText: Copyright © 2026 ReallyMe LLC. All rights reserved
//
// SPDX-License-Identifier: Apache-2.0

use crypto_core::{CryptoError, RngFailureKind, RngOutputKind};
use getrandom::{rand_core::TryRng, SysRng};

/// A source of cryptographically secure random bytes.
pub trait SecureRandom {
    /// Fills `output` with secure random bytes, tagging any error with `kind`.
    /// Returns an error if entropy is unavailable.
    fn fill_secure(&mut self, output: &mut [u8], kind: RngOutputKind) -> Result<(), CryptoError>;
}

/// [`SecureRandom`] implementation backed by the operating system's CSPRNG.
#[derive(Default)]
pub struct OsSecureRandom;

impl SecureRandom for OsSecureRandom {
    fn fill_secure(&mut self, output: &mut [u8], kind: RngOutputKind) -> Result<(), CryptoError> {
        SysRng.try_fill_bytes(output).map_err(|_| CryptoError::Rng {
            output: kind,
            kind: RngFailureKind::EntropyUnavailable,
        })
    }
}