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Michael Buesch 77f6a13e19 Add support for signed integers		2 anni fa
examples	eefd55f4c0 Add example	2 anni fa
maintenance	dba4a7f1b9 Add optimized implementation for AVR	2 anni fa
src	77f6a13e19 Add support for signed integers	2 anni fa
.gitignore	412181aef0 Initial commit	2 anni fa
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README.md	90e0cf5d4d Add documentation for optimized code	2 anni fa
build.rs	412181aef0 Initial commit	2 anni fa

SHR3: 3-shift register random number generator

https://bues.ch/

The SHR3 generator can be used to generate non-crypto random bits with only very few computations.

It is suitable for running on very small and restricted hardware (e.g. small 8 bit microcontrollers). The SHR3 function is evaluated once per extracted random bit. The LSB of the SHR3 state is extracted as output.

The generator has a cycle of approximately 4_000_000_000 bits. Do not use it to extract large amounts of random bits (more than a hundred MiB or so), unless you can tolerate looping back to the beginning of the random stream. It will loop back to the beginning after 2**32 - 1 iterations.

This generator is not cryptographically secure! Do not use it for cryptographic applications.

Example usage:

    use shr3::prelude::*;

    let mut shr3 = Shr3::new();                 // SHR3 with default seed (1).
    let x: u8 = shr3.get();                     // Extract 8 bits from shr3.
    let y: u16 = shr3.get_bits(10);             // Extract 10 bits from shr3 and store in lower bits of y.
    assert_eq!(x, 0xF8);                        // Extracted random value.
    assert_eq!(y, 0x2CC);                       // Extracted random value.

    let mut shr3 = Shr3::new_state(42);         // SHR3 with custom seed (42).

    let mut shr3: Shr3 = Default::default();    // Alternative to Shr::new().

Example Cargo.toml dependencies

Add this to your Cargo.toml:

[dependencies]
shr3 = "0.1"

no_std

This crate does not require the Rust std library. It does not link to std.

Optimized implementation

This crate includes an optimized implementation for AVR 8-bit.

All other architectures use the generic implementation. On most architectures, this generic implementation will be compiled to rather efficient code.

License

Licensed under the Apache License version 2.0 or the MIT license, at your option.

README.md