refs/heads/android14-gsi - platform/external/rust/crates/arbitrary

commit	02d30c2c360ea27b00dca8597852e9df638139b5	[log] [tgz]
author	Android Build Coastguard Worker <[email protected]>	Fri Mar 10 04:19:20 2023 +0000
committer	Automerger Merge Worker <[email protected]>	Fri Mar 10 04:19:20 2023 +0000
tree	dc2692d0085b040a1674a3092cf72cedba7404ed
parent	c3bc8900effa71b1ce9a09ae5bb902720b18a1dd [diff]
parent	39c38fdbd1fbad18ba3e6d9d00d6f36616cb2f9f [diff]

tree: dc2692d0085b040a1674a3092cf72cedba7404ed

README.md

About

The Arbitrary crate lets you construct arbitrary instances of a type.

This crate is primarily intended to be combined with a fuzzer like libFuzzer and cargo-fuzz or AFL, and to help you turn the raw, untyped byte buffers that they produce into well-typed, valid, structured values. This allows you to combine structure-aware test case generation with coverage-guided, mutation-based fuzzers.

Documentation

Read the API documentation on docs.rs!

Example

Say you're writing a color conversion library, and you have an Rgb struct to represent RGB colors. You might want to implement Arbitrary for Rgb so that you could take arbitrary Rgb instances in a test function that asserts some property (for example, asserting that RGB converted to HSL and converted back to RGB always ends up exactly where we started).

Automatically Deriving `Arbitrary`

Automatically deriving the Arbitrary trait is the recommended way to implement Arbitrary for your types.

Automatically deriving Arbitrary requires you to enable the "derive" cargo feature:

# Cargo.toml

[dependencies]
arbitrary = { version = "1", features = ["derive"] }

And then you can simply add #[derive(Arbitrary)] annotations to your types:

// rgb.rs

use arbitrary::Arbitrary;

#[derive(Arbitrary)]
pub struct Rgb {
    pub r: u8,
    pub g: u8,
    pub b: u8,
}

Customizing single fields

This can be particular handy if your structure uses a type that does not implement Arbitrary or you want to have more customization for particular fields.

#[derive(Arbitrary)]
pub struct Rgba {
    // set `r` to Default::default()
    #[arbitrary(default)]
    pub r: u8,

    // set `g` to 255
    #[arbitrary(value = 255)]
    pub g: u8,

    // Generate `b` with a custom function of type
    //
    //    fn(&mut Unstructured) -> arbitrary::Result<T>
    //
    // where `T` is the field's type.
    #[arbitrary(with = arbitrary_b)]
    pub b: u8,

    // Generate `a` with a custom closure (shortuct to avoid a custom funciton)
    #[arbitrary(with = |u: &mut Unstructured| u.int_in_range(0..=64))]
    pub a: u8,
}

fn arbitrary_b(u: &mut Unstructured) -> arbitrary::Result<u8> {
    u.int_in_range(64..=128)
}

Implementing `Arbitrary` By Hand

Alternatively, you can write an Arbitrary implementation by hand:

// rgb.rs

use arbitrary::{Arbitrary, Result, Unstructured};

#[derive(Copy, Clone, Debug)]
pub struct Rgb {
    pub r: u8,
    pub g: u8,
    pub b: u8,
}

impl<'a> Arbitrary<'a> for Rgb {
    fn arbitrary(u: &mut Unstructured<'a>) -> Result<Self> {
        let r = u8::arbitrary(u)?;
        let g = u8::arbitrary(u)?;
        let b = u8::arbitrary(u)?;
        Ok(Rgb { r, g, b })
    }
}

License

Licensed under dual MIT or Apache-2.0 at your choice.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.