# rand_core

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Core traits and error types of the [rand] library, plus tools for implementing
RNGs.

This crate is intended for use when implementing the core trait, `RngCore`; it
defines the core traits to be implemented as well as several small functions to
aid in their implementation and types required for error handling.

The main [rand] crate re-exports most items defined in this crate, along with
tools to convert the integer samples generated by `RngCore` to many different
applications (including sampling from restricted ranges, conversion to floating
point, list permutations and secure initialisation of RNGs). Most users should
prefer to use the main [rand] crate.

Links:

-   [API documentation (master)](https://rust-random.github.io/rand/rand_core)
-   [API documentation (docs.rs)](https://docs.rs/rand_core)
-   [Changelog](CHANGELOG.md)

[rand]: https://crates.io/crates/rand


## Functionality

The `rand_core` crate provides:

-   base random number generator traits
-   error-reporting types
-   functionality to aid implementation of RNGs

The traits and error types are also available via `rand`.

## Crate Features

`rand_core` supports `no_std` and `alloc`-only configurations, as well as full
`std` functionality. The differences between `no_std` and full `std` are small,
comprising `RngCore` support for `Box<R>` types where `R: RngCore`, as well as
extensions to the `Error` type's functionality.

Due to [rust-lang/cargo#1596](https://github.com/rust-lang/cargo/issues/1596),
`rand_core` is built without `std` support by default. Since features are
unioned across the whole dependency tree, any crate using `rand` with its
default features will also enable `std` support in `rand_core`.

The `serde1` feature can be used to derive `Serialize` and `Deserialize` for RNG
implementations that use the `BlockRng` or `BlockRng64` wrappers.


# License

`rand_core` is distributed under the terms of both the MIT license and the
Apache License (Version 2.0).

See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
[COPYRIGHT](COPYRIGHT) for details.
