README.md
1# rand_core
2
3[](https://github.com/rust-random/rand/actions)
4[](https://crates.io/crates/rand_core)
5[](https://rust-random.github.io/book/)
6[](https://rust-random.github.io/rand/rand_core)
7[](https://docs.rs/rand_core)
8[](https://github.com/rust-random/rand#rust-version-requirements)
9
10Core traits and error types of the [rand] library, plus tools for implementing
11RNGs.
12
13This crate is intended for use when implementing the core trait, `RngCore`; it
14defines the core traits to be implemented as well as several small functions to
15aid in their implementation and types required for error handling.
16
17The main [rand] crate re-exports most items defined in this crate, along with
18tools to convert the integer samples generated by `RngCore` to many different
19applications (including sampling from restricted ranges, conversion to floating
20point, list permutations and secure initialisation of RNGs). Most users should
21prefer to use the main [rand] crate.
22
23Links:
24
25- [API documentation (master)](https://rust-random.github.io/rand/rand_core)
26- [API documentation (docs.rs)](https://docs.rs/rand_core)
27- [Changelog](https://github.com/rust-random/rand/blob/master/rand_core/CHANGELOG.md)
28
29[rand]: https://crates.io/crates/rand
30
31
32## Functionality
33
34The `rand_core` crate provides:
35
36- base random number generator traits
37- error-reporting types
38- functionality to aid implementation of RNGs
39
40The traits and error types are also available via `rand`.
41
42## Versions
43
44The current version is:
45```
46rand_core = "0.6.0"
47```
48
49Rand libs have inter-dependencies and make use of the
50[semver trick](https://github.com/dtolnay/semver-trick/) in order to make traits
51compatible across crate versions. (This is especially important for `RngCore`
52and `SeedableRng`.) A few crate releases are thus compatibility shims,
53depending on the *next* lib version (e.g. `rand_core` versions `0.2.2` and
54`0.3.1`). This means, for example, that `rand_core_0_4_0::SeedableRng` and
55`rand_core_0_3_0::SeedableRng` are distinct, incompatible traits, which can
56cause build errors. Usually, running `cargo update` is enough to fix any issues.
57
58## Crate Features
59
60`rand_core` supports `no_std` and `alloc`-only configurations, as well as full
61`std` functionality. The differences between `no_std` and full `std` are small,
62comprising `RngCore` support for `Box<R>` types where `R: RngCore`,
63`std::io::Read` support for types supporting `RngCore`, and
64extensions to the `Error` type's functionality.
65
66The `std` feature is *not enabled by default*. This is primarily to avoid build
67problems where one crate implicitly requires `rand_core` with `std` support and
68another crate requires `rand` *without* `std` support. However, the `rand` crate
69continues to enable `std` support by default, both for itself and `rand_core`.
70
71The `serde1` feature can be used to derive `Serialize` and `Deserialize` for RNG
72implementations that use the `BlockRng` or `BlockRng64` wrappers.
73
74
75# License
76
77`rand_core` is distributed under the terms of both the MIT license and the
78Apache License (Version 2.0).
79
80See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
81[COPYRIGHT](COPYRIGHT) for details.
82
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