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    // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! Pseudo random number generators are algorithms to produce *apparently
    //! random* numbers deterministically, and usually fairly quickly.
    //!
    //! So long as the algorithm is computationally secure, is initialised with
    //! sufficient entropy (i.e. unknown by an attacker), and its internal state is
    //! also protected (unknown to an attacker), the output will also be
    //! *computationally secure*. Computationally Secure Pseudo Random Number
    //! Generators (CSPRNGs) are thus suitable sources of random numbers for
    //! cryptography. There are a couple of gotchas here, however. First, the seed
    //! used for initialisation must be unknown. Usually this should be provided by
    //! the operating system and should usually be secure, however this may not
    //! always be the case (especially soon after startup). Second, user-space
    //! memory may be vulnerable, for example when written to swap space, and after
    //! forking a child process should reinitialise any user-space PRNGs. For this
    //! reason it may be preferable to source random numbers directly from the OS
    //! for cryptographic applications.
    //!
    //! PRNGs are also widely used for non-cryptographic uses: randomised
    //! algorithms, simulations, games. In these applications it is usually not
    //! important for numbers to be cryptographically *unguessable*, but even
    //! distribution and independence from other samples (from the point of view
    //! of someone unaware of the algorithm used, at least) may still be important.
    //! Good PRNGs should satisfy these properties, but do not take them for
    //! granted; Wikipedia's article on
    //! [Pseudorandom number generators](https://en.wikipedia.org/wiki/Pseudorandom_number_generator)
    //! provides some background on this topic.
    //!
    //! Care should be taken when seeding (initialising) PRNGs. Some PRNGs have
    //! short periods for some seeds. If one PRNG is seeded from another using the
    //! same algorithm, it is possible that both will yield the same sequence of
    //! values (with some lag).

    mod chacha;
    mod isaac;
    mod isaac64;
    mod xorshift;

    pub use self::chacha::ChaChaRng;
    pub use self::isaac::IsaacRng;
    pub use self::isaac64::Isaac64Rng;
    pub use self::xorshift::XorShiftRng;

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