std: Remove `rand` crate and module

This commit removes the `rand` crate from the standard library facade as
well as the `__rand` module in the standard library. Neither of these
were used in any meaningful way in the standard library itself. The only
need for randomness in libstd is to initialize the thread-local keys of
a `HashMap`, and that unconditionally used `OsRng` defined in the
standard library anyway.

The cruft of the `rand` crate and the extra `rand` support in the
standard library makes libstd slightly more difficult to port to new
platforms, namely WebAssembly which doesn't have any randomness at all
(without interfacing with JS). The purpose of this commit is to clarify
and streamline randomness in libstd, focusing on how it's only required
in one location, hashmap seeds.

Note that the `rand` crate out of tree has almost always been a drop-in
replacement for the `rand` crate in-tree, so any usage (accidental or
purposeful) of the crate in-tree should switch to the `rand` crate on
crates.io. This then also has the further benefit of avoiding
duplication (mostly) between the two crates!

1 files changed, 0 insertions, 286 deletions

diff --git a/src/libstd/rand/mod.rs b/src/libstd/rand/mod.rs
deleted file mode 100644
index 8da070e7a49..00000000000
--- a/src/libstd/rand/mod.rs
+++ /dev/null
@@ -1,286 +0,0 @@
-// Copyright 2013 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.
-
-//! Utilities for random number generation
-//!
-//! The key functions are `random()` and `Rng::gen()`. These are polymorphic
-//! and so can be used to generate any type that implements `Rand`. Type inference
-//! means that often a simple call to `rand::random()` or `rng.gen()` will
-//! suffice, but sometimes an annotation is required, e.g. `rand::random::<f64>()`.
-//!
-//! See the `distributions` submodule for sampling random numbers from
-//! distributions like normal and exponential.
-//!
-//! # Thread-local RNG
-//!
-//! There is built-in support for a RNG associated with each thread stored
-//! in thread-local storage. This RNG can be accessed via `thread_rng`, or
-//! used implicitly via `random`. This RNG is normally randomly seeded
-//! from an operating-system source of randomness, e.g. `/dev/urandom` on
-//! Unix systems, and will automatically reseed itself from this source
-//! after generating 32 KiB of random data.
-//!
-//! # Cryptographic security
-//!
-//! An application that requires an entropy source for cryptographic purposes
-//! must use `OsRng`, which reads randomness from the source that the operating
-//! system provides (e.g. `/dev/urandom` on Unixes or `CryptGenRandom()` on Windows).
-//! The other random number generators provided by this module are not suitable
-//! for such purposes.
-//!
-//! *Note*: many Unix systems provide `/dev/random` as well as `/dev/urandom`.
-//! This module uses `/dev/urandom` for the following reasons:
-//!
-//! -   On Linux, `/dev/random` may block if entropy pool is empty; `/dev/urandom` will not block.
-//!     This does not mean that `/dev/random` provides better output than
-//!     `/dev/urandom`; the kernel internally runs a cryptographically secure pseudorandom
-//!     number generator (CSPRNG) based on entropy pool for random number generation,
-//!     so the "quality" of `/dev/random` is not better than `/dev/urandom` in most cases.
-//!     However, this means that `/dev/urandom` can yield somewhat predictable randomness
-//!     if the entropy pool is very small, such as immediately after first booting.
-//!     Linux 3.17 added the `getrandom(2)` system call which solves the issue: it blocks if entropy
-//!     pool is not initialized yet, but it does not block once initialized.
-//!     `getrandom(2)` was based on `getentropy(2)`, an existing system call in OpenBSD.
-//!     `OsRng` tries to use `getrandom(2)` if available, and use `/dev/urandom` fallback if not.
-//!     If an application does not have `getrandom` and likely to be run soon after first booting,
-//!     or on a system with very few entropy sources, one should consider using `/dev/random` via
-//!     `ReaderRng`.
-//! -   On some systems (e.g. FreeBSD, OpenBSD and macOS) there is no difference
-//!     between the two sources. (Also note that, on some systems e.g. FreeBSD, both `/dev/random`
-//!     and `/dev/urandom` may block once if the CSPRNG has not seeded yet.)
-
-#![unstable(feature = "rand", issue = "27703")]
-
-use cell::RefCell;
-use fmt;
-use io;
-use mem;
-use rc::Rc;
-use sys;
-
-#[cfg(target_pointer_width = "32")]
-use core_rand::IsaacRng as IsaacWordRng;
-#[cfg(target_pointer_width = "64")]
-use core_rand::Isaac64Rng as IsaacWordRng;
-
-pub use core_rand::{Rand, Rng, SeedableRng};
-pub use core_rand::{XorShiftRng, IsaacRng, Isaac64Rng};
-pub use core_rand::reseeding;
-
-pub mod reader;
-
-/// The standard RNG. This is designed to be efficient on the current
-/// platform.
-#[derive(Copy, Clone)]
-pub struct StdRng {
-    rng: IsaacWordRng,
-}
-
-impl StdRng {
-    /// Create a randomly seeded instance of `StdRng`.
-    ///
-    /// This is a very expensive operation as it has to read
-    /// randomness from the operating system and use this in an
-    /// expensive seeding operation. If one is only generating a small
-    /// number of random numbers, or doesn't need the utmost speed for
-    /// generating each number, `thread_rng` and/or `random` may be more
-    /// appropriate.
-    ///
-    /// Reading the randomness from the OS may fail, and any error is
-    /// propagated via the `io::Result` return value.
-    pub fn new() -> io::Result<StdRng> {
-        OsRng::new().map(|mut r| StdRng { rng: r.gen() })
-    }
-}
-
-impl Rng for StdRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        self.rng.next_u32()
-    }
-
-    #[inline]
-    fn next_u64(&mut self) -> u64 {
-        self.rng.next_u64()
-    }
-}
-
-impl<'a> SeedableRng<&'a [usize]> for StdRng {
-    fn reseed(&mut self, seed: &'a [usize]) {
-        // the internal RNG can just be seeded from the above
-        // randomness.
-        self.rng.reseed(unsafe {mem::transmute(seed)})
-    }
-
-    fn from_seed(seed: &'a [usize]) -> StdRng {
-        StdRng { rng: SeedableRng::from_seed(unsafe {mem::transmute(seed)}) }
-    }
-}
-
-/// Controls how the thread-local RNG is reseeded.
-struct ThreadRngReseeder;
-
-impl reseeding::Reseeder<StdRng> for ThreadRngReseeder {
-    fn reseed(&mut self, rng: &mut StdRng) {
-        *rng = match StdRng::new() {
-            Ok(r) => r,
-            Err(e) => panic!("could not reseed thread_rng: {}", e)
-        }
-    }
-}
-const THREAD_RNG_RESEED_THRESHOLD: usize = 32_768;
-type ThreadRngInner = reseeding::ReseedingRng<StdRng, ThreadRngReseeder>;
-
-/// The thread-local RNG.
-#[derive(Clone)]
-pub struct ThreadRng {
-    rng: Rc<RefCell<ThreadRngInner>>,
-}
-
-impl fmt::Debug for ThreadRng {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.pad("ThreadRng { .. }")
-    }
-}
-
-/// Retrieve the lazily-initialized thread-local random number
-/// generator, seeded by the system. Intended to be used in method
-/// chaining style, e.g. `thread_rng().gen::<isize>()`.
-///
-/// The RNG provided will reseed itself from the operating system
-/// after generating a certain amount of randomness.
-///
-/// The internal RNG used is platform and architecture dependent, even
-/// if the operating system random number generator is rigged to give
-/// the same sequence always. If absolute consistency is required,
-/// explicitly select an RNG, e.g. `IsaacRng` or `Isaac64Rng`.
-pub fn thread_rng() -> ThreadRng {
-    // used to make space in TLS for a random number generator
-    thread_local!(static THREAD_RNG_KEY: Rc<RefCell<ThreadRngInner>> = {
-        let r = match StdRng::new() {
-            Ok(r) => r,
-            Err(e) => panic!("could not initialize thread_rng: {}", e)
-        };
-        let rng = reseeding::ReseedingRng::new(r,
-                                               THREAD_RNG_RESEED_THRESHOLD,
-                                               ThreadRngReseeder);
-        Rc::new(RefCell::new(rng))
-    });
-
-    ThreadRng { rng: THREAD_RNG_KEY.with(|t| t.clone()) }
-}
-
-impl Rng for ThreadRng {
-    fn next_u32(&mut self) -> u32 {
-        self.rng.borrow_mut().next_u32()
-    }
-
-    fn next_u64(&mut self) -> u64 {
-        self.rng.borrow_mut().next_u64()
-    }
-
-    #[inline]
-    fn fill_bytes(&mut self, bytes: &mut [u8]) {
-        self.rng.borrow_mut().fill_bytes(bytes)
-    }
-}
-
-/// A random number generator that retrieves randomness straight from
-/// the operating system. Platform sources:
-///
-/// - Unix-like systems (Linux, Android, macOS): read directly from
-///   `/dev/urandom`, or from `getrandom(2)` system call if available.
-/// - Windows: calls `CryptGenRandom`, using the default cryptographic
-///   service provider with the `PROV_RSA_FULL` type.
-/// - iOS: calls SecRandomCopyBytes as /dev/(u)random is sandboxed.
-/// - OpenBSD: uses the `getentropy(2)` system call.
-///
-/// This does not block.
-pub struct OsRng(sys::rand::OsRng);
-
-impl OsRng {
-    /// Create a new `OsRng`.
-    pub fn new() -> io::Result<OsRng> {
-        sys::rand::OsRng::new().map(OsRng)
-    }
-}
-
-impl Rng for OsRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        self.0.next_u32()
-    }
-
-    #[inline]
-    fn next_u64(&mut self) -> u64 {
-        self.0.next_u64()
-    }
-
-    #[inline]
-    fn fill_bytes(&mut self, bytes: &mut [u8]) {
-        self.0.fill_bytes(bytes)
-    }
-}
-
-
-#[cfg(test)]
-mod tests {
-    use sync::mpsc::channel;
-    use rand::Rng;
-    use super::OsRng;
-    use thread;
-
-    #[test]
-    fn test_os_rng() {
-        let mut r = OsRng::new().unwrap();
-
-        r.next_u32();
-        r.next_u64();
-
-        let mut v = [0; 1000];
-        r.fill_bytes(&mut v);
-    }
-
-    #[test]
-    #[cfg_attr(target_os = "emscripten", ignore)]
-    fn test_os_rng_tasks() {
-
-        let mut txs = vec![];
-        for _ in 0..20 {
-            let (tx, rx) = channel();
-            txs.push(tx);
-
-            thread::spawn(move|| {
-                // wait until all the threads are ready to go.
-                rx.recv().unwrap();
-
-                // deschedule to attempt to interleave things as much
-                // as possible (XXX: is this a good test?)
-                let mut r = OsRng::new().unwrap();
-                thread::yield_now();
-                let mut v = [0; 1000];
-
-                for _ in 0..100 {
-                    r.next_u32();
-                    thread::yield_now();
-                    r.next_u64();
-                    thread::yield_now();
-                    r.fill_bytes(&mut v);
-                    thread::yield_now();
-                }
-            });
-        }
-
-        // start all the threads
-        for tx in &txs {
-            tx.send(()).unwrap();
-        }
-    }
-}