1 // Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Interface to random number generators in Rust.
13 //! This is an experimental library which lives underneath the standard library
14 //! in its dependency chain. This library is intended to define the interface
15 //! for random number generation and also provide utilities around doing so. It
16 //! is not recommended to use this library directly, but rather the official
17 //! interface through `std::rand`.
19 #![crate_name = "rand"]
20 #![crate_type = "rlib"]
21 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
22 html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
23 html_root_url = "https://doc.rust-lang.org/nightly/",
24 html_playground_url = "https://play.rust-lang.org/",
25 test(attr(deny(warnings))))]
26 #![cfg_attr(not(stage0), deny(warnings))]
28 #![unstable(feature = "rand",
29 reason = "use `rand` from crates.io",
31 #![feature(core_float)]
32 #![feature(core_intrinsics)]
33 #![feature(num_bits_bytes)]
34 #![feature(staged_api)]
36 #![feature(custom_attribute)]
37 #![allow(unused_attributes)]
39 #![cfg_attr(test, feature(test, rand))]
49 use core::marker::PhantomData;
51 pub use isaac::{IsaacRng, Isaac64Rng};
52 pub use chacha::ChaChaRng;
54 use distributions::{Range, IndependentSample};
55 use distributions::range::SampleRange;
58 const RAND_BENCH_N: u64 = 100;
60 pub mod distributions;
66 // Temporary trait to implement a few floating-point routines
67 // needed by librand; this is necessary because librand doesn't
68 // depend on libstd. This will go away when librand is integrated
71 trait FloatMath : Sized {
74 fn sqrt(self) -> Self;
75 fn powf(self, n: Self) -> Self;
78 impl FloatMath for f64 {
81 unsafe { intrinsics::expf64(self) }
86 unsafe { intrinsics::logf64(self) }
90 fn powf(self, n: f64) -> f64 {
91 unsafe { intrinsics::powf64(self, n) }
95 fn sqrt(self) -> f64 {
99 unsafe { intrinsics::sqrtf64(self) }
104 /// A type that can be randomly generated using an `Rng`.
106 pub trait Rand : Sized {
107 /// Generates a random instance of this type using the specified source of
109 fn rand<R: Rng>(rng: &mut R) -> Self;
112 /// A random number generator.
113 pub trait Rng : Sized {
114 /// Return the next random u32.
116 /// This rarely needs to be called directly, prefer `r.gen()` to
118 // FIXME #7771: Should be implemented in terms of next_u64
119 fn next_u32(&mut self) -> u32;
121 /// Return the next random u64.
123 /// By default this is implemented in terms of `next_u32`. An
124 /// implementation of this trait must provide at least one of
125 /// these two methods. Similarly to `next_u32`, this rarely needs
126 /// to be called directly, prefer `r.gen()` to `r.next_u64()`.
127 fn next_u64(&mut self) -> u64 {
128 ((self.next_u32() as u64) << 32) | (self.next_u32() as u64)
131 /// Return the next random f32 selected from the half-open
132 /// interval `[0, 1)`.
134 /// By default this is implemented in terms of `next_u32`, but a
135 /// random number generator which can generate numbers satisfying
136 /// the requirements directly can overload this for performance.
137 /// It is required that the return value lies in `[0, 1)`.
139 /// See `Closed01` for the closed interval `[0,1]`, and
140 /// `Open01` for the open interval `(0,1)`.
141 fn next_f32(&mut self) -> f32 {
142 const MANTISSA_BITS: usize = 24;
143 const IGNORED_BITS: usize = 8;
144 const SCALE: f32 = (1u64 << MANTISSA_BITS) as f32;
146 // using any more than `MANTISSA_BITS` bits will
147 // cause (e.g.) 0xffff_ffff to correspond to 1
148 // exactly, so we need to drop some (8 for f32, 11
149 // for f64) to guarantee the open end.
150 (self.next_u32() >> IGNORED_BITS) as f32 / SCALE
153 /// Return the next random f64 selected from the half-open
154 /// interval `[0, 1)`.
156 /// By default this is implemented in terms of `next_u64`, but a
157 /// random number generator which can generate numbers satisfying
158 /// the requirements directly can overload this for performance.
159 /// It is required that the return value lies in `[0, 1)`.
161 /// See `Closed01` for the closed interval `[0,1]`, and
162 /// `Open01` for the open interval `(0,1)`.
163 fn next_f64(&mut self) -> f64 {
164 const MANTISSA_BITS: usize = 53;
165 const IGNORED_BITS: usize = 11;
166 const SCALE: f64 = (1u64 << MANTISSA_BITS) as f64;
168 (self.next_u64() >> IGNORED_BITS) as f64 / SCALE
171 /// Fill `dest` with random data.
173 /// This has a default implementation in terms of `next_u64` and
174 /// `next_u32`, but should be overridden by implementations that
175 /// offer a more efficient solution than just calling those
176 /// methods repeatedly.
178 /// This method does *not* have a requirement to bear any fixed
179 /// relationship to the other methods, for example, it does *not*
180 /// have to result in the same output as progressively filling
181 /// `dest` with `self.gen::<u8>()`, and any such behaviour should
182 /// not be relied upon.
184 /// This method should guarantee that `dest` is entirely filled
185 /// with new data, and may panic if this is impossible
186 /// (e.g. reading past the end of a file that is being used as the
187 /// source of randomness).
188 fn fill_bytes(&mut self, dest: &mut [u8]) {
189 // this could, in theory, be done by transmuting dest to a
190 // [u64], but this is (1) likely to be undefined behaviour for
191 // LLVM, (2) has to be very careful about alignment concerns,
192 // (3) adds more `unsafe` that needs to be checked, (4)
193 // probably doesn't give much performance gain if
194 // optimisations are on.
199 // we could micro-optimise here by generating a u32 if
200 // we only need a few more bytes to fill the vector
202 num = self.next_u64();
206 *byte = (num & 0xff) as u8;
212 /// Return a random value of a `Rand` type.
214 fn gen<T: Rand>(&mut self) -> T {
218 /// Return an iterator that will yield an infinite number of randomly
220 fn gen_iter<'a, T: Rand>(&'a mut self) -> Generator<'a, T, Self> {
223 _marker: PhantomData,
227 /// Generate a random value in the range [`low`, `high`).
229 /// This is a convenience wrapper around
230 /// `distributions::Range`. If this function will be called
231 /// repeatedly with the same arguments, one should use `Range`, as
232 /// that will amortize the computations that allow for perfect
233 /// uniformity, as they only happen on initialization.
237 /// Panics if `low >= high`.
238 fn gen_range<T: PartialOrd + SampleRange>(&mut self, low: T, high: T) -> T {
239 assert!(low < high, "Rng.gen_range called with low >= high");
240 Range::new(low, high).ind_sample(self)
243 /// Return a bool with a 1 in n chance of true
244 fn gen_weighted_bool(&mut self, n: usize) -> bool {
245 n <= 1 || self.gen_range(0, n) == 0
248 /// Return an iterator of random characters from the set A-Z,a-z,0-9.
249 fn gen_ascii_chars<'a>(&'a mut self) -> AsciiGenerator<'a, Self> {
250 AsciiGenerator { rng: self }
253 /// Return a random element from `values`.
255 /// Return `None` if `values` is empty.
256 fn choose<'a, T>(&mut self, values: &'a [T]) -> Option<&'a T> {
257 if values.is_empty() {
260 Some(&values[self.gen_range(0, values.len())])
264 /// Shuffle a mutable slice in place.
265 fn shuffle<T>(&mut self, values: &mut [T]) {
266 let mut i = values.len();
268 // invariant: elements with index >= i have been locked in place.
270 // lock element i in place.
271 values.swap(i, self.gen_range(0, i + 1));
276 /// Iterator which will generate a stream of random items.
278 /// This iterator is created via the `gen_iter` method on `Rng`.
279 pub struct Generator<'a, T, R: 'a> {
281 _marker: PhantomData<T>,
284 impl<'a, T: Rand, R: Rng> Iterator for Generator<'a, T, R> {
287 fn next(&mut self) -> Option<T> {
292 /// Iterator which will continuously generate random ascii characters.
294 /// This iterator is created via the `gen_ascii_chars` method on `Rng`.
295 pub struct AsciiGenerator<'a, R: 'a> {
299 impl<'a, R: Rng> Iterator for AsciiGenerator<'a, R> {
302 fn next(&mut self) -> Option<char> {
303 const GEN_ASCII_STR_CHARSET: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
304 abcdefghijklmnopqrstuvwxyz\
306 Some(*self.rng.choose(GEN_ASCII_STR_CHARSET).unwrap() as char)
310 /// A random number generator that can be explicitly seeded to produce
311 /// the same stream of randomness multiple times.
312 pub trait SeedableRng<Seed>: Rng {
313 /// Reseed an RNG with the given seed.
314 fn reseed(&mut self, Seed);
316 /// Create a new RNG with the given seed.
317 fn from_seed(seed: Seed) -> Self;
320 /// An Xorshift[1] random number
323 /// The Xorshift algorithm is not suitable for cryptographic purposes
324 /// but is very fast. If you do not know for sure that it fits your
325 /// requirements, use a more secure one such as `IsaacRng` or `OsRng`.
327 /// [1]: Marsaglia, George (July 2003). ["Xorshift
328 /// RNGs"](http://www.jstatsoft.org/v08/i14/paper). *Journal of
329 /// Statistical Software*. Vol. 8 (Issue 14).
331 pub struct XorShiftRng {
339 /// Creates a new XorShiftRng instance which is not seeded.
341 /// The initial values of this RNG are constants, so all generators created
342 /// by this function will yield the same stream of random numbers. It is
343 /// highly recommended that this is created through `SeedableRng` instead of
345 pub fn new_unseeded() -> XorShiftRng {
355 impl Rng for XorShiftRng {
357 fn next_u32(&mut self) -> u32 {
359 let t = x ^ (x << 11);
364 self.w = w ^ (w >> 19) ^ (t ^ (t >> 8));
369 impl SeedableRng<[u32; 4]> for XorShiftRng {
370 /// Reseed an XorShiftRng. This will panic if `seed` is entirely 0.
371 fn reseed(&mut self, seed: [u32; 4]) {
372 assert!(!seed.iter().all(|&x| x == 0),
373 "XorShiftRng.reseed called with an all zero seed.");
381 /// Create a new XorShiftRng. This will panic if `seed` is entirely 0.
382 fn from_seed(seed: [u32; 4]) -> XorShiftRng {
383 assert!(!seed.iter().all(|&x| x == 0),
384 "XorShiftRng::from_seed called with an all zero seed.");
395 impl Rand for XorShiftRng {
396 fn rand<R: Rng>(rng: &mut R) -> XorShiftRng {
397 let mut tuple: (u32, u32, u32, u32) = rng.gen();
398 while tuple == (0, 0, 0, 0) {
401 let (x, y, z, w) = tuple;
411 /// A wrapper for generating floating point numbers uniformly in the
412 /// open interval `(0,1)` (not including either endpoint).
414 /// Use `Closed01` for the closed interval `[0,1]`, and the default
415 /// `Rand` implementation for `f32` and `f64` for the half-open
417 pub struct Open01<F>(pub F);
419 /// A wrapper for generating floating point numbers uniformly in the
420 /// closed interval `[0,1]` (including both endpoints).
422 /// Use `Open01` for the closed interval `(0,1)`, and the default
423 /// `Rand` implementation of `f32` and `f64` for the half-open
425 pub struct Closed01<F>(pub F);
429 use std::__rand as rand;
431 pub struct MyRng<R> {
435 impl<R: rand::Rng> ::Rng for MyRng<R> {
436 fn next_u32(&mut self) -> u32 {
437 rand::Rng::next_u32(&mut self.inner)
441 pub fn rng() -> MyRng<rand::ThreadRng> {
442 MyRng { inner: rand::thread_rng() }
445 pub fn weak_rng() -> MyRng<rand::ThreadRng> {
446 MyRng { inner: rand::thread_rng() }