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Diffstat (limited to 'vendor/fastrand/src/lib.rs')
| -rw-r--r-- | vendor/fastrand/src/lib.rs | 692 |
1 files changed, 692 insertions, 0 deletions
diff --git a/vendor/fastrand/src/lib.rs b/vendor/fastrand/src/lib.rs new file mode 100644 index 0000000..24de8dd --- /dev/null +++ b/vendor/fastrand/src/lib.rs @@ -0,0 +1,692 @@ +//! A simple and fast random number generator. +//! +//! The implementation uses [Wyrand](https://github.com/wangyi-fudan/wyhash), a simple and fast +//! generator but **not** cryptographically secure. +//! +//! # Examples +//! +//! Flip a coin: +//! +//! ``` +//! if fastrand::bool() { +//! println!("heads"); +//! } else { +//! println!("tails"); +//! } +//! ``` +//! +//! Generate a random `i32`: +//! +//! ``` +//! let num = fastrand::i32(..); +//! ``` +//! +//! Choose a random element in an array: +//! +//! ``` +//! let v = vec![1, 2, 3, 4, 5]; +//! let i = fastrand::usize(..v.len()); +//! let elem = v[i]; +//! ``` +//! +//! Sample values from an array with `O(n)` complexity (`n` is the length of array): +//! +//! ``` +//! fastrand::choose_multiple(vec![1, 4, 5].iter(), 2); +//! fastrand::choose_multiple(0..20, 12); +//! ``` +//! +//! +//! Shuffle an array: +//! +//! ``` +//! let mut v = vec![1, 2, 3, 4, 5]; +//! fastrand::shuffle(&mut v); +//! ``` +//! +//! Generate a random [`Vec`] or [`String`]: +//! +//! ``` +//! use std::iter::repeat_with; +//! +//! let v: Vec<i32> = repeat_with(|| fastrand::i32(..)).take(10).collect(); +//! let s: String = repeat_with(fastrand::alphanumeric).take(10).collect(); +//! ``` +//! +//! To get reproducible results on every run, initialize the generator with a seed: +//! +//! ``` +//! // Pick an arbitrary number as seed. +//! fastrand::seed(7); +//! +//! // Now this prints the same number on every run: +//! println!("{}", fastrand::u32(..)); +//! ``` +//! +//! To be more efficient, create a new [`Rng`] instance instead of using the thread-local +//! generator: +//! +//! ``` +//! use std::iter::repeat_with; +//! +//! let mut rng = fastrand::Rng::new(); +//! let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect(); +//! ``` +//! +//! This crate aims to expose a core set of useful randomness primitives. For more niche algorithms, +//! consider using the [`fastrand-contrib`] crate alongside this one. +//! +//! # Features +//! +//! - `std` (enabled by default): Enables the `std` library. This is required for the global +//! generator and global entropy. Without this feature, [`Rng`] can only be instantiated using +//! the [`with_seed`](Rng::with_seed) method. +//! - `js`: Assumes that WebAssembly targets are being run in a JavaScript environment. See the +//! [WebAssembly Notes](#webassembly-notes) section for more information. +//! +//! # WebAssembly Notes +//! +//! For non-WASI WASM targets, there is additional sublety to consider when utilizing the global RNG. +//! By default, `std` targets will use entropy sources in the standard library to seed the global RNG. +//! However, these sources are not available by default on WASM targets outside of WASI. +//! +//! If the `js` feature is enabled, this crate will assume that it is running in a JavaScript +//! environment. At this point, the [`getrandom`] crate will be used in order to access the available +//! entropy sources and seed the global RNG. If the `js` feature is not enabled, the global RNG will +//! use a predefined seed. +//! +//! [`fastrand-contrib`]: https://crates.io/crates/fastrand-contrib +//! [`getrandom`]: https://crates.io/crates/getrandom + +#![cfg_attr(not(feature = "std"), no_std)] +#![cfg_attr(docsrs, feature(doc_cfg))] +#![forbid(unsafe_code)] +#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)] +#![doc( + html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png" +)] +#![doc( + html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png" +)] + +#[cfg(feature = "alloc")] +extern crate alloc; + +use core::convert::{TryFrom, TryInto}; +use core::ops::{Bound, RangeBounds}; + +#[cfg(feature = "alloc")] +use alloc::vec::Vec; + +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +mod global_rng; + +#[cfg(feature = "std")] +pub use global_rng::*; + +/// A random number generator. +#[derive(Debug, PartialEq, Eq)] +pub struct Rng(u64); + +impl Clone for Rng { + /// Clones the generator by creating a new generator with the same seed. + fn clone(&self) -> Rng { + Rng::with_seed(self.0) + } +} + +impl Rng { + /// Generates a random `u32`. + #[inline] + fn gen_u32(&mut self) -> u32 { + self.gen_u64() as u32 + } + + /// Generates a random `u64`. + #[inline] + fn gen_u64(&mut self) -> u64 { + let s = self.0.wrapping_add(0xA0761D6478BD642F); + self.0 = s; + let t = u128::from(s) * u128::from(s ^ 0xE7037ED1A0B428DB); + (t as u64) ^ (t >> 64) as u64 + } + + /// Generates a random `u128`. + #[inline] + fn gen_u128(&mut self) -> u128 { + (u128::from(self.gen_u64()) << 64) | u128::from(self.gen_u64()) + } + + /// Generates a random `u32` in `0..n`. + #[inline] + fn gen_mod_u32(&mut self, n: u32) -> u32 { + // Adapted from: https://lemire.me/blog/2016/06/30/fast-random-shuffling/ + let mut r = self.gen_u32(); + let mut hi = mul_high_u32(r, n); + let mut lo = r.wrapping_mul(n); + if lo < n { + let t = n.wrapping_neg() % n; + while lo < t { + r = self.gen_u32(); + hi = mul_high_u32(r, n); + lo = r.wrapping_mul(n); + } + } + hi + } + + /// Generates a random `u64` in `0..n`. + #[inline] + fn gen_mod_u64(&mut self, n: u64) -> u64 { + // Adapted from: https://lemire.me/blog/2016/06/30/fast-random-shuffling/ + let mut r = self.gen_u64(); + let mut hi = mul_high_u64(r, n); + let mut lo = r.wrapping_mul(n); + if lo < n { + let t = n.wrapping_neg() % n; + while lo < t { + r = self.gen_u64(); + hi = mul_high_u64(r, n); + lo = r.wrapping_mul(n); + } + } + hi + } + + /// Generates a random `u128` in `0..n`. + #[inline] + fn gen_mod_u128(&mut self, n: u128) -> u128 { + // Adapted from: https://lemire.me/blog/2016/06/30/fast-random-shuffling/ + let mut r = self.gen_u128(); + let mut hi = mul_high_u128(r, n); + let mut lo = r.wrapping_mul(n); + if lo < n { + let t = n.wrapping_neg() % n; + while lo < t { + r = self.gen_u128(); + hi = mul_high_u128(r, n); + lo = r.wrapping_mul(n); + } + } + hi + } +} + +/// Computes `(a * b) >> 32`. +#[inline] +fn mul_high_u32(a: u32, b: u32) -> u32 { + (((a as u64) * (b as u64)) >> 32) as u32 +} + +/// Computes `(a * b) >> 64`. +#[inline] +fn mul_high_u64(a: u64, b: u64) -> u64 { + (((a as u128) * (b as u128)) >> 64) as u64 +} + +/// Computes `(a * b) >> 128`. +#[inline] +fn mul_high_u128(a: u128, b: u128) -> u128 { + // Adapted from: https://stackoverflow.com/a/28904636 + let a_lo = a as u64 as u128; + let a_hi = (a >> 64) as u64 as u128; + let b_lo = b as u64 as u128; + let b_hi = (b >> 64) as u64 as u128; + let carry = (a_lo * b_lo) >> 64; + let carry = ((a_hi * b_lo) as u64 as u128 + (a_lo * b_hi) as u64 as u128 + carry) >> 64; + a_hi * b_hi + ((a_hi * b_lo) >> 64) + ((a_lo * b_hi) >> 64) + carry +} + +macro_rules! rng_integer { + ($t:tt, $unsigned_t:tt, $gen:tt, $mod:tt, $doc:tt) => { + #[doc = $doc] + /// + /// Panics if the range is empty. + #[inline] + pub fn $t(&mut self, range: impl RangeBounds<$t>) -> $t { + let panic_empty_range = || { + panic!( + "empty range: {:?}..{:?}", + range.start_bound(), + range.end_bound() + ) + }; + + let low = match range.start_bound() { + Bound::Unbounded => core::$t::MIN, + Bound::Included(&x) => x, + Bound::Excluded(&x) => x.checked_add(1).unwrap_or_else(panic_empty_range), + }; + + let high = match range.end_bound() { + Bound::Unbounded => core::$t::MAX, + Bound::Included(&x) => x, + Bound::Excluded(&x) => x.checked_sub(1).unwrap_or_else(panic_empty_range), + }; + + if low > high { + panic_empty_range(); + } + + if low == core::$t::MIN && high == core::$t::MAX { + self.$gen() as $t + } else { + let len = high.wrapping_sub(low).wrapping_add(1); + low.wrapping_add(self.$mod(len as $unsigned_t as _) as $t) + } + } + }; +} + +impl Rng { + /// Creates a new random number generator with the initial seed. + #[inline] + #[must_use = "this creates a new instance of `Rng`; if you want to initialize the thread-local generator, use `fastrand::seed()` instead"] + pub fn with_seed(seed: u64) -> Self { + let mut rng = Rng(0); + + rng.seed(seed); + rng + } + + /// Clones the generator by deterministically deriving a new generator based on the initial + /// seed. + /// + /// This function can be used to create a new generator that is a "spinoff" of the old + /// generator. The new generator will not produce the same sequence of values as the + /// old generator. + /// + /// # Example + /// + /// ``` + /// // Seed two generators equally, and clone both of them. + /// let mut base1 = fastrand::Rng::with_seed(0x4d595df4d0f33173); + /// base1.bool(); // Use the generator once. + /// + /// let mut base2 = fastrand::Rng::with_seed(0x4d595df4d0f33173); + /// base2.bool(); // Use the generator once. + /// + /// let mut rng1 = base1.fork(); + /// let mut rng2 = base2.fork(); + /// + /// println!("rng1 returns {}", rng1.u32(..)); + /// println!("rng2 returns {}", rng2.u32(..)); + /// ``` + #[inline] + #[must_use = "this creates a new instance of `Rng`"] + pub fn fork(&mut self) -> Self { + Rng::with_seed(self.gen_u64()) + } + + /// Generates a random `char` in ranges a-z and A-Z. + #[inline] + pub fn alphabetic(&mut self) -> char { + const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"; + *self.choice(CHARS).unwrap() as char + } + + /// Generates a random `char` in ranges a-z, A-Z and 0-9. + #[inline] + pub fn alphanumeric(&mut self) -> char { + const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; + *self.choice(CHARS).unwrap() as char + } + + /// Generates a random `bool`. + #[inline] + pub fn bool(&mut self) -> bool { + self.u8(..) % 2 == 0 + } + + /// Generates a random digit in the given `base`. + /// + /// Digits are represented by `char`s in ranges 0-9 and a-z. + /// + /// Panics if the base is zero or greater than 36. + #[inline] + pub fn digit(&mut self, base: u32) -> char { + if base == 0 { + panic!("base cannot be zero"); + } + if base > 36 { + panic!("base cannot be larger than 36"); + } + let num = self.u8(..base as u8); + if num < 10 { + (b'0' + num) as char + } else { + (b'a' + num - 10) as char + } + } + + /// Generates a random `f32` in range `0..1`. + pub fn f32(&mut self) -> f32 { + let b = 32; + let f = core::f32::MANTISSA_DIGITS - 1; + f32::from_bits((1 << (b - 2)) - (1 << f) + (self.u32(..) >> (b - f))) - 1.0 + } + + /// Generates a random `f64` in range `0..1`. + pub fn f64(&mut self) -> f64 { + let b = 64; + let f = core::f64::MANTISSA_DIGITS - 1; + f64::from_bits((1 << (b - 2)) - (1 << f) + (self.u64(..) >> (b - f))) - 1.0 + } + + /// Collects `amount` values at random from the iterator into a vector. + /// + /// The length of the returned vector equals `amount` unless the iterator + /// contains insufficient elements, in which case it equals the number of + /// elements available. + /// + /// Complexity is `O(n)` where `n` is the length of the iterator. + #[cfg(feature = "alloc")] + #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))] + pub fn choose_multiple<T: Iterator>(&mut self, mut source: T, amount: usize) -> Vec<T::Item> { + // Adapted from: https://docs.rs/rand/latest/rand/seq/trait.IteratorRandom.html#method.choose_multiple + let mut reservoir = Vec::with_capacity(amount); + + reservoir.extend(source.by_ref().take(amount)); + + // Continue unless the iterator was exhausted + // + // note: this prevents iterators that "restart" from causing problems. + // If the iterator stops once, then so do we. + if reservoir.len() == amount { + for (i, elem) in source.enumerate() { + let end = i + 1 + amount; + let k = self.usize(0..end); + if let Some(slot) = reservoir.get_mut(k) { + *slot = elem; + } + } + } else { + // If less than one third of the `Vec` was used, reallocate + // so that the unused space is not wasted. There is a corner + // case where `amount` was much less than `self.len()`. + if reservoir.capacity() > 3 * reservoir.len() { + reservoir.shrink_to_fit(); + } + } + reservoir + } + + rng_integer!( + i8, + u8, + gen_u32, + gen_mod_u32, + "Generates a random `i8` in the given range." + ); + + rng_integer!( + i16, + u16, + gen_u32, + gen_mod_u32, + "Generates a random `i16` in the given range." + ); + + rng_integer!( + i32, + u32, + gen_u32, + gen_mod_u32, + "Generates a random `i32` in the given range." + ); + + rng_integer!( + i64, + u64, + gen_u64, + gen_mod_u64, + "Generates a random `i64` in the given range." + ); + + rng_integer!( + i128, + u128, + gen_u128, + gen_mod_u128, + "Generates a random `i128` in the given range." + ); + + #[cfg(target_pointer_width = "16")] + rng_integer!( + isize, + usize, + gen_u32, + gen_mod_u32, + "Generates a random `isize` in the given range." + ); + #[cfg(target_pointer_width = "32")] + rng_integer!( + isize, + usize, + gen_u32, + gen_mod_u32, + "Generates a random `isize` in the given range." + ); + #[cfg(target_pointer_width = "64")] + rng_integer!( + isize, + usize, + gen_u64, + gen_mod_u64, + "Generates a random `isize` in the given range." + ); + + /// Generates a random `char` in range a-z. + #[inline] + pub fn lowercase(&mut self) -> char { + const CHARS: &[u8] = b"abcdefghijklmnopqrstuvwxyz"; + *self.choice(CHARS).unwrap() as char + } + + /// Initializes this generator with the given seed. + #[inline] + pub fn seed(&mut self, seed: u64) { + self.0 = seed; + } + + /// Gives back **current** seed that is being held by this generator. + #[inline] + pub fn get_seed(&self) -> u64 { + self.0 + } + + /// Choose an item from an iterator at random. + /// + /// This function may have an unexpected result if the `len()` property of the + /// iterator does not match the actual number of items in the iterator. If + /// the iterator is empty, this returns `None`. + #[inline] + pub fn choice<I>(&mut self, iter: I) -> Option<I::Item> + where + I: IntoIterator, + I::IntoIter: ExactSizeIterator, + { + let mut iter = iter.into_iter(); + + // Get the item at a random index. + let len = iter.len(); + if len == 0 { + return None; + } + let index = self.usize(0..len); + + iter.nth(index) + } + + /// Shuffles a slice randomly. + #[inline] + pub fn shuffle<T>(&mut self, slice: &mut [T]) { + for i in 1..slice.len() { + slice.swap(i, self.usize(..=i)); + } + } + + /// Fill a byte slice with random data. + #[inline] + pub fn fill(&mut self, slice: &mut [u8]) { + // We fill the slice by chunks of 8 bytes, or one block of + // WyRand output per new state. + let mut chunks = slice.chunks_exact_mut(core::mem::size_of::<u64>()); + for chunk in chunks.by_ref() { + let n = self.gen_u64().to_ne_bytes(); + // Safe because the chunks are always 8 bytes exactly. + chunk.copy_from_slice(&n); + } + + let remainder = chunks.into_remainder(); + + // Any remainder will always be less than 8 bytes. + if !remainder.is_empty() { + // Generate one last block of 8 bytes of entropy + let n = self.gen_u64().to_ne_bytes(); + + // Use the remaining length to copy from block + remainder.copy_from_slice(&n[..remainder.len()]); + } + } + + rng_integer!( + u8, + u8, + gen_u32, + gen_mod_u32, + "Generates a random `u8` in the given range." + ); + + rng_integer!( + u16, + u16, + gen_u32, + gen_mod_u32, + "Generates a random `u16` in the given range." + ); + + rng_integer!( + u32, + u32, + gen_u32, + gen_mod_u32, + "Generates a random `u32` in the given range." + ); + + rng_integer!( + u64, + u64, + gen_u64, + gen_mod_u64, + "Generates a random `u64` in the given range." + ); + + rng_integer!( + u128, + u128, + gen_u128, + gen_mod_u128, + "Generates a random `u128` in the given range." + ); + + #[cfg(target_pointer_width = "16")] + rng_integer!( + usize, + usize, + gen_u32, + gen_mod_u32, + "Generates a random `usize` in the given range." + ); + #[cfg(target_pointer_width = "32")] + rng_integer!( + usize, + usize, + gen_u32, + gen_mod_u32, + "Generates a random `usize` in the given range." + ); + #[cfg(target_pointer_width = "64")] + rng_integer!( + usize, + usize, + gen_u64, + gen_mod_u64, + "Generates a random `usize` in the given range." + ); + #[cfg(target_pointer_width = "128")] + rng_integer!( + usize, + usize, + gen_u128, + gen_mod_u128, + "Generates a random `usize` in the given range." + ); + + /// Generates a random `char` in range A-Z. + #[inline] + pub fn uppercase(&mut self) -> char { + const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ"; + *self.choice(CHARS).unwrap() as char + } + + /// Generates a random `char` in the given range. + /// + /// Panics if the range is empty. + #[inline] + pub fn char(&mut self, range: impl RangeBounds<char>) -> char { + let panic_empty_range = || { + panic!( + "empty range: {:?}..{:?}", + range.start_bound(), + range.end_bound() + ) + }; + + let surrogate_start = 0xd800u32; + let surrogate_len = 0x800u32; + + let low = match range.start_bound() { + Bound::Unbounded => 0u8 as char, + Bound::Included(&x) => x, + Bound::Excluded(&x) => { + let scalar = if x as u32 == surrogate_start - 1 { + surrogate_start + surrogate_len + } else { + x as u32 + 1 + }; + char::try_from(scalar).unwrap_or_else(|_| panic_empty_range()) + } + }; + + let high = match range.end_bound() { + Bound::Unbounded => core::char::MAX, + Bound::Included(&x) => x, + Bound::Excluded(&x) => { + let scalar = if x as u32 == surrogate_start + surrogate_len { + surrogate_start - 1 + } else { + (x as u32).wrapping_sub(1) + }; + char::try_from(scalar).unwrap_or_else(|_| panic_empty_range()) + } + }; + + if low > high { + panic_empty_range(); + } + + let gap = if (low as u32) < surrogate_start && (high as u32) >= surrogate_start { + surrogate_len + } else { + 0 + }; + let range = high as u32 - low as u32 - gap; + let mut val = self.u32(0..=range) + low as u32; + if val >= surrogate_start { + val += gap; + } + val.try_into().unwrap() + } +} |