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-rw-r--r--rand/src/rand_impls.rs299
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diff --git a/rand/src/rand_impls.rs b/rand/src/rand_impls.rs
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-// Copyright 2013-2014 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.
-
-//! The implementations of `Rand` for the built-in types.
-
-use core::{char, mem};
-
-use {Rand,Rng};
-
-impl Rand for isize {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> isize {
- if mem::size_of::<isize>() == 4 {
- rng.gen::<i32>() as isize
- } else {
- rng.gen::<i64>() as isize
- }
- }
-}
-
-impl Rand for i8 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> i8 {
- rng.next_u32() as i8
- }
-}
-
-impl Rand for i16 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> i16 {
- rng.next_u32() as i16
- }
-}
-
-impl Rand for i32 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> i32 {
- rng.next_u32() as i32
- }
-}
-
-impl Rand for i64 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> i64 {
- rng.next_u64() as i64
- }
-}
-
-#[cfg(feature = "i128_support")]
-impl Rand for i128 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> i128 {
- rng.gen::<u128>() as i128
- }
-}
-
-impl Rand for usize {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> usize {
- if mem::size_of::<usize>() == 4 {
- rng.gen::<u32>() as usize
- } else {
- rng.gen::<u64>() as usize
- }
- }
-}
-
-impl Rand for u8 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> u8 {
- rng.next_u32() as u8
- }
-}
-
-impl Rand for u16 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> u16 {
- rng.next_u32() as u16
- }
-}
-
-impl Rand for u32 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> u32 {
- rng.next_u32()
- }
-}
-
-impl Rand for u64 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> u64 {
- rng.next_u64()
- }
-}
-
-#[cfg(feature = "i128_support")]
-impl Rand for u128 {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> u128 {
- ((rng.next_u64() as u128) << 64) | (rng.next_u64() as u128)
- }
-}
-
-
-macro_rules! float_impls {
- ($mod_name:ident, $ty:ty, $mantissa_bits:expr, $method_name:ident) => {
- mod $mod_name {
- use {Rand, Rng, Open01, Closed01};
-
- const SCALE: $ty = (1u64 << $mantissa_bits) as $ty;
-
- impl Rand for $ty {
- /// Generate a floating point number in the half-open
- /// interval `[0,1)`.
- ///
- /// See `Closed01` for the closed interval `[0,1]`,
- /// and `Open01` for the open interval `(0,1)`.
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> $ty {
- rng.$method_name()
- }
- }
- impl Rand for Open01<$ty> {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> Open01<$ty> {
- // add a small amount (specifically 2 bits below
- // the precision of f64/f32 at 1.0), so that small
- // numbers are larger than 0, but large numbers
- // aren't pushed to/above 1.
- Open01(rng.$method_name() + 0.25 / SCALE)
- }
- }
- impl Rand for Closed01<$ty> {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> Closed01<$ty> {
- // rescale so that 1.0 - epsilon becomes 1.0
- // precisely.
- Closed01(rng.$method_name() * SCALE / (SCALE - 1.0))
- }
- }
- }
- }
-}
-float_impls! { f64_rand_impls, f64, 53, next_f64 }
-float_impls! { f32_rand_impls, f32, 24, next_f32 }
-
-impl Rand for char {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> char {
- // a char is 21 bits
- const CHAR_MASK: u32 = 0x001f_ffff;
- loop {
- // Rejection sampling. About 0.2% of numbers with at most
- // 21-bits are invalid codepoints (surrogates), so this
- // will succeed first go almost every time.
- match char::from_u32(rng.next_u32() & CHAR_MASK) {
- Some(c) => return c,
- None => {}
- }
- }
- }
-}
-
-impl Rand for bool {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> bool {
- rng.gen::<u8>() & 1 == 1
- }
-}
-
-macro_rules! tuple_impl {
- // use variables to indicate the arity of the tuple
- ($($tyvar:ident),* ) => {
- // the trailing commas are for the 1 tuple
- impl<
- $( $tyvar : Rand ),*
- > Rand for ( $( $tyvar ),* , ) {
-
- #[inline]
- fn rand<R: Rng>(_rng: &mut R) -> ( $( $tyvar ),* , ) {
- (
- // use the $tyvar's to get the appropriate number of
- // repeats (they're not actually needed)
- $(
- _rng.gen::<$tyvar>()
- ),*
- ,
- )
- }
- }
- }
-}
-
-impl Rand for () {
- #[inline]
- fn rand<R: Rng>(_: &mut R) -> () { () }
-}
-tuple_impl!{A}
-tuple_impl!{A, B}
-tuple_impl!{A, B, C}
-tuple_impl!{A, B, C, D}
-tuple_impl!{A, B, C, D, E}
-tuple_impl!{A, B, C, D, E, F}
-tuple_impl!{A, B, C, D, E, F, G}
-tuple_impl!{A, B, C, D, E, F, G, H}
-tuple_impl!{A, B, C, D, E, F, G, H, I}
-tuple_impl!{A, B, C, D, E, F, G, H, I, J}
-tuple_impl!{A, B, C, D, E, F, G, H, I, J, K}
-tuple_impl!{A, B, C, D, E, F, G, H, I, J, K, L}
-
-macro_rules! array_impl {
- {$n:expr, $t:ident, $($ts:ident,)*} => {
- array_impl!{($n - 1), $($ts,)*}
-
- impl<T> Rand for [T; $n] where T: Rand {
- #[inline]
- fn rand<R: Rng>(_rng: &mut R) -> [T; $n] {
- [_rng.gen::<$t>(), $(_rng.gen::<$ts>()),*]
- }
- }
- };
- {$n:expr,} => {
- impl<T> Rand for [T; $n] {
- fn rand<R: Rng>(_rng: &mut R) -> [T; $n] { [] }
- }
- };
-}
-
-array_impl!{32, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,}
-
-impl<T:Rand> Rand for Option<T> {
- #[inline]
- fn rand<R: Rng>(rng: &mut R) -> Option<T> {
- if rng.gen() {
- Some(rng.gen())
- } else {
- None
- }
- }
-}
-
-#[cfg(test)]
-mod tests {
- use {Rng, thread_rng, Open01, Closed01};
-
- struct ConstantRng(u64);
- impl Rng for ConstantRng {
- fn next_u32(&mut self) -> u32 {
- let ConstantRng(v) = *self;
- v as u32
- }
- fn next_u64(&mut self) -> u64 {
- let ConstantRng(v) = *self;
- v
- }
- }
-
- #[test]
- fn floating_point_edge_cases() {
- // the test for exact equality is correct here.
- assert!(ConstantRng(0xffff_ffff).gen::<f32>() != 1.0);
- assert!(ConstantRng(0xffff_ffff_ffff_ffff).gen::<f64>() != 1.0);
- }
-
- #[test]
- fn rand_open() {
- // this is unlikely to catch an incorrect implementation that
- // generates exactly 0 or 1, but it keeps it sane.
- let mut rng = thread_rng();
- for _ in 0..1_000 {
- // strict inequalities
- let Open01(f) = rng.gen::<Open01<f64>>();
- assert!(0.0 < f && f < 1.0);
-
- let Open01(f) = rng.gen::<Open01<f32>>();
- assert!(0.0 < f && f < 1.0);
- }
- }
-
- #[test]
- fn rand_closed() {
- let mut rng = thread_rng();
- for _ in 0..1_000 {
- // strict inequalities
- let Closed01(f) = rng.gen::<Closed01<f64>>();
- assert!(0.0 <= f && f <= 1.0);
-
- let Closed01(f) = rng.gen::<Closed01<f32>>();
- assert!(0.0 <= f && f <= 1.0);
- }
- }
-}
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